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Date: Tue, 26 Mar 2024 16:57:01 +0100
From: Louis Chauvet <louis.chauvet@bootlin.com>
To: =?iso-8859-1?Q?Ma=EDra?= Canal <mcanal@igalia.com>
Cc: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>,
	Melissa Wen <melissa.srw@gmail.com>,
	Haneen Mohammed <hamohammed.sa@gmail.com>,
	Daniel Vetter <daniel@ffwll.ch>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <mripard@kernel.org>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	David Airlie <airlied@gmail.com>, arthurgrillo@riseup.net,
	Jonathan Corbet <corbet@lwn.net>, pekka.paalanen@haloniitty.fi,
	dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
	jeremie.dautheribes@bootlin.com, miquel.raynal@bootlin.com,
	thomas.petazzoni@bootlin.com, seanpaul@google.com,
	marcheu@google.com, nicolejadeyee@google.com
Subject: Re: [PATCH v5 10/16] drm/vkms: Re-introduce line-per-line
 composition algorithm
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	Melissa Wen <melissa.srw@gmail.com>,
	Haneen Mohammed <hamohammed.sa@gmail.com>,
	Daniel Vetter <daniel@ffwll.ch>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <mripard@kernel.org>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	David Airlie <airlied@gmail.com>, arthurgrillo@riseup.net,
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References: <20240313-yuv-v5-0-e610cbd03f52@bootlin.com>
 <20240313-yuv-v5-10-e610cbd03f52@bootlin.com>
 <b661b8c2-552c-4256-ad0b-b8a7b9bbed34@igalia.com>
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In-Reply-To: <b661b8c2-552c-4256-ad0b-b8a7b9bbed34@igalia.com>

Le 25/03/24 - 11:15, Ma?ra Canal a ?crit :
> On 3/13/24 14:45, Louis Chauvet wrote:
> > Re-introduce a line-by-line composition algorithm for each pixel format.
> > This allows more performance by not requiring an indirection per pixel
> > read. This patch is focused on readability of the code.
> > 
> > Line-by-line composition was introduced by [1] but rewritten back to
> > pixel-by-pixel algorithm in [2]. At this time, nobody noticed the impact
> > on performance, and it was merged.
> > 
> > This patch is almost a revert of [2], but in addition efforts have been
> > made to increase readability and maintainability of the rotation handling.
> > The blend function is now divided in two parts:
> > - Transformation of coordinates from the output referential to the source
> > referential
> > - Line conversion and blending
> > 
> > Most of the complexity of the rotation management is avoided by using
> > drm_rect_* helpers. The remaining complexity is around the clipping, to
> > avoid reading/writing outside source/destination buffers.
> > 
> > The pixel conversion is now done line-by-line, so the read_pixel_t was
> > replaced with read_pixel_line_t callback. This way the indirection is only
> > required once per line and per plane, instead of once per pixel and per
> > plane.
> > 
> > The read_line_t callbacks are very similar for most pixel format, but it
> > is required to avoid performance impact. Some helpers for color
> > conversion were introduced to avoid code repetition:
> > - *_to_argb_u16: perform colors conversion. They should be inlined by the
> >    compiler, and they are used to avoid repetition between multiple variants
> >    of the same format (argb/xrgb and maybe in the future for formats like
> >    bgr formats).
> > 
> > This new algorithm was tested with:
> > - kms_plane (for color conversions)
> > - kms_rotation_crc (for rotations of planes)
> > - kms_cursor_crc (for translations of planes)
> > - kms_rotation (for all rotations and formats combinations) [3]
> > The performance gain was mesured with:
> > - kms_fb_stress
> 
> Could you tell us what was the performance gain?

I will measure the gain to put the correct number here, but it was at 
least twice faster.
