Hi,
On 02/12/2025 21:02, Linus Walleij wrote:
> commit c9b1150a68d9362a0827609fc0dc1664c0d8bfe1
> "drm/atomic-helper: Re-order bridge chain pre-enable and post-disable"
> caused regressions in all bridges that e.g. send DSI commands in
> their .prepare() and .unprepare() callbacks when used with R-Car DU.
>
> This is needed on R-Car DU, where the CRTC provides clock to LVDS
> and DSI, and has to be started before a bridge may call .prepare,
> which may trigger e.g. a DSI transfer.
>
> This specifically fixes the case where ILI9881C is connected to R-Car
> DU DSI. The ILI9881C panel driver does DSI command transfer in its
> struct drm_panel_funcs .prepare function, which is currently called
> before R-Car DU rcar_du_crtc_atomic_enable() rcar_mipi_dsi_pclk_enable()
> and the DSI command transfer times out.
>
> Fixes: c9b1150a68d9 ("drm/atomic-helper: Re-order bridge chain pre-enable and
> post-disable")
> Link:
> https://lore.kernel.org/all/20251107230517.471894-1-marek.vasut%2Brenesas%40mailbox.org/
> Tested-by: Geert Uytterhoeven <[email protected]>
> Co-developed-by: Marek Vasut <[email protected]>
> Signed-off-by: Marek Vasut <[email protected]>
> Tested-by: Marek Vasut <[email protected]>
> Reviewed-by: Maxime Ripard <[email protected]>
> Signed-off-by: Linus Walleij <[email protected]>
> ---
> This is a modified version of Marek's patch using the approach
> from MCDE. I'm pretty sure this driver also needs the original
> semantic ording during disablement, and it surely doesn't hurt
> to restore it too.
> ---
> drivers/gpu/drm/renesas/rcar-du/rcar_du_kms.c | 33
> ++++++++++++++++++++++++---
> 1 file changed, 30 insertions(+), 3 deletions(-)
>
Acked-by: Aradhya Bhatia <[email protected]>
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