[PATCH v9 0/6] uvcvideo: Fixes for hw timestamping

[PATCH v9 0/6] uvcvideo: Fixes for hw timestamping

[Ricardo Ribalda]

Add some fixes for fixing hw timestamp on some Logitech and SunplusIT
cameras. The issues have been previously reported to the manufacturers.

Also include a patch to fix the current hw timestamping logic for ANY
uvc 1.5 model running at under 16 fps.

@HungNien, the logic for empty_ts has slightly changed since v4, would
be great if you could test it on your end.

To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: linux-media@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: hn.chen <hn.chen@sunplusit.com>
Tested-by: HungNien Chen <hn.chen@sunplusit.com>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>

---
Changes in v9:
- Fix bug on add_sample(). Sorry about that, click on send too fast :S
- Link to v8: https://lore.kernel.org/r/20220920-resend-hwtimestamp-v8-0-0edaca2e2ab3@chromium.org

Changes in v8: Thanks Sergey!
- Move last_sof save into uvc_video_clock_add_sample().
- Improve comments on add_sample().
- Link to v7: https://lore.kernel.org/r/20220920-resend-hwtimestamp-v7-0-cf1d78bb8821@chromium.org

Changes in v7: Thanks Sergey!
- Fix all negative modulus, including old bug
- Improve doc for 1/4 second accuracy.
- Link to v6: https://lore.kernel.org/r/20220920-resend-hwtimestamp-v6-0-c7a99299ec35@chromium.org

Changes in v6 (Thanks Sergey!):
- Rebase on top of linus/master
- Add missing host_sof assignment, ups :(. Sorry about that!
- Improve comments for empty TS quirk
- Link to v5: https://lore.kernel.org/r/20220920-resend-hwtimestamp-v5-0-660679c6e148@chromium.org

Changes in v5: Thanks Dan
- Check for !buf on empty TS packets.
- Link to v4: https://lore.kernel.org/r/20220920-resend-hwtimestamp-v4-0-a8ddc1358a29@chromium.org

Changes in v4 (Thanks Laurent!):
- Rebase on top of pinchart/next/uvc
- Use heuristic for UVC_QUIRK_IGNORE_EMPTY_TS
- Link to v3: https://lore.kernel.org/r/20220920-resend-hwtimestamp-v3-0-db9faee7f47d@chromium.org

Changes in v3 (Thanks Laurent!):
- Rebase on top of pinchart/uvc/next
- Fix hw timestampt handling for slow FPS
  - Improve commit message
- Quirk for invalid dev_sof in Logi C922
  - Improve commit message
- Allow hw clock updates with buffers not full
  - Fix typo and improve messages
- Refactor clock circular buffer
  - Improve commit message
- Quirk for autosuspend in Logi C910
  - Improve commit message
  - Add comments around the quirk
- Create UVC_QUIRK_IGNORE_EMPTY_TS quirk
  - Improve comments
- Allow quirking by entity guid
   - unsinged int
- Extend documentation of uvc_video_clock_decode()
   - uvcvideo on commit message
   - Improve comment
- Link to v2: https://lore.kernel.org/r/20220920-resend-hwtimestamp-v2-0-d8d0616bb612@chromium.org

Changes in v2:
- Require 1/4 sec of data before using the hw timestamps
- Add Tested-by SunplusIT
- Link to v1: https://lore.kernel.org/r/20220920-resend-hwtimestamp-v1-0-e9c14b258404@chromium.org

---
Ricardo Ribalda (6):
      media: uvcvideo: Fix negative modulus calculation
      media: uvcvideo: Ignore empty TS packets
      media: uvcvideo: Quirk for invalid dev_sof in Logitech C922
      media: uvcvideo: Allow hw clock updates with buffers not full
      media: uvcvideo: Refactor clock circular buffer
      media: uvcvideo: Fix hw timestamp handling for slow FPS

 drivers/media/usb/uvc/uvc_driver.c |   9 +++
 drivers/media/usb/uvc/uvc_video.c  | 141 +++++++++++++++++++++++++------------
 drivers/media/usb/uvc/uvcvideo.h   |   2 +
 3 files changed, 108 insertions(+), 44 deletions(-)
---
base-commit: 63355b9884b3d1677de6bd1517cd2b8a9bf53978
change-id: 20220920-resend-hwtimestamp-b3e22729284d

Best regards,
-- 
Ricardo Ribalda <ribalda@chromium.org>

[PATCH v9 1/6] media: uvcvideo: Fix negative modulus calculation

[Ricardo Ribalda]

If head is 0, last will be addressing the index 0 instead of clock->size
-1. Luckily clock->head is unsiged, otherwise it would be addressing
0xffffffff.

Nontheless, this is not the intented behaviour and should be fixed.

Fixes: 66847ef013cc ("[media] uvcvideo: Add UVC timestamps support")
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 drivers/media/usb/uvc/uvc_video.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index d4b023d4de7c..4ff4ab4471fe 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -732,7 +732,7 @@ void uvc_video_clock_update(struct uvc_streaming *stream,
 		goto done;
 
 	first = &clock->samples[clock->head];
-	last = &clock->samples[(clock->head - 1) % clock->size];
+	last = &clock->samples[(clock->head - 1 + clock->size) % clock->size];
 
 	/* First step, PTS to SOF conversion. */
 	delta_stc = buf->pts - (1UL << 31);

-- 
2.40.0.rc1.284.g88254d51c5-goog-b4-0.11.0-dev-696ae

[PATCH v9 2/6] media: uvcvideo: Ignore empty TS packets

[Ricardo Ribalda]

Some SunplusIT 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 SunplusIT and from other OEMs that rebrand
SunplusIT products. So quirking based on VID:PID will be problematic.

All the affected modules have the following extension unit:
VideoControl Interface Descriptor:
  guidExtensionCode         {82066163-7050-ab49-b8cc-b3855e8d221d}

But the vendor plans to use that GUID in the future and fix the bug,
this means that we should use heuristic to figure out the broken
packets.

This patch takes care of this.

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@sunplusit.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 drivers/media/usb/uvc/uvc_video.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index 4ff4ab4471fe..1f416c494acc 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -478,6 +478,7 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
 	ktime_t time;
 	u16 host_sof;
 	u16 dev_sof;
+	u32 dev_stc;
 
 	switch (data[1] & (UVC_STREAM_PTS | UVC_STREAM_SCR)) {
 	case UVC_STREAM_PTS | UVC_STREAM_SCR:
@@ -526,6 +527,23 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
 	if (dev_sof == stream->clock.last_sof)
 		return;
 
+	dev_stc = get_unaligned_le32(&data[header_size - 6]);
+
+	/*
+	 * STC (Source Time Clock) is the clock used by the camera. The UVC 1.5
+	 * standard states that it "must be captured when the first video data
+	 * of a video frame is put on the USB bus".
+	 * Most of the vendors, clear the `UVC_STREAM_SCR` bit when the data is
+	 * not valid, other vendors always set the `UVC_STREAM_SCR` bit and
+	 * expect that the driver only samples the stc if there is data on the
+	 * packet.
+	 * Ignore all the hardware timestamp information if there is no data
+	 * and stc and sof are zero.
+	 */
+	if (buf && buf->bytesused == 0 && len == header_size &&
+	    dev_stc == 0 && dev_sof == 0)
+		return;
+
 	stream->clock.last_sof = dev_sof;
 
 	host_sof = usb_get_current_frame_number(stream->dev->udev);
@@ -564,7 +582,7 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
 	spin_lock_irqsave(&stream->clock.lock, flags);
 
 	sample = &stream->clock.samples[stream->clock.head];
-	sample->dev_stc = get_unaligned_le32(&data[header_size - 6]);
+	sample->dev_stc = dev_stc;
 	sample->dev_sof = dev_sof;
 	sample->host_sof = host_sof;
 	sample->host_time = time;

-- 
2.40.0.rc1.284.g88254d51c5-goog-b4-0.11.0-dev-696ae

[PATCH v9 3/6] media: uvcvideo: Quirk for invalid dev_sof in Logitech C922

[Ricardo Ribalda]

Logitech C922 internal SOF does not increases at a stable rate of 1kHz.
This causes that the device_sof and the host_sof run at different rates,
breaking the clock domain conversion algorithm. 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

Instead of disabling completely the hardware timestamping for such
hardware we take the assumption that the packet handling jitter is
under 2ms and use the host_sof as dev_sof.

We can think of the UVC hardware clock as a system with a coarse clock
(the SOF) and a fine clock (the PTS). The coarse clock can be replaced
with a clock on the same frequency, if the jitter of such clock is
smaller than its sampling rate. That way we can save some of the
precision of the fine clock.

To probe this point we have run three experiments on the Logitech C922.
On that experiment we run the camera at 33fps and we analyse the
difference in msec between a frame and its predecessor. If we display
the histogram of that value, a thinner histogram will mean a better
meassurement. The results for:
- original hw timestamp: https://ibb.co/D1HJJ4x
- pure software timestamp: https://ibb.co/QC9MgVK
- modified hw timestamp: https://ibb.co/8s9dBdk

This bug in the camera firmware has been confirmed by the vendor.

lsusb -v

Bus 001 Device 044: ID 046d:085c Logitech, Inc. C922 Pro Stream Webcam
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass          239 Miscellaneous Device
  bDeviceSubClass         2
  bDeviceProtocol         1 Interface Association
  bMaxPacketSize0        64
  idVendor           0x046d Logitech, Inc.
  idProduct          0x085c C922 Pro Stream Webcam
  bcdDevice            0.16
  iManufacturer           0
  iProduct                2 C922 Pro Stream Webcam
  iSerial                 1 80B912DF
  bNumConfigurations      1

Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 drivers/media/usb/uvc/uvc_driver.c | 9 +++++++++
 drivers/media/usb/uvc/uvc_video.c  | 8 ++++++++
 drivers/media/usb/uvc/uvcvideo.h   | 1 +
 3 files changed, 18 insertions(+)

diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index 7aefa76a42b3..678a5736c9df 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -2549,6 +2549,15 @@ 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 1f416c494acc..4d566edb73e7 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -547,6 +547,14 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
 	stream->clock.last_sof = dev_sof;
 
 	host_sof = usb_get_current_frame_number(stream->dev->udev);
+
+	/*
+	 * On some devices, like the Logitech C922, the device SOF does not run
+	 * at a stable rate of 1kHz. For those devices use the host SOF instead.
+	 */
+	if (stream->dev->quirks & UVC_QUIRK_INVALID_DEVICE_SOF)
+		dev_sof = host_sof;
+
 	time = uvc_video_get_time();
 
 	/*
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index 9a596c8d894a..07b2fdb80adf 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -73,6 +73,7 @@
 #define UVC_QUIRK_FORCE_Y8		0x00000800
 #define UVC_QUIRK_FORCE_BPP		0x00001000
 #define UVC_QUIRK_WAKE_AUTOSUSPEND	0x00002000
+#define UVC_QUIRK_INVALID_DEVICE_SOF	0x00004000
 
 /* Format flags */
 #define UVC_FMT_FLAG_COMPRESSED		0x00000001

-- 
2.40.0.rc1.284.g88254d51c5-goog-b4-0.11.0-dev-696ae

[PATCH v9 4/6] media: uvcvideo: Allow hw clock updates with buffers not full

[Ricardo Ribalda]

With UVC 1.5 we get as little as one clock sample per frame. Which means
that it takes 32 frames to move from the software timestamp to the
hardware timestamp method.

This results in abrupt changes in the timestamping after 32 frames (~1
second), resulting in noticeable artifacts when used for encoding.

With this patch we modify the update algorithm to work with whatever
amount of values are available.

