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    SubjectRe: [RFC PATCH 4/6] drm/msm/dsi: Use DSC slice(s) packet size to compute word count
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    On 12/13/2022 3:22 PM, Marijn Suijten wrote:
    > According to downstream the value to use for WORD_COUNT is
    > bytes_per_pkt, which denotes the number of bytes in a packet based on
    > how many slices have been configured by the panel driver times the
    > width of a slice times the number of bytes per pixel.
    >
    > The DSC panels seen thus far use one byte per pixel, only one slice
    > per packet, and a slice width of half the panel width leading to the
    > desired bytes_per_pkt+1 value to be equal to hdisplay/2+1. This however
    > isn't the case anymore for panels that configure two slices per packet,
    > where the value should now be hdisplay+1.
    >
    > Note that the aforementioned panel (on a Sony Xperia XZ3, sdm845) with
    > slice_count=1 has also been tested to successfully accept slice_count=2,
    > which would have shown corrupted output previously.
    >
    > Fixes: 08802f515c3c ("drm/msm/dsi: Add support for DSC configuration")
    > Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org>

    Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
    > ---
    > drivers/gpu/drm/msm/dsi/dsi_host.c | 2 +-
    > 1 file changed, 1 insertion(+), 1 deletion(-)
    >
    > diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
    > index b83cf70b1adb..0686c35a6fd4 100644
    > --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
    > +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
    > @@ -989,7 +989,7 @@ static void dsi_timing_setup(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
    > if (!msm_host->dsc)
    > wc = hdisplay * dsi_get_bpp(msm_host->format) / 8 + 1;
    > else
    > - wc = mode->hdisplay / 2 + 1;
    > + wc = msm_host->dsc->slice_chunk_size * msm_host->dsc->slice_count + 1;
    >
    > dsi_write(msm_host, REG_DSI_CMD_MDP_STREAM0_CTRL,
    > DSI_CMD_MDP_STREAM0_CTRL_WORD_COUNT(wc) |

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