[PATCH v4 7/9] drm: vkms: Refactor the plane composer to accept new formats

Igor Torrente igormtorrente at gmail.com
Mon Feb 21 01:02:12 UTC 2022


Hi Melissa,

On 2/9/22 18:45, Melissa Wen wrote:
> On 02/08, Igor Torrente wrote:
>> Hi Melissa,
>>
>> On 2/8/22 07:40, Melissa Wen wrote:
>>> On 01/21, Igor Torrente wrote:
>>>> Currently the blend function only accepts XRGB_8888 and ARGB_8888
>>>> as a color input.
>>>>
>>>> This patch refactors all the functions related to the plane composition
>>>> to overcome this limitation.
>>>>
>>>> A new internal format(`struct pixel`) is introduced to deal with all
>>>> possible inputs. It consists of 16 bits fields that represent each of
>>>> the channels.
>>>>
>>>> The pixels blend is done using this internal format. And new handlers
>>>> are being added to convert a specific format to/from this internal format.
>>>>
>>>> So the blend operation depends on these handlers to convert to this common
>>>> format. The blended result, if necessary, is converted to the writeback
>>>> buffer format.
>>>>
>>>> This patch introduces three major differences to the blend function.
>>>> 1 - All the planes are blended at once.
>>>> 2 - The blend calculus is done as per line instead of per pixel.
>>>> 3 - It is responsible to calculates the CRC and writing the writeback
>>>>       buffer(if necessary).
>>>>
>>>> These changes allow us to allocate way less memory in the intermediate
>>>> buffer to compute these operations. Because now we don't need to
>>>> have the entire intermediate image lines at once, just one line is
>>>> enough.
>>>>
>>>> | Memory consumption (output dimensions) |
>>>> |:--------------------------------------:|
>>>> |       Current      |     This patch    |
>>>> |:------------------:|:-----------------:|
>>>> |   Width * Heigth   |     2 * Width     |
>>>>
>>>> Beyond memory, we also have a minor performance benefit from all
>>>> these changes. Results running the IGT tests `*kms_cursor_crc*`:
>>>>
>>> First, thanks for this improvement.
>>>
>>> Some recent changes in kms_cursor_crc caused VKMS to fail in most test
>>> cases (iirc, only size-change and alpha-opaque are passing currently).
>>
>> I updated my igt and kernel(from drm_misc/drm-misc-next) to the latest
>> commit[1][2] and I'm getting mixed results. Sometimes most of the test
>> passes, sometimes almost nothing passes.
> hmm.. is it happening when running kms_cursor_crc? Is the results
> variation random or is it possible to follow a set of steps to reproduce
> it? When failing, what is the reason displayed by the log?

I investigated it a little bit and discovered that the KMS
cursor(".*kms_cursor_crc*" ) are failing after the execution of
writeback tests(".*kms_writeback.*").

I don't know what is causing it, but they are failing while trying to 
commit the KMS changes.

out.txt:
IGT-Version: 1.26-NO-GIT (x86_64) (Linux: 5.17.0-rc2 x86_64)
Stack trace:
   #0 ../lib/igt_core.c:1754 __igt_fail_assert()
   #1 ../lib/igt_kms.c:3795 do_display_commit()
   #2 ../lib/igt_kms.c:3901 igt_display_commit2()
   #3 ../tests/kms_cursor_crc.c:820 __igt_unique____real_main814()
   #4 ../tests/kms_cursor_crc.c:814 main()
   #5 ../csu/libc-start.c:308 __libc_start_main()
   #6 [_start+0x2a]
Subtest pipe-A-cursor-size-change: FAIL

err.txt:
(kms_cursor_crc:1936) igt_kms-CRITICAL: Test assertion failure function 
do_display_commit, file ../lib/igt_kms.c:3795:
(kms_cursor_crc:1936) igt_kms-CRITICAL: Failed assertion: ret == 0
(kms_cursor_crc:1936) igt_kms-CRITICAL: Last errno: 22, Invalid argument
(kms_cursor_crc:1936) igt_kms-CRITICAL: error: -22 != 0

> 
>  From my side, only the first two subtest of kms_cursor_crc is passing
> before this patch. And after your changes here, all subtests are
> successful again, except those related to 32x10 cursor size (that needs
> futher investigation). I didn't check how the recent changes in
> kms_cursor_crc affect VKMS performance on it, but I bet that clearing
> the alpha channel is the reason to have the performance back.

