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Hi, Angelo:
On Thu, 2024-02-15 at 09:53 +0100, AngeloGioacchino Del Regno wrote:
> Instead of open coding, use the mipi_dsi_pixel_format_to_bpp() helper
> function from drm_mipi_dsi.h in mtk_dsi_poweron() and for validation
> in mtk_dsi_bridge_mode_valid().
>
> Note that this function changes the behavior of this driver:
> previously,
> in case of unknown formats, it would (wrongly) assume that it should
> account for a 24-bits format - now it will return an error and refuse
> to set clocks and/or enable the DSI.
>
> This is done because setting the wrong data rate will only produce a
> garbage output that the display will misinterpret both because this
> driver doesn't actually provide any extra-spec format support and/or
> because the data rate (hence, the HS clock) will be wrong.
Reviewed-by: CK Hu <ck.hu@mediatek.com>
>
> Reviewed-by: Alexandre Mergnat <amergnat@baylibre.com>
> Signed-off-by: AngeloGioacchino Del Regno <
> angelogioacchino.delregno@collabora.com>
> ---
> drivers/gpu/drm/mediatek/mtk_dsi.c | 26 +++++++++-----------------
> 1 file changed, 9 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c
> b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index b644505de98a..9501f4019199 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -598,19 +598,12 @@ static int mtk_dsi_poweron(struct mtk_dsi *dsi)
> if (++dsi->refcount != 1)
> return 0;
>
> -switch (dsi->format) {
> -case MIPI_DSI_FMT_RGB565:
> -bit_per_pixel = 16;
> -break;
> -case MIPI_DSI_FMT_RGB666_PACKED:
> -bit_per_pixel = 18;
> -break;
> -case MIPI_DSI_FMT_RGB666:
> -case MIPI_DSI_FMT_RGB888:
> -default:
> -bit_per_pixel = 24;
> -break;
> +ret = mipi_dsi_pixel_format_to_bpp(dsi->format);
> +if (ret < 0) {
> +dev_err(dev, "Unknown MIPI DSI format %d\n", dsi-
> >format);
> +return ret;
> }
> +bit_per_pixel = ret;
>
> dsi->data_rate = DIV_ROUND_UP_ULL(dsi->vm.pixelclock *
> bit_per_pixel,
> dsi->lanes);
> @@ -793,12 +786,11 @@ mtk_dsi_bridge_mode_valid(struct drm_bridge
> *bridge,
> const struct drm_display_mode *mode)
> {
> struct mtk_dsi *dsi = bridge_to_dsi(bridge);
> -u32 bpp;
> +int bpp;
>
> -if (dsi->format == MIPI_DSI_FMT_RGB565)
> -bpp = 16;
> -else
> -bpp = 24;
> +bpp = mipi_dsi_pixel_format_to_bpp(dsi->format);
> +if (bpp < 0)
> +return MODE_ERROR;
>
> if (mode->clock * bpp / dsi->lanes > 1500000)
> return MODE_CLOCK_HIGH;
</pre>
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