Tested-by: HungNien Chen <hn.chen@sunplusit.com>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 drivers/media/usb/uvc/uvc_video.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index 4d566edb73e7..6d0243ea0e07 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -754,10 +754,10 @@ void uvc_video_clock_update(struct uvc_streaming *stream,
 
 	spin_lock_irqsave(&clock->lock, flags);
 
-	if (clock->count < clock->size)
+	if (clock->count < 2)
 		goto done;
 
-	first = &clock->samples[clock->head];
+	first = &clock->samples[(clock->head - clock->count + clock->size) % clock->size];
 	last = &clock->samples[(clock->head - 1 + clock->size) % clock->size];
 
 	/* First step, PTS to SOF conversion. */
@@ -772,6 +772,17 @@ void uvc_video_clock_update(struct uvc_streaming *stream,
 	if (y2 < y1)
 		y2 += 2048 << 16;
 
+	/*
+	 * Have at least 1/4 of a second of timestamps before we
+	 * try to do any calculation. Otherwise we do not have enough
+	 * precision. This value was determined by running Android CTS
+	 * on different devices.
+	 * Dev_sof runs at 1KHz, and we have a fixed point precision of
+	 * 16 bits.
+	 */
+	if ((y2 - y1) < ( (1000 / 4) << 16))
+		goto done;
+
 	y = (u64)(y2 - y1) * (1ULL << 31) + (u64)y1 * (u64)x2
 	  - (u64)y2 * (u64)x1;
 	y = div_u64(y, x2 - x1);

-- 
2.40.0.rc1.284.g88254d51c5-goog-b4-0.11.0-dev-696ae

[PATCH v9 5/6] media: uvcvideo: Refactor clock circular buffer

[Ricardo Ribalda]

Isolate all the changes related to the clock circular buffer to its own
function, that way we can make changes easier to the buffer logic.

Also simplify the lock, by removing the circular buffer clock handling
from uvc_video_clock_decode().

And now that we are at it, unify the API of the clock functions.

Tested-by: HungNien Chen <hn.chen@sunplusit.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 drivers/media/usb/uvc/uvc_video.c | 84 ++++++++++++++++++---------------------
 1 file changed, 38 insertions(+), 46 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index 6d0243ea0e07..1db0d1bc80e6 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -466,19 +466,30 @@ static inline ktime_t uvc_video_get_time(void)
 		return ktime_get_real();
 }
 
+static void uvc_video_clock_add_sample(struct uvc_clock *clock,
+				       const struct uvc_clock_sample *sample)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&clock->lock, flags);
+
+	memcpy(&clock->samples[clock->head], sample, sizeof(*sample));
+	clock->head = (clock->head + 1) % clock->size;
+	clock->count = min(clock->count + 1, clock->size);
+
+	spin_unlock_irqrestore(&clock->lock, flags);
+
+	clock->last_sof = sample->dev_sof;
+}
+
 static void
 uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
 		       const u8 *data, int len)
 {
-	struct uvc_clock_sample *sample;
+	struct uvc_clock_sample sample;
 	unsigned int header_size;
 	bool has_pts = false;
 	bool has_scr = false;
-	unsigned long flags;
-	ktime_t time;
-	u16 host_sof;
-	u16 dev_sof;
-	u32 dev_stc;
 
 	switch (data[1] & (UVC_STREAM_PTS | UVC_STREAM_SCR)) {
 	case UVC_STREAM_PTS | UVC_STREAM_SCR:
@@ -523,11 +534,11 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
 	 * all the data packets of the same frame contains the same SOF. In that
 	 * case only the first one will match the host_sof.
 	 */
-	dev_sof = get_unaligned_le16(&data[header_size - 2]);
-	if (dev_sof == stream->clock.last_sof)
+	sample.dev_sof = get_unaligned_le16(&data[header_size - 2]);
+	if (sample.dev_sof == stream->clock.last_sof)
 		return;
 
-	dev_stc = get_unaligned_le32(&data[header_size - 6]);
+	sample.dev_stc = get_unaligned_le32(&data[header_size - 6]);
 
 	/*
 	 * STC (Source Time Clock) is the clock used by the camera. The UVC 1.5
@@ -541,21 +552,19 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
 	 * and stc and sof are zero.
 	 */
 	if (buf && buf->bytesused == 0 && len == header_size &&
-	    dev_stc == 0 && dev_sof == 0)
+	    sample.dev_stc == 0 && sample.dev_sof == 0)
 		return;
 
-	stream->clock.last_sof = dev_sof;
-
-	host_sof = usb_get_current_frame_number(stream->dev->udev);
+	sample.host_sof = usb_get_current_frame_number(stream->dev->udev);
 
 	/*
 	 * On some devices, like the Logitech C922, the device SOF does not run
 	 * at a stable rate of 1kHz. For those devices use the host SOF instead.
 	 */
 	if (stream->dev->quirks & UVC_QUIRK_INVALID_DEVICE_SOF)
-		dev_sof = host_sof;
+		sample.dev_sof = sample.host_sof;
 
-	time = uvc_video_get_time();
+	sample.host_time = uvc_video_get_time();
 
 	/*
 	 * The UVC specification allows device implementations that can't obtain
@@ -578,46 +587,29 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
 	 * the 8 LSBs of the delta are kept.
 	 */
 	if (stream->clock.sof_offset == (u16)-1) {
-		u16 delta_sof = (host_sof - dev_sof) & 255;
+		u16 delta_sof = (sample.host_sof - sample.dev_sof) & 255;
 		if (delta_sof >= 10)
 			stream->clock.sof_offset = delta_sof;
 		else
 			stream->clock.sof_offset = 0;
 	}
 
-	dev_sof = (dev_sof + stream->clock.sof_offset) & 2047;
-
-	spin_lock_irqsave(&stream->clock.lock, flags);
-
-	sample = &stream->clock.samples[stream->clock.head];
-	sample->dev_stc = dev_stc;
-	sample->dev_sof = dev_sof;
-	sample->host_sof = host_sof;
-	sample->host_time = time;
-
-	/* Update the sliding window head and count. */
-	stream->clock.head = (stream->clock.head + 1) % stream->clock.size;
+	sample.dev_sof = (sample.dev_sof + stream->clock.sof_offset) & 2047;
+	sample.dev_stc = get_unaligned_le32(&data[header_size - 6]);
 
-	if (stream->clock.count < stream->clock.size)
-		stream->clock.count++;
-
-	spin_unlock_irqrestore(&stream->clock.lock, flags);
+	uvc_video_clock_add_sample(&stream->clock, &sample);
 }
 
-static void uvc_video_clock_reset(struct uvc_streaming *stream)
+static void uvc_video_clock_reset(struct uvc_clock *clock)
 {
-	struct uvc_clock *clock = &stream->clock;
-
 	clock->head = 0;
 	clock->count = 0;
 	clock->last_sof = -1;
 	clock->sof_offset = -1;
 }
 
-static int uvc_video_clock_init(struct uvc_streaming *stream)
+static int uvc_video_clock_init(struct uvc_clock *clock)
 {
-	struct uvc_clock *clock = &stream->clock;
-
 	spin_lock_init(&clock->lock);
 	clock->size = 32;
 
@@ -626,15 +618,15 @@ static int uvc_video_clock_init(struct uvc_streaming *stream)
 	if (clock->samples == NULL)
 		return -ENOMEM;
 
-	uvc_video_clock_reset(stream);
+	uvc_video_clock_reset(clock);
 
 	return 0;
 }
 
-static void uvc_video_clock_cleanup(struct uvc_streaming *stream)
+static void uvc_video_clock_cleanup(struct uvc_clock *clock)
 {
-	kfree(stream->clock.samples);
-	stream->clock.samples = NULL;
+	kfree(clock->samples);
+	clock->samples = NULL;
 }
 
 /*
@@ -2108,7 +2100,7 @@ int uvc_video_resume(struct uvc_streaming *stream, int reset)
 
 	stream->frozen = 0;
 
-	uvc_video_clock_reset(stream);
+	uvc_video_clock_reset(&stream->clock);
 
 	if (!uvc_queue_streaming(&stream->queue))
 		return 0;
@@ -2257,7 +2249,7 @@ int uvc_video_start_streaming(struct uvc_streaming *stream)
 {
 	int ret;
 
-	ret = uvc_video_clock_init(stream);
+	ret = uvc_video_clock_init(&stream->clock);
 	if (ret < 0)
 		return ret;
 
@@ -2275,7 +2267,7 @@ int uvc_video_start_streaming(struct uvc_streaming *stream)
 error_video:
 	usb_set_interface(stream->dev->udev, stream->intfnum, 0);
 error_commit:
-	uvc_video_clock_cleanup(stream);
+	uvc_video_clock_cleanup(&stream->clock);
 
 	return ret;
 }
@@ -2303,5 +2295,5 @@ void uvc_video_stop_streaming(struct uvc_streaming *stream)
 		usb_clear_halt(stream->dev->udev, pipe);
 	}
 
-	uvc_video_clock_cleanup(stream);
+	uvc_video_clock_cleanup(&stream->clock);
 }

-- 
2.40.0.rc1.284.g88254d51c5-goog-b4-0.11.0-dev-696ae

[PATCH v9 6/6] media: uvcvideo: Fix hw timestamp handling for slow FPS

[Ricardo Ribalda]

In UVC 1.5 we get a single clock value per frame. With the current
buffer size of 32, FPS slowers than 32 might roll-over twice.

The current code cannot handle two roll-over and provide invalid
timestamps.

Revome all the samples from the circular buffer that are more than two
rollovers old, so the algorithm always provides good timestamps.

Note that we are removing values that are more than one second old,
which means that there is enough distance between the two points that
we use for the interpolation to provide good values.

Tested-by: HungNien Chen <hn.chen@sunplusit.com>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 drivers/media/usb/uvc/uvc_video.c | 24 ++++++++++++++++++++++++
 drivers/media/usb/uvc/uvcvideo.h  |  1 +
 2 files changed, 25 insertions(+)

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index 1db0d1bc80e6..c58b51207be6 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -471,8 +471,31 @@ static void uvc_video_clock_add_sample(struct uvc_clock *clock,
 {
 	unsigned long flags;
 
+	/*
+	 * If we write new data on the position where we had the last
+	 * overflow, remove the overflow pointer. There is no overflow
+	 * on the whole circular buffer.
+	 */
+	if (clock->head == clock->last_sof_overflow)
+		clock->last_sof_overflow = -1;
+
 	spin_lock_irqsave(&clock->lock, flags);
 
+	/* Handle overflows */
+	if (clock->count > 0 && clock->last_sof > sample->dev_sof) {
+		/*
+		 * Remove data from the circular buffer that is older than the
+		 * last overflow. We only support one overflow per circular
+		 * buffer.
+		 */
+		if (clock->last_sof_overflow != -1) {
+			clock->count = (clock->head - clock->last_sof_overflow
+					+ clock->count)	% clock->count;
+		}
+		clock->last_sof_overflow = clock->head;
+	}
+
+	/* Add sample */
 	memcpy(&clock->samples[clock->head], sample, sizeof(*sample));
 	clock->head = (clock->head + 1) % clock->size;
 	clock->count = min(clock->count + 1, clock->size);
@@ -605,6 +628,7 @@ static void uvc_video_clock_reset(struct uvc_clock *clock)
 	clock->head = 0;
 	clock->count = 0;
 	clock->last_sof = -1;
+	clock->last_sof_overflow = -1;
 	clock->sof_offset = -1;
 }
 
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index 07b2fdb80adf..bf9f5162b833 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -499,6 +499,7 @@ struct uvc_streaming {
 		unsigned int head;
 		unsigned int count;
 		unsigned int size;
+		unsigned int last_sof_overflow;
 
 		u16 last_sof;
 		u16 sof_offset;

-- 
2.40.0.rc1.284.g88254d51c5-goog-b4-0.11.0-dev-696ae

Re: [PATCH v9 1/6] media: uvcvideo: Fix negative modulus calculation

[Sergey Senozhatsky]

On (23/03/15 14:30), Ricardo Ribalda wrote:
> 
> If head is 0, last will be addressing the index 0 instead of clock->size
> -1. Luckily clock->head is unsiged, otherwise it would be addressing
> 0xffffffff.
> 
> Nontheless, this is not the intented behaviour and should be fixed.
> 
> Fixes: 66847ef013cc ("[media] uvcvideo: Add UVC timestamps support")
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>

Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>

Re: [PATCH v9 6/6] media: uvcvideo: Fix hw timestamp handling for slow FPS

[Sergey Senozhatsky]

On (23/03/15 14:30), Ricardo Ribalda wrote:
> In UVC 1.5 we get a single clock value per frame. With the current
> buffer size of 32, FPS slowers than 32 might roll-over twice.
> 
> The current code cannot handle two roll-over and provide invalid
> timestamps.
> 
> Revome all the samples from the circular buffer that are more than two
> rollovers old, so the algorithm always provides good timestamps.
> 
> Note that we are removing values that are more than one second old,
> which means that there is enough distance between the two points that
> we use for the interpolation to provide good values.
> 
> Tested-by: HungNien Chen <hn.chen@sunplusit.com>
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>

Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>

[..]
> +	if (clock->count > 0 && clock->last_sof > sample->dev_sof) {
> +		/*
> +		 * Remove data from the circular buffer that is older than the
> +		 * last overflow. We only support one overflow per circular
> +		 * buffer.
> +		 */
> +		if (clock->last_sof_overflow != -1) {
> +			clock->count = (clock->head - clock->last_sof_overflow
> +					+ clock->count)	% clock->count;

A minor nit: there is a tab between `clock->count)` and `% clock->count` :)

Re: [PATCH v9 4/6] media: uvcvideo: Allow hw clock updates with buffers not full

[Sergey Senozhatsky]

On (23/03/15 14:30), Ricardo Ribalda wrote:
> With UVC 1.5 we get as little as one clock sample per frame. Which means
> that it takes 32 frames to move from the software timestamp to the
> hardware timestamp method.
> 
> This results in abrupt changes in the timestamping after 32 frames (~1
> second), resulting in noticeable artifacts when used for encoding.
> 
> With this patch we modify the update algorithm to work with whatever
> amount of values are available.
> 
> Tested-by: HungNien Chen <hn.chen@sunplusit.com>
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>

Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>

> +	 * Have at least 1/4 of a second of timestamps before we
> +	 * try to do any calculation. Otherwise we do not have enough
> +	 * precision. This value was determined by running Android CTS
> +	 * on different devices.
> +	 * Dev_sof runs at 1KHz, and we have a fixed point precision of
> +	 * 16 bits.
> +	 */
> +	if ((y2 - y1) < ( (1000 / 4) << 16))

A minor nit: extra space `( (` :)

Re: [PATCH v9 1/6] media: uvcvideo: Fix negative modulus calculation

[Laurent Pinchart]

Hi Ricardo,

Thank you for the patch.

