Re: [PATCH v2] usb: core: hub: Add quirks for reducing device address timeout

Hardik Gajjar
2023-10-10T10:31:56Z

On Mon, Oct 09, 2023 at 07:43:09PM +0200, Greg KH wrote:
> On Mon, Oct 09, 2023 at 06:14:02PM +0200, Hardik Gajjar wrote:
> > Currently, the timeout for the set address command is fixed at
> > 5 seconds in the xhci driver. This means the host waits up to 5
> > seconds to receive a response for the set_address command from
> > the device.
> >
> > In the automotive context, most smartphone enumerations, including
> > screen projection, should ideally complete within 3 seconds.
> > Achieving this is impossible in scenarios where the set_address is
> > not successful and waits for a timeout.
> >
> > The shortened address device timeout quirks provide the flexibility
> > to align with a 3-second time limit in the event of errors.
> > By swiftly triggering a failure response and swiftly initiating
> > retry procedures, these quirks ensure efficient and rapid recovery,
> > particularly in automotive contexts where rapid smartphone enumeration
> > and screen projection are vital.
>
> So you have known-broken devices where you want a shorter error timeout?
> But you don't list those devices in this patch adding the quirk
> settings, shouldn't that be required, otherwise this looks like an
> unused quirk.
Yes, we have identified the device (hub) that is causing the issue. However,
I would prefer not to force this timeout globally. Instead, I can dynamically
control it by writing to the /sys/bus/usb/drivers/hub/module/parameter/quirks
file from init.rc (Android) during the boot-up process.
>
> > The quirk will set the timeout to 500 ms from 5 seconds.
> >
> > To use the quirk, please write "vendor_id:product_id:p" to
> > /sys/bus/usb/drivers/hub/module/parameter/quirks
> >
> > For example,
> > echo "0x2c48:0x0132:p" > /sys/bus/usb/drivers/hub/module/parameter/quirks"
> >
> > Signed-off-by: Hardik Gajjar <hgajjar@de.adit-jv.com>
> > ---
> > changes since version 1:
> > - implement quirk instead of new API in xhci driver
> > ---
> > drivers/usb/core/hub.c | 15 +++++++++++++--
> > drivers/usb/core/quirks.c | 3 +++
> > drivers/usb/host/xhci-mem.c | 1 +
> > drivers/usb/host/xhci-ring.c | 3 ++-
> > drivers/usb/host/xhci.c | 9 +++++----
> > drivers/usb/host/xhci.h | 1 +
> > include/linux/usb/hcd.h | 3 ++-
> > include/linux/usb/quirks.h | 3 +++
> > 8 files changed, 30 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> > index 3c54b218301c..975449b03426 100644
> > --- a/drivers/usb/core/hub.c
> > +++ b/drivers/usb/core/hub.c
> > @@ -54,6 +54,9 @@
> > #define USB_TP_TRANSMISSION_DELAY_MAX 65535 /* ns */
> > #define USB_PING_RESPONSE_TIME 400 /* ns */
> >
> > +#define USB_DEFAULT_ADDR_DEVICE_TIMEOUT (HZ * 5) /* 5000ms */
> > +#define USB_SHORT_ADDR_DEVICE_TIMEOUT 125 /* ~500ms */
> > +
> > /* Protect struct usb_device->state and ->children members
> > * Note: Both are also protected by ->dev.sem, except that ->state can
> > * change to USB_STATE_NOTATTACHED even when the semaphore isn't held. */
> > @@ -4626,8 +4629,16 @@ EXPORT_SYMBOL_GPL(usb_ep0_reinit);
> > static int hub_set_address(struct usb_device *udev, int devnum)
> > {
> > int retval;
> > + int timeout = USB_DEFAULT_ADDR_DEVICE_TIMEOUT;
> > struct usb_hcd *hcd = bus_to_hcd(udev->bus);
> >
> > + struct usb_hub *hub = usb_hub_to_struct_hub(udev->parent);
> > +
> > + if (hub->hdev->quirks & USB_QUIRK_SHORT_DEVICE_ADDR_TIMEOUT)
> > + timeout = USB_SHORT_ADDR_DEVICE_TIMEOUT;
> > +
> > + dev_dbg(&udev->dev, "address_device timeout %d\n", timeout);
>
> Is this debugging code still needed?
