Re: [PATCH v6 17/17] drm/vkms: Add support for DRM_FORMAT_R*

[Pekka Paalanen <pekka.paalanen@collabora.com>]

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On Tue, 09 Apr 2024 15:25:35 +0200
Louis Chauvet <louis.chauvet@bootlin.com> wrote:

> This add the support for:
> - R1/R2/R4/R8
> 
> R1 format was tested with [1] and [2].
> 
> [1]: https://lore.kernel.org/r/20240313-new_rotation-v2-0-6230fd5cae59@bootlin.com
> [2]: https://lore.kernel.org/igt-dev/20240306-b4-kms_tests-v1-0-8fe451efd2ac@bootlin.com/
> 
> Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
> ---
>  drivers/gpu/drm/vkms/vkms_formats.c | 101 ++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/vkms/vkms_plane.c   |   4 ++
>  2 files changed, 105 insertions(+)
> 
> diff --git a/drivers/gpu/drm/vkms/vkms_formats.c b/drivers/gpu/drm/vkms/vkms_formats.c
> index ca9028c1ef1a..7f49995686fd 100644
> --- a/drivers/gpu/drm/vkms/vkms_formats.c
> +++ b/drivers/gpu/drm/vkms/vkms_formats.c
> @@ -237,6 +237,11 @@ static struct pixel_argb_u16 argb_u16_from_RGB565(const u16 *pixel)
>  	return out_pixel;
>  }
>  
> +static struct pixel_argb_u16 argb_u16_from_gray8(u8 gray)
> +{
> +	return argb_u16_from_u8888(255, gray, gray, gray);
> +}
> +
>  VISIBLE_IF_KUNIT struct pixel_argb_u16 argb_u16_from_yuv888(u8 y, u8 channel_1, u8 channel_2,
>  							   const struct conversion_matrix *matrix)
>  {
> @@ -302,6 +307,94 @@ static void magenta_to_argb_u16(const struct vkms_plane_state *plane, int x_star
>  	}
>  }
>  
> +static void Rx_read_line(const struct vkms_plane_state *plane, int x_start,
> +			 int y_start, enum pixel_read_direction direction, int count,
> +			 struct pixel_argb_u16 out_pixel[], u8 bit_per_pixel, u8 lum_per_level)

Hi Louis,

I guess for R1, R2 and R4, you would get both bit_per_pixel and
lum_per_level from the pixel format info?

bits_per_pixel = drm_format_info_bpp(...)

lum_per_level = 0xFF / (1 << bits_per_pixel - 1) = 0xFF / mask

or even 0xFFFF so you get the 16-bit value directly.

> +{
> +	struct pixel_argb_u16 *end = out_pixel + count;
> +	u8 *src_pixels;
> +	int rem_x, rem_y;
> +
> +	WARN_ONCE(drm_format_info_block_height(plane->frame_info->fb->format, 0) != 1,
> +		  "%s() only support formats with block_h == 1", __func__);
> +
> +	packed_pixels_addr(plane->frame_info, x_start, y_start, 0, &src_pixels, &rem_x, &rem_y);
> +	int bit_offset = (8-bit_per_pixel) - rem_x * bit_per_pixel;
> +	int step = get_block_step_byte(plane->frame_info->fb, direction, 0);
> +	int mask = (0x1 << bit_per_pixel) - 1;

Bit masks are best unsigned, because a signed shift-right of a value
will replicate the old highest bit to all the new high bits. That might
be a surprise if the old value happens to be negative.