 
> > 
> > [1]: commit 8ba1648567e2 ("drm: vkms: Refactor the plane composer to accept
> >       new formats")
> >       https://lore.kernel.org/all/20220905190811.25024-7-igormtorrente@gmail.com/
> > [2]: commit 322d716a3e8a ("drm/vkms: isolate pixel conversion
> >       functionality")
> >       https://lore.kernel.org/all/20230418130525.128733-2-mcanal@igalia.com/
> > [3]:
> > 
> > Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
> > ---
> >   drivers/gpu/drm/vkms/vkms_composer.c | 167 +++++++++++++++++++------
> >   drivers/gpu/drm/vkms/vkms_drv.h      |  27 ++--
> >   drivers/gpu/drm/vkms/vkms_formats.c  | 236 ++++++++++++++++++++++-------------
> >   drivers/gpu/drm/vkms/vkms_formats.h  |   2 +-
> >   drivers/gpu/drm/vkms/vkms_plane.c    |   5 +-
> >   5 files changed, 292 insertions(+), 145 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
> > index 989bcf59f375..5d78c33dbf41 100644
> > --- a/drivers/gpu/drm/vkms/vkms_composer.c
> > +++ b/drivers/gpu/drm/vkms/vkms_composer.c
> > @@ -41,7 +41,7 @@ static void pre_mul_alpha_blend(const struct line_buffer *stage_buffer,
> >   				struct line_buffer *output_buffer, int x_start, int pixel_count)
> >   {
> >   	struct pixel_argb_u16 *out = &output_buffer->pixels[x_start];
> > -	const struct pixel_argb_u16 *in = stage_buffer->pixels;
> > +	const struct pixel_argb_u16 *in = &stage_buffer->pixels[x_start];
> >   
> >   	for (int i = 0; i < pixel_count; i++) {
> >   		out[i].a = (u16)0xffff;
> > @@ -51,33 +51,6 @@ static void pre_mul_alpha_blend(const struct line_buffer *stage_buffer,
> >   	}
> >   }
> >   
> > -static int get_y_pos(struct vkms_frame_info *frame_info, int y)
> > -{
> > -	if (frame_info->rotation & DRM_MODE_REFLECT_Y)
> > -		return drm_rect_height(&frame_info->rotated) - y - 1;
> > -
> > -	switch (frame_info->rotation & DRM_MODE_ROTATE_MASK) {
> > -	case DRM_MODE_ROTATE_90:
> > -		return frame_info->rotated.x2 - y - 1;
> > -	case DRM_MODE_ROTATE_270:
> > -		return y + frame_info->rotated.x1;
> > -	default:
> > -		return y;
> > -	}
> > -}
> > -
> > -static bool check_limit(struct vkms_frame_info *frame_info, int pos)
> > -{
> > -	if (drm_rotation_90_or_270(frame_info->rotation)) {
> > -		if (pos >= 0 && pos < drm_rect_width(&frame_info->rotated))
> > -			return true;
> > -	} else {
> > -		if (pos >= frame_info->rotated.y1 && pos < frame_info->rotated.y2)
> > -			return true;
> > -	}
> > -
> > -	return false;
> > -}
> >   
> >   static void fill_background(const struct pixel_argb_u16 *background_color,
> >   			    struct line_buffer *output_buffer)
> > @@ -215,34 +188,146 @@ static void blend(struct vkms_writeback_job *wb,
> >   {
> >   	struct vkms_plane_state **plane = crtc_state->active_planes;
> >   	u32 n_active_planes = crtc_state->num_active_planes;
> > -	int y_pos, x_dst, x_limit;
> >   
> >   	const struct pixel_argb_u16 background_color = { .a = 0xffff };
> >   
> > -	size_t crtc_y_limit = crtc_state->base.crtc->mode.vdisplay;
> > +	int crtc_y_limit = crtc_state->base.crtc->mode.vdisplay;
> > +	int crtc_x_limit = crtc_state->base.crtc->mode.hdisplay;
> 
> Shouldn't it be `unsigned int`?

It was a suggestion from Pekka.

> >   
> >   	/*
> >   	 * The planes are composed line-by-line to avoid heavy memory usage. It is a necessary
> >   	 * complexity to avoid poor blending performance.
> >   	 *
> > -	 * The function vkms_compose_row is used to read a line, pixel-by-pixel, into the staging
> > -	 * buffer.
> > +	 * The function pixel_read_line callback is used to read a line, using an efficient
> > +	 * algorithm for a specific format, into the staging buffer.
> >   	 */
> >   	for (size_t y = 0; y < crtc_y_limit; y++) {
> >   		fill_background(&background_color, output_buffer);
> >   
> >   		/* The active planes are composed associatively in z-order. */
> >   		for (size_t i = 0; i < n_active_planes; i++) {
> > -			x_dst = plane[i]->frame_info->dst.x1;
> > -			x_limit = min_t(size_t, drm_rect_width(&plane[i]->frame_info->dst),
> > -					stage_buffer->n_pixels);
> > -			y_pos = get_y_pos(plane[i]->frame_info, y);
> > +			struct vkms_plane_state *current_plane = plane[i];
> >   
> > -			if (!check_limit(plane[i]->frame_info, y_pos))
> > +			/* Avoid rendering useless lines */
> > +			if (y < current_plane->frame_info->dst.y1 ||
> > +			    y >= current_plane->frame_info->dst.y2)
> >   				continue;
> >   
> > -			vkms_compose_row(stage_buffer, plane[i], y_pos);
> > -			pre_mul_alpha_blend(stage_buffer, output_buffer, x_dst, x_limit);
> > +			/*
> > +			 * dst_line is the line to copy. The initial coordinates are inside the
> > +			 * destination framebuffer, and then drm_rect_* helpers are used to
> > +			 * compute the correct position into the source framebuffer.