will remove in patch v3
>
> > /*
> > * The host controller will choose the device address,
> > * instead of the core having chosen it earlier
> > @@ -4639,11 +4650,11 @@ static int hub_set_address(struct usb_device *udev, int devnum)
> > if (udev->state != USB_STATE_DEFAULT)
> > return -EINVAL;
> > if (hcd->driver->address_device)
> > - retval = hcd->driver->address_device(hcd, udev);
> > + retval = hcd->driver->address_device(hcd, udev, timeout);
> > else
> > retval = usb_control_msg(udev, usb_sndaddr0pipe(),
> > USB_REQ_SET_ADDRESS, 0, devnum, 0,
> > - NULL, 0, USB_CTRL_SET_TIMEOUT);
> > + NULL, 0, jiffies_to_msecs(timeout));
> > if (retval == 0) {
> > update_devnum(udev, devnum);
> > /* Device now using proper address. */
> > diff --git a/drivers/usb/core/quirks.c b/drivers/usb/core/quirks.c
> > index 15e9bd180a1d..01ed26bd41f0 100644
> > --- a/drivers/usb/core/quirks.c
> > +++ b/drivers/usb/core/quirks.c
> > @@ -138,6 +138,9 @@ static int quirks_param_set(const char *value, const struct kernel_param *kp)
> > case 'o':
> > flags |= USB_QUIRK_HUB_SLOW_RESET;
> > break;
> > + case 'p':
> > + flags |= USB_QUIRK_SHORT_DEVICE_ADDR_TIMEOUT;
> > + break;
> > /* Ignore unrecognized flag characters */
> > }
> > }
> > diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
> > index 8714ab5bf04d..492433fdac77 100644
> > --- a/drivers/usb/host/xhci-mem.c
> > +++ b/drivers/usb/host/xhci-mem.c
> > @@ -1729,6 +1729,7 @@ struct xhci_command *xhci_alloc_command(struct xhci_hcd *xhci,
> > }
> >
> > command->status = 0;
> > + command->timeout = 0;
> > INIT_LIST_HEAD(&command->cmd_list);
> > return command;
> > }
> > diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
> > index 1dde53f6eb31..0bd19a1efdec 100644
> > --- a/drivers/usb/host/xhci-ring.c
> > +++ b/drivers/usb/host/xhci-ring.c
> > @@ -4301,7 +4301,8 @@ static int queue_command(struct xhci_hcd *xhci, struct xhci_command *cmd,
> > /* if there are no other commands queued we start the timeout timer */
> > if (list_empty(&xhci->cmd_list)) {
> > xhci->current_cmd = cmd;
> > - xhci_mod_cmd_timer(xhci, XHCI_CMD_DEFAULT_TIMEOUT);
> > + xhci_mod_cmd_timer(xhci, (cmd->timeout) ? cmd->timeout :
> > + XHCI_CMD_DEFAULT_TIMEOUT);
> > }
> >
> > list_add_tail(&cmd->cmd_list, &xhci->cmd_list);
> > diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> > index e1b1b64a0723..1d088ceb2b74 100644
> > --- a/drivers/usb/host/xhci.c
> > +++ b/drivers/usb/host/xhci.c
> > @@ -4002,7 +4002,7 @@ int xhci_alloc_dev(struct usb_hcd *hcd, struct usb_device *udev)
> > * SetAddress request to the device.
> > */
> > static int xhci_setup_device(struct usb_hcd *hcd, struct usb_device *udev,
> > - enum xhci_setup_dev setup)
> > + enum xhci_setup_dev setup, int timeout)
>
> What is the units of timeout here?
The timeout is in jiffies. Should we consider adding 'jiffies' in the variable name
for clarity? I searched the kernel source code but couldn't find a reference for the
unit of timeout in jiffies.
Nevertheless, I will add a comment in patch v3 for clarification.
