Re: [PATCH v9 09/21] drm/mediatek: Fix XRGB setting error in OVL

["CK Hu (胡俊光)" <ck.hu@mediatek.com>]

On Fri, 2024-06-14 at 10:46 +0800, Shawn Sung wrote:
> From: Hsiao Chien Sung <shawn.sung@mediatek.com>
> 
> CONST_BLD must be enabled for XRGB formats although the alpha channel
> can be ignored, or OVL will still read the value from memory.
> This error only affects CRC generation.
> 
> Fixes: c410fa9b07c3 ("drm/mediatek: Add AFBC support to Mediatek DRM driver")

Fixes: 119f5173628a ("drm/mediatek: Add DRM Driver for Mediatek SoC MT8173.")

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/gpu/drm/mediatek?h=v6.10-rc3&id=119f5173628aa7a0c3cf9db83460d40709e8241d

Regards,
CK


> Signed-off-by: Hsiao Chien Sung <shawn.sung@mediatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_disp_ovl.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> index 946b87ec48ca..fd390fb83d0e 100644
> --- a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> +++ b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> @@ -38,6 +38,7 @@
>  #define DISP_REG_OVL_PITCH_MSB(n)		(0x0040 + 0x20 * (n))
>  #define OVL_PITCH_MSB_2ND_SUBBUF			BIT(16)
>  #define DISP_REG_OVL_PITCH(n)			(0x0044 + 0x20 * (n))
> +#define OVL_CONST_BLEND					BIT(28)
>  #define DISP_REG_OVL_RDMA_CTRL(n)		(0x00c0 + 0x20 * (n))
>  #define DISP_REG_OVL_RDMA_GMC(n)		(0x00c8 + 0x20 * (n))
>  #define DISP_REG_OVL_ADDR_MT2701		0x0040
> @@ -428,6 +429,7 @@ void mtk_ovl_layer_config(struct device *dev, unsigned int idx,
>  	unsigned int fmt = pending->format;
>  	unsigned int offset = (pending->y << 16) | pending->x;
>  	unsigned int src_size = (pending->height << 16) | pending->width;
> +	unsigned int ignore_pixel_alpha = 0;
>  	unsigned int con;
>  	bool is_afbc = pending->modifier != DRM_FORMAT_MOD_LINEAR;
>  	union overlay_pitch {
> @@ -449,6 +451,14 @@ void mtk_ovl_layer_config(struct device *dev, unsigned int idx,
>  	if (state->base.fb && state->base.fb->format->has_alpha)
>  		con |= OVL_CON_AEN | OVL_CON_ALPHA;
>  
> +	/* CONST_BLD must be enabled for XRGB formats although the alpha channel
> +	 * can be ignored, or OVL will still read the value from memory.
> +	 * For RGB888 related formats, whether CONST_BLD is enabled or not won't
> +	 * affect the result. Therefore we use !has_alpha as the condition.
> +	 */
> +	if (state->base.fb && !state->base.fb->format->has_alpha)
> +		ignore_pixel_alpha = OVL_CONST_BLEND;
> +
>  	if (pending->rotation & DRM_MODE_REFLECT_Y) {
>  		con |= OVL_CON_VIRT_FLIP;
>  		addr += (pending->height - 1) * pending->pitch;
> @@ -464,8 +474,8 @@ void mtk_ovl_layer_config(struct device *dev, unsigned int idx,
>  
>  	mtk_ddp_write_relaxed(cmdq_pkt, con, &ovl->cmdq_reg, ovl->regs,
>  			      DISP_REG_OVL_CON(idx));
> -	mtk_ddp_write_relaxed(cmdq_pkt, overlay_pitch.split_pitch.lsb, &ovl->cmdq_reg, ovl->regs,
> -			      DISP_REG_OVL_PITCH(idx));
> +	mtk_ddp_write_relaxed(cmdq_pkt, overlay_pitch.split_pitch.lsb | ignore_pixel_alpha,
> +			      &ovl->cmdq_reg, ovl->regs, DISP_REG_OVL_PITCH(idx));
>  	mtk_ddp_write_relaxed(cmdq_pkt, src_size, &ovl->cmdq_reg, ovl->regs,
>  			      DISP_REG_OVL_SRC_SIZE(idx));
>  	mtk_ddp_write_relaxed(cmdq_pkt, offset, &ovl->cmdq_reg, ovl->regs,