linux-kernel - [PATCH v2 3/8] media: uvc: Create UVC_QUIRK_IGNORE_EMPTY

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Message-Id: <20220920-resend-hwtimestamp-v2-3-d8d0616bb612@chromium.org>
Date:   Thu, 03 Nov 2022 14:40:44 +0100
From:   Ricardo Ribalda <ribalda@...omium.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     HungNien Chen <hn.chen@...plusit.com>,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        Ricardo Ribalda <ribalda@...omium.org>
Subject: [PATCH v2 3/8] media: uvc: Create UVC_QUIRK_IGNORE_EMPTY_TS quirk

Some Sunplus cameras took a borderline interpretation of the UVC 1.5
standard, and fill the PTS and SCR fields with invalid data if the
package does not contain data.

"STC must be captured when the first video data of a video frame is put
on the USB bus."

Eg:

buffer: 0xa7755c00 len 000012 header:0x8c stc 00000000 sof 0000 pts 00000000
buffer: 0xa7755c00 len 000012 header:0x8c stc 00000000 sof 0000 pts 00000000
buffer: 0xa7755c00 len 000668 header:0x8c stc 73779dba sof 070c pts 7376d37a

This borderline/buggy interpretation has been implemented in a variety
of devices, from directly Sunplus and from other OEMs that rebrand
Sunplus products.

Luckily we can identify the affected modules by looking at the guid of
one of the extension units:

VideoControl Interface Descriptor:
  guidExtensionCode         {82066163-7050-ab49-b8cc-b3855e8d221d}

This patch adds a new quirk to take care of this.

Complete lsusb of one of the affected cameras:

Bus 001 Device 003: ID 1bcf:2a01 Sunplus Innovation Technology Inc.
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.01
  bDeviceClass          239 Miscellaneous Device
  bDeviceSubClass         2 ?
  bDeviceProtocol         1 Interface Association
  bMaxPacketSize0        64
  idVendor           0x1bcf Sunplus Innovation Technology Inc.
  idProduct          0x2a01
  bcdDevice            0.02
  iManufacturer           1 SunplusIT Inc
  iProduct                2 HanChen Wise Camera
  iSerial                 3 01.00.00
  bNumConfigurations      1

Tested-by: HungNien Chen <hn.chen@...plusit.com>
Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>

diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index c63ecfd4617d..80ef0f0e04b0 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -1497,6 +1497,17 @@ static const struct uvc_entity_quirk {
 	u8 guid[16];
 	u32 quirks;
 } uvc_entity_quirk[] = {
+	/*
+	 * Some SunPlus uvc 1.5 device firmware expects that packages with
+	 * no frame data are ignored by the host.
+	 * Therefore it does not clear the PTS/SCR bits in the header, and
+	 * breaks the timestamp decode algorithm.
+	 */
+	{
+		.guid = {0x82, 0x06, 0x61, 0x63, 0x70, 0x50, 0xab, 0x49,
+			 0xb8, 0xcc, 0xb3, 0x85, 0x5e, 0x8d, 0x22, 0x1d},
+		.quirks = UVC_QUIRK_IGNORE_EMPTY_TS,
+	},
 };
 
 static void uvc_entity_quirks(struct uvc_device *dev)
diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index ab56e65ca324..a5b184e71ad7 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -500,6 +500,14 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
 	if (len < header_size)
 		return;
 
+	/*
+	 * Ignore the hardware timestamp on frames with no data on
+	 * miss-behaving devices.
+	 */
+	if (stream->dev->quirks & UVC_QUIRK_IGNORE_EMPTY_TS &&
+	    len == header_size)
+		return;
+
 	/*
 	 * Extract the timestamps:
 	 *
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index 24c911aeebce..f395b67fe95a 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -212,6 +212,7 @@
 #define UVC_QUIRK_RESTORE_CTRLS_ON_INIT	0x00000400
 #define UVC_QUIRK_FORCE_Y8		0x00000800
 #define UVC_QUIRK_FORCE_BPP		0x00001000
+#define UVC_QUIRK_IGNORE_EMPTY_TS	0x00002000
 
 /* Format flags */
 #define UVC_FMT_FLAG_COMPRESSED		0x00000001

-- 
b4 0.11.0-dev-d93f8