Re: [PATCH v5 14/20] staging: media: tegra-video: move MIPI calibration calls from VI to CSI

From: Hans Verkuil
Date: Fri Apr 14 2023 - 11:51:57 EST

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Hi Luca,

I just encountered an error in this patch, so I have rejected the PR I made.

See below for the details:

On 07/04/2023 15:38, Luca Ceresoli wrote:
> The CSI module does not handle all the MIPI lane calibration procedure,
> leaving a small part of it to the VI module. In doing this,
> tegra_channel_enable_stream() (vi.c) manipulates the private data of the
> upstream subdev casting it to struct 'tegra_csi_channel', which will be
> wrong after introducing a VIP (parallel video input) channel.
>
> This prevents adding support for the VIP module. It also breaks the
> logical isolation between modules.
>
> Since the lane calibration requirement does not exist in the parallel input
> module, moving the calibration function to a per-module op is not
> optimal. Instead move the calibration procedure in the CSI module, together
> with the rest of the calibration procedures. After this change,
> tegra_channel_enable_stream() just calls v4l2_subdev_call() to ask for a
> stream start/stop to the CSI module, which in turn knows all the
> CSI-specific details to implement it.
>
> Signed-off-by: Luca Ceresoli <luca.ceresoli@xxxxxxxxxxx>
> Reviewed-by: Dmitry Osipenko <digetx@xxxxxxxxx>
>
> ---
>
> No changes in v5
>
> Changed in v4:
> - Added review tags
>
> No changes in v3
> No changes in v2
> ---
> drivers/staging/media/tegra-video/csi.c | 44 ++++++++++++++++++++
> drivers/staging/media/tegra-video/vi.c | 54 ++-----------------------
> 2 files changed, 48 insertions(+), 50 deletions(-)
>
> diff --git a/drivers/staging/media/tegra-video/csi.c b/drivers/staging/media/tegra-video/csi.c
> index 9a03d5ccdf3c..b93fc879ef3a 100644
> --- a/drivers/staging/media/tegra-video/csi.c
> +++ b/drivers/staging/media/tegra-video/csi.c
> @@ -328,12 +328,42 @@ static int tegra_csi_enable_stream(struct v4l2_subdev *subdev)
> }
>
> csi_chan->pg_mode = chan->pg_mode;
> +
> + /*
> + * Tegra CSI receiver can detect the first LP to HS transition.
> + * So, start the CSI stream-on prior to sensor stream-on and
> + * vice-versa for stream-off.
> + */
> ret = csi->ops->csi_start_streaming(csi_chan);
> if (ret < 0)
> goto finish_calibration;
>
> + if (csi_chan->mipi) {
> + struct v4l2_subdev *src_subdev;
> + /*
> + * TRM has incorrectly documented to wait for done status from
> + * calibration logic after CSI interface power on.
> + * As per the design, calibration results are latched and applied
> + * to the pads only when the link is in LP11 state which will happen
> + * during the sensor stream-on.
> + * CSI subdev stream-on triggers start of MIPI pads calibration.
> + * Wait for calibration to finish here after sensor subdev stream-on.
> + */
> + src_subdev = tegra_channel_get_remote_source_subdev(chan);
> + ret = v4l2_subdev_call(src_subdev, video, s_stream, true);
> + err = tegra_mipi_finish_calibration(csi_chan->mipi);
> +
> + if (ret < 0 && ret != -ENOIOCTLCMD)
> + goto disable_csi_stream;

If there was an error from s_stream, then tegra_mipi_finish_calibration is called
and it goes to disable_csi_stream...

> +
> + if (err < 0)
> + dev_warn(csi->dev, "MIPI calibration failed: %d\n", err);
> + }
> +
> return 0;
>
> +disable_csi_stream:
> + csi->ops->csi_stop_streaming(csi_chan);
> finish_calibration:
> if (csi_chan->mipi)
> tegra_mipi_finish_calibration(csi_chan->mipi);

...but here tegra_mipi_finish_calibration() is called again, leading to an unlock
imbalance.

