Patch "drm/msm/dsi: fix hdisplay calculation when programming dsi registers" has been added to the 6.19-stable tree

This is a note to let you know that I've just added the patch titled

drm/msm/dsi: fix hdisplay calculation when programming dsi registers

to the 6.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drm-msm-dsi-fix-hdisplay-calculation-when-programmin.patch
and it can be found in the queue-6.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

commit 5c8236c2f2cd9998509b0b2bb7cff4c7098dcaf6

Author: Pengyu Luo <[email protected]>
Date:   Sat Feb 14 18:51:28 2026 +0800

drm/msm/dsi: fix hdisplay calculation when programming dsi registers

[ Upstream commit ac47870fd795549f03d57e0879fc730c79119f4b ]

Recently, the hdisplay calculation is working for 3:1 compressed ratio only. If we have a video panel with DSC BPP = 8, and BPC = 10, we still use the default bits_per_pclk = 24, then we get the wrong hdisplay. We can draw the conclusion by cross-comparing the calculation with the calculation in dsi_adjust_pclk_for_compression().

Since CMD mode does not use this, we can remove !(msm_host->mode_flags & MIPI_DSI_MODE_VIDEO) safely.

Fixes efcbd6f9cdeb ("drm/msm/dsi: Enable widebus for DSI")

Signed-off-by Pengyu Luo <[email protected]>

Reviewed-by Dmitry Baryshkov <[email protected]>

Patchwork: https://patchwork.freedesktop.org/patch/704822/

Link https://lore.kernel.org/r/[email protected] open here

Signed-off-by Dmitry Baryshkov <[email protected]>

Signed-off-by Sasha Levin <[email protected]>

drivers/gpu/drm/msm/dsi/dsi_host.c +8 -6

index e0de545d40775..e8e83ee61eb09 100644
@@ -993,7 +993,7 @@ static void dsi_timing_setup(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
 
        if (msm_host->dsc) {
                struct drm_dsc_config *dsc = msm_host->dsc;
-               u32 bytes_per_pclk;
+               u32 bits_per_pclk;
 
                /* update dsc params with timing params */
                if (!dsc || !mode->hdisplay || !mode->vdisplay) {

@@ -1015,7 +1015,9 @@ static void dsi_timing_setup(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
 
                /*
                 * DPU sends 3 bytes per pclk cycle to DSI. If widebus is
-                * enabled, bus width is extended to 6 bytes.
+                * enabled, MDP always sends out 48-bit compressed data per
+                * pclk and on average, DSI consumes an amount of compressed
+                * data equivalent to the uncompressed pixel depth per pclk.
                 *
                 * Calculate the number of pclks needed to transmit one line of
                 * the compressed data.

@@ -1027,12 +1029,12 @@ static void dsi_timing_setup(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
                 * unused anyway.
                 */
                h_total -= hdisplay;
-               if (wide_bus_enabled && !(msm_host->mode_flags & MIPI_DSI_MODE_VIDEO))
-                       bytes_per_pclk = 6;
+               if (wide_bus_enabled)
+                       bits_per_pclk = mipi_dsi_pixel_format_to_bpp(msm_host->format);
                else
-                       bytes_per_pclk = 3;
+                       bits_per_pclk = 24;
 
-               hdisplay = DIV_ROUND_UP(msm_dsc_get_bytes_per_line(msm_host->dsc), bytes_per_pclk);
+               hdisplay = DIV_ROUND_UP(msm_dsc_get_bytes_per_line(msm_host->dsc) * 8, bits_per_pclk);
 
                h_total += hdisplay;
                ha_end = ha_start + hdisplay;

Quoted 12 lines · Sasha Levin

This is a note to let you know that I've just added the patch titled

drm/msm/dsi: fix hdisplay calculation when programming dsi registers

to the 6.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drm-msm-dsi-fix-hdisplay-calculation-when-programmin.patch
and it can be found in the queue-6.19 subdirectory.

Quoted 4 lines

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Please drop it for all stable trees, this patch has an impact on CMD panels. Fixes have been submitted, but not merged yet.