> > +			 */
> > +			struct drm_rect dst_line = DRM_RECT_INIT(
> 
> Please, run checkpatch on this patch.

I ran checkpatch and ignored this warn for readability, I did not found 
better solution.

But as you suggested, I will split this big function in smaller one, so it 
should solve this.

> > +				current_plane->frame_info->dst.x1, y,
> > +				drm_rect_width(&current_plane->frame_info->dst), 1);
> > +			struct drm_rect tmp_src;
> > +
> > +			drm_rect_fp_to_int(&tmp_src, &current_plane->frame_info->src);
> > +
> > +			/*
> > +			 * [1]: Clamping src_line to the crtc_x_limit to avoid writing outside of
> > +			 * the destination buffer
> > +			 */
> > +			dst_line.x1 = max_t(int, dst_line.x1, 0);
> > +			dst_line.x2 = min_t(int, dst_line.x2, crtc_x_limit);
> > +			/* The destination is completely outside of the crtc. */
> > +			if (dst_line.x2 <= dst_line.x1)
> > +				continue;
> > +
> > +			struct drm_rect src_line = dst_line;
> > +
> > +			/*
> > +			 * Transform the coordinate x/y from the crtc to coordinates into
> > +			 * coordinates for the src buffer.
> > +			 *
> > +			 * - Cancel the offset of the dst buffer.
> > +			 * - Invert the rotation. This assumes that
> > +			 *   dst = drm_rect_rotate(src, rotation) (dst and src have the
> > +			 *   same size, but can be rotated).
> > +			 * - Apply the offset of the source rectangle to the coordinate.
> > +			 */
> > +			drm_rect_translate(&src_line, -current_plane->frame_info->dst.x1,
> > +					   -current_plane->frame_info->dst.y1);
> > +			drm_rect_rotate_inv(&src_line,
> > +					    drm_rect_width(&tmp_src),
> > +					    drm_rect_height(&tmp_src),
> > +					    current_plane->frame_info->rotation);
> > +			drm_rect_translate(&src_line, tmp_src.x1, tmp_src.y1);
> > +
> > +			/* Get the correct reading direction in the source buffer. */
> > +
> > +			enum pixel_read_direction direction =
> > +				direction_for_rotation(current_plane->frame_info->rotation);
> > +
> > +			int x_start = src_line.x1;
> > +			int y_start = src_line.y1;
> > +			int pixel_count;
> > +			/* [2]: Compute and clamp the number of pixel to read */
> > +			if (direction == READ_LEFT_TO_RIGHT || direction == READ_RIGHT_TO_LEFT) {
> > +				/*
> > +				 * In horizontal reading, the src_line width is the number of pixel
> > +				 * to read
> > +				 */
> > +				pixel_count = drm_rect_width(&src_line);
> > +				if (x_start < 0) {
> > +					pixel_count += x_start;
> > +					x_start = 0;
> > +				}
> > +				if (x_start + pixel_count > current_plane->frame_info->fb->width) {
> > +					pixel_count =
> > +						(int)current_plane->frame_info->fb->width - x_start;
> > +				}
> > +			} else {
> > +				/*
> > +				 * In vertical reading, the src_line height is the number of pixel
> > +				 * to read
> > +				 */
> > +				pixel_count = drm_rect_height(&src_line);
> > +				if (y_start < 0) {
> > +					pixel_count += y_start;
> > +					y_start = 0;
> > +				}
> > +				if (y_start + pixel_count > current_plane->frame_info->fb->height) {
> > +					pixel_count =
> > +						(int)current_plane->frame_info->fb->width - y_start;
> > +				}
> > +			}
> > +
> > +			if (pixel_count <= 0) {
> > +				/* Nothing to read, so avoid multiple function calls for nothing */
> > +				continue;
> > +			}
> > +
> > +			/*
> > +			 * Modify the starting point to take in account the rotation
> > +			 *
> > +			 * src_line is the top-left corner, so when reading READ_RIGHT_TO_LEFT or
> > +			 * READ_BOTTOM_TO_TOP, it must be changed to the top-right/bottom-left
> > +			 * corner.