Yeah, I also don't understand why the 32x10 cursor tests are failing.

>>
>> [1] a96674e7 (tests/api_intel_bb: Handle different alignments in
>> delta-check)
>> [2] b21a142fd205 (drm/nouveau/backlight: Just set all backlight types as
>> RAW)
>>
>>> But saying that performance improvement here would cause a
>>> misunderstanding when reviewing the change history. Can you update this
>>> statistics here? I think you can specify the IGT hash to specify the
>>> test case version or you can pick another test for comparison.
>>
>> OK, I will do both.
>>
>>>> |                 Frametime                  |
>>>> |:------------------------------------------:|
>>>> |  Implementation |  Current  |  This commit |
>>>> |:---------------:|:---------:|:------------:|
>>>> | frametime range |  8~22 ms  |    5~18 ms   |
>>>> |     Average     |  10.0 ms  |    7.3 ms    |
>>>>
>>>> Reported-by: kernel test robot <lkp at intel.com>
>>> A little confusing for me to have this reported-by tag without any
>>> explanation of what was reported and fixed. Can you specify it?
>>>> Signed-off-by: Igor Torrente <igormtorrente at gmail.com>
>>>> ---
>>>> V2: Improves the performance drastically, by perfoming the operations
>>>>       per-line and not per-pixel(Pekka Paalanen).
>>>>       Minor improvements(Pekka Paalanen).
>>>>
>>>> V3: Changes the code to blend the planes all at once. This improves
>>>>       performance, memory consumption, and removes much of the weirdness
>>>>       of the V2(Pekka Paalanen and me).
>>>>       Minor improvements(Pekka Paalanen and me).
>>>>
>>>> V4: Rebase the code and adapt it to the new NUM_OVERLAY_PLANES constant.
>>> Can you move version changes up so that they are not ignored?
>>>
>>> I also pointed out minor code style issue below.
>>> With these comments addressed, you can add my r-b tag in the next
>>> version.
>>>> ---
>>>>    drivers/gpu/drm/vkms/Makefile        |   1 +
>>>>    drivers/gpu/drm/vkms/vkms_composer.c | 335 +++++++++++++--------------
>>>>    drivers/gpu/drm/vkms/vkms_formats.c  | 138 +++++++++++
>>>>    drivers/gpu/drm/vkms/vkms_formats.h  |  31 +++
>>>>    4 files changed, 333 insertions(+), 172 deletions(-)
>>>>    create mode 100644 drivers/gpu/drm/vkms/vkms_formats.c
>>>>    create mode 100644 drivers/gpu/drm/vkms/vkms_formats.h
>>>>
>>>> diff --git a/drivers/gpu/drm/vkms/Makefile b/drivers/gpu/drm/vkms/Makefile
>>>> index 72f779cbfedd..1b28a6a32948 100644
>>>> --- a/drivers/gpu/drm/vkms/Makefile
>>>> +++ b/drivers/gpu/drm/vkms/Makefile
>>>> @@ -3,6 +3,7 @@ vkms-y := \
>>>>    	vkms_drv.o \
>>>>    	vkms_plane.o \
>>>>    	vkms_output.o \
>>>> +	vkms_formats.o \
>>>>    	vkms_crtc.o \
>>>>    	vkms_composer.o \
>>>>    	vkms_writeback.o
>>>> diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
>>>> index 95029d2ebcac..9f70fcf84fb9 100644
>>>> --- a/drivers/gpu/drm/vkms/vkms_composer.c
>>>> +++ b/drivers/gpu/drm/vkms/vkms_composer.c
>>>> @@ -9,202 +9,210 @@
>>>>    #include <drm/drm_vblank.h>
>>>>    #include "vkms_drv.h"
>>>> +#include "vkms_formats.h"
>>>> -static u32 get_pixel_from_buffer(int x, int y, const u8 *buffer,
>>>> -				 const struct vkms_frame_info *frame_info)
>>>> +static u16 pre_mul_blend_channel(u16 src, u16 dst, u16 alpha)
>>>>    {
>>>> -	u32 pixel;
>>>> -	int src_offset = frame_info->offset + (y * frame_info->pitch)
>>>> -					    + (x * frame_info->cpp);
>>>> +	u32 new_color;
>>>> -	pixel = *(u32 *)&buffer[src_offset];
