Re: [PATCH] usb: dwc3: debugfs: add snapshot to dump requests trbs events

Re: [PATCH] usb: dwc3: debugfs: add snapshot to dump requests trbs events

[Felipe Balbi]

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On Mon, Apr 28, 2014 at 04:49:23PM -0400, Zhuang Jin Can wrote:
> Adds a debugfs file "snapshot" to dump dwc3 requests, trbs and events.

you need to explain what are you trying to provide to our users here.

What "problem" are you trying to solve ?

> As ep0 requests are more complex than others. It's not included in this
> patch.

For ep0, you could at least print the endpoint phase we are currently
in and if we have requests in flight or not.

> Signed-off-by: Zhuang Jin Can <jin.can.zhuang@intel.com>
> ---
>  drivers/usb/dwc3/core.h    |    4 +
>  drivers/usb/dwc3/debugfs.c |  192 ++++++++++++++++++++++++++++++++++++++++++++
>  drivers/usb/dwc3/gadget.h  |   41 ++++++++++
>  3 files changed, 237 insertions(+)
> 
> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> index 57332e3..9d04ddd 100644
> --- a/drivers/usb/dwc3/core.h
> +++ b/drivers/usb/dwc3/core.h
> @@ -849,6 +849,10 @@ struct dwc3_event_devt {
>  	u32	type:4;
>  	u32	reserved15_12:4;
>  	u32	event_info:9;
> +
> +#define DEVT_EVTINFO_SUPERSPEED	(1 << 4)
> +#define DEVT_EVTINFO_HIRD(n)	(((n) & (0xf << 5)) >> 5)
> +
>  	u32	reserved31_25:7;
>  } __packed;
>  
> diff --git a/drivers/usb/dwc3/debugfs.c b/drivers/usb/dwc3/debugfs.c
> index 9ac37fe..078d147 100644
> --- a/drivers/usb/dwc3/debugfs.c
> +++ b/drivers/usb/dwc3/debugfs.c
> @@ -618,6 +618,191 @@ static const struct file_operations dwc3_link_state_fops = {
>  	.release		= single_release,
>  };
>  
> +static void dwc3_dump_requests(struct seq_file *s, struct list_head *head,
> +					const char *list_name)
> +{
> +	struct dwc3_request	*req;
> +
> +	if (list_empty(head)) {
> +		seq_printf(s, "list %s is empty\n", list_name);
> +		return;
> +	}
> +
> +	seq_printf(s, "list %s:\n", list_name);
> +	list_for_each_entry(req, head, list) {
> +		struct usb_request *request = &req->request;
> +
> +		seq_printf(s, "usb_request@0x%p: buf@0x%p(dma@0x%pad), len=%d\n",
> +			request, request->buf, &request->dma,
> +			request->length);
> +
> +		if (req->queued)
> +			seq_printf(s, "\tstatus=%d: actual=%d; start_slot=%u: trb@0x%p(dma@0x%pad)\n",
> +				request->status, request->actual,
> +				req->start_slot, req->trb,
> +				&req->trb_dma);
> +	}
> +}
> +
> +static void dwc3_dump_trbs(struct seq_file *s, struct dwc3_ep *dep)
> +{
> +	struct dwc3_trb	*trb;
> +	int i;
> +
> +	seq_printf(s, "busy_slot = %u, free_slot = %u\n",
> +				dep->busy_slot & DWC3_TRB_MASK,
> +				dep->free_slot & DWC3_TRB_MASK);
> +
> +	for (i = 0; i < DWC3_TRB_NUM; i++) {
> +		trb = &dep->trb_pool[i];
> +		if (i == (dep->busy_slot & DWC3_TRB_MASK)) {

I really dislike these Yoda Conditionals. Fix this up.

> +			seq_puts(s, "busy_slot--|\n");
> +			seq_puts(s, "           \\\n");
> +		}
> +		if (i == (dep->free_slot & DWC3_TRB_MASK)) {
> +			seq_puts(s, "free_slot--|\n");
> +			seq_puts(s, "           \\\n");
> +		}
> +		seq_printf(s, "trb[%02d](dma@0x%pad): %08x(bpl), %08x(bph), %08x(size), %08x(ctrl)\n",

I'm not sure you need to print out the TRB address. bpl, bph, size and
ctrl are desired though.

> +			i, &dep->trb_pool_dma + i * sizeof(*trb),
> +			trb->bpl, trb->bph, trb->size, trb->ctrl);

this will be pretty difficult to parse by a human. I would rather see
you creating one directory per TRB (and also one directory per
endpoint) which holds the details for that entity, so that it looks
like:

dwc3
|-- current_state	(or perhaps a better name, but snapshot isn't very good either)
    |-- ep2
    |   |-- direction
    |   |-- maxpacket
    |   |-- number
    |   |-- state
    |   |-- stream_capable
    |   |-- type
    |   |-- trbs
    |   |   |-- trb0
    |   |   |   |-- bph
    |   |   |   |-- bpl
    |   |   |   |-- ctrl
    |   |   |   |-- size
    |   |   |-- trb1
    |   |   |   |-- bph
    |   |   |   |-- bpl
    |   |   |   |-- ctrl
    |   |   |   |-- size
    |   |   |-- trb2
    |   |   |   |-- bph
    |   |   |   |-- bpl
    |   |   |   |-- ctrl
    |   |   |   |-- size
    |   |   |-- trb3
    |   |   |   |-- bph
    |   |   |   |-- bpl
    |   |   |   |-- ctrl
    |   |   |   |-- size
    .   .   .
    .   .   .
    .   .   .
    |   |-- request0
    |   |   |-- direction
    |   |   |-- mapped
    |   |   |-- queued
    |   |   |-- trb0	(symlink to actual trb directory)
    |   |   |-- ep2		(symlink to actual ep2 directory)
    |   |   |-- usbrequest
    |   |       |-- actual
    |   |       |-- length
    |   |       |-- no_interrupt
    |   |       |-- num_mapped_sgs
    |   |       |-- num_sgs
    |   |       |-- short_not_ok
    |   |       |-- status
    |   |       |-- stream_id
    |   |       |-- zero
    |   |-- request1
    |   |   |-- direction
    |   |   |-- mapped
    |   |   |-- queued
    |   |   |-- trb1	(symlink to actual trb directory)
    |   |   |-- ep2		(symlink to actual ep2 directory)
    |   |   |-- usbrequest
    |   |       |-- actual
    |   |       |-- length
    |   |       |-- no_interrupt
    |   |       |-- num_mapped_sgs
    |   |       |-- num_sgs
    |   |       |-- short_not_ok
    |   |       |-- status
    |   |       |-- stream_id
    |   |       |-- zero
    .   .   .   .
    .   .   .   .
    .   .   .   .


and so forth. That way we get a structured view of everything the
controller and the driver are managing.

> +static void dwc3_dump_dev_event(struct seq_file *s,
> +			const struct dwc3_event_devt *event)
> +{
> +	seq_puts(s, "[0]DEV ");
> +	seq_printf(s, "[1:7]%s ",
> +		event->device_event == DWC3_EVENT_TYPE_DEV ? "TYPE_DEV" :
> +		event->device_event == DWC3_EVENT_TYPE_CARKIT ? "TYPE_CARKIT" :
> +		event->device_event == DWC3_EVENT_TYPE_I2C ? "TYPE_CARKIT" :
> +		"TYPE_UNKOWN");
> +	seq_printf(s, "[8:11]%s ", dwc3_gadget_event_string(event->type));
> +
> +	if (event->type == DWC3_DEVICE_EVENT_LINK_STATUS_CHANGE ||
> +		event->type == DWC3_DEVICE_EVENT_HIBER_REQ) {
> +
> +		seq_printf(s, "[16:20]%s %s ",
> +			dwc3_link_state_string(
> +				event->event_info & DEVT_EVTINFO_SUPERSPEED,
> +				event->event_info & DWC3_LINK_STATE_MASK),
> +				event->event_info & DEVT_EVTINFO_SUPERSPEED ?
> +				"SS" : "HS");
> +
> +		if (!(event->event_info & DEVT_EVTINFO_SUPERSPEED))
> +			seq_printf(s, "[21:24]HIRD %u ",
> +				DEVT_EVTINFO_HIRD(event->event_info));
> +	}
> +}
> +
> +static void dwc3_dump_ep_event(struct seq_file *s,
> +			const struct dwc3_event_depevt *event)
> +{
> +	seq_puts(s, "[0]EP ");
> +	seq_printf(s, "[1:5]ep%d ", event->endpoint_number);
> +	seq_printf(s, "[6:9]%s ",
> +		dwc3_ep_event_string(event->endpoint_event));
> +
> +	switch (event->endpoint_event) {
> +	case DWC3_DEPEVT_XFERCOMPLETE:
> +	case DWC3_DEPEVT_XFERINPROGRESS:
> +		if (event->status & DEPEVT_STATUS_BUSERR)
> +			seq_puts(s, "[12]BUSERR ");
> +		if (event->status & DEPEVT_STATUS_SHORT)
> +			seq_puts(s, "[13]SHORT ");
> +		if (event->status & DEPEVT_STATUS_IOC)
> +			seq_puts(s, "[14]IOC ");
> +		if (event->status & DEPEVT_STATUS_LST)
> +			seq_puts(s, "[15]LST ");
> +		break;
> +	case DWC3_DEPEVT_XFERNOTREADY:
> +		if ((event->status & 0x3) == 1)
> +			seq_puts(s, "[12:13]Data_Stage ");
> +		else if ((event->status & 0x3) == 2)
> +			seq_puts(s, "[12:13]Status_Stage ");
> +		if (event->status & DEPEVT_STATUS_TRANSFER_ACTIVE)
> +			seq_puts(s, "[15]XferActive ");
> +		else
> +			seq_puts(s, "[15]XferNotActive ");
> +		break;
> +	case DWC3_DEPEVT_EPCMDCMPLT:
> +		if (event->status & BIT(0))
> +			seq_puts(s, "[12:15]Invalid Transfer Resource ");
> +		break;
> +	default:
> +		seq_puts(s, "[12:15]UNKOWN ");
> +	}
> +	seq_printf(s, "[16:31]PARAM 0x%04x ", event->parameters);
> +}
> +
> +static void dwc3_dump_event_buf(struct seq_file *s,
> +			struct dwc3_event_buffer *evt)
> +{
> +	union dwc3_event	event;
> +	int			i;
> +
> +	seq_printf(s, "evt->buf@0x%p(dma@0x%pad), length=%u, lpos=%u, count=%u, flags=%s\n",
> +		evt->buf, &evt->dma,
> +		evt->length, evt->lpos, evt->count,
> +		evt->flags & DWC3_EVENT_PENDING ? "pending" : "0");
> +
> +	for (i = 0; i < evt->length; i += 4) {
> +		event.raw = *(u32 *) (evt->buf + i);
> +		if (i == evt->lpos) {
> +			seq_puts(s, "lpos-------|\n");
> +			seq_puts(s, "           \\\n");
> +		}
> +		seq_printf(s, "event[%d]: %08x ", i, event.raw);
> +
> +		if (event.type.is_devspec)
> +			dwc3_dump_dev_event(s, &event.devt);
> +		else
> +			dwc3_dump_ep_event(s, &event.depevt);
> +		seq_puts(s, "\n");
> +	}

how well have you tested this ? I'm not entirely sure you should be
reading the event buffer at any time you want, though I might be wrong.

It's still a bit easier to reproduce part of the event handling here. I
think it's best to make a choice of caching the last 5 events in a ring
buffer and provide a helper for IRQ handlers to push events into the
ring buffer, then from here you just iterate over that ring buffer
instead of accessing our actual event buffer.

Also note that we can hold up to 64 events in our event buffer so this
call could take a looooooot of time to complete and you probably don't
need all that information anyway because you can get them by just
enabling VERBOSE_DEBUG on dwc3 and capturing the entire driver behavior
on dmesg.

> +static int dwc3_snapshot_show(struct seq_file *s, void *unused)
> +{
> +	struct dwc3		*dwc = s->private;
> +	unsigned long		flags;
> +	int			i;
> +
> +	spin_lock_irqsave(&dwc->lock, flags);
> +	for (i = 2; i < DWC3_ENDPOINTS_NUM; i++) {

some platforms don't have all 32 physical endpoints, we just had a bug
fix for that, see commit 32702e9.