> > +			 */
> > +			if (direction == READ_RIGHT_TO_LEFT) {
> > +				// x_start is now the right point
> > +				x_start += pixel_count - 1;
> > +			} else if (direction == READ_BOTTOM_TO_TOP) {
> > +				// y_start is now the bottom point
> > +				y_start += pixel_count - 1;
> > +			}
> 
> Any chance this code could be a separate function? I believe it would
> make it more readable.

I will try do split this big function, good idea. At least I can try to 
extract the inner loop content to separate "manage all the planes" from 
"manage the rotation of a plane".

I think it will solve the previous checkpatch issue.

Thanks,
Louis Chauvet

> Best Regards,
> - Ma?ra
> 
> > +
> > +			/*
> > +			 * Perform the conversion and the blending
> > +			 *
> > +			 * Here we know that the read line (x_start, y_start, pixel_count) is
> > +			 * inside the source buffer [2] and we don't write outside the stage
> > +			 * buffer [1]
> > +			 */
> > +			current_plane->pixel_read_line(
> > +				current_plane, x_start, y_start, direction, pixel_count,
> > +				&stage_buffer->pixels[current_plane->frame_info->dst.x1]);
> > +
> > +			pre_mul_alpha_blend(stage_buffer, output_buffer,
> > +					    current_plane->frame_info->dst.x1,
> > +					    pixel_count);
> >   		}
> >   
> >   		apply_lut(crtc_state, output_buffer);
> > @@ -250,7 +335,7 @@ static void blend(struct vkms_writeback_job *wb,
> >   		*crc32 = crc32_le(*crc32, (void *)output_buffer->pixels, row_size);
> >   
> >   		if (wb)
> > -			vkms_writeback_row(wb, output_buffer, y_pos);
> > +			vkms_writeback_row(wb, output_buffer, y);
> >   	}
> >   }
> >   
> > @@ -261,7 +346,7 @@ static int check_format_funcs(struct vkms_crtc_state *crtc_state,
> >   	u32 n_active_planes = crtc_state->num_active_planes;
> >   
> >   	for (size_t i = 0; i < n_active_planes; i++)
> > -		if (!planes[i]->pixel_read)
> > +		if (!planes[i]->pixel_read_line)
> >   			return -1;
> >   
> >   	if (active_wb && !active_wb->pixel_write)
> > diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> > index 985e7a92b7bc..23e1d247468d 100644
> > --- a/drivers/gpu/drm/vkms/vkms_drv.h
> > +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> > @@ -39,7 +39,6 @@
> >   struct vkms_frame_info {
> >   	struct drm_framebuffer *fb;
> >   	struct drm_rect src, dst;
> > -	struct drm_rect rotated;
> >   	struct iosys_map map[DRM_FORMAT_MAX_PLANES];
> >   	unsigned int rotation;
> >   };
> > @@ -80,26 +79,37 @@ enum pixel_read_direction {
> >   	READ_LEFT_TO_RIGHT
> >   };
> >   
> > +struct vkms_plane_state;
> > +
> >   /**
> > - * typedef pixel_read_t - These functions are used to read a pixel in the source frame,
> > + * typedef pixel_read_line_t - These functions are used to read a pixel line in the source frame,
> >    * convert it to `struct pixel_argb_u16` and write it to @out_pixel.
> >    *
> > - * @in_pixel: Pointer to the pixel to read
> > - * @out_pixel: Pointer to write the converted pixel
> > + * @plane: Plane used as source for the pixel value
> > + * @x_start: X (width) coordinate of the first pixel to copy. The caller must ensure that x_start
> > + * is positive and smaller than @plane->frame_info->fb->width.
> > + * @y_start: Y (width) coordinate of the first pixel to copy. The caller must ensure that y_start
> > + * is positive and smaller than @plane->frame_info->fb->height.
> > + * @direction: Direction to use for the copy, starting at @x_start/@y_start
> > + * @count: Number of pixels to copy
> > + * @out_pixel: Pointer where to write the pixel values. They will be written from @out_pixel[0]
> > + * to @out_pixel[@count]. The caller must ensure that out_pixel have a length of at least @count.