On Wed, Mar 15, 2023 at 02:30:12PM +0100, Ricardo Ribalda wrote:
> If head is 0, last will be addressing the index 0 instead of clock->size
> -1. Luckily clock->head is unsiged, otherwise it would be addressing
> 0xffffffff.

I'm not following you. In the expression

	(clock->head - 1) % clock->size

clock->head is an unsigned int, and 1 as a signed int, so the result of
the subtraction is promoted to an unsigned int. When clock->head is 0, the expression evaluates to

	0xffffffff % clock->size

clock->size is a power of two (hardcoded to 32 at the moment), so the
expression evaluates to 31, as intended.

Am I missing something ?

> Nontheless, this is not the intented behaviour and should be fixed.
> 
> Fixes: 66847ef013cc ("[media] uvcvideo: Add UVC timestamps support")
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
>  drivers/media/usb/uvc/uvc_video.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> index d4b023d4de7c..4ff4ab4471fe 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -732,7 +732,7 @@ void uvc_video_clock_update(struct uvc_streaming *stream,
>  		goto done;
>  
>  	first = &clock->samples[clock->head];
> -	last = &clock->samples[(clock->head - 1) % clock->size];
> +	last = &clock->samples[(clock->head - 1 + clock->size) % clock->size];
>  
>  	/* First step, PTS to SOF conversion. */
>  	delta_stc = buf->pts - (1UL << 31);

-- 
Regards,

Laurent Pinchart

Re: [PATCH v9 1/6] media: uvcvideo: Fix negative modulus calculation

[Ricardo Ribalda]

Hi Laurent

On Mon, 12 Feb 2024 at 23:59, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Ricardo,
>
> Thank you for the patch.
>
> On Wed, Mar 15, 2023 at 02:30:12PM +0100, Ricardo Ribalda wrote:
> > If head is 0, last will be addressing the index 0 instead of clock->size
> > -1. Luckily clock->head is unsiged, otherwise it would be addressing
> > 0xffffffff.
>
> I'm not following you. In the expression
>
>         (clock->head - 1) % clock->size
>
> clock->head is an unsigned int, and 1 as a signed int, so the result of
> the subtraction is promoted to an unsigned int. When clock->head is 0, the expression evaluates to
>
>         0xffffffff % clock->size
>
> clock->size is a power of two (hardcoded to 32 at the moment), so the
> expression evaluates to 31, as intended.
>
> Am I missing something ?

Take a look to: https://godbolt.org/z/xYeqTx6ba

The expression only works because the size is a power of two. In this
set I am allowing sizes that are not powers of two.

Regards!




>
> > Nontheless, this is not the intented behaviour and should be fixed.
> >
> > Fixes: 66847ef013cc ("[media] uvcvideo: Add UVC timestamps support")
> > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > ---
> >  drivers/media/usb/uvc/uvc_video.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > index d4b023d4de7c..4ff4ab4471fe 100644
> > --- a/drivers/media/usb/uvc/uvc_video.c
> > +++ b/drivers/media/usb/uvc/uvc_video.c
> > @@ -732,7 +732,7 @@ void uvc_video_clock_update(struct uvc_streaming *stream,
> >               goto done;
> >
> >       first = &clock->samples[clock->head];
> > -     last = &clock->samples[(clock->head - 1) % clock->size];
> > +     last = &clock->samples[(clock->head - 1 + clock->size) % clock->size];
> >
> >       /* First step, PTS to SOF conversion. */
> >       delta_stc = buf->pts - (1UL << 31);
>
> --
> Regards,
>
> Laurent Pinchart



--
Ricardo Ribalda

Re: [PATCH v9 1/6] media: uvcvideo: Fix negative modulus calculation

[Laurent Pinchart]

Hi Ricardo,

On Mon, Feb 19, 2024 at 11:28:03AM +0100, Ricardo Ribalda wrote:
> On Mon, 12 Feb 2024 at 23:59, Laurent Pinchart wrote:
> > On Wed, Mar 15, 2023 at 02:30:12PM +0100, Ricardo Ribalda wrote:
> > > If head is 0, last will be addressing the index 0 instead of clock->size
> > > -1. Luckily clock->head is unsiged, otherwise it would be addressing
> > > 0xffffffff.
> >
> > I'm not following you. In the expression
> >
> >         (clock->head - 1) % clock->size
> >
> > clock->head is an unsigned int, and 1 as a signed int, so the result of
> > the subtraction is promoted to an unsigned int. When clock->head is 0, the expression evaluates to
> >
> >         0xffffffff % clock->size
> >
> > clock->size is a power of two (hardcoded to 32 at the moment), so the
> > expression evaluates to 31, as intended.
> >
> > Am I missing something ?
> 
> Take a look to: https://godbolt.org/z/xYeqTx6ba
> 
> The expression only works because the size is a power of two. In this
> set I am allowing sizes that are not powers of two.

Could you then update the commit message to explain that ?

I'll review the rest of the series this week.

> > > Nontheless, this is not the intented behaviour and should be fixed.
> > >
> > > Fixes: 66847ef013cc ("[media] uvcvideo: Add UVC timestamps support")
> > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > > ---
> > >  drivers/media/usb/uvc/uvc_video.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > > index d4b023d4de7c..4ff4ab4471fe 100644
> > > --- a/drivers/media/usb/uvc/uvc_video.c
> > > +++ b/drivers/media/usb/uvc/uvc_video.c
> > > @@ -732,7 +732,7 @@ void uvc_video_clock_update(struct uvc_streaming *stream,
> > >               goto done;
> > >
> > >       first = &clock->samples[clock->head];
> > > -     last = &clock->samples[(clock->head - 1) % clock->size];
> > > +     last = &clock->samples[(clock->head - 1 + clock->size) % clock->size];
> > >
> > >       /* First step, PTS to SOF conversion. */
> > >       delta_stc = buf->pts - (1UL << 31);

-- 
Regards,

Laurent Pinchart

Re: [PATCH v9 1/6] media: uvcvideo: Fix negative modulus calculation

[Ricardo Ribalda]

Hi Laurent

On Mon, 19 Feb 2024 at 11:40, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Ricardo,
>
> On Mon, Feb 19, 2024 at 11:28:03AM +0100, Ricardo Ribalda wrote:
> > On Mon, 12 Feb 2024 at 23:59, Laurent Pinchart wrote:
> > > On Wed, Mar 15, 2023 at 02:30:12PM +0100, Ricardo Ribalda wrote:
> > > > If head is 0, last will be addressing the index 0 instead of clock->size
> > > > -1. Luckily clock->head is unsiged, otherwise it would be addressing
> > > > 0xffffffff.
> > >
> > > I'm not following you. In the expression
> > >
> > >         (clock->head - 1) % clock->size
> > >
> > > clock->head is an unsigned int, and 1 as a signed int, so the result of
> > > the subtraction is promoted to an unsigned int. When clock->head is 0, the expression evaluates to
> > >
> > >         0xffffffff % clock->size
> > >
> > > clock->size is a power of two (hardcoded to 32 at the moment), so the
> > > expression evaluates to 31, as intended.
> > >
> > > Am I missing something ?
> >
> > Take a look to: https://godbolt.org/z/xYeqTx6ba
> >
> > The expression only works because the size is a power of two. In this
> > set I am allowing sizes that are not powers of two.
>
> Could you then update the commit message to explain that ?
>
> I'll review the rest of the series this week.
Thanks

Will update with the following text after the review:

The tail of the list lives at the position before the head. This is
mathematically noted as
```
(head-1)  mod size.
```

Unfortunately C, does not have a modulus operator, but a remainder
operator (%).
The reminder operation has a different result than the modulus if
(head -1) is a negative number and size is not a power of two.

Adding size to (head-1) allows the code to run with any value of size.

>
> > > > Nontheless, this is not the intented behaviour and should be fixed.
> > > >
> > > > Fixes: 66847ef013cc ("[media] uvcvideo: Add UVC timestamps support")
> > > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > > > ---
> > > >  drivers/media/usb/uvc/uvc_video.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > > > index d4b023d4de7c..4ff4ab4471fe 100644
> > > > --- a/drivers/media/usb/uvc/uvc_video.c
> > > > +++ b/drivers/media/usb/uvc/uvc_video.c
> > > > @@ -732,7 +732,7 @@ void uvc_video_clock_update(struct uvc_streaming *stream,
> > > >               goto done;
> > > >
> > > >       first = &clock->samples[clock->head];
> > > > -     last = &clock->samples[(clock->head - 1) % clock->size];
> > > > +     last = &clock->samples[(clock->head - 1 + clock->size) % clock->size];
> > > >
> > > >       /* First step, PTS to SOF conversion. */
> > > >       delta_stc = buf->pts - (1UL << 31);
>
> --
> Regards,
>
> Laurent Pinchart



-- 
Ricardo Ribalda

Re: [PATCH v9 1/6] media: uvcvideo: Fix negative modulus calculation

[Laurent Pinchart]

Hi Ricardo,

On Mon, Feb 19, 2024 at 04:07:12PM +0100, Ricardo Ribalda wrote:
> On Mon, 19 Feb 2024 at 11:40, Laurent Pinchart wrote:
> > On Mon, Feb 19, 2024 at 11:28:03AM +0100, Ricardo Ribalda wrote:
> > > On Mon, 12 Feb 2024 at 23:59, Laurent Pinchart wrote:
> > > > On Wed, Mar 15, 2023 at 02:30:12PM +0100, Ricardo Ribalda wrote:
> > > > > If head is 0, last will be addressing the index 0 instead of clock->size
> > > > > -1. Luckily clock->head is unsiged, otherwise it would be addressing
> > > > > 0xffffffff.
> > > >
> > > > I'm not following you. In the expression
> > > >
> > > >         (clock->head - 1) % clock->size
> > > >
> > > > clock->head is an unsigned int, and 1 as a signed int, so the result of
> > > > the subtraction is promoted to an unsigned int. When clock->head is 0, the expression evaluates to
> > > >
> > > >         0xffffffff % clock->size
> > > >
> > > > clock->size is a power of two (hardcoded to 32 at the moment), so the
> > > > expression evaluates to 31, as intended.
> > > >
> > > > Am I missing something ?
> > >
> > > Take a look to: https://godbolt.org/z/xYeqTx6ba
> > >
> > > The expression only works because the size is a power of two. In this
> > > set I am allowing sizes that are not powers of two.
> >
> > Could you then update the commit message to explain that ?
> >
> > I'll review the rest of the series this week.
> Thanks
> 
> Will update with the following text after the review:
> 
> The tail of the list lives at the position before the head. This is
> mathematically noted as
> ```
> (head-1)  mod size.
> ```
> 
> Unfortunately C, does not have a modulus operator, but a remainder
> operator (%).
> The reminder operation has a different result than the modulus if
> (head -1) is a negative number and size is not a power of two.
> 
> Adding size to (head-1) allows the code to run with any value of size.

Could you please add

This does not change the current behaviour of the driver, as the size is
always a power of two, but prepares for reworks that will change the
size to a non power of two.

or something similar ?