> +		struct dwc3_ep	*dep = dwc->eps[i];
> +
> +		if (!(dep->flags & DWC3_EP_ENABLED))
> +			continue;
> +
> +		seq_printf(s, "[%s]\n", dep->name);
> +		dwc3_dump_requests(s, &dep->request_list, "request_list");
> +		dwc3_dump_requests(s, &dep->req_queued, "req_queued");
> +		if (!list_empty(&dep->req_queued))
> +			dwc3_dump_trbs(s, dep);
> +		seq_puts(s, "\n");
> +	}
> +
> +	for (i = 0; i < dwc->num_event_buffers; i++)
> +		dwc3_dump_event_buf(s, dwc->ev_buffs[i]);
> +	spin_unlock_irqrestore(&dwc->lock, flags);
> +
> +	return 0;
> +}
> +
> +static int dwc3_snapshot_open(struct inode *inode, struct file *file)
> +{
> +	return single_open(file, dwc3_snapshot_show, inode->i_private);
> +}
> +
> +static const struct file_operations dwc3_snapshot_fops = {
> +	.open			= dwc3_snapshot_open,
> +	.read			= seq_read,
> +	.llseek			= seq_lseek,
> +	.release		= single_release,
> +};
> +
>  int dwc3_debugfs_init(struct dwc3 *dwc)
>  {
>  	struct dentry		*root;
> @@ -672,6 +857,13 @@ int dwc3_debugfs_init(struct dwc3 *dwc)
>  			ret = -ENOMEM;
>  			goto err1;
>  		}
> +
> +		file = debugfs_create_file("snapshot", S_IRUGO, root,
> +				dwc, &dwc3_snapshot_fops);
> +		if (!file) {
> +			ret = -ENOMEM;
> +			goto err1;
> +		}
>  	}
>  
>  	return 0;
> diff --git a/drivers/usb/dwc3/gadget.h b/drivers/usb/dwc3/gadget.h
> index a0ee75b..f589323 100644
> --- a/drivers/usb/dwc3/gadget.h
> +++ b/drivers/usb/dwc3/gadget.h
> @@ -120,6 +120,8 @@ static inline const char *dwc3_gadget_event_string(u8 event)
>  		return "Link Status Change";
>  	case DWC3_DEVICE_EVENT_WAKEUP:
>  		return "WakeUp";
> +	case DWC3_DEVICE_EVENT_HIBER_REQ:
> +		return "Hibernation Request";

this should be in a separate patch.

>  	case DWC3_DEVICE_EVENT_EOPF:
>  		return "End-Of-Frame";
>  	case DWC3_DEVICE_EVENT_SOF:
> @@ -159,4 +161,43 @@ static inline const char *dwc3_ep_event_string(u8 event)
>  	return "UNKNOWN";
>  }
>  
> +/**
> + * dwc3_link_state_string - returns link state
> + * @link_state: the link state code
> + */
> +static inline const char *dwc3_link_state_string(u8 is_ss, u8 link_state)
> +{
> +	switch (link_state) {
> +	case DWC3_LINK_STATE_U0:
> +		return is_ss ? "U0" : "L0";
> +	case DWC3_LINK_STATE_U1:
> +		return "U1";
> +	case DWC3_LINK_STATE_U2:
> +		return is_ss ? "U2" : "L1";
> +	case DWC3_LINK_STATE_U3:
> +		return is_ss ? "U3" : "L2";
> +	case DWC3_LINK_STATE_SS_DIS:
> +		return is_ss ? "SS.Disabled" : "L3";
> +	case DWC3_LINK_STATE_RX_DET:
> +		return is_ss ? "Rx.Detect" : "Early_Suspend";
> +	case DWC3_LINK_STATE_SS_INACT:
> +		return "SS.Inactive";
> +	case DWC3_LINK_STATE_POLL:
> +		return "Poll";
> +	case DWC3_LINK_STATE_RECOV:
> +		return "Recovery";
> +	case DWC3_LINK_STATE_HRESET:
> +		return "HRESET";
> +	case DWC3_LINK_STATE_CMPLY:
> +		return "Compliance";
> +	case DWC3_LINK_STATE_LPBK:
> +		return "Loopback";
> +	case DWC3_LINK_STATE_RESET:
> +		return "Reset";
> +	case DWC3_LINK_STATE_RESUME:
> +		return "Resume";
> +	}

should be part of a separate patch, also I recently added my version of
this, see the archives (although I didn't care for differentiating U0
from L0 depending on speed, but that's not really a big deal IMO).

cheers

-- 
balbi

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RE: [PATCH] usb: dwc3: debugfs: add snapshot to dump requests trbs events

[Paul Zimmerman]

> From: linux-usb-owner@vger.kernel.org [mailto:linux-usb-owner@vger.kernel.org] On Behalf Of Felipe Balbi
> Sent: Monday, April 28, 2014 8:56 AM
> 
> On Mon, Apr 28, 2014 at 04:49:23PM -0400, Zhuang Jin Can wrote:
> > Adds a debugfs file "snapshot" to dump dwc3 requests, trbs and events.

< snip > 

> > +	for (i = 0; i < evt->length; i += 4) {
> > +		event.raw = *(u32 *) (evt->buf + i);
> > +		if (i == evt->lpos) {
> > +			seq_puts(s, "lpos-------|\n");
> > +			seq_puts(s, "           \\\n");
> > +		}
> > +		seq_printf(s, "event[%d]: %08x ", i, event.raw);
> > +
> > +		if (event.type.is_devspec)
> > +			dwc3_dump_dev_event(s, &event.devt);
> > +		else
> > +			dwc3_dump_ep_event(s, &event.depevt);
> > +		seq_puts(s, "\n");
> > +	}
> 
> how well have you tested this ? I'm not entirely sure you should be
> reading the event buffer at any time you want, though I might be wrong.

Just FYI, it is fine to read from the event buffer memory at any time.
But of course, if you happen to read from a location at the same time
the core is writing to it, you may read either the old value or the new,
depending on the timing. So the results might not be 100% reliable.

-- 
Paul

Re: [PATCH] usb: dwc3: debugfs: add snapshot to dump requests trbs events

[Felipe Balbi]

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On Mon, Apr 28, 2014 at 07:58:43PM +0000, Paul Zimmerman wrote:
> > From: linux-usb-owner@vger.kernel.org [mailto:linux-usb-owner@vger.kernel.org] On Behalf Of Felipe Balbi
> > Sent: Monday, April 28, 2014 8:56 AM
> > 
> > On Mon, Apr 28, 2014 at 04:49:23PM -0400, Zhuang Jin Can wrote:
> > > Adds a debugfs file "snapshot" to dump dwc3 requests, trbs and events.
> 
> < snip > 
> 
> > > +	for (i = 0; i < evt->length; i += 4) {
> > > +		event.raw = *(u32 *) (evt->buf + i);
> > > +		if (i == evt->lpos) {
> > > +			seq_puts(s, "lpos-------|\n");
> > > +			seq_puts(s, "           \\\n");
> > > +		}
> > > +		seq_printf(s, "event[%d]: %08x ", i, event.raw);
> > > +
> > > +		if (event.type.is_devspec)
> > > +			dwc3_dump_dev_event(s, &event.devt);
> > > +		else
> > > +			dwc3_dump_ep_event(s, &event.depevt);
> > > +		seq_puts(s, "\n");
> > > +	}
> > 
> > how well have you tested this ? I'm not entirely sure you should be
> > reading the event buffer at any time you want, though I might be wrong.
> 
> Just FYI, it is fine to read from the event buffer memory at any time.
> But of course, if you happen to read from a location at the same time
> the core is writing to it, you may read either the old value or the new,
> depending on the timing. So the results might not be 100% reliable.

Thanks, based on this I'll stick to my
"use-a-ring-buffer-to-store-last-5-events" suggestion :-)

-- 
balbi

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Re: [PATCH] usb: dwc3: debugfs: add snapshot to dump requests trbs events

[Zhuang Jin Can]

On Mon, Apr 28, 2014 at 10:55:36AM -0500, Felipe Balbi wrote:
> On Mon, Apr 28, 2014 at 04:49:23PM -0400, Zhuang Jin Can wrote:
> > Adds a debugfs file "snapshot" to dump dwc3 requests, trbs and events.
> 
> you need to explain what are you trying to provide to our users here.
> 
> What "problem" are you trying to solve ?
> 
The interface enables users to easily peek into requests, trbs and
events to know the current transfer state of each request.
If an transfer is stuck, user can use the interface to check why it's
stuck (e.g. Is it because a gadget doesn't queued the request? Or it's
queued but it's not primed to the controller? Or It's primed to the
controller but the TRBs and events indicate the transfer never completes?).
User can immediately narrow down the issue without enabling verbose log or
reproduce the issue again. It's helpful when we need to deal with some
hard-to-reproduce bugs or timing sensitive bugs can't be reproduced with
verbose log enabled.

> > As ep0 requests are more complex than others. It's not included in this
> > patch.
> 
> For ep0, you could at least print the endpoint phase we are currently
> in and if we have requests in flight or not.
> 
Agree. Will add it in [PATCH v2].

> > Signed-off-by: Zhuang Jin Can <jin.can.zhuang@intel.com>
> > ---
> >  drivers/usb/dwc3/core.h    |    4 +
> >  drivers/usb/dwc3/debugfs.c |  192 ++++++++++++++++++++++++++++++++++++++++++++
> >  drivers/usb/dwc3/gadget.h  |   41 ++++++++++
> >  3 files changed, 237 insertions(+)
> > 
> > diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> > index 57332e3..9d04ddd 100644
> > --- a/drivers/usb/dwc3/core.h
> > +++ b/drivers/usb/dwc3/core.h
> > @@ -849,6 +849,10 @@ struct dwc3_event_devt {
> >  	u32	type:4;
> >  	u32	reserved15_12:4;
> >  	u32	event_info:9;
> > +
> > +#define DEVT_EVTINFO_SUPERSPEED	(1 << 4)
> > +#define DEVT_EVTINFO_HIRD(n)	(((n) & (0xf << 5)) >> 5)
> > +
> >  	u32	reserved31_25:7;
> >  } __packed;
> >  
> > diff --git a/drivers/usb/dwc3/debugfs.c b/drivers/usb/dwc3/debugfs.c
> > index 9ac37fe..078d147 100644
> > --- a/drivers/usb/dwc3/debugfs.c
> > +++ b/drivers/usb/dwc3/debugfs.c
> > @@ -618,6 +618,191 @@ static const struct file_operations dwc3_link_state_fops = {
> >  	.release		= single_release,
> >  };
> >  
> > +static void dwc3_dump_requests(struct seq_file *s, struct list_head *head,
> > +					const char *list_name)
> > +{
> > +	struct dwc3_request	*req;
> > +
> > +	if (list_empty(head)) {
> > +		seq_printf(s, "list %s is empty\n", list_name);
> > +		return;
> > +	}
> > +
> > +	seq_printf(s, "list %s:\n", list_name);
> > +	list_for_each_entry(req, head, list) {
> > +		struct usb_request *request = &req->request;
> > +
> > +		seq_printf(s, "usb_request@0x%p: buf@0x%p(dma@0x%pad), len=%d\n",
> > +			request, request->buf, &request->dma,
> > +			request->length);
> > +
> > +		if (req->queued)
> > +			seq_printf(s, "\tstatus=%d: actual=%d; start_slot=%u: trb@0x%p(dma@0x%pad)\n",
> > +				request->status, request->actual,
> > +				req->start_slot, req->trb,
> > +				&req->trb_dma);
> > +	}
> > +}
> > +
> > +static void dwc3_dump_trbs(struct seq_file *s, struct dwc3_ep *dep)
> > +{
> > +	struct dwc3_trb	*trb;
> > +	int i;
> > +
> > +	seq_printf(s, "busy_slot = %u, free_slot = %u\n",
> > +				dep->busy_slot & DWC3_TRB_MASK,
> > +				dep->free_slot & DWC3_TRB_MASK);
> > +
> > +	for (i = 0; i < DWC3_TRB_NUM; i++) {
> > +		trb = &dep->trb_pool[i];
> > +		if (i == (dep->busy_slot & DWC3_TRB_MASK)) {
> 
> I really dislike these Yoda Conditionals. Fix this up.
> 
Agree. Will fix it in [PATCH v2].