This is the callstack:

[ 109.894502] IMX274 5-001a: s_stream failed

[ 109.900203] =====================================
[ 109.904898] WARNING: bad unlock balance detected!
[ 109.909594] 6.3.0-rc2-tegra #16 Not tainted
[ 109.913774] -------------------------------------
[ 109.918470] v4l2-ctl/2000 is trying to release lock (&mipi->lock) at:
[ 109.924911] [<ffff80000866b828>] tegra_mipi_finish_calibration+0x84/0xb0
[ 109.931621] but there are no more locks to release!
[ 109.936489]
other info that might help us debug this:
[ 109.943004] 1 lock held by v4l2-ctl/2000:
[ 109.947009] #0: ffff000083bcf6a8 (&chan->video_lock){....}-{3:3}, at: __video_do_ioctl+0xdc/0x3c8
[ 109.955987]
stack backtrace:
[ 109.960336] CPU: 2 PID: 2000 Comm: v4l2-ctl Not tainted 6.3.0-rc2-tegra #16
[ 109.967290] Hardware name: NVIDIA Jetson TX1 Developer Kit (DT)
[ 109.973200] Call trace:
[ 109.975642] dump_backtrace+0xa0/0xfc
[ 109.979308] show_stack+0x18/0x24
[ 109.982622] dump_stack_lvl+0x48/0x60
[ 109.986285] dump_stack+0x18/0x24
[ 109.989598] print_unlock_imbalance_bug+0x130/0x148
[ 109.994472] lock_release+0x1bc/0x248
[ 109.998131] __mutex_unlock_slowpath+0x48/0x2cc
[ 110.002657] mutex_unlock+0x20/0x2c
[ 110.006141] tegra_mipi_finish_calibration+0x84/0xb0
[ 110.011102] tegra_csi_s_stream+0x260/0x318
[ 110.015286] call_s_stream+0x80/0xcc
[ 110.018857] tegra_channel_set_stream+0x58/0xe4
[ 110.023386] tegra210_vi_start_streaming+0xb0/0x1c8
[ 110.028262] tegra_channel_start_streaming+0x54/0x134
[ 110.033311] vb2_start_streaming+0xbc/0x1b8
[ 110.037491] vb2_core_streamon+0x158/0x260
[ 110.041582] vb2_ioctl_streamon+0x4c/0x90
[ 110.045589] v4l_streamon+0x24/0x30
[ 110.049076] __video_do_ioctl+0x160/0x3c8
[ 110.053082] video_usercopy+0x1f0/0x658
[ 110.056916] video_ioctl2+0x18/0x28
[ 110.060404] v4l2_ioctl+0x40/0x60
[ 110.063715] __arm64_sys_ioctl+0xac/0xf0
[ 110.067638] invoke_syscall+0x48/0x114
[ 110.071385] el0_svc_common.constprop.0+0x44/0xec
[ 110.076086] do_el0_svc+0x38/0x98
[ 110.079398] el0_svc+0x2c/0x84
[ 110.082454] el0t_64_sync_handler+0xf4/0x120
[ 110.086722] el0t_64_sync+0x190/0x194