> > > > > Nontheless, this is not the intented behaviour and should be fixed.
> > > > >
> > > > > Fixes: 66847ef013cc ("[media] uvcvideo: Add UVC timestamps support")

I think this should be dropped, the patch doesn't fix an issue, but
prepares for further changes that add new features. I'd also like to
update the commit message to avoid stating "Fix", to avoid this being
picked for stable kernels automatically.

> > > > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > > > > ---
> > > > >  drivers/media/usb/uvc/uvc_video.c | 2 +-
> > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > > > > index d4b023d4de7c..4ff4ab4471fe 100644
> > > > > --- a/drivers/media/usb/uvc/uvc_video.c
> > > > > +++ b/drivers/media/usb/uvc/uvc_video.c
> > > > > @@ -732,7 +732,7 @@ void uvc_video_clock_update(struct uvc_streaming *stream,
> > > > >               goto done;
> > > > >
> > > > >       first = &clock->samples[clock->head];
> > > > > -     last = &clock->samples[(clock->head - 1) % clock->size];
> > > > > +     last = &clock->samples[(clock->head - 1 + clock->size) % clock->size];
> > > > >
> > > > >       /* First step, PTS to SOF conversion. */
> > > > >       delta_stc = buf->pts - (1UL << 31);

-- 
Regards,

Laurent Pinchart

Re: [PATCH v9 2/6] media: uvcvideo: Ignore empty TS packets

[Laurent Pinchart]

Hi Ricardo,

Thank you for the patch.

On Wed, Mar 15, 2023 at 02:30:13PM +0100, Ricardo Ribalda wrote:
> Some SunplusIT 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:

"Some SunplusIT devices send, e.g.,"

> 
> 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

"while the UVC specification meant that the first two packets shouldn't
have had the SCR bit set in the header."

> 
> This borderline/buggy interpretation has been implemented in a variety
> of devices, from directly SunplusIT and from other OEMs that rebrand
> SunplusIT products. So quirking based on VID:PID will be problematic.
> 
> All the affected modules have the following extension unit:
> VideoControl Interface Descriptor:
>   guidExtensionCode         {82066163-7050-ab49-b8cc-b3855e8d221d}
> 
> But the vendor plans to use that GUID in the future and fix the bug,
> this means that we should use heuristic to figure out the broken
> packets.

Because it would have been too easy otherwise of course :-)

> 
> This patch takes care of this.
> 
> 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@sunplusit.com>
> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
>  drivers/media/usb/uvc/uvc_video.c | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> index 4ff4ab4471fe..1f416c494acc 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -478,6 +478,7 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
>  	ktime_t time;
>  	u16 host_sof;
>  	u16 dev_sof;
> +	u32 dev_stc;
>  
>  	switch (data[1] & (UVC_STREAM_PTS | UVC_STREAM_SCR)) {
>  	case UVC_STREAM_PTS | UVC_STREAM_SCR:
> @@ -526,6 +527,23 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
>  	if (dev_sof == stream->clock.last_sof)
>  		return;
>  
> +	dev_stc = get_unaligned_le32(&data[header_size - 6]);
> +
> +	/*
> +	 * STC (Source Time Clock) is the clock used by the camera. The UVC 1.5
> +	 * standard states that it "must be captured when the first video data
> +	 * of a video frame is put on the USB bus".
> +	 * Most of the vendors, clear the `UVC_STREAM_SCR` bit when the data is
> +	 * not valid, other vendors always set the `UVC_STREAM_SCR` bit and
> +	 * expect that the driver only samples the stc if there is data on the
> +	 * packet.
> +	 * Ignore all the hardware timestamp information if there is no data
> +	 * and stc and sof are zero.
> +	 */

I'd like to expand this a bit (partly to make sure I understand the
issue correctly):

        /*
         * STC (Source Time Clock) is the clock used by the camera. The UVC 1.5
         * standard states that it "must be captured when the first video data
         * of a video frame is put on the USB bus". This is generally understood
         * as requiring devices to clear the payload header's SCR bit before
         * the first packet containing video data.
         *
         * Most vendors follow that interpretation, but some (namely SunplusIT)
         * always set the `UVC_STREAM_SCR` bit, fill the SCR field with 0's,
         * and expect that the driver only processes the SCR if there is data in
         * the packet.
         *
         * Ignore all the hardware timestamp information if we haven't received
         * any data for this frame yet, the packet contains no data, and both
         * STC and SOF are zero. This heuristics should be safe on compliant
         * devices. This should be safe with compliant devices, as in the very
         * unlikely case where a UVC 1.1 device would send timing information
         * only before the first packet containing data, and both STC and SOF
         * happen to be zero for a particular frame, we would only miss one
         * clock sample and the clock recovery algorithm wouldn't suffer from
         * this condition.
         */

Is this correct (and fine with you) ? If so,

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> +	if (buf && buf->bytesused == 0 && len == header_size &&
> +	    dev_stc == 0 && dev_sof == 0)
> +		return;
> +
>  	stream->clock.last_sof = dev_sof;
>  
>  	host_sof = usb_get_current_frame_number(stream->dev->udev);
> @@ -564,7 +582,7 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
>  	spin_lock_irqsave(&stream->clock.lock, flags);
>  
>  	sample = &stream->clock.samples[stream->clock.head];
> -	sample->dev_stc = get_unaligned_le32(&data[header_size - 6]);
> +	sample->dev_stc = dev_stc;
>  	sample->dev_sof = dev_sof;
>  	sample->host_sof = host_sof;
>  	sample->host_time = time;
> 

-- 
Regards,

Laurent Pinchart

Re: [PATCH v9 3/6] media: uvcvideo: Quirk for invalid dev_sof in Logitech C922

[Laurent Pinchart]

Hi Ricardo,

Thank you for the patch.

On Wed, Mar 15, 2023 at 02:30:14PM +0100, Ricardo Ribalda wrote:
> Logitech C922 internal SOF does not increases at a stable rate of 1kHz.

The next thing you know they will redefine to value of pi to be 3.

> This causes that the device_sof and the host_sof run at different rates,
> breaking the clock domain conversion algorithm. 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
> 
> Instead of disabling completely the hardware timestamping for such
> hardware we take the assumption that the packet handling jitter is
> under 2ms and use the host_sof as dev_sof.
> 
> We can think of the UVC hardware clock as a system with a coarse clock
> (the SOF) and a fine clock (the PTS). The coarse clock can be replaced
> with a clock on the same frequency, if the jitter of such clock is
> smaller than its sampling rate. That way we can save some of the
> precision of the fine clock.
> 
> To probe this point we have run three experiments on the Logitech C922.
> On that experiment we run the camera at 33fps and we analyse the
> difference in msec between a frame and its predecessor. If we display
> the histogram of that value, a thinner histogram will mean a better
> meassurement. The results for:
> - original hw timestamp: https://ibb.co/D1HJJ4x
> - pure software timestamp: https://ibb.co/QC9MgVK
> - modified hw timestamp: https://ibb.co/8s9dBdk
> 
> This bug in the camera firmware has been confirmed by the vendor.
> 
> lsusb -v
> 
> Bus 001 Device 044: ID 046d:085c Logitech, Inc. C922 Pro Stream Webcam
> Device Descriptor:
>   bLength                18
>   bDescriptorType         1
>   bcdUSB               2.00
>   bDeviceClass          239 Miscellaneous Device
>   bDeviceSubClass         2
>   bDeviceProtocol         1 Interface Association
>   bMaxPacketSize0        64
>   idVendor           0x046d Logitech, Inc.
>   idProduct          0x085c C922 Pro Stream Webcam
>   bcdDevice            0.16
>   iManufacturer           0
>   iProduct                2 C922 Pro Stream Webcam
>   iSerial                 1 80B912DF
>   bNumConfigurations      1
> 
> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
>  drivers/media/usb/uvc/uvc_driver.c | 9 +++++++++
>  drivers/media/usb/uvc/uvc_video.c  | 8 ++++++++
>  drivers/media/usb/uvc/uvcvideo.h   | 1 +
>  3 files changed, 18 insertions(+)
> 
> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> index 7aefa76a42b3..678a5736c9df 100644
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -2549,6 +2549,15 @@ 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 1f416c494acc..4d566edb73e7 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -547,6 +547,14 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
>  	stream->clock.last_sof = dev_sof;
>  
>  	host_sof = usb_get_current_frame_number(stream->dev->udev);
> +
> +	/*
> +	 * On some devices, like the Logitech C922, the device SOF does not run
> +	 * at a stable rate of 1kHz. For those devices use the host SOF instead.

I'm still not very convinced, as without a formal proof I think there's
some luck involved, and it may break later. This being said, given that
this is gated by a quirk, it won't impact other devices, and we can deal
with regressions when they happen. Could we record it here:

	 * On some devices, like the Logitech C922, the device SOF does not run
	 * at a stable rate of 1kHz. For those devices use the host SOF instead.
	 * This improves the timestamp precision in the tests performed so far,
	 * even if the exact reason hasn't been fully determined.

or something along those lines ?

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> +	 */
> +	if (stream->dev->quirks & UVC_QUIRK_INVALID_DEVICE_SOF)
> +		dev_sof = host_sof;
> +
>  	time = uvc_video_get_time();
>  
>  	/*
> diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> index 9a596c8d894a..07b2fdb80adf 100644
> --- a/drivers/media/usb/uvc/uvcvideo.h
> +++ b/drivers/media/usb/uvc/uvcvideo.h
> @@ -73,6 +73,7 @@
>  #define UVC_QUIRK_FORCE_Y8		0x00000800
>  #define UVC_QUIRK_FORCE_BPP		0x00001000
>  #define UVC_QUIRK_WAKE_AUTOSUSPEND	0x00002000
> +#define UVC_QUIRK_INVALID_DEVICE_SOF	0x00004000
>  
>  /* Format flags */
>  #define UVC_FMT_FLAG_COMPRESSED		0x00000001
> 

-- 
Regards,

Laurent Pinchart

Re: [PATCH v9 4/6] media: uvcvideo: Allow hw clock updates with buffers not full

[Laurent Pinchart]

Hi Ricardo,

Thank you for the patch.

On Wed, Mar 15, 2023 at 02:30:15PM +0100, Ricardo Ribalda wrote:
> With UVC 1.5 we get as little as one clock sample per frame. Which means
> that it takes 32 frames to move from the software timestamp to the
> hardware timestamp method.
> 
> This results in abrupt changes in the timestamping after 32 frames (~1
> second), resulting in noticeable artifacts when used for encoding.
> 
> With this patch we modify the update algorithm to work with whatever
> amount of values are available.
> 
> Tested-by: HungNien Chen <hn.chen@sunplusit.com>
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
>  drivers/media/usb/uvc/uvc_video.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> index 4d566edb73e7..6d0243ea0e07 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -754,10 +754,10 @@ void uvc_video_clock_update(struct uvc_streaming *stream,
>  
>  	spin_lock_irqsave(&clock->lock, flags);
>  
> -	if (clock->count < clock->size)
> +	if (clock->count < 2)
>  		goto done;
>  
> -	first = &clock->samples[clock->head];
> +	first = &clock->samples[(clock->head - clock->count + clock->size) % clock->size];
>  	last = &clock->samples[(clock->head - 1 + clock->size) % clock->size];
>  
>  	/* First step, PTS to SOF conversion. */
> @@ -772,6 +772,17 @@ void uvc_video_clock_update(struct uvc_streaming *stream,
>  	if (y2 < y1)
>  		y2 += 2048 << 16;
>  
> +	/*
> +	 * Have at least 1/4 of a second of timestamps before we
> +	 * try to do any calculation. Otherwise we do not have enough
> +	 * precision. This value was determined by running Android CTS
> +	 * on different devices.

Either a blank line for a new paragraph, or no line break.

> +	 * Dev_sof runs at 1KHz, and we have a fixed point precision of

s/Dev_sof/dev_sof/

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> +	 * 16 bits.
> +	 */
> +	if ((y2 - y1) < ( (1000 / 4) << 16))
> +		goto done;
> +
>  	y = (u64)(y2 - y1) * (1ULL << 31) + (u64)y1 * (u64)x2
>  	  - (u64)y2 * (u64)x1;
>  	y = div_u64(y, x2 - x1);
> 

-- 
Regards,

Laurent Pinchart

Re: [PATCH v9 5/6] media: uvcvideo: Refactor clock circular buffer

[Laurent Pinchart]

Hi Ricardo,

Thank you for the patch.

