Hi, Louis:
Louis-Alexis Eyraud <louisalexis.eyr...@collabora.com> 於 2025年7月1日 週二 下午3:31寫道：
>
> Since commit c9b1150a68d9 ("drm/atomic-helper: Re-order bridge chain
> pre-enable and post-disable"), the bridge pre_enable callbacks are now
> called before crtc enable, and the bridge post_disable callbacks after
> the crtc disable.
> In the mediatek-drm driver, this change leads to transfer errors on
> mtk_dsi_host_transfer callback processing during the panel bridge
> pre-enable sequence because the DSI host bridge pre_enable and CRTC
> enable sequences, that are enabling the required clocks and PHY using
> mtk_dsi_poweron function, are called after.
>
> So, in order to fix this call order issue, request the DSI host bridge
> be pre-enabled before panel bridge by setting pre_enable_prev_first
> flag on DSI device bridge in the mtk_dsi_host_attach function.
Applied to mediatek-drm-fixes [1], thanks.
[1]
https://git.kernel.org/pub/scm/linux/kernel/git/chunkuang.hu/linux.git/log/?h=mediatek-drm-fixes
Regards,
Chun-Kuang.
>
> Fixes: c9b1150a68d9 ("drm/atomic-helper: Re-order bridge chain pre-enable and
> post-disable")
> Signed-off-by: Louis-Alexis Eyraud <louisalexis.eyr...@collabora.com>
> ---
> This patch fixes an issue that can be observed on boards such as
> MediatekGenio 1200-EVK or 350-EVK with a kernel based on linux-next
> (tag: next-20250635) since commit c9b1150a68d9 ("drm/atomic-helper:
> Re-order bridge chain pre-enable and post-disable").
> In boot logs, there are multiples errors such as IRQ timeouts and
> panel init errors, leading the DSI panel not being enabled:
>
> Example on Genio 1200-EVK:
> ```
> [drm] Wait DSI IRQ(0x00000002) Timeout
> panel-himax-hx8279 1c008000.dsi.0: sending generic data b0 05 failed:
> -62
> [drm] Wait DSI IRQ(0x00000008) Timeout
> [drm:mtk_dsi_host_transfer [mediatek_drm]] *ERROR* failed to switch cmd
> mode
> panel-himax-hx8279 1c008000.dsi.0: sending DCS SET_DISPLAY_ON failed:
> -62
> ```
> ---
> drivers/gpu/drm/mediatek/mtk_dsi.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c
> b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index
> d7726091819c4762698b41060b3d4d8d27940238..0e2bcd5f67b767d92f2697a5b8183f67ee178a38
> 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -1002,6 +1002,12 @@ static int mtk_dsi_host_attach(struct mipi_dsi_host
> *host,
> return PTR_ERR(dsi->next_bridge);
> }
>
> + /*
> + * set flag to request the DSI host bridge be pre-enabled before
> device bridge
> + * in the chain, so the DSI host is ready when the device bridge is
> pre-enabled
> + */
> + dsi->next_bridge->pre_enable_prev_first = true;
> +
> drm_bridge_add(&dsi->bridge);
>
> ret = component_add(host->dev, &mtk_dsi_component_ops);
>
> ---
> base-commit: c6a68d8f7b81a6ce8962885408cc2d0c1f8b9470
> change-id: 20250630-mediatek-drm-fix-dsi-panel-init-1a4b534c40a6
>
> Best regards,
> --
> Louis-Alexis Eyraud <louisalexis.eyr...@collabora.com>
>