> >    */
> > -typedef void (*pixel_read_t)(const u8 *in_pixel, struct pixel_argb_u16 *out_pixel);
> > +typedef void (*pixel_read_line_t)(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[]);
> >   
> >   /**
> >    * vkms_plane_state - Driver specific plane state
> >    * @base: base plane state
> >    * @frame_info: data required for composing computation
> > - * @pixel_read: function to read a pixel in this plane. The creator of a vkms_plane_state must
> > - * ensure that this pointer is valid
> > + * @pixel_read_line: function to read a pixel line in this plane. The creator of a vkms_plane_state
> > + * must ensure that this pointer is valid
> >    */
> >   struct vkms_plane_state {
> >   	struct drm_shadow_plane_state base;
> >   	struct vkms_frame_info *frame_info;
> > -	pixel_read_t pixel_read;
> > +	pixel_read_line_t pixel_read_line;
> >   };
> >   
> >   struct vkms_plane {
> > @@ -204,7 +214,6 @@ int vkms_verify_crc_source(struct drm_crtc *crtc, const char *source_name,
> >   /* Composer Support */
> >   void vkms_composer_worker(struct work_struct *work);
> >   void vkms_set_composer(struct vkms_output *out, bool enabled);
> > -void vkms_compose_row(struct line_buffer *stage_buffer, struct vkms_plane_state *plane, int y);
> >   void vkms_writeback_row(struct vkms_writeback_job *wb, const struct line_buffer *src_buffer, int y);
> >   
> >   /* Writeback */
> > diff --git a/drivers/gpu/drm/vkms/vkms_formats.c b/drivers/gpu/drm/vkms/vkms_formats.c
> > index 743b6fd06db5..1449a0e6c706 100644
> > --- a/drivers/gpu/drm/vkms/vkms_formats.c
> > +++ b/drivers/gpu/drm/vkms/vkms_formats.c
> > @@ -105,77 +105,45 @@ static int get_step_next_block(struct drm_framebuffer *fb, enum pixel_read_direc
> >   	return 0;
> >   }
> >   
> > -static void *get_packed_src_addr(const struct vkms_frame_info *frame_info, int y,
> > -				 int plane_index)
> > -{
> > -	int x_src = frame_info->src.x1 >> 16;
> > -	int y_src = y - frame_info->rotated.y1 + (frame_info->src.y1 >> 16);
> > -	u8 *addr;
> > -	int rem_x, rem_y;
> > -
> > -	packed_pixels_addr(frame_info, x_src, y_src, plane_index, &addr, &rem_x, &rem_y);
> > -	return addr;
> > -}
> > -
> > -static int get_x_position(const struct vkms_frame_info *frame_info, int limit, int x)
> > -{
> > -	if (frame_info->rotation & (DRM_MODE_REFLECT_X | DRM_MODE_ROTATE_270))
> > -		return limit - x - 1;
> > -	return x;
> > -}
> > -
> >   /*
> > - * The following  functions take pixel data from the buffer and convert them to the format
> > + * The following  functions take pixel data (a, r, g, b, pixel, ...), convert them to the format
> >    * ARGB16161616 in out_pixel.
> >    *
> > - * They are used in the `vkms_compose_row` function to handle multiple formats.
> > + * They are used in the `read_line`s functions to avoid duplicate work for some pixel formats.
> >    */
> >   
> > -static void ARGB8888_to_argb_u16(const u8 *in_pixel, struct pixel_argb_u16 *out_pixel)
> > +static struct pixel_argb_u16 argb_u16_from_u8888(int a, int r, int g, int b)
> >   {
> > +	struct pixel_argb_u16 out_pixel;
> >   	/*
> >   	 * The 257 is the "conversion ratio". This number is obtained by the
> >   	 * (2^16 - 1) / (2^8 - 1) division. Which, in this case, tries to get
> >   	 * the best color value in a pixel format with more possibilities.
> >   	 * A similar idea applies to others RGB color conversions.
