[PATCH v4 1/3] drm/bridge: samsung-dsim: enable MFLUSH_VS for Exynos 7870 DSIM
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SUPERSEDED: 1 (1M)
From: Kaustabh Chakraborty <hidden>
Date: 2026-08-09 08:28:22
Also in:
dri-devel, linux-samsung-soc, lkml, stable
Subsystem:
drm driver for samsung mipi dsim bridge, drm drivers, drm drivers and misc gpu patches, drm drivers for bridge chips, the rest · Maintainers:
Inki Dae, Jagan Teki, Marek Szyprowski, David Airlie, Simona Vetter, Maarten Lankhorst, Maxime Ripard, Thomas Zimmermann, Andrzej Hajda, Neil Armstrong, Robert Foss, Linus Torvalds
Revision v4 of 7 in this series; 1 review trailer (1 from subsystem maintainers).
Revisions (7)
Commit a36c533ad3e1 ("drm/bridge: samsung-dsim: Always flush display
FIFO on vsync pulse") intends to enable FIFO flushing at v-sync pulse by
not setting the active-low MFLUSH_VS bit.
However, in Exynos 7870 DSIM, the MFLUSH_VS bit is active-high. There is
no publicly available documentation to the best of my knowledge, but
downstream kernel code [1] supports this claim. Enable the bit for
Exynos 7870.
Fixes: a36c533ad3e1 ("drm/bridge: samsung-dsim: Always flush display FIFO on vsync pulse")
Cc: <redacted> # v6.17 and later
Link: https://github.com/samsungexynos7870/android_kernel_samsung_exynos7870/blob/a3762bb1761ae/drivers/video/fbdev/exynos/decon_7870/dsim_reg_7870.c#L699 [1]
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kaustabh Chakraborty <redacted>
---
drivers/gpu/drm/bridge/samsung-dsim.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
index 25ab475309e8..fc42acc6b9ef 100644
--- a/drivers/gpu/drm/bridge/samsung-dsim.c
+++ b/drivers/gpu/drm/bridge/samsung-dsim.c@@ -1089,6 +1089,13 @@ static int samsung_dsim_init_link(struct samsung_dsim *dsi) reg |= DSIM_HBP_DISABLE_MODE; if (dsi->mode_flags & MIPI_DSI_MODE_VIDEO_NO_HSA) reg |= DSIM_HSA_DISABLE_MODE; + + /* + * For some hardware types, DSIM_MFLUSH_VS bit needs to be + * enabled as its active-high. + */ + if (dsi->plat_data->hw_type == DSIM_TYPE_EXYNOS7870) + reg |= DSIM_MFLUSH_VS; } if (dsi->mode_flags & MIPI_DSI_MODE_NO_EOT_PACKET)
--
2.54.0