Claude review: drm/msm/dsi: Restore widebus calculation for CMDMode panels

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Overall Series Review

Subject: drm/msm/dsi: Restore widebus calculation for CMDMode panels
Author: Marijn Suijten <marijn.suijten@somainline.org>
Patches: 4
Reviewed: 2026-03-13T14:40:21.566414

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This is a single-patch fix for a regression introduced by commit ac47870fd795 ("drm/msm/dsi: fix hdisplay calculation when programming dsi registers"). That commit removed the command-mode widebus path that set `bits_per_pclk = 48`, incorrectly claiming CMD mode doesn't use this code path. The result is that all DSI DSC command-mode panels on SM8350+ (with widebus support) broke — the `hdisplay` calculation became wrong because `mipi_dsi_pixel_format_to_bpp()` returns 24 for RGB888, identical to the non-widebus case, so widebus effectively did nothing.

The fix is logically correct and restores the original behavior for CMD mode while preserving the video-mode change from ac47870fd795.

**Note:** The current drm-next tree (line 1030 of `dsi_host.c`) already has a different refactoring of this area that uses `bytes_per_pclk` (3/6) instead of `bits_per_pclk` (24/48), and already includes the `!(msm_host->mode_flags & MIPI_DSI_MODE_VIDEO)` guard. This means the regression may have already been fixed differently on drm-next, and this patch targets a tree where ac47870fd795 exists but that subsequent refactoring hasn't landed. The maintainers should verify which tree this needs to go into (likely a stable backport target).

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