> > +			seq_puts(s, "busy_slot--|\n");
> > +			seq_puts(s, "           \\\n");
> > +		}
> > +		if (i == (dep->free_slot & DWC3_TRB_MASK)) {
> > +			seq_puts(s, "free_slot--|\n");
> > +			seq_puts(s, "           \\\n");
> > +		}
> > +		seq_printf(s, "trb[%02d](dma@0x%pad): %08x(bpl), %08x(bph), %08x(size), %08x(ctrl)\n",
> 
> I'm not sure you need to print out the TRB address. bpl, bph, size and
> ctrl are desired though.
> 
printing out the TRB DMA address helps user to locate the start TRB of a
request. I admit that we can achive the same purose using the "start_slot"
of the request. I'll remove it in [PATCH v2].

> > +			i, &dep->trb_pool_dma + i * sizeof(*trb),
> > +			trb->bpl, trb->bph, trb->size, trb->ctrl);
> 
> this will be pretty difficult to parse by a human. I would rather see
> you creating one directory per TRB (and also one directory per
> endpoint) which holds the details for that entity, so that it looks
> like:
> 
> dwc3
> |-- current_state	(or perhaps a better name, but snapshot isn't very good either)
Actually, it's hard to find a perfect name. "current_state" or "snapshot" doesn't
make too much difference to me. If "current_state" makes more sense to you, I
can change to use this name. Or let me know if you have a better suggestion.

>     |-- ep2
>     |   |-- direction
>     |   |-- maxpacket
>     |   |-- number
>     |   |-- state
>     |   |-- stream_capable
>     |   |-- type
>     |   |-- trbs
>     |   |   |-- trb0
>     |   |   |   |-- bph
>     |   |   |   |-- bpl
>     |   |   |   |-- ctrl
>     |   |   |   |-- size
>     |   |   |-- trb1
>     |   |   |   |-- bph
>     |   |   |   |-- bpl
>     |   |   |   |-- ctrl
>     |   |   |   |-- size
>     |   |   |-- trb2
>     |   |   |   |-- bph
>     |   |   |   |-- bpl
>     |   |   |   |-- ctrl
>     |   |   |   |-- size
>     |   |   |-- trb3
>     |   |   |   |-- bph
>     |   |   |   |-- bpl
>     |   |   |   |-- ctrl
>     |   |   |   |-- size
>     .   .   .
>     .   .   .
>     .   .   .
>     |   |-- request0
>     |   |   |-- direction
>     |   |   |-- mapped
>     |   |   |-- queued
>     |   |   |-- trb0	(symlink to actual trb directory)
>     |   |   |-- ep2		(symlink to actual ep2 directory)
>     |   |   |-- usbrequest
>     |   |       |-- actual
>     |   |       |-- length
>     |   |       |-- no_interrupt
>     |   |       |-- num_mapped_sgs
>     |   |       |-- num_sgs
>     |   |       |-- short_not_ok
>     |   |       |-- status
>     |   |       |-- stream_id
>     |   |       |-- zero
>     |   |-- request1
>     |   |   |-- direction
>     |   |   |-- mapped
>     |   |   |-- queued
>     |   |   |-- trb1	(symlink to actual trb directory)
>     |   |   |-- ep2		(symlink to actual ep2 directory)
>     |   |   |-- usbrequest
>     |   |       |-- actual
>     |   |       |-- length
>     |   |       |-- no_interrupt
>     |   |       |-- num_mapped_sgs
>     |   |       |-- num_sgs
>     |   |       |-- short_not_ok
>     |   |       |-- status
>     |   |       |-- stream_id
>     |   |       |-- zero
>     .   .   .   .
>     .   .   .   .
>     .   .   .   .
> 
> 
> and so forth. That way we get a structured view of everything the
> controller and the driver are managing.
> 
The patch intends to dump the most important RUNTIME information the driver is
dealing with the controller, STATIC information is not valuable here as we can
get them before running. I consider information like "direction", "maxpactsize",
"types" are STATIC, as they're not going to change once they are configured.
Dumping everying is not the intention of the patch. (Sorry that the name
"snapshot" confused you and I didn't describe the intention well).

So are you suggesting to organize the information in multiple debugfs
directories and files or just to print information with appropriate indents so that
users can easily read it? IMO, organizing them in multiple files makes
it impossible for the user to lock dwc3->lock and get information
atomically. The problem of reading them separately is that it won't give
you the consistent information regarding the current transfer state.

> > +static void dwc3_dump_dev_event(struct seq_file *s,
> > +			const struct dwc3_event_devt *event)
> > +{
> > +	seq_puts(s, "[0]DEV ");
> > +	seq_printf(s, "[1:7]%s ",
> > +		event->device_event == DWC3_EVENT_TYPE_DEV ? "TYPE_DEV" :
> > +		event->device_event == DWC3_EVENT_TYPE_CARKIT ? "TYPE_CARKIT" :
> > +		event->device_event == DWC3_EVENT_TYPE_I2C ? "TYPE_CARKIT" :
> > +		"TYPE_UNKOWN");
> > +	seq_printf(s, "[8:11]%s ", dwc3_gadget_event_string(event->type));
> > +
> > +	if (event->type == DWC3_DEVICE_EVENT_LINK_STATUS_CHANGE ||
> > +		event->type == DWC3_DEVICE_EVENT_HIBER_REQ) {
> > +
> > +		seq_printf(s, "[16:20]%s %s ",
> > +			dwc3_link_state_string(
> > +				event->event_info & DEVT_EVTINFO_SUPERSPEED,
> > +				event->event_info & DWC3_LINK_STATE_MASK),
> > +				event->event_info & DEVT_EVTINFO_SUPERSPEED ?
> > +				"SS" : "HS");
> > +
> > +		if (!(event->event_info & DEVT_EVTINFO_SUPERSPEED))
> > +			seq_printf(s, "[21:24]HIRD %u ",
> > +				DEVT_EVTINFO_HIRD(event->event_info));
> > +	}
> > +}
> > +
> > +static void dwc3_dump_ep_event(struct seq_file *s,
> > +			const struct dwc3_event_depevt *event)
> > +{
> > +	seq_puts(s, "[0]EP ");
> > +	seq_printf(s, "[1:5]ep%d ", event->endpoint_number);
> > +	seq_printf(s, "[6:9]%s ",
> > +		dwc3_ep_event_string(event->endpoint_event));
> > +
> > +	switch (event->endpoint_event) {
> > +	case DWC3_DEPEVT_XFERCOMPLETE:
> > +	case DWC3_DEPEVT_XFERINPROGRESS:
> > +		if (event->status & DEPEVT_STATUS_BUSERR)
> > +			seq_puts(s, "[12]BUSERR ");
> > +		if (event->status & DEPEVT_STATUS_SHORT)
> > +			seq_puts(s, "[13]SHORT ");
> > +		if (event->status & DEPEVT_STATUS_IOC)
> > +			seq_puts(s, "[14]IOC ");
> > +		if (event->status & DEPEVT_STATUS_LST)
> > +			seq_puts(s, "[15]LST ");
> > +		break;
> > +	case DWC3_DEPEVT_XFERNOTREADY:
> > +		if ((event->status & 0x3) == 1)
> > +			seq_puts(s, "[12:13]Data_Stage ");
> > +		else if ((event->status & 0x3) == 2)
> > +			seq_puts(s, "[12:13]Status_Stage ");
> > +		if (event->status & DEPEVT_STATUS_TRANSFER_ACTIVE)
> > +			seq_puts(s, "[15]XferActive ");
> > +		else
> > +			seq_puts(s, "[15]XferNotActive ");
> > +		break;
> > +	case DWC3_DEPEVT_EPCMDCMPLT:
> > +		if (event->status & BIT(0))
> > +			seq_puts(s, "[12:15]Invalid Transfer Resource ");
> > +		break;
> > +	default:
> > +		seq_puts(s, "[12:15]UNKOWN ");
> > +	}
> > +	seq_printf(s, "[16:31]PARAM 0x%04x ", event->parameters);
> > +}
> > +
> > +static void dwc3_dump_event_buf(struct seq_file *s,
> > +			struct dwc3_event_buffer *evt)
> > +{
> > +	union dwc3_event	event;
> > +	int			i;
> > +
> > +	seq_printf(s, "evt->buf@0x%p(dma@0x%pad), length=%u, lpos=%u, count=%u, flags=%s\n",
> > +		evt->buf, &evt->dma,
> > +		evt->length, evt->lpos, evt->count,
> > +		evt->flags & DWC3_EVENT_PENDING ? "pending" : "0");
> > +
> > +	for (i = 0; i < evt->length; i += 4) {
> > +		event.raw = *(u32 *) (evt->buf + i);
> > +		if (i == evt->lpos) {
> > +			seq_puts(s, "lpos-------|\n");
> > +			seq_puts(s, "           \\\n");
> > +		}
> > +		seq_printf(s, "event[%d]: %08x ", i, event.raw);
> > +
> > +		if (event.type.is_devspec)
> > +			dwc3_dump_dev_event(s, &event.devt);
> > +		else
> > +			dwc3_dump_ep_event(s, &event.depevt);
> > +		seq_puts(s, "\n");
> > +	}
> 
> how well have you tested this ? I'm not entirely sure you should be
> reading the event buffer at any time you want, though I might be wrong.
> 
> It's still a bit easier to reproduce part of the event handling here. I
> think it's best to make a choice of caching the last 5 events in a ring
> buffer and provide a helper for IRQ handlers to push events into the
> ring buffer, then from here you just iterate over that ring buffer
> instead of accessing our actual event buffer.
> 
Thanks Paul Zimmerman and you for reminding me that fact that controller
may write to the event buffers when we're reading them.

Instead of trying to make things perfect and complex, the interface is just
to dump the events while leaving the responsibilty to developers to judge
if the events are reliable.
Developer should be able to sense if the data is reliable depending on when he
dumps the data. If a transfer is stuck and controller doesn't generate anymore
events, then the data is reliable, and this is the main senario this patch wants
to handle. If a transfer is stuck but controller keeps generating events due to
other transfers, there's nothing we can do about it, as the new events will
quickly overwrite the ring, and developer will know the events are not valuable.
If you dump the events when all transfers are still on-going, it just provides
you some a history of the events to sense how it looks like, and you
know the data might not be reliable. And this usage is not really helpful
for debugging or not used at all, as you should have no intereset to
check the events if everythings goes well.
I think above is acceptable for debugging purpose, it's simple without
introducing any overhead or timing effect.

> Also note that we can hold up to 64 events in our event buffer so this
> call could take a looooooot of time to complete and you probably don't
> need all that information anyway because you can get them by just
> enabling VERBOSE_DEBUG on dwc3 and capturing the entire driver behavior
> on dmesg.
> 
Even though a user may be scared by the lots of events, when a failure happens,
he actually wants to read as many events as he can to see what happened
before the failure. 5 events is not enough, user can at most only see one
or two transfers through these 5 events or nothing if the last few
events are generated from other transfers which are unrelated to the
failure. The time to dump the events doesn't matter as it's for debugging and
most often usage is after a transfer is stuck.

