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    Subject[PATCH 5.13 199/266] drm/amd/display: Reject non-zero src_y and src_x for video planes
    Date
    From: Harry Wentland <harry.wentland@amd.com>

    commit c6c6a712199ab355ce333fa5764a59506bb107c1 upstream.

    [Why]
    This hasn't been well tested and leads to complete system hangs on DCN1
    based systems, possibly others.

    The system hang can be reproduced by gesturing the video on the YouTube
    Android app on ChromeOS into full screen.

    [How]
    Reject atomic commits with non-zero drm_plane_state.src_x or src_y values.

    v2:
    - Add code comment describing the reason we're rejecting non-zero
    src_x and src_y
    - Drop gerrit Change-Id
    - Add stable CC
    - Based on amd-staging-drm-next

    v3: removed trailing whitespace

    Signed-off-by: Harry Wentland <harry.wentland@amd.com>
    Cc: stable@vger.kernel.org
    Cc: nicholas.kazlauskas@amd.com
    Cc: amd-gfx@lists.freedesktop.org
    Cc: alexander.deucher@amd.com
    Cc: Roman.Li@amd.com
    Cc: hersenxs.wu@amd.com
    Cc: danny.wang@amd.com
    Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
    Acked-by: Christian König <christian.koenig@amd.com>
    Reviewed-by: Hersen Wu <hersenxs.wu@amd.com>
    Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 17 +++++++++++++++++
    1 file changed, 17 insertions(+)

    --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
    +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
    @@ -4049,6 +4049,23 @@ static int fill_dc_scaling_info(const st
    scaling_info->src_rect.y != 0))
    return -EINVAL;

    + /*
    + * For reasons we don't (yet) fully understand a non-zero
    + * src_y coordinate into an NV12 buffer can cause a
    + * system hang. To avoid hangs (and maybe be overly cautious)
    + * let's reject both non-zero src_x and src_y.
    + *
    + * We currently know of only one use-case to reproduce a
    + * scenario with non-zero src_x and src_y for NV12, which
    + * is to gesture the YouTube Android app into full screen
    + * on ChromeOS.
    + */
    + if (state->fb &&
    + state->fb->format->format == DRM_FORMAT_NV12 &&
    + (scaling_info->src_rect.x != 0 ||
    + scaling_info->src_rect.y != 0))
    + return -EINVAL;
    +
    scaling_info->src_rect.width = state->src_w >> 16;
    if (scaling_info->src_rect.width == 0)
    return -EINVAL;

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