Hi, Hsin-yi:
On Mon, 2021-07-12 at 17:46 +0800, Hsin-Yi Wang wrote:
> atomic_get_output_bus_fmts() is only called when the bridge is the last
> element in the bridge chain.
>
> If mtk-dpi is not the last bridge, the format of output_bus_cfg is
> MEDIA_BUS_FMT_FIXED, and mtk_dpi_dual_edge() will fail to write correct
> value to regs.
Reviewed-by: CK Hu <ck.hu@xxxxxxxxxxxx>
>
> Fixes: ec8747c52434 ("drm/mediatek: dpi: Add bus format negotiation")
> Signed-off-by: Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx>
> ---
> drivers/gpu/drm/mediatek/mtk_dpi.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_dpi.c b/drivers/gpu/drm/mediatek/mtk_dpi.c
> index bced555648b01..25c565f9179cc 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dpi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dpi.c
> @@ -610,6 +610,10 @@ static int mtk_dpi_bridge_atomic_check(struct drm_bridge *bridge,
>
> out_bus_format = bridge_state->output_bus_cfg.format;
>
> + if (out_bus_format == MEDIA_BUS_FMT_FIXED)
> + if (dpi->conf->num_output_fmts)
> + out_bus_format = dpi->conf->output_fmts[0];
> +
> dev_dbg(dpi->dev, "input format 0x%04x, output format 0x%04x\n",
> bridge_state->input_bus_cfg.format,
> bridge_state->output_bus_cfg.format);