> > +static int dwc3_snapshot_show(struct seq_file *s, void *unused)
> > +{
> > +	struct dwc3		*dwc = s->private;
> > +	unsigned long		flags;
> > +	int			i;
> > +
> > +	spin_lock_irqsave(&dwc->lock, flags);
> > +	for (i = 2; i < DWC3_ENDPOINTS_NUM; i++) {
> 
> some platforms don't have all 32 physical endpoints, we just had a bug
> fix for that, see commit 32702e9.
> 
Will fix it as below:
	for (i = 2; i < DWC3_ENDPOINTS_NUM; i++) {
		struct dwc3_ep	*dep = dwc->eps[i];

		if (!dep || !(dep->flags & DWC3_EP_ENABLED))
			continue;
		
> > +		struct dwc3_ep	*dep = dwc->eps[i];
> > +
> > +		if (!(dep->flags & DWC3_EP_ENABLED))
> > +			continue;
> > +
> > +		seq_printf(s, "[%s]\n", dep->name);
> > +		dwc3_dump_requests(s, &dep->request_list, "request_list");
> > +		dwc3_dump_requests(s, &dep->req_queued, "req_queued");
> > +		if (!list_empty(&dep->req_queued))
> > +			dwc3_dump_trbs(s, dep);
> > +		seq_puts(s, "\n");
> > +	}
> > +
> > +	for (i = 0; i < dwc->num_event_buffers; i++)
> > +		dwc3_dump_event_buf(s, dwc->ev_buffs[i]);
> > +	spin_unlock_irqrestore(&dwc->lock, flags);
> > +
> > +	return 0;
> > +}
> > +
> > +static int dwc3_snapshot_open(struct inode *inode, struct file *file)
> > +{
> > +	return single_open(file, dwc3_snapshot_show, inode->i_private);
> > +}
> > +
> > +static const struct file_operations dwc3_snapshot_fops = {
> > +	.open			= dwc3_snapshot_open,
> > +	.read			= seq_read,
> > +	.llseek			= seq_lseek,
> > +	.release		= single_release,
> > +};
> > +
> >  int dwc3_debugfs_init(struct dwc3 *dwc)
> >  {
> >  	struct dentry		*root;
> > @@ -672,6 +857,13 @@ int dwc3_debugfs_init(struct dwc3 *dwc)
> >  			ret = -ENOMEM;
> >  			goto err1;
> >  		}
> > +
> > +		file = debugfs_create_file("snapshot", S_IRUGO, root,
> > +				dwc, &dwc3_snapshot_fops);
> > +		if (!file) {
> > +			ret = -ENOMEM;
> > +			goto err1;
> > +		}
> >  	}
> >  
> >  	return 0;
> > diff --git a/drivers/usb/dwc3/gadget.h b/drivers/usb/dwc3/gadget.h
> > index a0ee75b..f589323 100644
> > --- a/drivers/usb/dwc3/gadget.h
> > +++ b/drivers/usb/dwc3/gadget.h
> > @@ -120,6 +120,8 @@ static inline const char *dwc3_gadget_event_string(u8 event)
> >  		return "Link Status Change";
> >  	case DWC3_DEVICE_EVENT_WAKEUP:
> >  		return "WakeUp";
> > +	case DWC3_DEVICE_EVENT_HIBER_REQ:
> > +		return "Hibernation Request";
> 
> this should be in a separate patch.
> 
Agree. Will add it in a another patch.

> >  	case DWC3_DEVICE_EVENT_EOPF:
> >  		return "End-Of-Frame";
> >  	case DWC3_DEVICE_EVENT_SOF:
> > @@ -159,4 +161,43 @@ static inline const char *dwc3_ep_event_string(u8 event)
> >  	return "UNKNOWN";
> >  }
> >  
> > +/**
> > + * dwc3_link_state_string - returns link state
> > + * @link_state: the link state code
> > + */
> > +static inline const char *dwc3_link_state_string(u8 is_ss, u8 link_state)
> > +{
> > +	switch (link_state) {
> > +	case DWC3_LINK_STATE_U0:
> > +		return is_ss ? "U0" : "L0";
> > +	case DWC3_LINK_STATE_U1:
> > +		return "U1";
> > +	case DWC3_LINK_STATE_U2:
> > +		return is_ss ? "U2" : "L1";
> > +	case DWC3_LINK_STATE_U3:
> > +		return is_ss ? "U3" : "L2";
> > +	case DWC3_LINK_STATE_SS_DIS:
> > +		return is_ss ? "SS.Disabled" : "L3";
> > +	case DWC3_LINK_STATE_RX_DET:
> > +		return is_ss ? "Rx.Detect" : "Early_Suspend";
> > +	case DWC3_LINK_STATE_SS_INACT:
> > +		return "SS.Inactive";
> > +	case DWC3_LINK_STATE_POLL:
> > +		return "Poll";
> > +	case DWC3_LINK_STATE_RECOV:
> > +		return "Recovery";
> > +	case DWC3_LINK_STATE_HRESET:
> > +		return "HRESET";
> > +	case DWC3_LINK_STATE_CMPLY:
> > +		return "Compliance";
> > +	case DWC3_LINK_STATE_LPBK:
> > +		return "Loopback";
> > +	case DWC3_LINK_STATE_RESET:
> > +		return "Reset";
> > +	case DWC3_LINK_STATE_RESUME:
> > +		return "Resume";
> > +	}
> 
> should be part of a separate patch, also I recently added my version of
> this, see the archives (although I didn't care for differentiating U0
> from L0 depending on speed, but that's not really a big deal IMO).
> 
Agree. I'll remove this change and rebase on your change.

Thanks
Jincan

Re: [PATCH] usb: dwc3: debugfs: add snapshot to dump requests trbs events

[Felipe Balbi]

[-- Attachment #1: Type: text/plain, Size: 15474 bytes --]

Hi,

On Tue, Apr 29, 2014 at 05:21:42PM -0400, Zhuang Jin Can wrote:
> On Mon, Apr 28, 2014 at 10:55:36AM -0500, Felipe Balbi wrote:
> > On Mon, Apr 28, 2014 at 04:49:23PM -0400, Zhuang Jin Can wrote:
> > > Adds a debugfs file "snapshot" to dump dwc3 requests, trbs and events.
> > 
> > you need to explain what are you trying to provide to our users here.
> > 
> > What "problem" are you trying to solve ?
> > 
> The interface enables users to easily peek into requests, trbs and
> events to know the current transfer state of each request.
> If an transfer is stuck, user can use the interface to check why it's
> stuck (e.g. Is it because a gadget doesn't queued the request? Or it's
> queued but it's not primed to the controller? Or It's primed to the
> controller but the TRBs and events indicate the transfer never completes?).
> User can immediately narrow down the issue without enabling verbose log or
> reproduce the issue again. It's helpful when we need to deal with some
> hard-to-reproduce bugs or timing sensitive bugs can't be reproduced with
> verbose log enabled.

this should be part of the commit log in some shape or form.

> > > As ep0 requests are more complex than others. It's not included in this
> > > patch.
> > 
> > For ep0, you could at least print the endpoint phase we are currently
> > in and if we have requests in flight or not.
> > 
> Agree. Will add it in [PATCH v2].

tks

> > > +			seq_puts(s, "busy_slot--|\n");
> > > +			seq_puts(s, "           \\\n");
> > > +		}
> > > +		if (i == (dep->free_slot & DWC3_TRB_MASK)) {
> > > +			seq_puts(s, "free_slot--|\n");
> > > +			seq_puts(s, "           \\\n");
> > > +		}
> > > +		seq_printf(s, "trb[%02d](dma@0x%pad): %08x(bpl), %08x(bph), %08x(size), %08x(ctrl)\n",
> > 
> > I'm not sure you need to print out the TRB address. bpl, bph, size and
> > ctrl are desired though.
> > 
> printing out the TRB DMA address helps user to locate the start TRB of a
> request. I admit that we can achive the same purose using the "start_slot"
> of the request. I'll remove it in [PATCH v2].

thanks

> > > +			i, &dep->trb_pool_dma + i * sizeof(*trb),
> > > +			trb->bpl, trb->bph, trb->size, trb->ctrl);
> > 
> > this will be pretty difficult to parse by a human. I would rather see
> > you creating one directory per TRB (and also one directory per
> > endpoint) which holds the details for that entity, so that it looks
> > like:
> > 
> > dwc3
> > |-- current_state	(or perhaps a better name, but snapshot isn't very good either)
> Actually, it's hard to find a perfect name. "current_state" or "snapshot" doesn't
> make too much difference to me. If "current_state" makes more sense to you, I
> can change to use this name. Or let me know if you have a better suggestion.

the name is important as we will have to deal with it for the next 50
years. We also need to think about someone starting out on dwc3 5 years
from now or a QA engineer in whatever OEM trying to provide details of
the failure for the development team. It needs to be well thought out.

I don't have a better idea but snapshot gives me the idea that we will
end up with a copy of everything which we can revisit at any time and
that's not true. If we read this file twice there's no guarantee it'll
contain the same information.

> >     |-- ep2
> >     |   |-- direction
> >     |   |-- maxpacket
> >     |   |-- number
> >     |   |-- state
> >     |   |-- stream_capable
> >     |   |-- type
> >     |   |-- trbs
> >     |   |   |-- trb0
> >     |   |   |   |-- bph
> >     |   |   |   |-- bpl
> >     |   |   |   |-- ctrl
> >     |   |   |   |-- size
> >     |   |   |-- trb1
> >     |   |   |   |-- bph
> >     |   |   |   |-- bpl
> >     |   |   |   |-- ctrl
> >     |   |   |   |-- size
> >     |   |   |-- trb2
> >     |   |   |   |-- bph
> >     |   |   |   |-- bpl
> >     |   |   |   |-- ctrl
> >     |   |   |   |-- size
> >     |   |   |-- trb3
> >     |   |   |   |-- bph
> >     |   |   |   |-- bpl
> >     |   |   |   |-- ctrl
> >     |   |   |   |-- size
> >     .   .   .
> >     .   .   .
> >     .   .   .
> >     |   |-- request0
> >     |   |   |-- direction
> >     |   |   |-- mapped
> >     |   |   |-- queued
> >     |   |   |-- trb0	(symlink to actual trb directory)
> >     |   |   |-- ep2		(symlink to actual ep2 directory)
> >     |   |   |-- usbrequest
> >     |   |       |-- actual
> >     |   |       |-- length
> >     |   |       |-- no_interrupt
> >     |   |       |-- num_mapped_sgs
> >     |   |       |-- num_sgs
> >     |   |       |-- short_not_ok
> >     |   |       |-- status
> >     |   |       |-- stream_id
> >     |   |       |-- zero
> >     |   |-- request1
> >     |   |   |-- direction
> >     |   |   |-- mapped
> >     |   |   |-- queued
> >     |   |   |-- trb1	(symlink to actual trb directory)
> >     |   |   |-- ep2		(symlink to actual ep2 directory)
> >     |   |   |-- usbrequest
> >     |   |       |-- actual
> >     |   |       |-- length
> >     |   |       |-- no_interrupt
> >     |   |       |-- num_mapped_sgs
> >     |   |       |-- num_sgs
> >     |   |       |-- short_not_ok
> >     |   |       |-- status
> >     |   |       |-- stream_id
> >     |   |       |-- zero
> >     .   .   .   .
> >     .   .   .   .
> >     .   .   .   .
> > 
> > 
> > and so forth. That way we get a structured view of everything the
> > controller and the driver are managing.
> > 
> The patch intends to dump the most important RUNTIME information the driver is
> dealing with the controller, STATIC information is not valuable here as we can
> get them before running. I consider information like "direction", "maxpactsize",
> "types" are STATIC, as they're not going to change once they are configured.

they are still important and easy enough to print out. Sometimes
direction is the key information for a debug session. For example if a
Bulk OUT transaction of length 2000 never completes we *know* the reason
why.

We know OUT endpoints can't handle transfers which are not aligned to
wMaxPacketSize.

> Dumping everying is not the intention of the patch. (Sorry that the name

so ? I'm making a suggestion to improve the patch. Dumping only the
information you judged necessary during your debug sessions with no
consideration for other users isn't generally a good practice. I'm
trying to help you improve the patch so that it can be accepted.

Note that dumping all of that information out of a single file isn't
very nice either and it'll be difficult to parse, even for humans.

> So are you suggesting to organize the information in multiple debugfs
> directories and files or just to print information with appropriate indents so that

multiple directories.

> users can easily read it? IMO, organizing them in multiple files makes
> it impossible for the user to lock dwc3->lock and get information
> atomically. The problem of reading them separately is that it won't give
> you the consistent information regarding the current transfer state.

it depends on where you hold the lock. Also, now that I think of it, it
really seems like what you want is tracepoints on this driver, rather
than dumping a whole bunch of information out of a single read to a
single file. The kernel has a very nice tracing infrastructure and I'd
be really happy to read a patch adding support for that in this driver.