On Wed, Mar 15, 2023 at 02:30:16PM +0100, Ricardo Ribalda wrote:
> Isolate all the changes related to the clock circular buffer to its own
> function, that way we can make changes easier to the buffer logic.
> 
> Also simplify the lock, by removing the circular buffer clock handling
> from uvc_video_clock_decode().
> 
> And now that we are at it, unify the API of the clock functions.
> 
> Tested-by: HungNien Chen <hn.chen@sunplusit.com>
> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
>  drivers/media/usb/uvc/uvc_video.c | 84 ++++++++++++++++++---------------------
>  1 file changed, 38 insertions(+), 46 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> index 6d0243ea0e07..1db0d1bc80e6 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -466,19 +466,30 @@ static inline ktime_t uvc_video_get_time(void)
>  		return ktime_get_real();
>  }
>  
> +static void uvc_video_clock_add_sample(struct uvc_clock *clock,
> +				       const struct uvc_clock_sample *sample)
> +{
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&clock->lock, flags);
> +
> +	memcpy(&clock->samples[clock->head], sample, sizeof(*sample));

How about

	clock->samples[clock->head] = *sample;

?

> +	clock->head = (clock->head + 1) % clock->size;
> +	clock->count = min(clock->count + 1, clock->size);
> +
> +	spin_unlock_irqrestore(&clock->lock, flags);
> +
> +	clock->last_sof = sample->dev_sof;

Strictly speaking I wonder if this counts as "adding a sample". Any
objection against keeping it in the caller ?

> +}
> +
>  static void
>  uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
>  		       const u8 *data, int len)
>  {
> -	struct uvc_clock_sample *sample;
> +	struct uvc_clock_sample sample;
>  	unsigned int header_size;
>  	bool has_pts = false;
>  	bool has_scr = false;
> -	unsigned long flags;
> -	ktime_t time;
> -	u16 host_sof;
> -	u16 dev_sof;
> -	u32 dev_stc;
>  
>  	switch (data[1] & (UVC_STREAM_PTS | UVC_STREAM_SCR)) {
>  	case UVC_STREAM_PTS | UVC_STREAM_SCR:
> @@ -523,11 +534,11 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
>  	 * all the data packets of the same frame contains the same SOF. In that
>  	 * case only the first one will match the host_sof.
>  	 */
> -	dev_sof = get_unaligned_le16(&data[header_size - 2]);
> -	if (dev_sof == stream->clock.last_sof)
> +	sample.dev_sof = get_unaligned_le16(&data[header_size - 2]);
> +	if (sample.dev_sof == stream->clock.last_sof)
>  		return;
>  
> -	dev_stc = get_unaligned_le32(&data[header_size - 6]);
> +	sample.dev_stc = get_unaligned_le32(&data[header_size - 6]);
>  
>  	/*
>  	 * STC (Source Time Clock) is the clock used by the camera. The UVC 1.5
> @@ -541,21 +552,19 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
>  	 * and stc and sof are zero.
>  	 */
>  	if (buf && buf->bytesused == 0 && len == header_size &&
> -	    dev_stc == 0 && dev_sof == 0)
> +	    sample.dev_stc == 0 && sample.dev_sof == 0)
>  		return;
>  
> -	stream->clock.last_sof = dev_sof;
> -
> -	host_sof = usb_get_current_frame_number(stream->dev->udev);
> +	sample.host_sof = usb_get_current_frame_number(stream->dev->udev);
>  
>  	/*
>  	 * On some devices, like the Logitech C922, the device SOF does not run
>  	 * at a stable rate of 1kHz. For those devices use the host SOF instead.
>  	 */
>  	if (stream->dev->quirks & UVC_QUIRK_INVALID_DEVICE_SOF)
> -		dev_sof = host_sof;
> +		sample.dev_sof = sample.host_sof;
>  
> -	time = uvc_video_get_time();
> +	sample.host_time = uvc_video_get_time();
>  
>  	/*
>  	 * The UVC specification allows device implementations that can't obtain
> @@ -578,46 +587,29 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
>  	 * the 8 LSBs of the delta are kept.
>  	 */
>  	if (stream->clock.sof_offset == (u16)-1) {
> -		u16 delta_sof = (host_sof - dev_sof) & 255;
> +		u16 delta_sof = (sample.host_sof - sample.dev_sof) & 255;
>  		if (delta_sof >= 10)
>  			stream->clock.sof_offset = delta_sof;
>  		else
>  			stream->clock.sof_offset = 0;
>  	}
>  
> -	dev_sof = (dev_sof + stream->clock.sof_offset) & 2047;
> -
> -	spin_lock_irqsave(&stream->clock.lock, flags);
> -
> -	sample = &stream->clock.samples[stream->clock.head];
> -	sample->dev_stc = dev_stc;
> -	sample->dev_sof = dev_sof;
> -	sample->host_sof = host_sof;
> -	sample->host_time = time;
> -
> -	/* Update the sliding window head and count. */
> -	stream->clock.head = (stream->clock.head + 1) % stream->clock.size;
> +	sample.dev_sof = (sample.dev_sof + stream->clock.sof_offset) & 2047;
> +	sample.dev_stc = get_unaligned_le32(&data[header_size - 6]);

This is already done above.

With these small issues addressed,

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

>  
> -	if (stream->clock.count < stream->clock.size)
> -		stream->clock.count++;
> -
> -	spin_unlock_irqrestore(&stream->clock.lock, flags);
> +	uvc_video_clock_add_sample(&stream->clock, &sample);
>  }
>  
> -static void uvc_video_clock_reset(struct uvc_streaming *stream)
> +static void uvc_video_clock_reset(struct uvc_clock *clock)
>  {
> -	struct uvc_clock *clock = &stream->clock;
> -
>  	clock->head = 0;
>  	clock->count = 0;
>  	clock->last_sof = -1;
>  	clock->sof_offset = -1;
>  }
>  
> -static int uvc_video_clock_init(struct uvc_streaming *stream)
> +static int uvc_video_clock_init(struct uvc_clock *clock)
>  {
> -	struct uvc_clock *clock = &stream->clock;
> -
>  	spin_lock_init(&clock->lock);
>  	clock->size = 32;
>  
> @@ -626,15 +618,15 @@ static int uvc_video_clock_init(struct uvc_streaming *stream)
>  	if (clock->samples == NULL)
>  		return -ENOMEM;
>  
> -	uvc_video_clock_reset(stream);
> +	uvc_video_clock_reset(clock);
>  
>  	return 0;
>  }
>  
> -static void uvc_video_clock_cleanup(struct uvc_streaming *stream)
> +static void uvc_video_clock_cleanup(struct uvc_clock *clock)
>  {
> -	kfree(stream->clock.samples);
> -	stream->clock.samples = NULL;
> +	kfree(clock->samples);
> +	clock->samples = NULL;
>  }
>  
>  /*
> @@ -2108,7 +2100,7 @@ int uvc_video_resume(struct uvc_streaming *stream, int reset)
>  
>  	stream->frozen = 0;
>  
> -	uvc_video_clock_reset(stream);
> +	uvc_video_clock_reset(&stream->clock);
>  
>  	if (!uvc_queue_streaming(&stream->queue))
>  		return 0;
> @@ -2257,7 +2249,7 @@ int uvc_video_start_streaming(struct uvc_streaming *stream)
>  {
>  	int ret;
>  
> -	ret = uvc_video_clock_init(stream);
> +	ret = uvc_video_clock_init(&stream->clock);
>  	if (ret < 0)
>  		return ret;
>  
> @@ -2275,7 +2267,7 @@ int uvc_video_start_streaming(struct uvc_streaming *stream)
>  error_video:
>  	usb_set_interface(stream->dev->udev, stream->intfnum, 0);
>  error_commit:
> -	uvc_video_clock_cleanup(stream);
> +	uvc_video_clock_cleanup(&stream->clock);
>  
>  	return ret;
>  }
> @@ -2303,5 +2295,5 @@ void uvc_video_stop_streaming(struct uvc_streaming *stream)
>  		usb_clear_halt(stream->dev->udev, pipe);
>  	}
>  
> -	uvc_video_clock_cleanup(stream);
> +	uvc_video_clock_cleanup(&stream->clock);
>  }
> 

-- 
Regards,

Laurent Pinchart

Re: [PATCH v9 2/6] media: uvcvideo: Ignore empty TS packets

[Ricardo Ribalda]

Hi Laurent

Hi, I added some minor modifications, hope that it is fine with you.

Thanks!!

On Fri, 22 Mar 2024 at 00:26, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Ricardo,
>
> Thank you for the patch.
>
> On Wed, Mar 15, 2023 at 02:30:13PM +0100, Ricardo Ribalda wrote:
> > Some SunplusIT 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:
>
> "Some SunplusIT devices send, e.g.,"
>
> >
> > 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
>
> "while the UVC specification meant that the first two packets shouldn't
> have had the SCR bit set in the header."
>
> >
> > This borderline/buggy interpretation has been implemented in a variety
> > of devices, from directly SunplusIT and from other OEMs that rebrand
> > SunplusIT products. So quirking based on VID:PID will be problematic.
> >
> > All the affected modules have the following extension unit:
> > VideoControl Interface Descriptor:
> >   guidExtensionCode         {82066163-7050-ab49-b8cc-b3855e8d221d}
> >
> > But the vendor plans to use that GUID in the future and fix the bug,
> > this means that we should use heuristic to figure out the broken
> > packets.
>
> Because it would have been too easy otherwise of course :-)
>
> >
> > This patch takes care of this.
> >
> > 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@sunplusit.com>
> > Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > ---
> >  drivers/media/usb/uvc/uvc_video.c | 20 +++++++++++++++++++-
> >  1 file changed, 19 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > index 4ff4ab4471fe..1f416c494acc 100644
> > --- a/drivers/media/usb/uvc/uvc_video.c
> > +++ b/drivers/media/usb/uvc/uvc_video.c
> > @@ -478,6 +478,7 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
> >       ktime_t time;
> >       u16 host_sof;
> >       u16 dev_sof;
> > +     u32 dev_stc;
> >
> >       switch (data[1] & (UVC_STREAM_PTS | UVC_STREAM_SCR)) {
> >       case UVC_STREAM_PTS | UVC_STREAM_SCR:
> > @@ -526,6 +527,23 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
> >       if (dev_sof == stream->clock.last_sof)
> >               return;
> >
> > +     dev_stc = get_unaligned_le32(&data[header_size - 6]);
> > +
> > +     /*
> > +      * STC (Source Time Clock) is the clock used by the camera. The UVC 1.5
> > +      * standard states that it "must be captured when the first video data
> > +      * of a video frame is put on the USB bus".
> > +      * Most of the vendors, clear the `UVC_STREAM_SCR` bit when the data is
> > +      * not valid, other vendors always set the `UVC_STREAM_SCR` bit and
> > +      * expect that the driver only samples the stc if there is data on the
> > +      * packet.
> > +      * Ignore all the hardware timestamp information if there is no data
> > +      * and stc and sof are zero.
> > +      */
>
> I'd like to expand this a bit (partly to make sure I understand the
> issue correctly):
>
>         /*
>          * STC (Source Time Clock) is the clock used by the camera. The UVC 1.5
>          * standard states that it "must be captured when the first video data
>          * of a video frame is put on the USB bus". This is generally understood
>          * as requiring devices to clear the payload header's SCR bit before
>          * the first packet containing video data.
>          *
>          * Most vendors follow that interpretation, but some (namely SunplusIT)
namely SunplusIT on some devices
>          * always set the `UVC_STREAM_SCR` bit, fill the SCR field with 0's,
>          * and expect that the driver only processes the SCR if there is data in
>          * the packet.
>          *
>          * Ignore all the hardware timestamp information if we haven't received
>          * any data for this frame yet, the packet contains no data, and both
>          * STC and SOF are zero. This heuristics should be safe on compliant
>          * devices. This should be safe with compliant devices, as in the very
>          * unlikely case where a UVC 1.1 device would send timing information
>          * only before the first packet containing data, and both STC and SOF
>          * happen to be zero for a particular frame, we would only miss one
>          * clock sample and the clock recovery algorithm wouldn't suffer from
one clock sample from many
>          * this condition.
>          */
>
> Is this correct (and fine with you) ? If so,
>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>
> > +     if (buf && buf->bytesused == 0 && len == header_size &&
> > +         dev_stc == 0 && dev_sof == 0)
> > +             return;
> > +
> >       stream->clock.last_sof = dev_sof;
> >
> >       host_sof = usb_get_current_frame_number(stream->dev->udev);
> > @@ -564,7 +582,7 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
> >       spin_lock_irqsave(&stream->clock.lock, flags);
> >
> >       sample = &stream->clock.samples[stream->clock.head];
> > -     sample->dev_stc = get_unaligned_le32(&data[header_size - 6]);
> > +     sample->dev_stc = dev_stc;
> >       sample->dev_sof = dev_sof;
> >       sample->host_sof = host_sof;
> >       sample->host_time = time;
> >
>
> --
> Regards,
>
> Laurent Pinchart