>>>> +	new_color = (src * 0xffff + dst * (0xffff - alpha));
>>>> -	return pixel;
>>>> +	return DIV_ROUND_UP(new_color, 0xffff);
>>>>    }
>>>>    /**
>>>> - * compute_crc - Compute CRC value on output frame
>>>> + * pre_mul_alpha_blend - alpha blending equation
>>>> + * @src_frame_info: source framebuffer's metadata
>>>> + * @stage_buffer: The line with the pixels from src_plane
>>>> + * @output_buffer: A line buffer that receives all the blends output
>>>>     *
>>>> - * @vaddr: address to final framebuffer
>>>> - * @frame_info: framebuffer's metadata
>>>> + * Using the information from the `frame_info`, this blends only the
>>>> + * necessary pixels from the `stage_buffer` to the `output_buffer`
>>>> + * using premultiplied blend formula.
>>>>     *
>>>> - * returns CRC value computed using crc32 on the visible portion of
>>>> - * the final framebuffer at vaddr_out
>>>> + * The current DRM assumption is that pixel color values have been already
>>>> + * pre-multiplied with the alpha channel values. See more
>>>> + * drm_plane_create_blend_mode_property(). Also, this formula assumes a
>>>> + * completely opaque background.
>>>>     */
>>>> -static uint32_t compute_crc(const u8 *vaddr,
>>>> -			    const struct vkms_frame_info *frame_info)
>>>> +static void pre_mul_alpha_blend(struct vkms_frame_info *frame_info,
>>>> +				struct line_buffer *stage_buffer,
>>>> +				struct line_buffer *output_buffer)
>>>>    {
>>>> -	int x, y;
>>>> -	u32 crc = 0, pixel = 0;
>>>> -	int x_src = frame_info->src.x1 >> 16;
>>>> -	int y_src = frame_info->src.y1 >> 16;
>>>> -	int h_src = drm_rect_height(&frame_info->src) >> 16;
>>>> -	int w_src = drm_rect_width(&frame_info->src) >> 16;
>>>> -
>>>> -	for (y = y_src; y < y_src + h_src; ++y) {
>>>> -		for (x = x_src; x < x_src + w_src; ++x) {
>>>> -			pixel = get_pixel_from_buffer(x, y, vaddr, frame_info);
>>>> -			crc = crc32_le(crc, (void *)&pixel, sizeof(u32));
>>>> -		}
>>>> +	int x, x_dst = frame_info->dst.x1;
>>>> +	int x_limit = drm_rect_width(&frame_info->dst);
>>>> +	struct line_buffer *out = output_buffer + x_dst;
>>>> +	struct line_buffer *in = stage_buffer;
>>>> +
>>>> +	for (x = 0; x < x_limit; x++) {
>>>> +		out[x].a = (u16)0xffff;
>>>> +		out[x].r = pre_mul_blend_channel(in[x].r, out[x].r, in[x].a);
>>>> +		out[x].g = pre_mul_blend_channel(in[x].g, out[x].g, in[x].a);
>>>> +		out[x].b = pre_mul_blend_channel(in[x].b, out[x].b, in[x].a);
>>>>    	}
>>>> -
>>>> -	return crc;
>>>>    }
>>>> -static u8 blend_channel(u8 src, u8 dst, u8 alpha)
>>>> +static bool check_y_limit(struct vkms_frame_info *frame_info, int y)
>>>>    {
>>>> -	u32 pre_blend;
>>>> -	u8 new_color;
>>>> -
>>>> -	pre_blend = (src * 255 + dst * (255 - alpha));
>>>> -
>>>> -	/* Faster div by 255 */
>>>> -	new_color = ((pre_blend + ((pre_blend + 257) >> 8)) >> 8);
>>>> +	if (y >= frame_info->dst.y1 && y < frame_info->dst.y2)
>>>> +		return true;
>>>> -	return new_color;
>>>> +	return false;
>>>>    }
>>>>    /**
>>>> - * alpha_blend - alpha blending equation
>>>> - * @argb_src: src pixel on premultiplied alpha mode
>>>> - * @argb_dst: dst pixel completely opaque
>>>> - *
>>>> - * blend pixels using premultiplied blend formula. The current DRM assumption
>>>> - * is that pixel color values have been already pre-multiplied with the alpha
>>>> - * channel values. See more drm_plane_create_blend_mode_property(). Also, this
>>>> - * formula assumes a completely opaque background.