> > > +static void dwc3_dump_dev_event(struct seq_file *s,
> > > +			const struct dwc3_event_devt *event)
> > > +{
> > > +	seq_puts(s, "[0]DEV ");
> > > +	seq_printf(s, "[1:7]%s ",
> > > +		event->device_event == DWC3_EVENT_TYPE_DEV ? "TYPE_DEV" :
> > > +		event->device_event == DWC3_EVENT_TYPE_CARKIT ? "TYPE_CARKIT" :
> > > +		event->device_event == DWC3_EVENT_TYPE_I2C ? "TYPE_CARKIT" :
> > > +		"TYPE_UNKOWN");
> > > +	seq_printf(s, "[8:11]%s ", dwc3_gadget_event_string(event->type));
> > > +
> > > +	if (event->type == DWC3_DEVICE_EVENT_LINK_STATUS_CHANGE ||
> > > +		event->type == DWC3_DEVICE_EVENT_HIBER_REQ) {
> > > +
> > > +		seq_printf(s, "[16:20]%s %s ",
> > > +			dwc3_link_state_string(
> > > +				event->event_info & DEVT_EVTINFO_SUPERSPEED,
> > > +				event->event_info & DWC3_LINK_STATE_MASK),
> > > +				event->event_info & DEVT_EVTINFO_SUPERSPEED ?
> > > +				"SS" : "HS");
> > > +
> > > +		if (!(event->event_info & DEVT_EVTINFO_SUPERSPEED))
> > > +			seq_printf(s, "[21:24]HIRD %u ",
> > > +				DEVT_EVTINFO_HIRD(event->event_info));
> > > +	}
> > > +}
> > > +
> > > +static void dwc3_dump_ep_event(struct seq_file *s,
> > > +			const struct dwc3_event_depevt *event)
> > > +{
> > > +	seq_puts(s, "[0]EP ");
> > > +	seq_printf(s, "[1:5]ep%d ", event->endpoint_number);
> > > +	seq_printf(s, "[6:9]%s ",
> > > +		dwc3_ep_event_string(event->endpoint_event));
> > > +
> > > +	switch (event->endpoint_event) {
> > > +	case DWC3_DEPEVT_XFERCOMPLETE:
> > > +	case DWC3_DEPEVT_XFERINPROGRESS:
> > > +		if (event->status & DEPEVT_STATUS_BUSERR)
> > > +			seq_puts(s, "[12]BUSERR ");
> > > +		if (event->status & DEPEVT_STATUS_SHORT)
> > > +			seq_puts(s, "[13]SHORT ");
> > > +		if (event->status & DEPEVT_STATUS_IOC)
> > > +			seq_puts(s, "[14]IOC ");
> > > +		if (event->status & DEPEVT_STATUS_LST)
> > > +			seq_puts(s, "[15]LST ");
> > > +		break;
> > > +	case DWC3_DEPEVT_XFERNOTREADY:
> > > +		if ((event->status & 0x3) == 1)
> > > +			seq_puts(s, "[12:13]Data_Stage ");
> > > +		else if ((event->status & 0x3) == 2)
> > > +			seq_puts(s, "[12:13]Status_Stage ");
> > > +		if (event->status & DEPEVT_STATUS_TRANSFER_ACTIVE)
> > > +			seq_puts(s, "[15]XferActive ");
> > > +		else
> > > +			seq_puts(s, "[15]XferNotActive ");
> > > +		break;
> > > +	case DWC3_DEPEVT_EPCMDCMPLT:
> > > +		if (event->status & BIT(0))
> > > +			seq_puts(s, "[12:15]Invalid Transfer Resource ");
> > > +		break;
> > > +	default:
> > > +		seq_puts(s, "[12:15]UNKOWN ");
> > > +	}
> > > +	seq_printf(s, "[16:31]PARAM 0x%04x ", event->parameters);
> > > +}
> > > +
> > > +static void dwc3_dump_event_buf(struct seq_file *s,
> > > +			struct dwc3_event_buffer *evt)
> > > +{
> > > +	union dwc3_event	event;
> > > +	int			i;
> > > +
> > > +	seq_printf(s, "evt->buf@0x%p(dma@0x%pad), length=%u, lpos=%u, count=%u, flags=%s\n",
> > > +		evt->buf, &evt->dma,
> > > +		evt->length, evt->lpos, evt->count,
> > > +		evt->flags & DWC3_EVENT_PENDING ? "pending" : "0");
> > > +
> > > +	for (i = 0; i < evt->length; i += 4) {
> > > +		event.raw = *(u32 *) (evt->buf + i);
> > > +		if (i == evt->lpos) {
> > > +			seq_puts(s, "lpos-------|\n");
> > > +			seq_puts(s, "           \\\n");
> > > +		}
> > > +		seq_printf(s, "event[%d]: %08x ", i, event.raw);
> > > +
> > > +		if (event.type.is_devspec)
> > > +			dwc3_dump_dev_event(s, &event.devt);
> > > +		else
> > > +			dwc3_dump_ep_event(s, &event.depevt);
> > > +		seq_puts(s, "\n");
> > > +	}
> > 
> > how well have you tested this ? I'm not entirely sure you should be
> > reading the event buffer at any time you want, though I might be wrong.
> > 
> > It's still a bit easier to reproduce part of the event handling here. I
> > think it's best to make a choice of caching the last 5 events in a ring
> > buffer and provide a helper for IRQ handlers to push events into the
> > ring buffer, then from here you just iterate over that ring buffer
> > instead of accessing our actual event buffer.
> > 
> Thanks Paul Zimmerman and you for reminding me that fact that controller
> may write to the event buffers when we're reading them.
> 
> Instead of trying to make things perfect and complex, the interface is just
> to dump the events while leaving the responsibilty to developers to judge
> if the events are reliable.

That's a crappy interface then. Why would anybody use anything they
can't trust ?

> Developer should be able to sense if the data is reliable depending on when he
> dumps the data. If a transfer is stuck and controller doesn't generate anymore

or Developer might spend more time looking at somehting that doesn't
make sense and trying to figure out if the current trace is valid then
the time spent actually understanding the problem.

Logs are suppose to aid debugging and if the data isn't trustworthy we
will have developers spending time debugging the logs themselves. Sorry,
but I won't accept that.

> events, then the data is reliable, and this is the main senario this patch wants
> to handle. If a transfer is stuck but controller keeps generating events due to

that you already get with Verbose debug anyway and you get *all* that
data with a simple dmesg.

> other transfers, there's nothing we can do about it, as the new events will
> quickly overwrite the ring, and developer will know the events are not valuable.

and there goes a debug session down the drain, it turned out to be a
waste of time after all.

> If you dump the events when all transfers are still on-going, it just provides
> you some a history of the events to sense how it looks like, and you
> know the data might not be reliable. And this usage is not really helpful
> for debugging or not used at all, as you should have no intereset to
> check the events if everythings goes well.
> I think above is acceptable for debugging purpose, it's simple without
> introducing any overhead or timing effect.

wait, what ? everytime you read that file you hold the controller lock
god knows for how long and you say it doesn't introduce any timing
effect ?

Verbose logs have a lower overhead than what you're suggesting here.

> > Also note that we can hold up to 64 events in our event buffer so this
> > call could take a looooooot of time to complete and you probably don't
> > need all that information anyway because you can get them by just
> > enabling VERBOSE_DEBUG on dwc3 and capturing the entire driver behavior
> > on dmesg.
> > 
> Even though a user may be scared by the lots of events, when a failure happens,
> he actually wants to read as many events as he can to see what happened
> before the failure. 5 events is not enough, user can at most only see one
> or two transfers through these 5 events or nothing if the last few
> events are generated from other transfers which are unrelated to the
> failure. The time to dump the events doesn't matter as it's for debugging and
> most often usage is after a transfer is stuck.

right, so if the transfer is stuch there are no extra generated anyway.

And I continue to say that all of this information is already available
by enabling VERBOSE_DEBUG for this driver.

If you want to capture logs without VERBOSE_DEBUG tracepoints sound like
the way to go.

> > > +static int dwc3_snapshot_show(struct seq_file *s, void *unused)
> > > +{
> > > +	struct dwc3		*dwc = s->private;
> > > +	unsigned long		flags;
> > > +	int			i;
> > > +
> > > +	spin_lock_irqsave(&dwc->lock, flags);
> > > +	for (i = 2; i < DWC3_ENDPOINTS_NUM; i++) {
> > 
> > some platforms don't have all 32 physical endpoints, we just had a bug
> > fix for that, see commit 32702e9.
> > 
> Will fix it as below:
> 	for (i = 2; i < DWC3_ENDPOINTS_NUM; i++) {

no dude, iterate for IN eps and for OUT eps separately. We already have
dwc->num_in_eps and dwc->num_out_eps

ps: use tracepoints.

-- 
balbi

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Re: [PATCH] usb: dwc3: debugfs: add snapshot to dump requests trbs events

[Zhuang Jin Can]

Hi,

On Tue, Apr 29, 2014 at 11:10:42AM -0500, Felipe Balbi wrote:
> Hi,
> 
> On Tue, Apr 29, 2014 at 05:21:42PM -0400, Zhuang Jin Can wrote:
> > On Mon, Apr 28, 2014 at 10:55:36AM -0500, Felipe Balbi wrote:
> > > On Mon, Apr 28, 2014 at 04:49:23PM -0400, Zhuang Jin Can wrote:
> > > > Adds a debugfs file "snapshot" to dump dwc3 requests, trbs and events.
> > > 
> > > you need to explain what are you trying to provide to our users here.
> > > 
> > > What "problem" are you trying to solve ?
> > > 
> > The interface enables users to easily peek into requests, trbs and
> > events to know the current transfer state of each request.
> > If an transfer is stuck, user can use the interface to check why it's
> > stuck (e.g. Is it because a gadget doesn't queued the request? Or it's
> > queued but it's not primed to the controller? Or It's primed to the
> > controller but the TRBs and events indicate the transfer never completes?).
> > User can immediately narrow down the issue without enabling verbose log or
> > reproduce the issue again. It's helpful when we need to deal with some
> > hard-to-reproduce bugs or timing sensitive bugs can't be reproduced with
> > verbose log enabled.
> 
> this should be part of the commit log in some shape or form.
> 
Yes.

> > > > As ep0 requests are more complex than others. It's not included in this
> > > > patch.
> > > 
> > > For ep0, you could at least print the endpoint phase we are currently
> > > in and if we have requests in flight or not.
> > > 
> > Agree. Will add it in [PATCH v2].
> 
> tks
> 
> > > > +			seq_puts(s, "busy_slot--|\n");
> > > > +			seq_puts(s, "           \\\n");
> > > > +		}
> > > > +		if (i == (dep->free_slot & DWC3_TRB_MASK)) {
> > > > +			seq_puts(s, "free_slot--|\n");
> > > > +			seq_puts(s, "           \\\n");
> > > > +		}
> > > > +		seq_printf(s, "trb[%02d](dma@0x%pad): %08x(bpl), %08x(bph), %08x(size), %08x(ctrl)\n",
> > > 
> > > I'm not sure you need to print out the TRB address. bpl, bph, size and
> > > ctrl are desired though.
> > > 
> > printing out the TRB DMA address helps user to locate the start TRB of a
> > request. I admit that we can achive the same purose using the "start_slot"
> > of the request. I'll remove it in [PATCH v2].
> 
> thanks
> 
> > > > +			i, &dep->trb_pool_dma + i * sizeof(*trb),
> > > > +			trb->bpl, trb->bph, trb->size, trb->ctrl);
> > > 
> > > this will be pretty difficult to parse by a human. I would rather see
> > > you creating one directory per TRB (and also one directory per
> > > endpoint) which holds the details for that entity, so that it looks
> > > like:
> > > 
> > > dwc3
> > > |-- current_state	(or perhaps a better name, but snapshot isn't very good either)
> > Actually, it's hard to find a perfect name. "current_state" or "snapshot" doesn't
> > make too much difference to me. If "current_state" makes more sense to you, I
> > can change to use this name. Or let me know if you have a better suggestion.
> 
> the name is important as we will have to deal with it for the next 50
> years. We also need to think about someone starting out on dwc3 5 years
> from now or a QA engineer in whatever OEM trying to provide details of
> the failure for the development team. It needs to be well thought out.
> 
> I don't have a better idea but snapshot gives me the idea that we will
> end up with a copy of everything which we can revisit at any time and
> that's not true. If we read this file twice there's no guarantee it'll
> contain the same information.
> 
Let's discuss the name later after I explain more about the motivation.

[Motivation]
The patch is inspired from echi-dbg.c debugfs. It contains four files
"async", ""bandwidth", "periodic" and "registers".
The "registers" functions as what "regdump" does in dwc3. And the patch implements
a "snapshot" to do the similar things done by "async" and "periodic".
Because a way to inspect the content of data structures (i.e. TRBs, Events)
interacting with the controller is really important for debugging,
especially for HW issues. It just simply provides you a interface to check
what's currently in TRBs and event buffers (and nothing more, no more
guarantees). 
In EHCI, "async" and "periodic" also can't guarantee you the reliable data, as
you can't prevent the controller from writing the interacting data
structures (unless you stop it). It's developer's decision to how to analyze
the data. They're not perfect, but simple and helpful.

As far as I see, it's useful for below senarios:
1. Bugs can't be reproduced with VERBOSE_DEBUG, as printk introduces
timing effect. Some HW bugs are timing sensitive, even a single printk
will prevent you from reproducing the issue.
With "snapshot", we can check the TRBs, events, requests to see the
final status to get more clues to triage an issue.