-- 
Ricardo Ribalda

Re: [PATCH v9 3/6] media: uvcvideo: Quirk for invalid dev_sof in Logitech C922

[Ricardo Ribalda]

Hi Laurent

On Fri, 22 Mar 2024 at 00:44, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Ricardo,
>
> Thank you for the patch.
>
> On Wed, Mar 15, 2023 at 02:30:14PM +0100, Ricardo Ribalda wrote:
> > Logitech C922 internal SOF does not increases at a stable rate of 1kHz.
>
> The next thing you know they will redefine to value of pi to be 3.
>
> > This causes that the device_sof and the host_sof run at different rates,
> > breaking the clock domain conversion algorithm. 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
> >
> > Instead of disabling completely the hardware timestamping for such
> > hardware we take the assumption that the packet handling jitter is
> > under 2ms and use the host_sof as dev_sof.
> >
> > We can think of the UVC hardware clock as a system with a coarse clock
> > (the SOF) and a fine clock (the PTS). The coarse clock can be replaced
> > with a clock on the same frequency, if the jitter of such clock is
> > smaller than its sampling rate. That way we can save some of the
> > precision of the fine clock.
> >
> > To probe this point we have run three experiments on the Logitech C922.
> > On that experiment we run the camera at 33fps and we analyse the
> > difference in msec between a frame and its predecessor. If we display
> > the histogram of that value, a thinner histogram will mean a better
> > meassurement. The results for:
> > - original hw timestamp: https://ibb.co/D1HJJ4x
> > - pure software timestamp: https://ibb.co/QC9MgVK
> > - modified hw timestamp: https://ibb.co/8s9dBdk
> >
> > This bug in the camera firmware has been confirmed by the vendor.
> >
> > lsusb -v
> >
> > Bus 001 Device 044: ID 046d:085c Logitech, Inc. C922 Pro Stream Webcam
> > Device Descriptor:
> >   bLength                18
> >   bDescriptorType         1
> >   bcdUSB               2.00
> >   bDeviceClass          239 Miscellaneous Device
> >   bDeviceSubClass         2
> >   bDeviceProtocol         1 Interface Association
> >   bMaxPacketSize0        64
> >   idVendor           0x046d Logitech, Inc.
> >   idProduct          0x085c C922 Pro Stream Webcam
> >   bcdDevice            0.16
> >   iManufacturer           0
> >   iProduct                2 C922 Pro Stream Webcam
> >   iSerial                 1 80B912DF
> >   bNumConfigurations      1
> >
> > Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > ---
> >  drivers/media/usb/uvc/uvc_driver.c | 9 +++++++++
> >  drivers/media/usb/uvc/uvc_video.c  | 8 ++++++++
> >  drivers/media/usb/uvc/uvcvideo.h   | 1 +
> >  3 files changed, 18 insertions(+)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> > index 7aefa76a42b3..678a5736c9df 100644
> > --- a/drivers/media/usb/uvc/uvc_driver.c
> > +++ b/drivers/media/usb/uvc/uvc_driver.c
> > @@ -2549,6 +2549,15 @@ 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 1f416c494acc..4d566edb73e7 100644
> > --- a/drivers/media/usb/uvc/uvc_video.c
> > +++ b/drivers/media/usb/uvc/uvc_video.c
> > @@ -547,6 +547,14 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
> >       stream->clock.last_sof = dev_sof;
> >
> >       host_sof = usb_get_current_frame_number(stream->dev->udev);
> > +
> > +     /*
> > +      * On some devices, like the Logitech C922, the device SOF does not run
> > +      * at a stable rate of 1kHz. For those devices use the host SOF instead.
>
> I'm still not very convinced, as without a formal proof I think there's
> some luck involved, and it may break later. This being said, given that
> this is gated by a quirk, it won't impact other devices, and we can deal
> with regressions when they happen. Could we record it here:
>
>          * On some devices, like the Logitech C922, the device SOF does not run
>          * at a stable rate of 1kHz. For those devices use the host SOF instead.
>          * This improves the timestamp precision in the tests performed so far,
>          * even if the exact reason hasn't been fully determined.
>
> or something along those lines ?
How does this sound:


        /*
         * On some devices, like the Logitech C922, the device SOF does not run
         * at a stable rate of 1kHz. For those devices use the host SOF instead.
+        * In the tests performed so far, this improves the timestamp precision.
+        * This is probably explained by a small packet handling jitter from the
+        * host, but the exact reason hasn't been fully determined.
         */

>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>
> > +      */
> > +     if (stream->dev->quirks & UVC_QUIRK_INVALID_DEVICE_SOF)
> > +             dev_sof = host_sof;
> > +
> >       time = uvc_video_get_time();
> >
> >       /*
> > diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> > index 9a596c8d894a..07b2fdb80adf 100644
> > --- a/drivers/media/usb/uvc/uvcvideo.h
> > +++ b/drivers/media/usb/uvc/uvcvideo.h
> > @@ -73,6 +73,7 @@
> >  #define UVC_QUIRK_FORCE_Y8           0x00000800
> >  #define UVC_QUIRK_FORCE_BPP          0x00001000
> >  #define UVC_QUIRK_WAKE_AUTOSUSPEND   0x00002000
> > +#define UVC_QUIRK_INVALID_DEVICE_SOF 0x00004000
> >
> >  /* Format flags */
> >  #define UVC_FMT_FLAG_COMPRESSED              0x00000001
> >
>
> --
> Regards,
>
> Laurent Pinchart



-- 
Ricardo Ribalda

Re: [PATCH v9 3/6] media: uvcvideo: Quirk for invalid dev_sof in Logitech C922

[Laurent Pinchart]

On Fri, Mar 22, 2024 at 09:32:56AM +0100, Ricardo Ribalda wrote:
> On Fri, 22 Mar 2024 at 00:44, Laurent Pinchart wrote:
> > On Wed, Mar 15, 2023 at 02:30:14PM +0100, Ricardo Ribalda wrote:
> > > Logitech C922 internal SOF does not increases at a stable rate of 1kHz.
> >
> > The next thing you know they will redefine to value of pi to be 3.
> >
> > > This causes that the device_sof and the host_sof run at different rates,
> > > breaking the clock domain conversion algorithm. 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
> > >
> > > Instead of disabling completely the hardware timestamping for such
> > > hardware we take the assumption that the packet handling jitter is
> > > under 2ms and use the host_sof as dev_sof.
> > >
> > > We can think of the UVC hardware clock as a system with a coarse clock
> > > (the SOF) and a fine clock (the PTS). The coarse clock can be replaced
> > > with a clock on the same frequency, if the jitter of such clock is
> > > smaller than its sampling rate. That way we can save some of the
> > > precision of the fine clock.
> > >
> > > To probe this point we have run three experiments on the Logitech C922.
> > > On that experiment we run the camera at 33fps and we analyse the
> > > difference in msec between a frame and its predecessor. If we display
> > > the histogram of that value, a thinner histogram will mean a better
> > > meassurement. The results for:
> > > - original hw timestamp: https://ibb.co/D1HJJ4x
> > > - pure software timestamp: https://ibb.co/QC9MgVK
> > > - modified hw timestamp: https://ibb.co/8s9dBdk
> > >
> > > This bug in the camera firmware has been confirmed by the vendor.
> > >
> > > lsusb -v
> > >
> > > Bus 001 Device 044: ID 046d:085c Logitech, Inc. C922 Pro Stream Webcam
> > > Device Descriptor:
> > >   bLength                18
> > >   bDescriptorType         1
> > >   bcdUSB               2.00
> > >   bDeviceClass          239 Miscellaneous Device
> > >   bDeviceSubClass         2
> > >   bDeviceProtocol         1 Interface Association
> > >   bMaxPacketSize0        64
> > >   idVendor           0x046d Logitech, Inc.
> > >   idProduct          0x085c C922 Pro Stream Webcam
> > >   bcdDevice            0.16
> > >   iManufacturer           0
> > >   iProduct                2 C922 Pro Stream Webcam
> > >   iSerial                 1 80B912DF
> > >   bNumConfigurations      1
> > >
> > > Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > > ---
> > >  drivers/media/usb/uvc/uvc_driver.c | 9 +++++++++
> > >  drivers/media/usb/uvc/uvc_video.c  | 8 ++++++++
> > >  drivers/media/usb/uvc/uvcvideo.h   | 1 +
> > >  3 files changed, 18 insertions(+)
> > >
> > > diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> > > index 7aefa76a42b3..678a5736c9df 100644
> > > --- a/drivers/media/usb/uvc/uvc_driver.c
> > > +++ b/drivers/media/usb/uvc/uvc_driver.c
> > > @@ -2549,6 +2549,15 @@ 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 1f416c494acc..4d566edb73e7 100644
> > > --- a/drivers/media/usb/uvc/uvc_video.c
> > > +++ b/drivers/media/usb/uvc/uvc_video.c
> > > @@ -547,6 +547,14 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
> > >       stream->clock.last_sof = dev_sof;
> > >
> > >       host_sof = usb_get_current_frame_number(stream->dev->udev);
> > > +
> > > +     /*
> > > +      * On some devices, like the Logitech C922, the device SOF does not run
> > > +      * at a stable rate of 1kHz. For those devices use the host SOF instead.
> >
> > I'm still not very convinced, as without a formal proof I think there's
> > some luck involved, and it may break later. This being said, given that
> > this is gated by a quirk, it won't impact other devices, and we can deal
> > with regressions when they happen. Could we record it here:
> >
> >          * On some devices, like the Logitech C922, the device SOF does not run
> >          * at a stable rate of 1kHz. For those devices use the host SOF instead.
> >          * This improves the timestamp precision in the tests performed so far,
> >          * even if the exact reason hasn't been fully determined.
> >
> > or something along those lines ?
> 
> How does this sound:
> 
>         /*
>          * On some devices, like the Logitech C922, the device SOF does not run
>          * at a stable rate of 1kHz. For those devices use the host SOF instead.
> +        * In the tests performed so far, this improves the timestamp precision.
> +        * This is probably explained by a small packet handling jitter from the
> +        * host, but the exact reason hasn't been fully determined.
>          */

Sounds nicer than my text :-)

> > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> >
> > > +      */
> > > +     if (stream->dev->quirks & UVC_QUIRK_INVALID_DEVICE_SOF)
> > > +             dev_sof = host_sof;
> > > +
> > >       time = uvc_video_get_time();
> > >
> > >       /*
> > > diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> > > index 9a596c8d894a..07b2fdb80adf 100644
> > > --- a/drivers/media/usb/uvc/uvcvideo.h
> > > +++ b/drivers/media/usb/uvc/uvcvideo.h
> > > @@ -73,6 +73,7 @@
> > >  #define UVC_QUIRK_FORCE_Y8           0x00000800
> > >  #define UVC_QUIRK_FORCE_BPP          0x00001000
> > >  #define UVC_QUIRK_WAKE_AUTOSUSPEND   0x00002000
> > > +#define UVC_QUIRK_INVALID_DEVICE_SOF 0x00004000
> > >
> > >  /* Format flags */
> > >  #define UVC_FMT_FLAG_COMPRESSED              0x00000001
> > >

-- 
Regards,

Laurent Pinchart

Re: [PATCH v9 2/6] media: uvcvideo: Ignore empty TS packets

[Laurent Pinchart]

On Fri, Mar 22, 2024 at 09:22:39AM +0100, Ricardo Ribalda wrote:
> Hi Laurent
> 
> Hi, I added some minor modifications, hope that it is fine with you.

They look fine to me, thanks.

