linux-kernel - [PATCH] media: uvcvideo: Quirk for hardware with invalid sof

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Message-Id: <20210818202328.267644-1-ribalda@chromium.org>
Date:   Wed, 18 Aug 2021 22:23:28 +0200
From:   Ricardo Ribalda <ribalda@...omium.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Ricardo Ribalda <ribalda@...omium.org>
Subject: [PATCH] media: uvcvideo: Quirk for hardware with invalid sof

The hardware timestamping code has the assumption than the device_sof
and the host_sof run at the same frequency (2048 Hz).

Unfortunately, this is not the case for all the hardware. Add a quirk to
support such hardware.

Note on how to identify such hardware:
When running with "yavta -c /dev/videoX" Look for periodic jumps of the
fps. Eg:

30 (6) [-] none 30 614400 B 21.245557 21.395214 34.133 fps ts mono/SoE
31 (7) [-] none 31 614400 B 21.275327 21.427246 33.591 fps ts mono/SoE
32 (0) [-] none 32 614400 B 21.304739 21.459256 34.000 fps ts mono/SoE
33 (1) [-] none 33 614400 B 21.334324 21.495274 33.801 fps ts mono/SoE
34 (2) [-] none 34 614400 B 21.529237 21.527297 5.130 fps ts mono/SoE
35 (3) [-] none 35 614400 B 21.649416 21.559306 8.321 fps ts mono/SoE
36 (4) [-] none 36 614400 B 21.678789 21.595320 34.045 fps ts mono/SoE
...
99 (3) [-] none 99 614400 B 23.542226 23.696352 33.541 fps ts mono/SoE
100 (4) [-] none 100 614400 B 23.571578 23.728404 34.069 fps ts mono/SoE
101 (5) [-] none 101 614400 B 23.601425 23.760420 33.504 fps ts mono/SoE
102 (6) [-] none 102 614400 B 23.798324 23.796428 5.079 fps ts mono/SoE
103 (7) [-] none 103 614400 B 23.916271 23.828450 8.478 fps ts mono/SoE
104 (0) [-] none 104 614400 B 23.945720 23.860479 33.957 fps ts mono/SoE

They happen because the delta_sof calculated at
uvc_video_clock_host_sof(), wraps periodically, as both clocks drift.

Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
---
 drivers/media/usb/uvc/uvc_driver.c |  9 +++++++++
 drivers/media/usb/uvc/uvc_video.c  | 11 +++++++++--
 drivers/media/usb/uvc/uvcvideo.h   |  2 ++
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index 9a791d8ef200..d1e6cba10b15 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -2771,6 +2771,15 @@ static const struct usb_device_id uvc_ids[] = {
 	  .bInterfaceSubClass	= 1,
 	  .bInterfaceProtocol	= 0,
 	  .driver_info		= UVC_INFO_QUIRK(UVC_QUIRK_RESTORE_CTRLS_ON_INIT) },
+	/* Logitech HD Pro Webcam C922 */
+	{ .match_flags		= USB_DEVICE_ID_MATCH_DEVICE
+				| USB_DEVICE_ID_MATCH_INT_INFO,
+	  .idVendor		= 0x046d,
+	  .idProduct		= 0x085c,
+	  .bInterfaceClass	= USB_CLASS_VIDEO,
+	  .bInterfaceSubClass	= 1,
+	  .bInterfaceProtocol	= 0,
+	  .driver_info		= UVC_INFO_QUIRK(UVC_QUIRK_INVALID_DEVICE_SOF) },
 	/* Chicony CNF7129 (Asus EEE 100HE) */
 	{ .match_flags		= USB_DEVICE_ID_MATCH_DEVICE
 				| USB_DEVICE_ID_MATCH_INT_INFO,
diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index 6d0e474671a2..760ab015cf9c 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -518,13 +518,20 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
 	/* To limit the amount of data, drop SCRs with an SOF identical to the
 	 * previous one.
 	 */
-	dev_sof = get_unaligned_le16(&data[header_size - 2]);
+	if (stream->dev->quirks & UVC_QUIRK_INVALID_DEVICE_SOF)
+		dev_sof = usb_get_current_frame_number(stream->dev->udev);
+	else
+		dev_sof = get_unaligned_le16(&data[header_size - 2]);
+
 	if (dev_sof == stream->clock.last_sof)
 		return;
 
 	stream->clock.last_sof = dev_sof;
 
-	host_sof = usb_get_current_frame_number(stream->dev->udev);
+	if (stream->dev->quirks & UVC_QUIRK_INVALID_DEVICE_SOF)
+		host_sof = dev_sof;
+	else
+		host_sof = usb_get_current_frame_number(stream->dev->udev);
 	time = uvc_video_get_time();
 
 	/* The UVC specification allows device implementations that can't obtain
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index cce5e38133cd..89d909661915 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -209,6 +209,8 @@
 #define UVC_QUIRK_RESTORE_CTRLS_ON_INIT	0x00000400
 #define UVC_QUIRK_FORCE_Y8		0x00000800
 #define UVC_QUIRK_FORCE_BPP		0x00001000
+#define UVC_QUIRK_INVALID_DEVICE_SOF	0x00002000
+
 
 /* Format flags */
 #define UVC_FMT_FLAG_COMPRESSED		0x00000001
-- 
2.33.0.rc2.250.ged5fa647cd-goog