2. Some bugs are hard to reproduce, and can be seen once or
twice after many devices running for a long time. (e.g. MTBF runing with
ADB). And they most often uses the builds with debugfs available, ask
them to turn on VERBOSE_DEBUG and run the tests are not acceptable.
After the failure happens, if you ask the tester to turn on the VERBOSE_DEBUG
to reproduce the issue again. He may come back to you a week later with
an answer "I can't reproduce it. It's a random issue". 
With "snapshot", when the issue happens, tester can just dump the TRBs,
events to provide more data to a developer. It won't guarantee you to
root cause the issue, but something is better than nothing.

Regarding what are important to dump, regarding the motivation, they should be
TRBs and Events which are the parts interfacing with HW. But only dumping them is
not enough, it's useless if user can't tell which TRB belongs to which
endpont and request. That's why I also dump the necessary info about the
requests and endpoints to track their relationship. Infos like maxpacket
size, direction, types are not really important regarding this. You can
get the information by running it once and see the printks. And they're
common properties which can just be handed off to udc core.

> > >     |-- ep2
> > >     |   |-- direction
> > >     |   |-- maxpacket
> > >     |   |-- number
> > >     |   |-- state
> > >     |   |-- stream_capable
> > >     |   |-- type
> > >     |   |-- trbs
> > >     |   |   |-- trb0
> > >     |   |   |   |-- bph
> > >     |   |   |   |-- bpl
> > >     |   |   |   |-- ctrl
> > >     |   |   |   |-- size
> > >     |   |   |-- trb1
> > >     |   |   |   |-- bph
> > >     |   |   |   |-- bpl
> > >     |   |   |   |-- ctrl
> > >     |   |   |   |-- size
> > >     |   |   |-- trb2
> > >     |   |   |   |-- bph
> > >     |   |   |   |-- bpl
> > >     |   |   |   |-- ctrl
> > >     |   |   |   |-- size
> > >     |   |   |-- trb3
> > >     |   |   |   |-- bph
> > >     |   |   |   |-- bpl
> > >     |   |   |   |-- ctrl
> > >     |   |   |   |-- size
> > >     .   .   .
> > >     .   .   .
> > >     .   .   .
> > >     |   |-- request0
> > >     |   |   |-- direction
> > >     |   |   |-- mapped
> > >     |   |   |-- queued
> > >     |   |   |-- trb0	(symlink to actual trb directory)
> > >     |   |   |-- ep2		(symlink to actual ep2 directory)
> > >     |   |   |-- usbrequest
> > >     |   |       |-- actual
> > >     |   |       |-- length
> > >     |   |       |-- no_interrupt
> > >     |   |       |-- num_mapped_sgs
> > >     |   |       |-- num_sgs
> > >     |   |       |-- short_not_ok
> > >     |   |       |-- status
> > >     |   |       |-- stream_id
> > >     |   |       |-- zero
> > >     |   |-- request1
> > >     |   |   |-- direction
> > >     |   |   |-- mapped
> > >     |   |   |-- queued
> > >     |   |   |-- trb1	(symlink to actual trb directory)
> > >     |   |   |-- ep2		(symlink to actual ep2 directory)
> > >     |   |   |-- usbrequest
> > >     |   |       |-- actual
> > >     |   |       |-- length
> > >     |   |       |-- no_interrupt
> > >     |   |       |-- num_mapped_sgs
> > >     |   |       |-- num_sgs
> > >     |   |       |-- short_not_ok
> > >     |   |       |-- status
> > >     |   |       |-- stream_id
> > >     |   |       |-- zero
> > >     .   .   .   .
> > >     .   .   .   .
> > >     .   .   .   .
> > > 
> > > 
> > > and so forth. That way we get a structured view of everything the
> > > controller and the driver are managing.
> > > 
> > The patch intends to dump the most important RUNTIME information the driver is
> > dealing with the controller, STATIC information is not valuable here as we can
> > get them before running. I consider information like "direction", "maxpactsize",
> > "types" are STATIC, as they're not going to change once they are configured.
> 
> they are still important and easy enough to print out. Sometimes
> direction is the key information for a debug session. For example if a
> Bulk OUT transaction of length 2000 never completes we *know* the reason
> why.
> 
> We know OUT endpoints can't handle transfers which are not aligned to
> wMaxPacketSize.
> 
Explained in [Motivation], these info can be got by VERBOSE_DEBUG by running it once.
It's not the "snapshot" really want to handle.

> > Dumping everying is not the intention of the patch. (Sorry that the name
> 
> so ? I'm making a suggestion to improve the patch. Dumping only the
> information you judged necessary during your debug sessions with no
> consideration for other users isn't generally a good practice. I'm
> trying to help you improve the patch so that it can be accepted.
> 
> Note that dumping all of that information out of a single file isn't
> very nice either and it'll be difficult to parse, even for humans.
> 
Explained in [Motivation].

> > So are you suggesting to organize the information in multiple debugfs
> > directories and files or just to print information with appropriate indents so that
> 
> multiple directories.
> 
Explained in [Motivation]. echi-dbg.c also uses a single file to dump the
structures. But I admit that dumping event buffers can be in a separate file.

> > users can easily read it? IMO, organizing them in multiple files makes
> > it impossible for the user to lock dwc3->lock and get information
> > atomically. The problem of reading them separately is that it won't give
> > you the consistent information regarding the current transfer state.
> 
> it depends on where you hold the lock. Also, now that I think of it, it
> really seems like what you want is tracepoints on this driver, rather
> than dumping a whole bunch of information out of a single read to a
> single file. The kernel has a very nice tracing infrastructure and I'd
> be really happy to read a patch adding support for that in this driver.
> 
Explained in [Motivation], I'm sorry that I have no experience of using
tracepoint:(, so I googled it, and found that I can't use them to
achieve the same purpose as "snapshot". But I maybe wrong.

> > > > +static void dwc3_dump_dev_event(struct seq_file *s,
> > > > +			const struct dwc3_event_devt *event)
> > > > +{
> > > > +	seq_puts(s, "[0]DEV ");
> > > > +	seq_printf(s, "[1:7]%s ",
> > > > +		event->device_event == DWC3_EVENT_TYPE_DEV ? "TYPE_DEV" :
> > > > +		event->device_event == DWC3_EVENT_TYPE_CARKIT ? "TYPE_CARKIT" :
> > > > +		event->device_event == DWC3_EVENT_TYPE_I2C ? "TYPE_CARKIT" :
> > > > +		"TYPE_UNKOWN");
> > > > +	seq_printf(s, "[8:11]%s ", dwc3_gadget_event_string(event->type));
> > > > +
> > > > +	if (event->type == DWC3_DEVICE_EVENT_LINK_STATUS_CHANGE ||
> > > > +		event->type == DWC3_DEVICE_EVENT_HIBER_REQ) {
> > > > +
> > > > +		seq_printf(s, "[16:20]%s %s ",
> > > > +			dwc3_link_state_string(
> > > > +				event->event_info & DEVT_EVTINFO_SUPERSPEED,
> > > > +				event->event_info & DWC3_LINK_STATE_MASK),
> > > > +				event->event_info & DEVT_EVTINFO_SUPERSPEED ?
> > > > +				"SS" : "HS");
> > > > +
> > > > +		if (!(event->event_info & DEVT_EVTINFO_SUPERSPEED))
> > > > +			seq_printf(s, "[21:24]HIRD %u ",
> > > > +				DEVT_EVTINFO_HIRD(event->event_info));
> > > > +	}
> > > > +}
> > > > +
> > > > +static void dwc3_dump_ep_event(struct seq_file *s,
> > > > +			const struct dwc3_event_depevt *event)
> > > > +{
> > > > +	seq_puts(s, "[0]EP ");
> > > > +	seq_printf(s, "[1:5]ep%d ", event->endpoint_number);
> > > > +	seq_printf(s, "[6:9]%s ",
> > > > +		dwc3_ep_event_string(event->endpoint_event));
> > > > +
> > > > +	switch (event->endpoint_event) {
> > > > +	case DWC3_DEPEVT_XFERCOMPLETE:
> > > > +	case DWC3_DEPEVT_XFERINPROGRESS:
> > > > +		if (event->status & DEPEVT_STATUS_BUSERR)
> > > > +			seq_puts(s, "[12]BUSERR ");
> > > > +		if (event->status & DEPEVT_STATUS_SHORT)
> > > > +			seq_puts(s, "[13]SHORT ");
> > > > +		if (event->status & DEPEVT_STATUS_IOC)
> > > > +			seq_puts(s, "[14]IOC ");
> > > > +		if (event->status & DEPEVT_STATUS_LST)
> > > > +			seq_puts(s, "[15]LST ");
> > > > +		break;
> > > > +	case DWC3_DEPEVT_XFERNOTREADY:
> > > > +		if ((event->status & 0x3) == 1)
> > > > +			seq_puts(s, "[12:13]Data_Stage ");
> > > > +		else if ((event->status & 0x3) == 2)
> > > > +			seq_puts(s, "[12:13]Status_Stage ");
> > > > +		if (event->status & DEPEVT_STATUS_TRANSFER_ACTIVE)
> > > > +			seq_puts(s, "[15]XferActive ");
> > > > +		else
> > > > +			seq_puts(s, "[15]XferNotActive ");
> > > > +		break;
> > > > +	case DWC3_DEPEVT_EPCMDCMPLT:
> > > > +		if (event->status & BIT(0))
> > > > +			seq_puts(s, "[12:15]Invalid Transfer Resource ");
> > > > +		break;
> > > > +	default:
> > > > +		seq_puts(s, "[12:15]UNKOWN ");
> > > > +	}
> > > > +	seq_printf(s, "[16:31]PARAM 0x%04x ", event->parameters);
> > > > +}
> > > > +
> > > > +static void dwc3_dump_event_buf(struct seq_file *s,
> > > > +			struct dwc3_event_buffer *evt)
> > > > +{
> > > > +	union dwc3_event	event;
> > > > +	int			i;
> > > > +
> > > > +	seq_printf(s, "evt->buf@0x%p(dma@0x%pad), length=%u, lpos=%u, count=%u, flags=%s\n",
> > > > +		evt->buf, &evt->dma,
> > > > +		evt->length, evt->lpos, evt->count,
> > > > +		evt->flags & DWC3_EVENT_PENDING ? "pending" : "0");
> > > > +
> > > > +	for (i = 0; i < evt->length; i += 4) {
> > > > +		event.raw = *(u32 *) (evt->buf + i);
> > > > +		if (i == evt->lpos) {
> > > > +			seq_puts(s, "lpos-------|\n");
> > > > +			seq_puts(s, "           \\\n");
> > > > +		}
> > > > +		seq_printf(s, "event[%d]: %08x ", i, event.raw);
> > > > +
> > > > +		if (event.type.is_devspec)
> > > > +			dwc3_dump_dev_event(s, &event.devt);
> > > > +		else
> > > > +			dwc3_dump_ep_event(s, &event.depevt);
> > > > +		seq_puts(s, "\n");
> > > > +	}
> > > 
> > > how well have you tested this ? I'm not entirely sure you should be
> > > reading the event buffer at any time you want, though I might be wrong.
> > > 
> > > It's still a bit easier to reproduce part of the event handling here. I
> > > think it's best to make a choice of caching the last 5 events in a ring
> > > buffer and provide a helper for IRQ handlers to push events into the
> > > ring buffer, then from here you just iterate over that ring buffer
> > > instead of accessing our actual event buffer.
> > > 
> > Thanks Paul Zimmerman and you for reminding me that fact that controller
> > may write to the event buffers when we're reading them.
> > 
> > Instead of trying to make things perfect and complex, the interface is just
> > to dump the events while leaving the responsibilty to developers to judge
> > if the events are reliable.
> 
> That's a crappy interface then. Why would anybody use anything they
> can't trust ?
> 
Explained in [Motivation]. Simply treat it as an interface just dumping the
structures.

> > Developer should be able to sense if the data is reliable depending on when he
> > dumps the data. If a transfer is stuck and controller doesn't generate anymore
> 
> or Developer might spend more time looking at somehting that doesn't
> make sense and trying to figure out if the current trace is valid then
> the time spent actually understanding the problem.
> 
> Logs are suppose to aid debugging and if the data isn't trustworthy we
> will have developers spending time debugging the logs themselves. Sorry,
> but I won't accept that.
> 
Explained in [Motivation]. Something is better than nothing. Debugging
is not just about looking at the data and "Oh, here it is". Analyze the
data. It's developer's responsibilty to check how the data is correlated
with a specific failure.