> On Fri, 22 Mar 2024 at 00:26, Laurent Pinchart wrote:
> > On Wed, Mar 15, 2023 at 02:30:13PM +0100, Ricardo Ribalda wrote:
> > > Some SunplusIT 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:
> >
> > "Some SunplusIT devices send, e.g.,"
> >
> > >
> > > 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
> >
> > "while the UVC specification meant that the first two packets shouldn't
> > have had the SCR bit set in the header."
> >
> > >
> > > This borderline/buggy interpretation has been implemented in a variety
> > > of devices, from directly SunplusIT and from other OEMs that rebrand
> > > SunplusIT products. So quirking based on VID:PID will be problematic.
> > >
> > > All the affected modules have the following extension unit:
> > > VideoControl Interface Descriptor:
> > >   guidExtensionCode         {82066163-7050-ab49-b8cc-b3855e8d221d}
> > >
> > > But the vendor plans to use that GUID in the future and fix the bug,
> > > this means that we should use heuristic to figure out the broken
> > > packets.
> >
> > Because it would have been too easy otherwise of course :-)
> >
> > >
> > > This patch takes care of this.
> > >
> > > 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@sunplusit.com>
> > > Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > > ---
> > >  drivers/media/usb/uvc/uvc_video.c | 20 +++++++++++++++++++-
> > >  1 file changed, 19 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > > index 4ff4ab4471fe..1f416c494acc 100644
> > > --- a/drivers/media/usb/uvc/uvc_video.c
> > > +++ b/drivers/media/usb/uvc/uvc_video.c
> > > @@ -478,6 +478,7 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
> > >       ktime_t time;
> > >       u16 host_sof;
> > >       u16 dev_sof;
> > > +     u32 dev_stc;
> > >
> > >       switch (data[1] & (UVC_STREAM_PTS | UVC_STREAM_SCR)) {
> > >       case UVC_STREAM_PTS | UVC_STREAM_SCR:
> > > @@ -526,6 +527,23 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
> > >       if (dev_sof == stream->clock.last_sof)
> > >               return;
> > >
> > > +     dev_stc = get_unaligned_le32(&data[header_size - 6]);
> > > +
> > > +     /*
> > > +      * STC (Source Time Clock) is the clock used by the camera. The UVC 1.5
> > > +      * standard states that it "must be captured when the first video data
> > > +      * of a video frame is put on the USB bus".
> > > +      * Most of the vendors, clear the `UVC_STREAM_SCR` bit when the data is
> > > +      * not valid, other vendors always set the `UVC_STREAM_SCR` bit and
> > > +      * expect that the driver only samples the stc if there is data on the
> > > +      * packet.
> > > +      * Ignore all the hardware timestamp information if there is no data
> > > +      * and stc and sof are zero.
> > > +      */
> >
> > I'd like to expand this a bit (partly to make sure I understand the
> > issue correctly):
> >
> >         /*
> >          * STC (Source Time Clock) is the clock used by the camera. The UVC 1.5
> >          * standard states that it "must be captured when the first video data
> >          * of a video frame is put on the USB bus". This is generally understood
> >          * as requiring devices to clear the payload header's SCR bit before
> >          * the first packet containing video data.
> >          *
> >          * Most vendors follow that interpretation, but some (namely SunplusIT)
> namely SunplusIT on some devices
> >          * always set the `UVC_STREAM_SCR` bit, fill the SCR field with 0's,
> >          * and expect that the driver only processes the SCR if there is data in
> >          * the packet.
> >          *
> >          * Ignore all the hardware timestamp information if we haven't received
> >          * any data for this frame yet, the packet contains no data, and both
> >          * STC and SOF are zero. This heuristics should be safe on compliant
> >          * devices. This should be safe with compliant devices, as in the very
> >          * unlikely case where a UVC 1.1 device would send timing information
> >          * only before the first packet containing data, and both STC and SOF
> >          * happen to be zero for a particular frame, we would only miss one
> >          * clock sample and the clock recovery algorithm wouldn't suffer from
> one clock sample from many
> >          * this condition.
> >          */
> >
> > Is this correct (and fine with you) ? If so,
> >
> > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> >
> > > +     if (buf && buf->bytesused == 0 && len == header_size &&
> > > +         dev_stc == 0 && dev_sof == 0)
> > > +             return;
> > > +
> > >       stream->clock.last_sof = dev_sof;
> > >
> > >       host_sof = usb_get_current_frame_number(stream->dev->udev);
> > > @@ -564,7 +582,7 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
> > >       spin_lock_irqsave(&stream->clock.lock, flags);
> > >
> > >       sample = &stream->clock.samples[stream->clock.head];
> > > -     sample->dev_stc = get_unaligned_le32(&data[header_size - 6]);
> > > +     sample->dev_stc = dev_stc;
> > >       sample->dev_sof = dev_sof;
> > >       sample->host_sof = host_sof;
> > >       sample->host_time = time;
> > >

-- 
Regards,

Laurent Pinchart

Re: [PATCH v9 1/6] media: uvcvideo: Fix negative modulus calculation

[Laurent Pinchart]

On Thu, Mar 21, 2024 at 11:50:48PM +0200, Laurent Pinchart wrote:
> On Mon, Feb 19, 2024 at 04:07:12PM +0100, Ricardo Ribalda wrote:
> > On Mon, 19 Feb 2024 at 11:40, Laurent Pinchart wrote:
> > > On Mon, Feb 19, 2024 at 11:28:03AM +0100, Ricardo Ribalda wrote:
> > > > On Mon, 12 Feb 2024 at 23:59, Laurent Pinchart wrote:
> > > > > On Wed, Mar 15, 2023 at 02:30:12PM +0100, Ricardo Ribalda wrote:
> > > > > > If head is 0, last will be addressing the index 0 instead of clock->size
> > > > > > -1. Luckily clock->head is unsiged, otherwise it would be addressing
> > > > > > 0xffffffff.
> > > > >
> > > > > I'm not following you. In the expression
> > > > >
> > > > >         (clock->head - 1) % clock->size
> > > > >
> > > > > clock->head is an unsigned int, and 1 as a signed int, so the result of
> > > > > the subtraction is promoted to an unsigned int. When clock->head is 0, the expression evaluates to
> > > > >
> > > > >         0xffffffff % clock->size
> > > > >
> > > > > clock->size is a power of two (hardcoded to 32 at the moment), so the
> > > > > expression evaluates to 31, as intended.
> > > > >
> > > > > Am I missing something ?
> > > >
> > > > Take a look to: https://godbolt.org/z/xYeqTx6ba
> > > >
> > > > The expression only works because the size is a power of two. In this
> > > > set I am allowing sizes that are not powers of two.
> > >
> > > Could you then update the commit message to explain that ?
> > >
> > > I'll review the rest of the series this week.
> > Thanks
> > 
> > Will update with the following text after the review:
> > 
> > The tail of the list lives at the position before the head. This is
> > mathematically noted as
> > ```
> > (head-1)  mod size.
> > ```
> > 
> > Unfortunately C, does not have a modulus operator, but a remainder
> > operator (%).
> > The reminder operation has a different result than the modulus if
> > (head -1) is a negative number and size is not a power of two.
> > 
> > Adding size to (head-1) allows the code to run with any value of size.
> 
> Could you please add
> 
> This does not change the current behaviour of the driver, as the size is
> always a power of two, but prepares for reworks that will change the
> size to a non power of two.
> 
> or something similar ?
> 
> > > > > > Nontheless, this is not the intented behaviour and should be fixed.
> > > > > >
> > > > > > Fixes: 66847ef013cc ("[media] uvcvideo: Add UVC timestamps support")
> 
> I think this should be dropped, the patch doesn't fix an issue, but
> prepares for further changes that add new features. I'd also like to
> update the commit message to avoid stating "Fix", to avoid this being
> picked for stable kernels automatically.

After reviewing the whole series, it seems that clock->size stays at its
current value of 32. Do we thus need this patch ?

> > > > > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > > > > > ---
> > > > > >  drivers/media/usb/uvc/uvc_video.c | 2 +-
> > > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > > >
> > > > > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > > > > > index d4b023d4de7c..4ff4ab4471fe 100644
> > > > > > --- a/drivers/media/usb/uvc/uvc_video.c
> > > > > > +++ b/drivers/media/usb/uvc/uvc_video.c
> > > > > > @@ -732,7 +732,7 @@ void uvc_video_clock_update(struct uvc_streaming *stream,
> > > > > >               goto done;
> > > > > >
> > > > > >       first = &clock->samples[clock->head];
> > > > > > -     last = &clock->samples[(clock->head - 1) % clock->size];
> > > > > > +     last = &clock->samples[(clock->head - 1 + clock->size) % clock->size];
> > > > > >
> > > > > >       /* First step, PTS to SOF conversion. */
> > > > > >       delta_stc = buf->pts - (1UL << 31);

-- 
Regards,

Laurent Pinchart

Re: [PATCH v9 1/6] media: uvcvideo: Fix negative modulus calculation

[Ricardo Ribalda]

Hi Laurent

On Fri, 22 Mar 2024 at 10:19, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> On Thu, Mar 21, 2024 at 11:50:48PM +0200, Laurent Pinchart wrote:
> > On Mon, Feb 19, 2024 at 04:07:12PM +0100, Ricardo Ribalda wrote:
> > > On Mon, 19 Feb 2024 at 11:40, Laurent Pinchart wrote:
> > > > On Mon, Feb 19, 2024 at 11:28:03AM +0100, Ricardo Ribalda wrote:
> > > > > On Mon, 12 Feb 2024 at 23:59, Laurent Pinchart wrote:
> > > > > > On Wed, Mar 15, 2023 at 02:30:12PM +0100, Ricardo Ribalda wrote:
> > > > > > > If head is 0, last will be addressing the index 0 instead of clock->size
> > > > > > > -1. Luckily clock->head is unsiged, otherwise it would be addressing
> > > > > > > 0xffffffff.
> > > > > >
> > > > > > I'm not following you. In the expression
> > > > > >
> > > > > >         (clock->head - 1) % clock->size
> > > > > >
> > > > > > clock->head is an unsigned int, and 1 as a signed int, so the result of
> > > > > > the subtraction is promoted to an unsigned int. When clock->head is 0, the expression evaluates to
> > > > > >
> > > > > >         0xffffffff % clock->size
> > > > > >
> > > > > > clock->size is a power of two (hardcoded to 32 at the moment), so the
> > > > > > expression evaluates to 31, as intended.
> > > > > >
> > > > > > Am I missing something ?
> > > > >
> > > > > Take a look to: https://godbolt.org/z/xYeqTx6ba
> > > > >
> > > > > The expression only works because the size is a power of two. In this
> > > > > set I am allowing sizes that are not powers of two.
> > > >
> > > > Could you then update the commit message to explain that ?
> > > >
> > > > I'll review the rest of the series this week.
> > > Thanks
> > >
> > > Will update with the following text after the review:
> > >
> > > The tail of the list lives at the position before the head. This is
> > > mathematically noted as
> > > ```
> > > (head-1)  mod size.
> > > ```
> > >
> > > Unfortunately C, does not have a modulus operator, but a remainder
> > > operator (%).
> > > The reminder operation has a different result than the modulus if
> > > (head -1) is a negative number and size is not a power of two.
> > >
> > > Adding size to (head-1) allows the code to run with any value of size.
> >
> > Could you please add
> >
> > This does not change the current behaviour of the driver, as the size is
> > always a power of two, but prepares for reworks that will change the
> > size to a non power of two.
> >
> > or something similar ?
> >
> > > > > > > Nontheless, this is not the intented behaviour and should be fixed.
> > > > > > >
> > > > > > > Fixes: 66847ef013cc ("[media] uvcvideo: Add UVC timestamps support")
> >
> > I think this should be dropped, the patch doesn't fix an issue, but
> > prepares for further changes that add new features. I'd also like to
> > update the commit message to avoid stating "Fix", to avoid this being
> > picked for stable kernels automatically.
>
> After reviewing the whole series, it seems that clock->size stays at its
> current value of 32. Do we thus need this patch ?

I remember that at some point, when I changed the size, it had been
really painful to figure out why the code was not working.

I'd rather keep this patch with a different commit message.

"""
This does not change the current behaviour of the driver, as the size is
always a power of two, but avoid tedious debugging if we ever change its size.
"""

WDYT?


>
> > > > > > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > > > > > > ---
> > > > > > >  drivers/media/usb/uvc/uvc_video.c | 2 +-
> > > > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > > > >
> > > > > > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > > > > > > index d4b023d4de7c..4ff4ab4471fe 100644
> > > > > > > --- a/drivers/media/usb/uvc/uvc_video.c
> > > > > > > +++ b/drivers/media/usb/uvc/uvc_video.c
> > > > > > > @@ -732,7 +732,7 @@ void uvc_video_clock_update(struct uvc_streaming *stream,
> > > > > > >               goto done;
> > > > > > >
> > > > > > >       first = &clock->samples[clock->head];
> > > > > > > -     last = &clock->samples[(clock->head - 1) % clock->size];
> > > > > > > +     last = &clock->samples[(clock->head - 1 + clock->size) % clock->size];
> > > > > > >
> > > > > > >       /* First step, PTS to SOF conversion. */
> > > > > > >       delta_stc = buf->pts - (1UL << 31);
>
> --
> Regards,
>
> Laurent Pinchart



-- 
Ricardo Ribalda

Re: [PATCH v9 6/6] media: uvcvideo: Fix hw timestamp handling for slow FPS

[Laurent Pinchart]

Hi Ricardo,

Thank you for the patch.

