From: Jayesh Choudhary <[email protected]> [ Upstream commit cfb29225db20c56432a8525366321c0c09edfb2e ]
TIDSS uses crtc_* fields to propagate its registers and set the clock rates. So set the CRTC modesetting timing parameters with the adjusted mode when needed, to set correct values. Cc: Tomi Valkeinen <[email protected]> Signed-off-by: Jayesh Choudhary <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Tomi Valkeinen <[email protected]> Signed-off-by: Sasha Levin <[email protected]> --- LLM Generated explanations, may be completely bogus: YES - What it fixes - The patch computes the CRTC timing fields (crtc_clock, crtc_htotal, crtc_vtotal, etc.) in the adjusted mode during modesets. Without this, those fields remain unset, which breaks consumers that rely on them (notably DRM’s vblank timestamping and some bridges that expect crtc_* to be valid). - In TIDSS today, atomic enable programs the pixel clock from mode->clock and programs timings from mode->hsync_start/htotal etc., so hardware programming itself doesn’t use crtc_* directly. However, the DRM core expects crtc_* in the adjusted mode to be valid for vblank calculations and helpers. - Changes in this patch - Converts the local mode pointer to non-const so it can be passed to the mutating helper: - drivers/gpu/drm/tidss/tidss_crtc.c:94 - After validating the adjusted mode, it initializes the crtc_* timing members when a modeset is needed: - drivers/gpu/drm/tidss/tidss_crtc.c:102 - drivers/gpu/drm/tidss/tidss_crtc.c:104 - New: if (drm_atomic_crtc_needs_modeset(crtc_state)) drm_mode_set_crtcinfo(mode, 0); - The rest of the function remains unchanged, returning the existing bus check: - drivers/gpu/drm/tidss/tidss_crtc.c:111 - Why this matters (core interactions) - Atomic helpers compute vblank timestamping constants from the new crtc state’s adjusted mode and they explicitly use the crtc_* members: - drivers/gpu/drm/drm_atomic_helper.c:1437 - drivers/gpu/drm/drm_vblank.c:651 - If crtc_clock is 0 (because crtc_* fields weren’t populated), DRM reports it can’t calculate constants and bails: - drivers/gpu/drm/drm_vblank.c:728 - By setting crtc_* in adjusted_mode before the commit helpers run, vblank timing setup becomes correct and robust. - Scope and risk - Small, contained change in a single driver file (one variable type tweak + one call). - No architectural changes; no feature additions. - Safe for non-interlaced modes (TIDSS rejects interlace already: drivers/gpu/drm/tidss/tidss_dispc.c:1377–1380). - Doesn’t change how TIDSS programs hardware timings: dispc still uses mode->{h*, v*, flags} (drivers/gpu/drm/tidss/tidss_dispc.c:1218–1269), and pixel clock still comes from mode->clock (drivers/gpu/drm/tidss/tidss_crtc.c:227–229). - Improves correctness for DRM subsystems that rely on crtc_* (vblank, some bridges). - Stable backport criteria - Fixes a real bug that can cause broken/missing vblank timing and potentially wrong rates in downstream components that use crtc_*. - Minimal and self-contained. - No user-visible API/ABI changes and low regression risk. - Applies to all stable trees that include TIDSS and the atomic helper flow; dependencies (drm_mode_set_crtcinfo and drm_atomic_crtc_needs_modeset) are longstanding. Conclusion: This is a targeted bugfix with low risk and clear benefit for correctness in the DRM atomic pipeline; it should be backported to stable. drivers/gpu/drm/tidss/tidss_crtc.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/tidss/tidss_crtc.c b/drivers/gpu/drm/tidss/tidss_crtc.c index 17efd77ce7f23..da89fd01c3376 100644 --- a/drivers/gpu/drm/tidss/tidss_crtc.c +++ b/drivers/gpu/drm/tidss/tidss_crtc.c @@ -91,7 +91,7 @@ static int tidss_crtc_atomic_check(struct drm_crtc *crtc, struct dispc_device *dispc = tidss->dispc; struct tidss_crtc *tcrtc = to_tidss_crtc(crtc); u32 hw_videoport = tcrtc->hw_videoport; - const struct drm_display_mode *mode; + struct drm_display_mode *mode; enum drm_mode_status ok; dev_dbg(ddev->dev, "%s\n", __func__); @@ -108,6 +108,9 @@ static int tidss_crtc_atomic_check(struct drm_crtc *crtc, return -EINVAL; } + if (drm_atomic_crtc_needs_modeset(crtc_state)) + drm_mode_set_crtcinfo(mode, 0); + return dispc_vp_bus_check(dispc, hw_videoport, crtc_state); } -- 2.51.0