>>>> - */
>>>> -static void alpha_blend(const u8 *argb_src, u8 *argb_dst)
>>>> -{
>>>> -	u8 alpha;
>>>> -
>>>> -	alpha = argb_src[3];
>>>> -	argb_dst[0] = blend_channel(argb_src[0], argb_dst[0], alpha);
>>>> -	argb_dst[1] = blend_channel(argb_src[1], argb_dst[1], alpha);
>>>> -	argb_dst[2] = blend_channel(argb_src[2], argb_dst[2], alpha);
>>>> -}
>>>> -
>>>> -/**
>>>> - * x_blend - blending equation that ignores the pixel alpha
>>>> - *
>>>> - * overwrites RGB color value from src pixel to dst pixel.
>>>> - */
>>>> -static void x_blend(const u8 *xrgb_src, u8 *xrgb_dst)
>>>> -{
>>>> -	memcpy(xrgb_dst, xrgb_src, sizeof(u8) * 3);
>>>> -}
>>>> -
>>>> -/**
>>>> - * blend - blend value at vaddr_src with value at vaddr_dst
>>>> - * @vaddr_dst: destination address
>>>> - * @vaddr_src: source address
>>>> - * @dst_frame_info: destination framebuffer's metadata
>>>> - * @src_frame_info: source framebuffer's metadata
>>>> - * @pixel_blend: blending equation based on plane format
>>>> + * @wb_frame_info: The writeback frame buffer metadata
>>>> + * @wb_fmt_func: The format tranformatio function to the wb buffer
>>>> + * @crtc_state: The crtc state
>>>> + * @plane_fmt_func: A format tranformation function to each plane
>>>> + * @crc32: The crc output of the final frame
>>>> + * @output_buffer: A buffer of a row that will receive the result of the blend(s)
>>>> + * @stage_buffer: The line with the pixels from src_compositor
>>>>     *
>>>> - * Blend the vaddr_src value with the vaddr_dst value using a pixel blend
>>>> - * equation according to the supported plane formats DRM_FORMAT_(A/XRGB8888)
>>>> - * and clearing alpha channel to an completely opaque background. This function
>>>> - * uses buffer's metadata to locate the new composite values at vaddr_dst.
>>>> + * This function blends the pixels (Using the `pre_mul_alpha_blend`)
>>>> + * from all planes, calculates the crc32 of the output from the former step,
>>>> + * and, if necessary, convert and store the output to the writeback buffer.