On Wed, Mar 15, 2023 at 02:30:17PM +0100, Ricardo Ribalda wrote:
> In UVC 1.5 we get a single clock value per frame. With the current
> buffer size of 32, FPS slowers than 32 might roll-over twice.
> 
> The current code cannot handle two roll-over and provide invalid
> timestamps.
> 
> Revome all the samples from the circular buffer that are more than two

s/Revome/Remove/

> rollovers old, so the algorithm always provides good timestamps.

Wouldn't it be better to support multiple rollovers instead ?

> Note that we are removing values that are more than one second old,
> which means that there is enough distance between the two points that
> we use for the interpolation to provide good values.
> 
> Tested-by: HungNien Chen <hn.chen@sunplusit.com>
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
>  drivers/media/usb/uvc/uvc_video.c | 24 ++++++++++++++++++++++++
>  drivers/media/usb/uvc/uvcvideo.h  |  1 +
>  2 files changed, 25 insertions(+)
> 
> diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> index 1db0d1bc80e6..c58b51207be6 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -471,8 +471,31 @@ static void uvc_video_clock_add_sample(struct uvc_clock *clock,
>  {
>  	unsigned long flags;
>  
> +	/*
> +	 * If we write new data on the position where we had the last
> +	 * overflow, remove the overflow pointer. There is no overflow
> +	 * on the whole circular buffer.
> +	 */
> +	if (clock->head == clock->last_sof_overflow)
> +		clock->last_sof_overflow = -1;
> +
>  	spin_lock_irqsave(&clock->lock, flags);
>  
> +	/* Handle overflows */
> +	if (clock->count > 0 && clock->last_sof > sample->dev_sof) {
> +		/*
> +		 * Remove data from the circular buffer that is older than the
> +		 * last overflow. We only support one overflow per circular
> +		 * buffer.
> +		 */
> +		if (clock->last_sof_overflow != -1) {
> +			clock->count = (clock->head - clock->last_sof_overflow
> +					+ clock->count)	% clock->count;
> +		}
> +		clock->last_sof_overflow = clock->head;
> +	}
> +
> +	/* Add sample */
>  	memcpy(&clock->samples[clock->head], sample, sizeof(*sample));
>  	clock->head = (clock->head + 1) % clock->size;
>  	clock->count = min(clock->count + 1, clock->size);
> @@ -605,6 +628,7 @@ static void uvc_video_clock_reset(struct uvc_clock *clock)
>  	clock->head = 0;
>  	clock->count = 0;
>  	clock->last_sof = -1;
> +	clock->last_sof_overflow = -1;
>  	clock->sof_offset = -1;
>  }
>  
> diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> index 07b2fdb80adf..bf9f5162b833 100644
> --- a/drivers/media/usb/uvc/uvcvideo.h
> +++ b/drivers/media/usb/uvc/uvcvideo.h
> @@ -499,6 +499,7 @@ struct uvc_streaming {
>  		unsigned int head;
>  		unsigned int count;
>  		unsigned int size;
> +		unsigned int last_sof_overflow;
>  
>  		u16 last_sof;
>  		u16 sof_offset;
> 

-- 
Regards,

Laurent Pinchart

Re: [PATCH v9 1/6] media: uvcvideo: Fix negative modulus calculation

[Laurent Pinchart]

On Fri, Mar 22, 2024 at 10:29:03AM +0100, Ricardo Ribalda wrote:
> On Fri, 22 Mar 2024 at 10:19, Laurent Pinchart wrote:
> > On Thu, Mar 21, 2024 at 11:50:48PM +0200, Laurent Pinchart wrote:
> > > On Mon, Feb 19, 2024 at 04:07:12PM +0100, Ricardo Ribalda wrote:
> > > > On Mon, 19 Feb 2024 at 11:40, Laurent Pinchart wrote:
> > > > > On Mon, Feb 19, 2024 at 11:28:03AM +0100, Ricardo Ribalda wrote:
> > > > > > On Mon, 12 Feb 2024 at 23:59, Laurent Pinchart wrote:
> > > > > > > On Wed, Mar 15, 2023 at 02:30:12PM +0100, Ricardo Ribalda wrote:
> > > > > > > > If head is 0, last will be addressing the index 0 instead of clock->size
> > > > > > > > -1. Luckily clock->head is unsiged, otherwise it would be addressing
> > > > > > > > 0xffffffff.
> > > > > > >
> > > > > > > I'm not following you. In the expression
> > > > > > >
> > > > > > >         (clock->head - 1) % clock->size
> > > > > > >
> > > > > > > clock->head is an unsigned int, and 1 as a signed int, so the result of
> > > > > > > the subtraction is promoted to an unsigned int. When clock->head is 0, the expression evaluates to
> > > > > > >
> > > > > > >         0xffffffff % clock->size
> > > > > > >
> > > > > > > clock->size is a power of two (hardcoded to 32 at the moment), so the
> > > > > > > expression evaluates to 31, as intended.
> > > > > > >
> > > > > > > Am I missing something ?
> > > > > >
> > > > > > Take a look to: https://godbolt.org/z/xYeqTx6ba
> > > > > >
> > > > > > The expression only works because the size is a power of two. In this
> > > > > > set I am allowing sizes that are not powers of two.
> > > > >
> > > > > Could you then update the commit message to explain that ?
> > > > >
> > > > > I'll review the rest of the series this week.
> > > > Thanks
> > > >
> > > > Will update with the following text after the review:
> > > >
> > > > The tail of the list lives at the position before the head. This is
> > > > mathematically noted as
> > > > ```
> > > > (head-1)  mod size.
> > > > ```
> > > >
> > > > Unfortunately C, does not have a modulus operator, but a remainder
> > > > operator (%).
> > > > The reminder operation has a different result than the modulus if
> > > > (head -1) is a negative number and size is not a power of two.
> > > >
> > > > Adding size to (head-1) allows the code to run with any value of size.
> > >
> > > Could you please add
> > >
> > > This does not change the current behaviour of the driver, as the size is
> > > always a power of two, but prepares for reworks that will change the
> > > size to a non power of two.
> > >
> > > or something similar ?
> > >
> > > > > > > > Nontheless, this is not the intented behaviour and should be fixed.
> > > > > > > >
> > > > > > > > Fixes: 66847ef013cc ("[media] uvcvideo: Add UVC timestamps support")
> > >
> > > I think this should be dropped, the patch doesn't fix an issue, but
> > > prepares for further changes that add new features. I'd also like to
> > > update the commit message to avoid stating "Fix", to avoid this being
> > > picked for stable kernels automatically.
> >
> > After reviewing the whole series, it seems that clock->size stays at its
> > current value of 32. Do we thus need this patch ?
> 
> I remember that at some point, when I changed the size, it had been
> really painful to figure out why the code was not working.
> 
> I'd rather keep this patch with a different commit message.
> 
> """
> This does not change the current behaviour of the driver, as the size is
> always a power of two, but avoid tedious debugging if we ever change its size.
> """
> 
> WDYT?

I'm OK with that.

> > > > > > > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > > > > > > > ---
> > > > > > > >  drivers/media/usb/uvc/uvc_video.c | 2 +-
> > > > > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > > > > >
> > > > > > > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > > > > > > > index d4b023d4de7c..4ff4ab4471fe 100644
> > > > > > > > --- a/drivers/media/usb/uvc/uvc_video.c
> > > > > > > > +++ b/drivers/media/usb/uvc/uvc_video.c
> > > > > > > > @@ -732,7 +732,7 @@ void uvc_video_clock_update(struct uvc_streaming *stream,
> > > > > > > >               goto done;
> > > > > > > >
> > > > > > > >       first = &clock->samples[clock->head];
> > > > > > > > -     last = &clock->samples[(clock->head - 1) % clock->size];
> > > > > > > > +     last = &clock->samples[(clock->head - 1 + clock->size) % clock->size];
> > > > > > > >
> > > > > > > >       /* First step, PTS to SOF conversion. */
> > > > > > > >       delta_stc = buf->pts - (1UL << 31);

-- 
Regards,

Laurent Pinchart

Re: [PATCH v9 6/6] media: uvcvideo: Fix hw timestamp handling for slow FPS

[Ricardo Ribalda]

Hi

On Fri, 22 Mar 2024 at 10:35, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Ricardo,
>
> Thank you for the patch.
>
> On Wed, Mar 15, 2023 at 02:30:17PM +0100, Ricardo Ribalda wrote:
> > In UVC 1.5 we get a single clock value per frame. With the current
> > buffer size of 32, FPS slowers than 32 might roll-over twice.
> >
> > The current code cannot handle two roll-over and provide invalid
> > timestamps.
> >
> > Revome all the samples from the circular buffer that are more than two
>
> s/Revome/Remove/
>
> > rollovers old, so the algorithm always provides good timestamps.
>
> Wouldn't it be better to support multiple rollovers instead ?

I believe one second is enough to provide a good ramp for the clock
interpolation,
with as little as 1/4 we are getting results good enough to pass CTS.

To support multiple roll-ups we would need to keep track of the
"generation" of every timestamp, and numerical overflows will start to
be an issue....

IMO it is better to fix what we have broken and If we ever need more
accuracy we could add a follow-up patch later.


>
> > Note that we are removing values that are more than one second old,
> > which means that there is enough distance between the two points that
> > we use for the interpolation to provide good values.
> >
> > Tested-by: HungNien Chen <hn.chen@sunplusit.com>
> > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > ---
> >  drivers/media/usb/uvc/uvc_video.c | 24 ++++++++++++++++++++++++
> >  drivers/media/usb/uvc/uvcvideo.h  |  1 +
> >  2 files changed, 25 insertions(+)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > index 1db0d1bc80e6..c58b51207be6 100644
> > --- a/drivers/media/usb/uvc/uvc_video.c
> > +++ b/drivers/media/usb/uvc/uvc_video.c
> > @@ -471,8 +471,31 @@ static void uvc_video_clock_add_sample(struct uvc_clock *clock,
> >  {
> >       unsigned long flags;
> >
> > +     /*
> > +      * If we write new data on the position where we had the last
> > +      * overflow, remove the overflow pointer. There is no overflow
> > +      * on the whole circular buffer.
> > +      */
> > +     if (clock->head == clock->last_sof_overflow)
> > +             clock->last_sof_overflow = -1;
> > +
> >       spin_lock_irqsave(&clock->lock, flags);
> >
> > +     /* Handle overflows */
> > +     if (clock->count > 0 && clock->last_sof > sample->dev_sof) {
> > +             /*
> > +              * Remove data from the circular buffer that is older than the
> > +              * last overflow. We only support one overflow per circular
> > +              * buffer.
> > +              */
> > +             if (clock->last_sof_overflow != -1) {
> > +                     clock->count = (clock->head - clock->last_sof_overflow
> > +                                     + clock->count) % clock->count;
> > +             }
> > +             clock->last_sof_overflow = clock->head;
> > +     }
> > +
> > +     /* Add sample */
> >       memcpy(&clock->samples[clock->head], sample, sizeof(*sample));
> >       clock->head = (clock->head + 1) % clock->size;
> >       clock->count = min(clock->count + 1, clock->size);
> > @@ -605,6 +628,7 @@ static void uvc_video_clock_reset(struct uvc_clock *clock)
> >       clock->head = 0;
> >       clock->count = 0;
> >       clock->last_sof = -1;
> > +     clock->last_sof_overflow = -1;
> >       clock->sof_offset = -1;
> >  }
> >
> > diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> > index 07b2fdb80adf..bf9f5162b833 100644
> > --- a/drivers/media/usb/uvc/uvcvideo.h
> > +++ b/drivers/media/usb/uvc/uvcvideo.h
> > @@ -499,6 +499,7 @@ struct uvc_streaming {
> >               unsigned int head;
> >               unsigned int count;
> >               unsigned int size;
> > +             unsigned int last_sof_overflow;
> >
> >               u16 last_sof;
> >               u16 sof_offset;
> >
>
> --
> Regards,
>
> Laurent Pinchart



-- 
Ricardo Ribalda