[PATCH v2 2/3] drm/format-helper: Add drm_fb_xrgb8888_to_xrgb2101010_toio()

[Thomas Zimmermann]

Hi

Am 07.12.21 um 08:29 schrieb Hector Martin:
> Add XRGB8888 emulation support for devices that can only do XRGB2101010.
> 
> This is chiefly useful for simpledrm on Apple devices where the
> bootloader-provided framebuffer is 10-bit.
> 
> Signed-off-by: Hector Martin <marcan at marcan.st>
> ---
>   drivers/gpu/drm/drm_format_helper.c | 62 +++++++++++++++++++++++++++++
>   include/drm/drm_format_helper.h     |  3 ++
>   2 files changed, 65 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_format_helper.c b/drivers/gpu/drm/drm_format_helper.c
> index dbe3e830096e..edd611d3ab6a 100644
> --- a/drivers/gpu/drm/drm_format_helper.c
> +++ b/drivers/gpu/drm/drm_format_helper.c
> @@ -409,6 +409,59 @@ void drm_fb_xrgb8888_to_rgb888_toio(void __iomem *dst, unsigned int dst_pitch,
>   }
>   EXPORT_SYMBOL(drm_fb_xrgb8888_to_rgb888_toio);
>   
> +static void drm_fb_xrgb8888_to_xrgb2101010_line(u32 *dbuf, const u32 *sbuf,
> +						unsigned int pixels)
> +{
> +	unsigned int x;
> +
> +	for (x = 0; x < pixels; x++) {
> +		*dbuf++ = ((sbuf[x] & 0x000000FF) << 2) |
> +			  ((sbuf[x] & 0x0000FF00) << 4) |
> +			  ((sbuf[x] & 0x00FF0000) << 6);

This isn't quite right. The lowest two destination bits in each 
component will always be zero. You have to do the shifting as above and 
for each component the two highest source bits have to be OR'ed into the 
two lowest destination bits. For example the source bits in a component 
are numbered 7 to 0

  | 7 6 5 4 3 2 1 0 |

then the destination bits should be

  | 7 6 5 4 3 2 1 0 7 6 |

Best regards
Thomas

> +	}
> +}
> +
> +/**
> + * drm_fb_xrgb8888_to_xrgb2101010_toio - Convert XRGB8888 to XRGB2101010 clip
> + * buffer
> + * @dst: XRGB2101010 destination buffer (iomem)
> + * @dst_pitch: Number of bytes between two consecutive scanlines within dst
> + * @vaddr: XRGB8888 source buffer
> + * @fb: DRM framebuffer
> + * @clip: Clip rectangle area to copy
> + *
> + * Drivers can use this function for XRGB2101010 devices that don't natively
> + * support XRGB8888.
> + */
> +void drm_fb_xrgb8888_to_xrgb2101010_toio(void __iomem *dst,
> +					 unsigned int dst_pitch, const void *vaddr,
> +					 const struct drm_framebuffer *fb,
> +					 const struct drm_rect *clip)
> +{
> +	size_t linepixels = clip->x2 - clip->x1;
> +	size_t dst_len = linepixels * sizeof(u32);
> +	unsigned y, lines = clip->y2 - clip->y1;
> +	void *dbuf;
> +
> +	if (!dst_pitch)
> +		dst_pitch = dst_len;
> +
> +	dbuf = kmalloc(dst_len, GFP_KERNEL);
> +	if (!dbuf)
> +		return;
> +
> +	vaddr += clip_offset(clip, fb->pitches[0], sizeof(u32));
> +	for (y = 0; y < lines; y++) {
> +		drm_fb_xrgb8888_to_xrgb2101010_line(dbuf, vaddr, linepixels);
> +		memcpy_toio(dst, dbuf, dst_len);
> +		vaddr += fb->pitches[0];
> +		dst += dst_pitch;
> +	}
> +
> +	kfree(dbuf);
> +}
> +EXPORT_SYMBOL(drm_fb_xrgb8888_to_xrgb2101010_toio);
> +
>   /**
>    * drm_fb_xrgb8888_to_gray8 - Convert XRGB8888 to grayscale
>    * @dst: 8-bit grayscale destination buffer
> @@ -500,6 +553,10 @@ int drm_fb_blit_toio(void __iomem *dst, unsigned int dst_pitch, uint32_t dst_for
>   		fb_format = DRM_FORMAT_XRGB8888;
>   	if (dst_format == DRM_FORMAT_ARGB8888)
>   		dst_format = DRM_FORMAT_XRGB8888;
> +	if (fb_format == DRM_FORMAT_ARGB2101010)
> +		fb_format = DRM_FORMAT_XRGB2101010;
> +	if (dst_format == DRM_FORMAT_ARGB2101010)
> +		dst_format = DRM_FORMAT_XRGB2101010;
>   
>   	if (dst_format == fb_format) {
>   		drm_fb_memcpy_toio(dst, dst_pitch, vmap, fb, clip);
> @@ -515,6 +572,11 @@ int drm_fb_blit_toio(void __iomem *dst, unsigned int dst_pitch, uint32_t dst_for
>   			drm_fb_xrgb8888_to_rgb888_toio(dst, dst_pitch, vmap, fb, clip);
>   			return 0;
>   		}
> +	} else if (dst_format == DRM_FORMAT_XRGB2101010) {
> +		if (fb_format == DRM_FORMAT_XRGB8888) {
> +			drm_fb_xrgb8888_to_xrgb2101010_toio(dst, dst_pitch, vmap, fb, clip);
> +			return 0;
> +		}
>   	}
>   
>   	return -EINVAL;
> diff --git a/include/drm/drm_format_helper.h b/include/drm/drm_format_helper.h
> index 97e4c3223af3..b30ed5de0a33 100644
> --- a/include/drm/drm_format_helper.h
> +++ b/include/drm/drm_format_helper.h
> @@ -33,6 +33,9 @@ void drm_fb_xrgb8888_to_rgb888(void *dst, unsigned int dst_pitch, const void *sr
>   void drm_fb_xrgb8888_to_rgb888_toio(void __iomem *dst, unsigned int dst_pitch,
>   				    const void *vaddr, const struct drm_framebuffer *fb,
>   				    const struct drm_rect *clip);
> +void drm_fb_xrgb8888_to_xrgb2101010_toio(void __iomem *dst, unsigned int dst_pitch,
> +					 const void *vaddr, const struct drm_framebuffer *fb,
> +					 const struct drm_rect *clip);
>   void drm_fb_xrgb8888_to_gray8(void *dst, unsigned int dst_pitch, const void *vaddr,
>   			      const struct drm_framebuffer *fb, const struct drm_rect *clip);
>   
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
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