>>>>     *
>>>>     * TODO: completely clear the primary plane (a = 0xff) before starting to blend
>>>>     * pixel color values
>>>>     */
>>>> -static void blend(void *vaddr_dst, void *vaddr_src,
>>>> -		  struct vkms_frame_info *dst_frame_info,
>>>> -		  struct vkms_frame_info *src_frame_info,
>>>> -		  void (*pixel_blend)(const u8 *, u8 *))
>>>> +static void blend(struct vkms_frame_info *wb_frame_info,
>>>> +		  format_transform_func wb_fmt_func,
>>>> +		  struct vkms_crtc_state *crtc_state,
>>>> +		  format_transform_func *plane_fmt_func,
>>>> +		  u32 *crc32, struct line_buffer *stage_buffer,
>>>> +		  struct line_buffer *output_buffer, s64 row_size)
>>>>    {
>>>> -	int i, j, j_dst, i_dst;
>>>> -	int offset_src, offset_dst;
>>>> -	u8 *pixel_dst, *pixel_src;
>>>> -
>>>> -	int x_src = src_frame_info->src.x1 >> 16;
>>>> -	int y_src = src_frame_info->src.y1 >> 16;
>>>> -
>>>> -	int x_dst = src_frame_info->dst.x1;
>>>> -	int y_dst = src_frame_info->dst.y1;
>>>> -	int h_dst = drm_rect_height(&src_frame_info->dst);
>>>> -	int w_dst = drm_rect_width(&src_frame_info->dst);
>>>> +	struct vkms_plane_state **plane = crtc_state->active_planes;
>>>> +	struct vkms_frame_info *primary_plane_info = plane[0]->frame_info;
>>>> +	u32 n_active_planes = crtc_state->num_active_planes;
>>>> +	int y_src = primary_plane_info->dst.y1;
>>>> +	int h_dst = drm_rect_height(&primary_plane_info->dst);
>>>>    	int y_limit = y_src + h_dst;
>>>> -	int x_limit = x_src + w_dst;
>>>> -
>>>> -	for (i = y_src, i_dst = y_dst; i < y_limit; ++i) {
>>>> -		for (j = x_src, j_dst = x_dst; j < x_limit; ++j) {
>>>> -			offset_dst = dst_frame_info->offset
>>>> -				     + (i_dst * dst_frame_info->pitch)
>>>> -				     + (j_dst++ * dst_frame_info->cpp);
>>>> -			offset_src = src_frame_info->offset
>>>> -				     + (i * src_frame_info->pitch)
>>>> -				     + (j * src_frame_info->cpp);
>>>> -
>>>> -			pixel_src = (u8 *)(vaddr_src + offset_src);
>>>> -			pixel_dst = (u8 *)(vaddr_dst + offset_dst);
>>>> -			pixel_blend(pixel_src, pixel_dst);
>>>> -			/* clearing alpha channel (0xff)*/
>>>> -			pixel_dst[3] = 0xff;
>>>> +	int y, i;
>>>> +
>>>> +	for (y = y_src; y < y_limit; y++) {
>>>> +		plane_fmt_func[0](primary_plane_info, y, output_buffer);
>>>> +
>>>> +		/* If there are other planes besides primary, we consider the active
>>>> +		 * planes should be in z-order and compose them associatively:
>>>> +		 * ((primary <- overlay) <- cursor)
>>>> +		 */
>>>> +		for (i = 1; i < n_active_planes; i++) {
>>>> +			if (!check_y_limit(plane[i]->frame_info, y))
>>>> +				continue;
>>>> +
>>>> +			plane_fmt_func[i](plane[i]->frame_info, y, stage_buffer);
>>>> +			pre_mul_alpha_blend(plane[i]->frame_info, stage_buffer,
>>>> +					    output_buffer);
>>>>    		}
>>>> -		i_dst++;
>>>> +
>>>> +		*crc32 = crc32_le(*crc32, (void *)output_buffer, row_size);
>>>> +
>>>> +		if (wb_frame_info)
>>>> +			wb_fmt_func(wb_frame_info, y, output_buffer);
>>>>    	}
>>>>    }
>>>> -static void compose_plane(struct vkms_frame_info *primary_plane_info,
>>>> -			  struct vkms_frame_info *plane_frame_info,
>>>> -			  void *vaddr_out)
>>>> +static void get_format_transform_functions(struct vkms_crtc_state *crtc_state,