> > events, then the data is reliable, and this is the main senario this patch wants
> > to handle. If a transfer is stuck but controller keeps generating events due to
> 
> that you already get with Verbose debug anyway and you get *all* that
> data with a simple dmesg.
> 
Explained in [Motivation], verbose debug has its limitations.

> > other transfers, there's nothing we can do about it, as the new events will
> > quickly overwrite the ring, and developer will know the events are not valuable.
> 
> and there goes a debug session down the drain, it turned out to be a
> waste of time after all.
> 
> > If you dump the events when all transfers are still on-going, it just provides
> > you some a history of the events to sense how it looks like, and you
> > know the data might not be reliable. And this usage is not really helpful
> > for debugging or not used at all, as you should have no intereset to
> > check the events if everythings goes well.
> > I think above is acceptable for debugging purpose, it's simple without
> > introducing any overhead or timing effect.
> 
> wait, what ? everytime you read that file you hold the controller lock
> god knows for how long and you say it doesn't introduce any timing
> effect ?
> 
> Verbose logs have a lower overhead than what you're suggesting here.
> 
If the test doesn't fail, you should have no interest to read the file.
So no overhead during running.
After the failure, you can read the file, the overhead is not a big deal
at this point.

> > > Also note that we can hold up to 64 events in our event buffer so this
> > > call could take a looooooot of time to complete and you probably don't
> > > need all that information anyway because you can get them by just
> > > enabling VERBOSE_DEBUG on dwc3 and capturing the entire driver behavior
> > > on dmesg.
> > > 
> > Even though a user may be scared by the lots of events, when a failure happens,
> > he actually wants to read as many events as he can to see what happened
> > before the failure. 5 events is not enough, user can at most only see one
> > or two transfers through these 5 events or nothing if the last few
> > events are generated from other transfers which are unrelated to the
> > failure. The time to dump the events doesn't matter as it's for debugging and
> > most often usage is after a transfer is stuck.
> 
> right, so if the transfer is stuch there are no extra generated anyway.
> 
> And I continue to say that all of this information is already available
> by enabling VERBOSE_DEBUG for this driver.
> 
> If you want to capture logs without VERBOSE_DEBUG tracepoints sound like
> the way to go.
> 
Explained in [Motivation], I'm not trying to capture logs without
VERBOSE_DEBUG.

> > > > +static int dwc3_snapshot_show(struct seq_file *s, void *unused)
> > > > +{
> > > > +	struct dwc3		*dwc = s->private;
> > > > +	unsigned long		flags;
> > > > +	int			i;
> > > > +
> > > > +	spin_lock_irqsave(&dwc->lock, flags);
> > > > +	for (i = 2; i < DWC3_ENDPOINTS_NUM; i++) {
> > > 
> > > some platforms don't have all 32 physical endpoints, we just had a bug
> > > fix for that, see commit 32702e9.
> > > 
> > Will fix it as below:
> > 	for (i = 2; i < DWC3_ENDPOINTS_NUM; i++) {
> 
> no dude, iterate for IN eps and for OUT eps separately. We already have
> dwc->num_in_eps and dwc->num_out_eps
> 
Will fix it. Thanks.


Thanks
Jincan

Re: [PATCH] usb: dwc3: debugfs: add snapshot to dump requests trbs events

[Felipe Balbi]

[-- Attachment #1: Type: text/plain, Size: 20776 bytes --]