> +
> +	if (direction == READ_LEFT_TO_RIGHT || direction == READ_RIGHT_TO_LEFT) {
> +		int restart_bit_offset;
> +		int step_bit_offset;
> +
> +		if (direction == READ_LEFT_TO_RIGHT) {
> +			restart_bit_offset = 8 - bit_per_pixel;
> +			step_bit_offset = -bit_per_pixel;
> +		} else {
> +			restart_bit_offset = 0;
> +			step_bit_offset = bit_per_pixel;
> +		}
> +
> +		while (out_pixel < end) {
> +			u8 val = ((*src_pixels) >> bit_offset) & mask;
> +
> +			*out_pixel = argb_u16_from_gray8(val * lum_per_level);
> +
> +			bit_offset += step_bit_offset;
> +			if (bit_offset < 0 || 8 <= bit_offset) {
> +				bit_offset = restart_bit_offset;
> +				src_pixels += step;
> +			}
> +			out_pixel += 1;
> +		}
> +	} else if (direction == READ_TOP_TO_BOTTOM || direction == READ_BOTTOM_TO_TOP) {
> +		while (out_pixel < end) {
> +			u8 val = (*src_pixels >> bit_offset) & mask;
> +			*out_pixel = argb_u16_from_gray8(val * lum_per_level);
> +			src_pixels += step;
> +			out_pixel += 1;
> +		}
> +	}
> +}
> +
> +static void R1_read_line(const struct vkms_plane_state *plane, int x_start,
> +			 int y_start, enum pixel_read_direction direction, int count,
> +			 struct pixel_argb_u16 out_pixel[])
> +{
> +	Rx_read_line(plane, x_start, y_start, direction, count, out_pixel, 1, 0xFF);
> +}
> +
> +static void R2_read_line(const struct vkms_plane_state *plane, int x_start,
> +			 int y_start, enum pixel_read_direction direction, int count,
> +			 struct pixel_argb_u16 out_pixel[])
> +{
> +	Rx_read_line(plane, x_start, y_start, direction, count, out_pixel, 2, 0x55);
> +}
> +
> +static void R4_read_line(const struct vkms_plane_state *plane, int x_start,
> +			 int y_start, enum pixel_read_direction direction, int count,
> +			 struct pixel_argb_u16 out_pixel[])
> +{
> +	Rx_read_line(plane, x_start, y_start, direction, count, out_pixel, 4, 0x11);
> +}
> +
> +static void R8_read_line(const struct vkms_plane_state *plane, int x_start,
> +			 int y_start, enum pixel_read_direction direction, int count,
> +			 struct pixel_argb_u16 out_pixel[])
> +{
> +	struct pixel_argb_u16 *end = out_pixel + count;
> +	u8 *src_pixels;
> +	int step = get_block_step_byte(plane->frame_info->fb, direction, 0);
> +
> +	packed_pixels_addr_1x1(plane->frame_info, x_start, y_start, 0, &src_pixels);
> +
> +	while (out_pixel < end) {
> +		*out_pixel = argb_u16_from_gray8(*src_pixels);
> +		src_pixels += step;
> +		out_pixel += 1;
> +	}
> +}
> +
>  static void ARGB8888_read_line(const struct vkms_plane_state *plane, int x_start, int y_start,
>  			       enum pixel_read_direction direction, int count,
>  			       struct pixel_argb_u16 out_pixel[])
> @@ -625,6 +718,14 @@ pixel_read_line_t get_pixel_read_line_function(u32 format)
>  	case DRM_FORMAT_YVU422:
>  	case DRM_FORMAT_YVU444:
>  		return &planar_yuv_read_line;
> +	case DRM_FORMAT_R1:
> +		return &R1_read_line;
> +	case DRM_FORMAT_R2:
> +		return &R2_read_line;
> +	case DRM_FORMAT_R4:
> +		return &R4_read_line;
> +	case DRM_FORMAT_R8:
> +		return &R8_read_line;
>  	default:
>  		/*
>  		 * This is a bug in vkms_plane_atomic_check(). All the supported
> diff --git a/drivers/gpu/drm/vkms/vkms_plane.c b/drivers/gpu/drm/vkms/vkms_plane.c
> index 8f764a108b00..67f891e7ac58 100644
> --- a/drivers/gpu/drm/vkms/vkms_plane.c
> +++ b/drivers/gpu/drm/vkms/vkms_plane.c
> @@ -30,6 +30,10 @@ static const u32 vkms_formats[] = {
>  	DRM_FORMAT_YVU420,
>  	DRM_FORMAT_YVU422,
>  	DRM_FORMAT_YVU444,
> +	DRM_FORMAT_R1,
> +	DRM_FORMAT_R2,
> +	DRM_FORMAT_R4,
> +	DRM_FORMAT_R8,
>  };
>  
>  static struct drm_plane_state *
> 

This patch looks good to me, and the R8_read_line() is ok to have
separately, I guess for performance reasons.

I suggested a way to reduce the repetition between R1, R2, R4 a little
bit. With or without that:

Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.com>


Thanks,
pq

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