> >   	 */
> > -	out_pixel->a = (u16)in_pixel[3] * 257;
> > -	out_pixel->r = (u16)in_pixel[2] * 257;
> > -	out_pixel->g = (u16)in_pixel[1] * 257;
> > -	out_pixel->b = (u16)in_pixel[0] * 257;
> > -}
> > +	out_pixel.a = (u16)a * 257;
> > +	out_pixel.r = (u16)r * 257;
> > +	out_pixel.g = (u16)g * 257;
> > +	out_pixel.b = (u16)b * 257;
> >   
> > -static void XRGB8888_to_argb_u16(const u8 *in_pixel, struct pixel_argb_u16 *out_pixel)
> > -{
> > -	out_pixel->a = (u16)0xffff;
> > -	out_pixel->r = (u16)in_pixel[2] * 257;
> > -	out_pixel->g = (u16)in_pixel[1] * 257;
> > -	out_pixel->b = (u16)in_pixel[0] * 257;
> > +	return out_pixel;
> >   }
> >   
> > -static void ARGB16161616_to_argb_u16(const u8 *in_pixel, struct pixel_argb_u16 *out_pixel)
> > +static struct pixel_argb_u16 argb_u16_from_u16161616(int a, int r, int g, int b)
> >   {
> > -	u16 *pixel = (u16 *)in_pixel;
> > +	struct pixel_argb_u16 out_pixel;
> >   
> > -	out_pixel->a = le16_to_cpu(pixel[3]);
> > -	out_pixel->r = le16_to_cpu(pixel[2]);
> > -	out_pixel->g = le16_to_cpu(pixel[1]);
> > -	out_pixel->b = le16_to_cpu(pixel[0]);
> > -}
> > +	out_pixel.a = le16_to_cpu(a);
> > +	out_pixel.r = le16_to_cpu(r);
> > +	out_pixel.g = le16_to_cpu(g);
> > +	out_pixel.b = le16_to_cpu(b);
> >   
> > -static void XRGB16161616_to_argb_u16(const u8 *in_pixel, struct pixel_argb_u16 *out_pixel)
> > -{
> > -	u16 *pixel = (u16 *)in_pixel;
> > -
> > -	out_pixel->a = (u16)0xffff;
> > -	out_pixel->r = le16_to_cpu(pixel[2]);
> > -	out_pixel->g = le16_to_cpu(pixel[1]);
> > -	out_pixel->b = le16_to_cpu(pixel[0]);
> > +	return out_pixel;
> >   }
> >   
> > -static void RGB565_to_argb_u16(const u8 *in_pixel, struct pixel_argb_u16 *out_pixel)
> > +static struct pixel_argb_u16 argb_u16_from_RGB565(const u16 *pixel)
> >   {
> > -	u16 *pixel = (u16 *)in_pixel;
> > +	struct pixel_argb_u16 out_pixel;
> >   
> >   	s64 fp_rb_ratio = drm_fixp_div(drm_int2fixp(65535), drm_int2fixp(31));
> >   	s64 fp_g_ratio = drm_fixp_div(drm_int2fixp(65535), drm_int2fixp(63));
> > @@ -185,12 +153,26 @@ static void RGB565_to_argb_u16(const u8 *in_pixel, struct pixel_argb_u16 *out_pi
> >   	s64 fp_g = drm_int2fixp((rgb_565 >> 5) & 0x3f);
> >   	s64 fp_b = drm_int2fixp(rgb_565 & 0x1f);
> >   
> > -	out_pixel->a = (u16)0xffff;
> > -	out_pixel->r = drm_fixp2int_round(drm_fixp_mul(fp_r, fp_rb_ratio));
> > -	out_pixel->g = drm_fixp2int_round(drm_fixp_mul(fp_g, fp_g_ratio));
> > -	out_pixel->b = drm_fixp2int_round(drm_fixp_mul(fp_b, fp_rb_ratio));
> > +	out_pixel.a = (u16)0xffff;
> > +	out_pixel.r = drm_fixp2int_round(drm_fixp_mul(fp_r, fp_rb_ratio));
> > +	out_pixel.g = drm_fixp2int_round(drm_fixp_mul(fp_g, fp_g_ratio));
> > +	out_pixel.b = drm_fixp2int_round(drm_fixp_mul(fp_b, fp_rb_ratio));
> > +
> > +	return out_pixel;
> >   }
> >   
> > +/*
> > + * The following functions are read_line function for each pixel format supported by VKMS.
> > + *
> > + * They read a line starting at the point @x_start,@y_start following the @direction. The result
> > + * is stored in @out_pixel and in the format ARGB16161616.
> > + *
> > + * Those function are very similar, but it is required for performance reason. In the past, some
> > + * experiment were done, and with a generic loop the performance are very reduced [1].
> > + *
> > + * [1]: https://lore.kernel.org/dri-devel/d258c8dc-78e9-4509-9037-a98f7f33b3a3@riseup.net/
> > + */
> > +
> >   /**
> >    * black_to_argb_u16() - pixel_read callback which always read black
> >    *
> > @@ -198,42 +180,116 @@ static void RGB565_to_argb_u16(const u8 *in_pixel, struct pixel_argb_u16 *out_pi
> >    * It is used to avoid null pointer to be used as a function. In theory, this function should
> >    * never be called, except if you found a bug in the driver/DRM core.