Hi,

On Thu, May 01, 2014 at 01:06:25AM -0400, Zhuang Jin Can wrote:
> Hi,
> 
> On Tue, Apr 29, 2014 at 11:10:42AM -0500, Felipe Balbi wrote:
> > Hi,
> > 
> > On Tue, Apr 29, 2014 at 05:21:42PM -0400, Zhuang Jin Can wrote:
> > > On Mon, Apr 28, 2014 at 10:55:36AM -0500, Felipe Balbi wrote:
> > > > On Mon, Apr 28, 2014 at 04:49:23PM -0400, Zhuang Jin Can wrote:
> > > > > Adds a debugfs file "snapshot" to dump dwc3 requests, trbs and events.
> > > > 
> > > > you need to explain what are you trying to provide to our users here.
> > > > 
> > > > What "problem" are you trying to solve ?
> > > > 
> > > The interface enables users to easily peek into requests, trbs and
> > > events to know the current transfer state of each request.
> > > If an transfer is stuck, user can use the interface to check why it's
> > > stuck (e.g. Is it because a gadget doesn't queued the request? Or it's
> > > queued but it's not primed to the controller? Or It's primed to the
> > > controller but the TRBs and events indicate the transfer never completes?).
> > > User can immediately narrow down the issue without enabling verbose log or
> > > reproduce the issue again. It's helpful when we need to deal with some
> > > hard-to-reproduce bugs or timing sensitive bugs can't be reproduced with
> > > verbose log enabled.
> > 
> > this should be part of the commit log in some shape or form.
> > 
> Yes.
> 
> > > > > As ep0 requests are more complex than others. It's not included in this
> > > > > patch.
> > > > 
> > > > For ep0, you could at least print the endpoint phase we are currently
> > > > in and if we have requests in flight or not.
> > > > 
> > > Agree. Will add it in [PATCH v2].
> > 
> > tks
> > 
> > > > > +			seq_puts(s, "busy_slot--|\n");
> > > > > +			seq_puts(s, "           \\\n");
> > > > > +		}
> > > > > +		if (i == (dep->free_slot & DWC3_TRB_MASK)) {
> > > > > +			seq_puts(s, "free_slot--|\n");
> > > > > +			seq_puts(s, "           \\\n");
> > > > > +		}
> > > > > +		seq_printf(s, "trb[%02d](dma@0x%pad): %08x(bpl), %08x(bph), %08x(size), %08x(ctrl)\n",
> > > > 
> > > > I'm not sure you need to print out the TRB address. bpl, bph, size and
> > > > ctrl are desired though.
> > > > 
> > > printing out the TRB DMA address helps user to locate the start TRB of a
> > > request. I admit that we can achive the same purose using the "start_slot"
> > > of the request. I'll remove it in [PATCH v2].
> > 
> > thanks
> > 
> > > > > +			i, &dep->trb_pool_dma + i * sizeof(*trb),
> > > > > +			trb->bpl, trb->bph, trb->size, trb->ctrl);
> > > > 
> > > > this will be pretty difficult to parse by a human. I would rather see
> > > > you creating one directory per TRB (and also one directory per
> > > > endpoint) which holds the details for that entity, so that it looks
> > > > like:
> > > > 
> > > > dwc3
> > > > |-- current_state	(or perhaps a better name, but snapshot isn't very good either)
> > > Actually, it's hard to find a perfect name. "current_state" or "snapshot" doesn't
> > > make too much difference to me. If "current_state" makes more sense to you, I
> > > can change to use this name. Or let me know if you have a better suggestion.
> > 
> > the name is important as we will have to deal with it for the next 50
> > years. We also need to think about someone starting out on dwc3 5 years
> > from now or a QA engineer in whatever OEM trying to provide details of
> > the failure for the development team. It needs to be well thought out.
> > 
> > I don't have a better idea but snapshot gives me the idea that we will
> > end up with a copy of everything which we can revisit at any time and
> > that's not true. If we read this file twice there's no guarantee it'll
> > contain the same information.
> > 
> Let's discuss the name later after I explain more about the motivation.
> 
> [Motivation]
> The patch is inspired from echi-dbg.c debugfs. It contains four files
> "async", ""bandwidth", "periodic" and "registers".
> The "registers" functions as what "regdump" does in dwc3. And the patch implements
> a "snapshot" to do the similar things done by "async" and "periodic".
> Because a way to inspect the content of data structures (i.e. TRBs, Events)
> interacting with the controller is really important for debugging,
> especially for HW issues. It just simply provides you a interface to check
> what's currently in TRBs and event buffers (and nothing more, no more
> guarantees). 
> In EHCI, "async" and "periodic" also can't guarantee you the reliable data, as
> you can't prevent the controller from writing the interacting data
> structures (unless you stop it). It's developer's decision to how to analyze
> the data. They're not perfect, but simple and helpful.
> 
> As far as I see, it's useful for below senarios:
> 1. Bugs can't be reproduced with VERBOSE_DEBUG, as printk introduces
> timing effect. Some HW bugs are timing sensitive, even a single printk
> will prevent you from reproducing the issue.
> With "snapshot", we can check the TRBs, events, requests to see the
> final status to get more clues to triage an issue.
> 
> 2. Some bugs are hard to reproduce, and can be seen once or
> twice after many devices running for a long time. (e.g. MTBF runing with
> ADB). And they most often uses the builds with debugfs available, ask
> them to turn on VERBOSE_DEBUG and run the tests are not acceptable.
> After the failure happens, if you ask the tester to turn on the VERBOSE_DEBUG
> to reproduce the issue again. He may come back to you a week later with
> an answer "I can't reproduce it. It's a random issue". 
> With "snapshot", when the issue happens, tester can just dump the TRBs,
> events to provide more data to a developer. It won't guarantee you to
> root cause the issue, but something is better than nothing.
> 
> Regarding what are important to dump, regarding the motivation, they should be
> TRBs and Events which are the parts interfacing with HW. But only dumping them is
> not enough, it's useless if user can't tell which TRB belongs to which
> endpont and request. That's why I also dump the necessary info about the
> requests and endpoints to track their relationship. Infos like maxpacket
> size, direction, types are not really important regarding this. You can
> get the information by running it once and see the printks. And they're
> common properties which can just be handed off to udc core.
> 
> > > >     |-- ep2
> > > >     |   |-- direction
> > > >     |   |-- maxpacket
> > > >     |   |-- number
> > > >     |   |-- state
> > > >     |   |-- stream_capable
> > > >     |   |-- type
> > > >     |   |-- trbs
> > > >     |   |   |-- trb0
> > > >     |   |   |   |-- bph
> > > >     |   |   |   |-- bpl
> > > >     |   |   |   |-- ctrl
> > > >     |   |   |   |-- size
> > > >     |   |   |-- trb1
> > > >     |   |   |   |-- bph
> > > >     |   |   |   |-- bpl
> > > >     |   |   |   |-- ctrl
> > > >     |   |   |   |-- size
> > > >     |   |   |-- trb2
> > > >     |   |   |   |-- bph
> > > >     |   |   |   |-- bpl
> > > >     |   |   |   |-- ctrl
> > > >     |   |   |   |-- size
> > > >     |   |   |-- trb3
> > > >     |   |   |   |-- bph
> > > >     |   |   |   |-- bpl
> > > >     |   |   |   |-- ctrl
> > > >     |   |   |   |-- size
> > > >     .   .   .
> > > >     .   .   .
> > > >     .   .   .
> > > >     |   |-- request0
> > > >     |   |   |-- direction
> > > >     |   |   |-- mapped
> > > >     |   |   |-- queued
> > > >     |   |   |-- trb0	(symlink to actual trb directory)
> > > >     |   |   |-- ep2		(symlink to actual ep2 directory)
> > > >     |   |   |-- usbrequest
> > > >     |   |       |-- actual
> > > >     |   |       |-- length
> > > >     |   |       |-- no_interrupt
> > > >     |   |       |-- num_mapped_sgs
> > > >     |   |       |-- num_sgs
> > > >     |   |       |-- short_not_ok
> > > >     |   |       |-- status
> > > >     |   |       |-- stream_id
> > > >     |   |       |-- zero
> > > >     |   |-- request1
> > > >     |   |   |-- direction
> > > >     |   |   |-- mapped
> > > >     |   |   |-- queued
> > > >     |   |   |-- trb1	(symlink to actual trb directory)
> > > >     |   |   |-- ep2		(symlink to actual ep2 directory)
> > > >     |   |   |-- usbrequest
> > > >     |   |       |-- actual
> > > >     |   |       |-- length
> > > >     |   |       |-- no_interrupt
> > > >     |   |       |-- num_mapped_sgs
> > > >     |   |       |-- num_sgs
> > > >     |   |       |-- short_not_ok
> > > >     |   |       |-- status
> > > >     |   |       |-- stream_id
> > > >     |   |       |-- zero
> > > >     .   .   .   .
> > > >     .   .   .   .
> > > >     .   .   .   .
> > > > 
> > > > 
> > > > and so forth. That way we get a structured view of everything the
> > > > controller and the driver are managing.
> > > > 
> > > The patch intends to dump the most important RUNTIME information the driver is
> > > dealing with the controller, STATIC information is not valuable here as we can
> > > get them before running. I consider information like "direction", "maxpactsize",
> > > "types" are STATIC, as they're not going to change once they are configured.
> > 
> > they are still important and easy enough to print out. Sometimes
> > direction is the key information for a debug session. For example if a
> > Bulk OUT transaction of length 2000 never completes we *know* the reason
> > why.
> > 
> > We know OUT endpoints can't handle transfers which are not aligned to
> > wMaxPacketSize.
> > 
> Explained in [Motivation], these info can be got by VERBOSE_DEBUG by running it once.
> It's not the "snapshot" really want to handle.
> 
> > > Dumping everying is not the intention of the patch. (Sorry that the name
> > 
> > so ? I'm making a suggestion to improve the patch. Dumping only the
> > information you judged necessary during your debug sessions with no
> > consideration for other users isn't generally a good practice. I'm
> > trying to help you improve the patch so that it can be accepted.
> > 
> > Note that dumping all of that information out of a single file isn't
> > very nice either and it'll be difficult to parse, even for humans.
> > 
> Explained in [Motivation].
> 
> > > So are you suggesting to organize the information in multiple debugfs
> > > directories and files or just to print information with appropriate indents so that
> > 
> > multiple directories.
> > 
> Explained in [Motivation]. echi-dbg.c also uses a single file to dump the
> structures. But I admit that dumping event buffers can be in a separate file.
> 
> > > users can easily read it? IMO, organizing them in multiple files makes
> > > it impossible for the user to lock dwc3->lock and get information
> > > atomically. The problem of reading them separately is that it won't give
> > > you the consistent information regarding the current transfer state.
> > 
> > it depends on where you hold the lock. Also, now that I think of it, it
> > really seems like what you want is tracepoints on this driver, rather
> > than dumping a whole bunch of information out of a single read to a
> > single file. The kernel has a very nice tracing infrastructure and I'd
> > be really happy to read a patch adding support for that in this driver.
> > 
> Explained in [Motivation], I'm sorry that I have no experience of using
> tracepoint:(, so I googled it, and found that I can't use them to
> achieve the same purpose as "snapshot". But I maybe wrong.
> 
> > > > > +static void dwc3_dump_dev_event(struct seq_file *s,
> > > > > +			const struct dwc3_event_devt *event)
> > > > > +{
> > > > > +	seq_puts(s, "[0]DEV ");
> > > > > +	seq_printf(s, "[1:7]%s ",
> > > > > +		event->device_event == DWC3_EVENT_TYPE_DEV ? "TYPE_DEV" :
> > > > > +		event->device_event == DWC3_EVENT_TYPE_CARKIT ? "TYPE_CARKIT" :
> > > > > +		event->device_event == DWC3_EVENT_TYPE_I2C ? "TYPE_CARKIT" :
> > > > > +		"TYPE_UNKOWN");
> > > > > +	seq_printf(s, "[8:11]%s ", dwc3_gadget_event_string(event->type));
> > > > > +
> > > > > +	if (event->type == DWC3_DEVICE_EVENT_LINK_STATUS_CHANGE ||
> > > > > +		event->type == DWC3_DEVICE_EVENT_HIBER_REQ) {
> > > > > +
> > > > > +		seq_printf(s, "[16:20]%s %s ",
> > > > > +			dwc3_link_state_string(
> > > > > +				event->event_info & DEVT_EVTINFO_SUPERSPEED,
> > > > > +				event->event_info & DWC3_LINK_STATE_MASK),
> > > > > +				event->event_info & DEVT_EVTINFO_SUPERSPEED ?
> > > > > +				"SS" : "HS");
> > > > > +
> > > > > +		if (!(event->event_info & DEVT_EVTINFO_SUPERSPEED))
> > > > > +			seq_printf(s, "[21:24]HIRD %u ",
> > > > > +				DEVT_EVTINFO_HIRD(event->event_info));
> > > > > +	}
> > > > > +}
> > > > > +
> > > > > +static void dwc3_dump_ep_event(struct seq_file *s,
> > > > > +			const struct dwc3_event_depevt *event)
> > > > > +{
> > > > > +	seq_puts(s, "[0]EP ");
> > > > > +	seq_printf(s, "[1:5]ep%d ", event->endpoint_number);
> > > > > +	seq_printf(s, "[6:9]%s ",
> > > > > +		dwc3_ep_event_string(event->endpoint_event));
> > > > > +
> > > > > +	switch (event->endpoint_event) {
> > > > > +	case DWC3_DEPEVT_XFERCOMPLETE:
> > > > > +	case DWC3_DEPEVT_XFERINPROGRESS:
> > > > > +		if (event->status & DEPEVT_STATUS_BUSERR)
> > > > > +			seq_puts(s, "[12]BUSERR ");
> > > > > +		if (event->status & DEPEVT_STATUS_SHORT)
> > > > > +			seq_puts(s, "[13]SHORT ");
> > > > > +		if (event->status & DEPEVT_STATUS_IOC)
> > > > > +			seq_puts(s, "[14]IOC ");
> > > > > +		if (event->status & DEPEVT_STATUS_LST)
> > > > > +			seq_puts(s, "[15]LST ");
> > > > > +		break;
> > > > > +	case DWC3_DEPEVT_XFERNOTREADY:
> > > > > +		if ((event->status & 0x3) == 1)
> > > > > +			seq_puts(s, "[12:13]Data_Stage ");
> > > > > +		else if ((event->status & 0x3) == 2)
> > > > > +			seq_puts(s, "[12:13]Status_Stage ");
> > > > > +		if (event->status & DEPEVT_STATUS_TRANSFER_ACTIVE)
> > > > > +			seq_puts(s, "[15]XferActive ");
> > > > > +		else
> > > > > +			seq_puts(s, "[15]XferNotActive ");
> > > > > +		break;
> > > > > +	case DWC3_DEPEVT_EPCMDCMPLT:
> > > > > +		if (event->status & BIT(0))
> > > > > +			seq_puts(s, "[12:15]Invalid Transfer Resource ");
> > > > > +		break;
> > > > > +	default:
> > > > > +		seq_puts(s, "[12:15]UNKOWN ");
> > > > > +	}
> > > > > +	seq_printf(s, "[16:31]PARAM 0x%04x ", event->parameters);
> > > > > +}
> > > > > +
> > > > > +static void dwc3_dump_event_buf(struct seq_file *s,
> > > > > +			struct dwc3_event_buffer *evt)
> > > > > +{
> > > > > +	union dwc3_event	event;
> > > > > +	int			i;
> > > > > +
> > > > > +	seq_printf(s, "evt->buf@0x%p(dma@0x%pad), length=%u, lpos=%u, count=%u, flags=%s\n",
> > > > > +		evt->buf, &evt->dma,
> > > > > +		evt->length, evt->lpos, evt->count,
> > > > > +		evt->flags & DWC3_EVENT_PENDING ? "pending" : "0");
> > > > > +
> > > > > +	for (i = 0; i < evt->length; i += 4) {
> > > > > +		event.raw = *(u32 *) (evt->buf + i);
> > > > > +		if (i == evt->lpos) {
> > > > > +			seq_puts(s, "lpos-------|\n");
> > > > > +			seq_puts(s, "           \\\n");
> > > > > +		}
> > > > > +		seq_printf(s, "event[%d]: %08x ", i, event.raw);
> > > > > +
> > > > > +		if (event.type.is_devspec)
> > > > > +			dwc3_dump_dev_event(s, &event.devt);
> > > > > +		else
> > > > > +			dwc3_dump_ep_event(s, &event.depevt);
> > > > > +		seq_puts(s, "\n");
> > > > > +	}
> > > > 
> > > > how well have you tested this ? I'm not entirely sure you should be
> > > > reading the event buffer at any time you want, though I might be wrong.
> > > > 
> > > > It's still a bit easier to reproduce part of the event handling here. I
> > > > think it's best to make a choice of caching the last 5 events in a ring
> > > > buffer and provide a helper for IRQ handlers to push events into the
> > > > ring buffer, then from here you just iterate over that ring buffer
> > > > instead of accessing our actual event buffer.
> > > > 
> > > Thanks Paul Zimmerman and you for reminding me that fact that controller
> > > may write to the event buffers when we're reading them.
> > > 
> > > Instead of trying to make things perfect and complex, the interface is just
> > > to dump the events while leaving the responsibilty to developers to judge
> > > if the events are reliable.
> > 
> > That's a crappy interface then. Why would anybody use anything they
> > can't trust ?
> > 
> Explained in [Motivation]. Simply treat it as an interface just dumping the
> structures.
> 
> > > Developer should be able to sense if the data is reliable depending on when he
> > > dumps the data. If a transfer is stuck and controller doesn't generate anymore
> > 
> > or Developer might spend more time looking at somehting that doesn't
> > make sense and trying to figure out if the current trace is valid then
> > the time spent actually understanding the problem.
> > 
> > Logs are suppose to aid debugging and if the data isn't trustworthy we
> > will have developers spending time debugging the logs themselves. Sorry,
> > but I won't accept that.
> > 
> Explained in [Motivation]. Something is better than nothing. Debugging
> is not just about looking at the data and "Oh, here it is". Analyze the
> data. It's developer's responsibilty to check how the data is correlated
> with a specific failure.
> 
> > > events, then the data is reliable, and this is the main senario this patch wants
> > > to handle. If a transfer is stuck but controller keeps generating events due to
> > 
> > that you already get with Verbose debug anyway and you get *all* that
> > data with a simple dmesg.
> > 
> Explained in [Motivation], verbose debug has its limitations.
> 
> > > other transfers, there's nothing we can do about it, as the new events will
> > > quickly overwrite the ring, and developer will know the events are not valuable.
> > 
> > and there goes a debug session down the drain, it turned out to be a
> > waste of time after all.
> > 
> > > If you dump the events when all transfers are still on-going, it just provides
> > > you some a history of the events to sense how it looks like, and you
> > > know the data might not be reliable. And this usage is not really helpful
> > > for debugging or not used at all, as you should have no intereset to
> > > check the events if everythings goes well.
> > > I think above is acceptable for debugging purpose, it's simple without
> > > introducing any overhead or timing effect.
> > 
> > wait, what ? everytime you read that file you hold the controller lock
> > god knows for how long and you say it doesn't introduce any timing
> > effect ?
> > 
> > Verbose logs have a lower overhead than what you're suggesting here.
> > 
> If the test doesn't fail, you should have no interest to read the file.
> So no overhead during running.
> After the failure, you can read the file, the overhead is not a big deal
> at this point.
> 
> > > > Also note that we can hold up to 64 events in our event buffer so this
> > > > call could take a looooooot of time to complete and you probably don't
> > > > need all that information anyway because you can get them by just
> > > > enabling VERBOSE_DEBUG on dwc3 and capturing the entire driver behavior
> > > > on dmesg.
> > > > 
> > > Even though a user may be scared by the lots of events, when a failure happens,
> > > he actually wants to read as many events as he can to see what happened
> > > before the failure. 5 events is not enough, user can at most only see one
> > > or two transfers through these 5 events or nothing if the last few
> > > events are generated from other transfers which are unrelated to the
> > > failure. The time to dump the events doesn't matter as it's for debugging and
> > > most often usage is after a transfer is stuck.
> > 
> > right, so if the transfer is stuch there are no extra generated anyway.
> > 
> > And I continue to say that all of this information is already available
> > by enabling VERBOSE_DEBUG for this driver.
> > 
> > If you want to capture logs without VERBOSE_DEBUG tracepoints sound like
> > the way to go.
> > 
> Explained in [Motivation], I'm not trying to capture logs without
> VERBOSE_DEBUG.

since you're just giving me a bunch of excuses to not modify your patch
which, well, was written for your own use case then I'll just ignore
this patch altogether.

When I get time, I'll add proper tracepoints to this driver which will
help many other engineers in many other use cases, not just one.

sorry but your patch is not good for acceptance in mainline.

-- 
balbi

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Re: [PATCH] usb: dwc3: debugfs: add snapshot to dump requests trbs events

[Zhuang Jin Can]

On Wed, Apr 30, 2014 at 12:14:42PM -0500, Felipe Balbi wrote:
> sorry but your patch is not good for acceptance in mainline.
> 
Thanks your time. 

Jincan