>
> > {
> > const char *act = setup == SETUP_CONTEXT_ONLY ? "context" : "address";
> > unsigned long flags;
> > @@ -4059,6 +4059,7 @@ static int xhci_setup_device(struct usb_hcd *hcd, struct usb_device *udev,
> > }
> >
> > command->in_ctx = virt_dev->in_ctx;
> > + command->timeout = timeout;
> >
> > slot_ctx = xhci_get_slot_ctx(xhci, virt_dev->in_ctx);
> > ctrl_ctx = xhci_get_input_control_ctx(virt_dev->in_ctx);
> > @@ -4185,14 +4186,14 @@ static int xhci_setup_device(struct usb_hcd *hcd, struct usb_device *udev,
> > return ret;
> > }
> >
> > -static int xhci_address_device(struct usb_hcd *hcd, struct usb_device *udev)
> > +static int xhci_address_device(struct usb_hcd *hcd, struct usb_device *udev, int timeout)
> > {
> > - return xhci_setup_device(hcd, udev, SETUP_CONTEXT_ADDRESS);
> > + return xhci_setup_device(hcd, udev, SETUP_CONTEXT_ADDRESS, timeout);
> > }
> >
> > static int xhci_enable_device(struct usb_hcd *hcd, struct usb_device *udev)
> > {
> > - return xhci_setup_device(hcd, udev, SETUP_CONTEXT_ONLY);
> > + return xhci_setup_device(hcd, udev, SETUP_CONTEXT_ONLY, 0);
>
> 0 is no timeout at all? Or max timeout? Where is this documented?
>
> And why is this only added to the xhci driver and not all other host
> controllers?
Because 'address_device' is only assigned in the xHCI driver, other host
drivers (OHCI, EHCI) issue 'set_address' requests directly from 'hub.c'
and utilize the timeout

I have already updated that API in this patch to utilize timeout.
>
> > }
> >
> > /*
> > diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
> > index 7e282b4522c0..ebdca8dd01c2 100644
> > --- a/drivers/usb/host/xhci.h
> > +++ b/drivers/usb/host/xhci.h
> > @@ -818,6 +818,7 @@ struct xhci_command {
> > struct completion *completion;
> > union xhci_trb *command_trb;
> > struct list_head cmd_list;
> > + int timeout;
>
> What is the units here.
The timeout is in jiffies. Should we consider adding 'jiffies' in the variable name
for clarity? I searched the kernel source code but couldn't find a reference for the
unit of timeout in jiffies.
Nevertheless, I will add a comment in patch v3 for clarification.
>
> > };
> >
> > /* drop context bitmasks */
> > diff --git a/include/linux/usb/hcd.h b/include/linux/usb/hcd.h
> > index 61d4f0b793dc..b0fda87ad3a2 100644
> > --- a/include/linux/usb/hcd.h
> > +++ b/include/linux/usb/hcd.h
> > @@ -373,7 +373,8 @@ struct hc_driver {
> > */
> > void (*reset_bandwidth)(struct usb_hcd *, struct usb_device *);
> > /* Returns the hardware-chosen device address */
> > - int (*address_device)(struct usb_hcd *, struct usb_device *udev);
> > + int (*address_device)(struct usb_hcd *, struct usb_device *udev,
> > + int timeout);
>
> Again, units please.
The timeout is in jiffies. Should we consider adding 'jiffies' in the variable name
for clarity? I searched the kernel source code but couldn't find a reference for the
unit of timeout in jiffies.
Nevertheless, I will add a comment in patch v3 for clarification.
>
> > /* prepares the hardware to send commands to the device */
> > int (*enable_device)(struct usb_hcd *, struct usb_device *udev);
> > /* Notifies the HCD after a hub descriptor is fetched.
> > diff --git a/include/linux/usb/quirks.h b/include/linux/usb/quirks.h
> > index eeb7c2157c72..0cb464e3eaf4 100644
> > --- a/include/linux/usb/quirks.h
> > +++ b/include/linux/usb/quirks.h
> > @@ -72,4 +72,7 @@
> > /* device has endpoints that should be ignored */
> > #define USB_QUIRK_ENDPOINT_IGNORE BIT(15)
> >
> > +/* short device address timeout */
> > +#define USB_QUIRK_SHORT_DEVICE_ADDR_TIMEOUT BIT(16)
>
> Don't you also need to have a Documentation/ update for the new
> user/kernel api you are adding?
>
When you recommend Documentation, I assume you suggest to add the
detailed comment in quirks.h to clear intention of the change.
I will update it in patch v3.
> thanks,
>
> greg k-h