> >    */
> > -static void black_to_argb_u16(const u8 *in_pixel, struct pixel_argb_u16 *out_pixel)
> > +static void black_to_argb_u16(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[])
> >   {
> > -	out_pixel->a = (u16)0xFFFF;
> > -	out_pixel->r = 0;
> > -	out_pixel->g = 0;
> > -	out_pixel->b = 0;
> > +	struct pixel_argb_u16 *end = out_pixel + count;
> > +
> > +	while (out_pixel < end) {
> > +		*out_pixel = argb_u16_from_u8888(255, 0, 0, 0);
> > +		out_pixel += 1;
> > +	}
> >   }
> >   
> > -/**
> > - * vkms_compose_row - compose a single row of a plane
> > - * @stage_buffer: output line with the composed pixels
> > - * @plane: state of the plane that is being composed
> > - * @y: y coordinate of the row
> > - *
> > - * This function composes a single row of a plane. It gets the source pixels
> > - * through the y coordinate (see get_packed_src_addr()) and goes linearly
> > - * through the source pixel, reading the pixels and converting it to
> > - * ARGB16161616 (see the pixel_read() callback). For rotate-90 and rotate-270,
> > - * the source pixels are not traversed linearly. The source pixels are queried
> > - * on each iteration in order to traverse the pixels vertically.
> > - */
> > -void vkms_compose_row(struct line_buffer *stage_buffer, struct vkms_plane_state *plane, int y)
> > +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[])
> >   {
> > -	struct pixel_argb_u16 *out_pixels = stage_buffer->pixels;
> > -	struct vkms_frame_info *frame_info = plane->frame_info;
> > -	u8 *src_pixels = get_packed_src_addr(frame_info, y, 0);
> > -	int limit = min_t(size_t, drm_rect_width(&frame_info->dst), stage_buffer->n_pixels);
> > +	struct pixel_argb_u16 *end = out_pixel + count;
> > +	u8 *src_pixels;
> > +	int rem_x, rem_y;
> > +
> > +	packed_pixels_addr(plane->frame_info, x_start, y_start, 0, &src_pixels, &rem_x, &rem_y);
> > +
> > +	int step = get_step_next_block(plane->frame_info->fb, direction, 0);
> > +
> > +	while (out_pixel < end) {
> > +		u8 *px = (u8 *)src_pixels;
> > +		*out_pixel = argb_u16_from_u8888(px[3], px[2], px[1], px[0]);
> > +		out_pixel += 1;
> > +		src_pixels += step;
> > +	}
> > +}
> > +
> > +static void XRGB8888_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 rem_x, rem_y;
> > +
> > +	packed_pixels_addr(plane->frame_info, x_start, y_start, 0, &src_pixels, &rem_x, &rem_y);
> > +
> > +	int step = get_step_next_block(plane->frame_info->fb, direction, 0);
> > +
> > +	while (out_pixel < end) {
> > +		u8 *px = (u8 *)src_pixels;
> > +		*out_pixel = argb_u16_from_u8888(255, px[2], px[1], px[0]);
> > +		out_pixel += 1;
> > +		src_pixels += step;
> > +	}
> > +}
> > +
> > +static void ARGB16161616_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 rem_x, rem_y;
> > +
> > +	packed_pixels_addr(plane->frame_info, x_start, y_start, 0, &src_pixels, &rem_x, &rem_y);
> > +
> > +	int step = get_step_next_block(plane->frame_info->fb, direction, 0);
> > +
> > +	while (out_pixel < end) {
> > +		u16 *px = (u16 *)src_pixels;
> > +		*out_pixel = argb_u16_from_u16161616(px[3], px[2], px[1], px[0]);
> > +		out_pixel += 1;
> > +		src_pixels += step;
> > +	}
> > +}
> > +
> > +static void XRGB16161616_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 rem_x, rem_y;
> > +
> > +	packed_pixels_addr(plane->frame_info, x_start, y_start, 0, &src_pixels, &rem_x, &rem_y);
> > +
> > +	int step = get_step_next_block(plane->frame_info->fb, direction, 0);
> > +
> > +	while (out_pixel < end) {
> > +		u16 *px = (u16 *)src_pixels;
> > +		*out_pixel = argb_u16_from_u16161616(0xFFFF, px[2], px[1], px[0]);
> > +		out_pixel += 1;
> > +		src_pixels += step;
> > +	}
> > +}
> > +
> > +static void RGB565_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 rem_x, rem_y;
> > +
> > +	packed_pixels_addr(plane->frame_info, x_start, y_start, 0, &src_pixels, &rem_x, &rem_y);
> >   
> > -	for (size_t x = 0; x < limit; x++, src_pixels += frame_info->fb->format->cpp[0]) {
> > -		int x_pos = get_x_position(frame_info, limit, x);
> > +	int step = get_step_next_block(plane->frame_info->fb, direction, 0);
> >   
> > -		if (drm_rotation_90_or_270(frame_info->rotation))
> > -			src_pixels = get_packed_src_addr(frame_info, x + frame_info->rotated.y1, 0)
> > -				+ frame_info->fb->format->cpp[0] * y;
> > +	while (out_pixel < end) {
> > +		u16 *px = (u16 *)src_pixels;
> >   
> > -		plane->pixel_read(src_pixels, &out_pixels[x_pos]);
> > +		*out_pixel = argb_u16_from_RGB565(px);
> > +		out_pixel += 1;
> > +		src_pixels += step;
> >   	}
> >   }
> >   
> > @@ -343,25 +399,25 @@ void vkms_writeback_row(struct vkms_writeback_job *wb,
> >   }
> >   
> >   /**
> > - * Retrieve the correct read_pixel function for a specific format.