Regards,

Hans

> @@ -352,10 +382,24 @@ static int tegra_csi_enable_stream(struct v4l2_subdev *subdev)
>
> static int tegra_csi_disable_stream(struct v4l2_subdev *subdev)
> {
> + struct tegra_vi_channel *chan = v4l2_get_subdev_hostdata(subdev);
> struct tegra_csi_channel *csi_chan = to_csi_chan(subdev);
> struct tegra_csi *csi = csi_chan->csi;
> int err;
>
> + /*
> + * Stream-off subdevices in reverse order to stream-on.
> + * Remote source subdev in TPG mode is same as CSI subdev.
> + */
> + if (csi_chan->mipi) {
> + struct v4l2_subdev *src_subdev;
> +
> + src_subdev = tegra_channel_get_remote_source_subdev(chan);
> + err = v4l2_subdev_call(src_subdev, video, s_stream, false);
> + if (err < 0 && err != -ENOIOCTLCMD)
> + dev_err_probe(csi->dev, err, "source subdev stream off failed\n");
> + }
> +
> csi->ops->csi_stop_streaming(csi_chan);
>
> if (csi_chan->mipi) {
> diff --git a/drivers/staging/media/tegra-video/vi.c b/drivers/staging/media/tegra-video/vi.c
> index b88532d8d2c9..c76c2a404889 100644
> --- a/drivers/staging/media/tegra-video/vi.c
> +++ b/drivers/staging/media/tegra-video/vi.c
> @@ -197,49 +197,15 @@ tegra_channel_get_remote_source_subdev(struct tegra_vi_channel *chan)
>
> static int tegra_channel_enable_stream(struct tegra_vi_channel *chan)
> {
> - struct v4l2_subdev *csi_subdev, *src_subdev;
> - struct tegra_csi_channel *csi_chan;
> - int ret, err;
> + struct v4l2_subdev *subdev;
> + int ret;
>
> - /*
> - * Tegra CSI receiver can detect the first LP to HS transition.
> - * So, start the CSI stream-on prior to sensor stream-on and
> - * vice-versa for stream-off.
> - */
> - csi_subdev = tegra_channel_get_remote_csi_subdev(chan);
> - ret = v4l2_subdev_call(csi_subdev, video, s_stream, true);
> + subdev = tegra_channel_get_remote_csi_subdev(chan);
> + ret = v4l2_subdev_call(subdev, video, s_stream, true);
> if (ret < 0 && ret != -ENOIOCTLCMD)
> return ret;
>
> - if (IS_ENABLED(CONFIG_VIDEO_TEGRA_TPG))
> - return 0;
> -
> - csi_chan = v4l2_get_subdevdata(csi_subdev);
> - /*
> - * TRM has incorrectly documented to wait for done status from
> - * calibration logic after CSI interface power on.
> - * As per the design, calibration results are latched and applied
> - * to the pads only when the link is in LP11 state which will happen
> - * during the sensor stream-on.
> - * CSI subdev stream-on triggers start of MIPI pads calibration.
> - * Wait for calibration to finish here after sensor subdev stream-on.
> - */
> - src_subdev = tegra_channel_get_remote_source_subdev(chan);
> - ret = v4l2_subdev_call(src_subdev, video, s_stream, true);
> - err = tegra_mipi_finish_calibration(csi_chan->mipi);
> -
> - if (ret < 0 && ret != -ENOIOCTLCMD)
> - goto err_disable_csi_stream;
> -
> - if (err < 0)
> - dev_warn(csi_chan->csi->dev,
> - "MIPI calibration failed: %d\n", err);
> -
> return 0;
> -
> -err_disable_csi_stream:
> - v4l2_subdev_call(csi_subdev, video, s_stream, false);
> - return ret;
> }
>
> static int tegra_channel_disable_stream(struct tegra_vi_channel *chan)
> @@ -247,18 +213,6 @@ static int tegra_channel_disable_stream(struct tegra_vi_channel *chan)
> struct v4l2_subdev *subdev;
> int ret;
>
> - /*
> - * Stream-off subdevices in reverse order to stream-on.
> - * Remote source subdev in TPG mode is same as CSI subdev.
> - */
> - subdev = tegra_channel_get_remote_source_subdev(chan);
> - ret = v4l2_subdev_call(subdev, video, s_stream, false);
> - if (ret < 0 && ret != -ENOIOCTLCMD)
> - return ret;
> -
> - if (IS_ENABLED(CONFIG_VIDEO_TEGRA_TPG))
> - return 0;
> -
> subdev = tegra_channel_get_remote_csi_subdev(chan);
> ret = v4l2_subdev_call(subdev, video, s_stream, false);
> if (ret < 0 && ret != -ENOIOCTLCMD)

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