Re: g_webcam Isoch high bandwidth transfer

[Felipe Balbi <felipe.balbi@linux.intel.com>]

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Hi,

Felipe Balbi <felipe.balbi@linux.intel.com> writes:
> Bin Liu <b-liu@ti.com> writes:
>> On Wed, Sep 21, 2016 at 11:01:21AM +0300, Felipe Balbi wrote:
>>> 
>>> Hi,
>>> 
>>> Bin Liu <b-liu@ti.com> writes:
>>> > Hi,
>>> >
>>> > I am trying to check Isoch high bandwidth transfer with g_webcam.ko in
>>> >  high-speed connection.
>>> >
>>> > First I hacked webcam.c as follows to enable 640x480@30fps mode.
>>> >
>>> > diff --git a/drivers/usb/gadget/legacy/webcam.c b/drivers/usb/gadget/legacy/webcam.c
>>> > index 72c976b..9eb315f 100644
>>> > --- a/drivers/usb/gadget/legacy/webcam.c
>>> > +++ b/drivers/usb/gadget/legacy/webcam.c
>>> > @@ -191,15 +191,15 @@ static const struct UVC_FRAME_UNCOMPRESSED(3) uvc_frame_yuv_360p = {
>>> >         .bFrameIndex            = 1,
>>> >         .bmCapabilities         = 0,
>>> >         .wWidth                 = cpu_to_le16(640),
>>> > -       .wHeight                = cpu_to_le16(360),
>>> > +       .wHeight                = cpu_to_le16(480),
>>> >         .dwMinBitRate           = cpu_to_le32(18432000),
>>> >         .dwMaxBitRate           = cpu_to_le32(55296000),
>>> > -       .dwMaxVideoFrameBufferSize      = cpu_to_le32(460800),
>>> > -       .dwDefaultFrameInterval = cpu_to_le32(666666),
>>> > +       .dwMaxVideoFrameBufferSize      = cpu_to_le32(614400),
>>> > +       .dwDefaultFrameInterval = cpu_to_le32(333333),
>>> >         .bFrameIntervalType     = 3,
>>> > -       .dwFrameInterval[0]     = cpu_to_le32(666666),
>>> > -       .dwFrameInterval[1]     = cpu_to_le32(1000000),
>>> > -       .dwFrameInterval[2]     = cpu_to_le32(5000000),
>>> > +       .dwFrameInterval[0]     = cpu_to_le32(333333),
>>> > +       .dwFrameInterval[1]     = cpu_to_le32(666666),
>>> > +       .dwFrameInterval[2]     = cpu_to_le32(1000000),
>>> >  };
>>> >
>>> > then loaded g_webcam.ko as
>>> >
>>> > # modprobe g_webcam streaming_maxpacket=3072
>>> >
>>> > The endpoint descriptor showing on the host is
>>> >
>>> >       Endpoint Descriptor:
>>> >         bLength                 7
>>> >         bDescriptorType         5
>>> >         bEndpointAddress     0x8d  EP 13 IN
>>> >         bmAttributes            5
>>> >           Transfer Type            Isochronous
>>> >           Synch Type               Asynchronous
>>> >           Usage Type               Data
>>> >         wMaxPacketSize     0x1400  3x 1024 bytes
>>> >         bInterval               1
>>> >
>>> > However the usb bus trace shows only one transaction with 1024-bytes packet in
>>> > every SOF. The host only sends one IN packet in every SOF, I am expecting 2~3
>>> > 1024-bytes transactions, since this would be required to transfer 640x480@30fps
>>> > YUV frames in high-speed.
>>> >
>>> > DId I miss anything in the setup?
>>> 
>>> MUSB or DWC3? This looks like a UDC bug to me. Can you show a screenshot
>>
>> Happened on both MUSB and DWC3.
>>
>>> of your bus analyzer? When host sends IN token, are you replying with
>>
>> The trace screenshot on DWC3 is attached.
>>
>>> DATA0, DATA1 or DATA2?
>>
>> Good hint! It is DATA0!
>
> yeah, should've been DATA2. I'll check if we're missing anything for
> High Bandwidth Iso on DWC3. Can you confirm if it works of tails on
> DWC3? On your follow-up mail you mentioned it's a bug in MUSB. What
> about DWC3?

I'm assuming DWC3 really breaks. Here's a patch for that:

8<---------------------------------- cut here ----------------------------------
From 62807011c00055785575bb39d92bfe8836817e2f Mon Sep 17 00:00:00 2001
From: Felipe Balbi <felipe.balbi@linux.intel.com>
Date: Thu, 22 Sep 2016 11:01:01 +0300
Subject: [PATCH] usb: dwc3: gadget: set PCM1 field of isochronous-first TRBs

In case of High-Speed, High-Bandwidth endpoints, we
need to tell DWC3 that we have more than one packet
per interval. We do that by setting PCM1 field of
Isochronous-First TRB.

Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
---
 drivers/usb/dwc3/gadget.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 602f12254161..106623faf060 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -787,6 +787,9 @@ static void dwc3_prepare_one_trb(struct dwc3_ep *dep,
 		unsigned length, unsigned chain, unsigned node)
 {
 	struct dwc3_trb		*trb;
+	struct dwc3		*dwc = dep->dwc;
+	struct usb_gadget	*gadget = &dwc->gadget;
+	enum usb_device_speed	speed = speed;
 
 	dwc3_trace(trace_dwc3_gadget, "%s: req %p dma %08llx length %d%s",
 			dep->name, req, (unsigned long long) dma,
@@ -813,10 +816,17 @@ static void dwc3_prepare_one_trb(struct dwc3_ep *dep,
 		break;
 
 	case USB_ENDPOINT_XFER_ISOC:
-		if (!node)
+		if (!node) {
 			trb->ctrl = DWC3_TRBCTL_ISOCHRONOUS_FIRST;
-		else
+
+			if (speed == USB_SPEED_HIGH) {
+				struct usb_endpoint *ep = &dep->endpoint;
+				u8 pkts = DIV_ROUNDUP(ep->maxpacket, 1024);
+				trb->size |= DWC3_TRB_SIZE_PCM1(pkts - 1);
+			}
+		} else {
 			trb->ctrl = DWC3_TRBCTL_ISOCHRONOUS;
+		}
 
 		/* always enable Interrupt on Missed ISOC */
 		trb->ctrl |= DWC3_TRB_CTRL_ISP_IMI;
-- 
2.10.0

Let me know if this helps DWC3, also, let me know how you're using
g_webcam, I'd like to test that out on my side too ;-)

-- 
balbi

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