> > + * Retrieve the correct read_line function for a specific format.
> >    * If the format is not supported by VKMS a warn is emitted and a dummy "always read black"
> >    * function is returned.
> >    *
> >    * @format: DRM_FORMAT_* value for which to obtain a conversion function (see [drm_fourcc.h])
> >    */
> > -pixel_read_t get_pixel_read_function(u32 format)
> > +pixel_read_line_t get_pixel_read_line_function(u32 format)
> >   {
> >   	switch (format) {
> >   	case DRM_FORMAT_ARGB8888:
> > -		return &ARGB8888_to_argb_u16;
> > +		return &ARGB8888_read_line;
> >   	case DRM_FORMAT_XRGB8888:
> > -		return &XRGB8888_to_argb_u16;
> > +		return &XRGB8888_read_line;
> >   	case DRM_FORMAT_ARGB16161616:
> > -		return &ARGB16161616_to_argb_u16;
> > +		return &ARGB16161616_read_line;
> >   	case DRM_FORMAT_XRGB16161616:
> > -		return &XRGB16161616_to_argb_u16;
> > +		return &XRGB16161616_read_line;
> >   	case DRM_FORMAT_RGB565:
> > -		return &RGB565_to_argb_u16;
> > +		return &RGB565_read_line;
> >   	default:
> >   		/*
> >   		 * This is a bug in vkms_plane_atomic_check. All the supported
> > diff --git a/drivers/gpu/drm/vkms/vkms_formats.h b/drivers/gpu/drm/vkms/vkms_formats.h
> > index 3ecea4563254..8d2bef95ff79 100644
> > --- a/drivers/gpu/drm/vkms/vkms_formats.h
> > +++ b/drivers/gpu/drm/vkms/vkms_formats.h
> > @@ -5,7 +5,7 @@
> >   
> >   #include "vkms_drv.h"
> >   
> > -pixel_read_t get_pixel_read_function(u32 format);
> > +pixel_read_line_t get_pixel_read_line_function(u32 format);
> >   
> >   pixel_write_t get_pixel_write_function(u32 format);
> >   
> > diff --git a/drivers/gpu/drm/vkms/vkms_plane.c b/drivers/gpu/drm/vkms/vkms_plane.c
> > index 10e9b23dab28..8875bed76410 100644
> > --- a/drivers/gpu/drm/vkms/vkms_plane.c
> > +++ b/drivers/gpu/drm/vkms/vkms_plane.c
> > @@ -112,7 +112,6 @@ static void vkms_plane_atomic_update(struct drm_plane *plane,
> >   	frame_info = vkms_plane_state->frame_info;
> >   	memcpy(&frame_info->src, &new_state->src, sizeof(struct drm_rect));
> >   	memcpy(&frame_info->dst, &new_state->dst, sizeof(struct drm_rect));
> > -	memcpy(&frame_info->rotated, &new_state->dst, sizeof(struct drm_rect));
> >   	frame_info->fb = fb;
> >   	memcpy(&frame_info->map, &shadow_plane_state->data, sizeof(frame_info->map));
> >   	drm_framebuffer_get(frame_info->fb);
> > @@ -122,10 +121,8 @@ static void vkms_plane_atomic_update(struct drm_plane *plane,
> >   									  DRM_MODE_REFLECT_X |
> >   									  DRM_MODE_REFLECT_Y);
> >   
> > -	drm_rect_rotate(&frame_info->rotated, drm_rect_width(&frame_info->rotated),
> > -			drm_rect_height(&frame_info->rotated), frame_info->rotation);
> >   
> > -	vkms_plane_state->pixel_read = get_pixel_read_function(fmt);
> > +	vkms_plane_state->pixel_read_line = get_pixel_read_line_function(fmt);
> >   }
> >   
> >   static int vkms_plane_atomic_check(struct drm_plane *plane,
> > 

-- 
Louis Chauvet, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com