Reviewed-by: Yannick Fertré <yannick.fer...@st.com>

On 02/01/2018 11:42 AM, Philippe Cornu wrote:
> ltdc supports natively some color formats with alpha (like
> ARGB8888, ARGB1555, ARGB4444...). Related non-alpha formats are
> supported too (ARGB8888->XRGB8888, ARGB4444->XRGB4444...) by
> adjusting ltdc blending factors.
>
> Note: Wayland/Weston requests by default the non-alpha XRGB8888
> color format.
>
> Signed-off-by: Philippe Cornu <philippe.co...@st.com>
> ---
>   drivers/gpu/drm/stm/ltdc.c | 33 +++++++++++++++++++++++++++++++--
>   1 file changed, 31 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
> index 90b3de516c91..f6f26fc0ae9e 100644
> --- a/drivers/gpu/drm/stm/ltdc.c
> +++ b/drivers/gpu/drm/stm/ltdc.c
> @@ -328,6 +328,26 @@ static inline u32 to_drm_pixelformat(enum ltdc_pix_fmt 
> pf)
>       }
>   }
>   
> +static inline u32 get_pixelformat_without_alpha(u32 drm)
> +{
> +     switch (drm) {
> +     case DRM_FORMAT_ARGB4444:
> +             return DRM_FORMAT_XRGB4444;
> +     case DRM_FORMAT_RGBA4444:
> +             return DRM_FORMAT_RGBX4444;
> +     case DRM_FORMAT_ARGB1555:
> +             return DRM_FORMAT_XRGB1555;
> +     case DRM_FORMAT_RGBA5551:
> +             return DRM_FORMAT_RGBX5551;
> +     case DRM_FORMAT_ARGB8888:
> +             return DRM_FORMAT_XRGB8888;
> +     case DRM_FORMAT_RGBA8888:
> +             return DRM_FORMAT_RGBX8888;
> +     default:
> +             return 0;
> +     }
> +}
> +
>   static irqreturn_t ltdc_irq_thread(int irq, void *arg)
>   {
>       struct drm_device *ddev = arg;
> @@ -680,6 +700,9 @@ static void ltdc_plane_atomic_update(struct drm_plane 
> *plane,
>   
>       /* Specifies the blending factors */
>       val = BF1_PAXCA | BF2_1PAXCA;
> +     if (!fb->format->has_alpha)
> +             val = BF1_CA | BF2_1CA;
> +
>       reg_update_bits(ldev->regs, LTDC_L1BFCR + lofs,
>                       LXBFCR_BF2 | LXBFCR_BF1, val);
>   
> @@ -747,8 +770,8 @@ static struct drm_plane *ltdc_plane_create(struct 
> drm_device *ddev,
>       struct device *dev = ddev->dev;
>       struct drm_plane *plane;
>       unsigned int i, nb_fmt = 0;
> -     u32 formats[NB_PF];
> -     u32 drm_fmt;
> +     u32 formats[NB_PF * 2];
> +     u32 drm_fmt, drm_fmt_no_alpha;
>       int ret;
>   
>       /* Get supported pixel formats */
> @@ -757,6 +780,12 @@ static struct drm_plane *ltdc_plane_create(struct 
> drm_device *ddev,
>               if (!drm_fmt)
>                       continue;
>               formats[nb_fmt++] = drm_fmt;
> +
> +             /* Add the no-alpha related format if any & supported */
> +             drm_fmt_no_alpha = get_pixelformat_without_alpha(drm_fmt);
> +             if (!drm_fmt_no_alpha)
> +                     continue;
> +             formats[nb_fmt++] = drm_fmt_no_alpha;
>       }
>   
>       plane = devm_kzalloc(dev, sizeof(*plane), GFP_KERNEL);
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