>>>> +					   format_transform_func plane_funcs[])
>>>>    {
>>>> -	struct drm_framebuffer *fb = plane_frame_info->fb;
>>>> -	void *vaddr;
>>>> -	void (*pixel_blend)(const u8 *p_src, u8 *p_dst);
>>>> +	struct vkms_plane_state **active_planes = crtc_state->active_planes;
>>>> +	u32 n_active_planes = crtc_state->num_active_planes, s_fmt;
>>>> +	int i;
>>>> -	if (WARN_ON(dma_buf_map_is_null(&primary_plane_info->map[0])))
>>>> -		return;
>>>> +	for (i = 0; i < n_active_planes; i++) {
>>>> +		s_fmt = active_planes[i]->frame_info->fb->format->format;
>>>> +		plane_funcs[i] = get_fmt_transform_function(s_fmt);
>>>> +	}
>>>> +}
>>>> -	vaddr = plane_frame_info->map[0].vaddr;
>>>> +static bool check_planes_x_bounds(struct vkms_crtc_state *crtc_state,
>>>> +				  struct vkms_frame_info *wb_frame_info)
>>>> +{
>>>> +	struct vkms_plane_state **planes = crtc_state->active_planes;
>>>> +	struct vkms_frame_info *primary_plane_info = planes[0]->frame_info;
>>>> +	int line_width = drm_rect_width(&primary_plane_info->dst);
>>>> +	u32 n_active_planes = crtc_state->num_active_planes;
>>>> +	int i;
>>>> -	if (fb->format->format == DRM_FORMAT_ARGB8888)
>>>> -		pixel_blend = &alpha_blend;
>>>> -	else
>>>> -		pixel_blend = &x_blend;
>>>> +	for (i = 0; i < n_active_planes; i++) {
>>>> +		int x_dst = planes[i]->frame_info->dst.x1;
>>>> +		int x_src = planes[i]->frame_info->src.x1 >> 16;
>>>> +		int x2_src = planes[i]->frame_info->src.x2 >> 16;
>>>> +		int x_limit = drm_rect_width(&planes[i]->frame_info->dst);
>>>> -	blend(vaddr_out, vaddr, primary_plane_info,
>>>> -	      plane_frame_info, pixel_blend);
>>>> +		if (x_dst + x_limit > line_width)
>>>> +			return false;
>>>> +		if (x_src + x_limit > x2_src)
>>>> +			return false;
>>>> +	}
>>>> +
>>>> +	return true;
>>>>    }
>>>> -static int compose_active_planes(void **vaddr_out,
>>>> -				 struct vkms_frame_info *primary_plane_info,
>>>> -				 struct vkms_crtc_state *crtc_state)
>>>> +static int compose_active_planes(struct vkms_frame_info *wb_frame_info,
>>>> +				 struct vkms_crtc_state *crtc_state,
>>>> +				 u32 *crc32)
>>>>    {
>>>> -	struct drm_framebuffer *fb = primary_plane_info->fb;
>>>> -	struct drm_gem_object *gem_obj = drm_gem_fb_get_obj(fb, 0);
>>>> -	const void *vaddr;
>>>> -	int i;
>>>> +	format_transform_func plane_funcs[NUM_OVERLAY_PLANES], wb_func = NULL;
>>>> +	int line_width, ret = 0, pixel_size = sizeof(struct line_buffer);
>>>> +	struct vkms_frame_info *primary_plane_info = NULL;
>>>> +	struct line_buffer *output_buffer, *stage_buffer;
>>>> +	struct vkms_plane_state *act_plane = NULL;
>>>> +	u32 wb_format;
>>>> -	if (!*vaddr_out) {
>>>> -		*vaddr_out = kvzalloc(gem_obj->size, GFP_KERNEL);
>>>> -		if (!*vaddr_out) {
>>>> -			DRM_ERROR("Cannot allocate memory for output frame.");
>>>> -			return -ENOMEM;
>>>> -		}
>>>> +	if (WARN_ON(pixel_size != 8))
>>>> +		return -EINVAL;
>>>> +
>>>> +	if (crtc_state->num_active_planes >= 1) {
>>>> +		act_plane = crtc_state->active_planes[0];
>>>> +		if (act_plane->base.base.plane->type == DRM_PLANE_TYPE_PRIMARY)
>>>> +			primary_plane_info = act_plane->frame_info;
>>>>    	}
>>>> +	if (!primary_plane_info)
>>>> +		return -EINVAL;
>>>> +
>>>>    	if (WARN_ON(dma_buf_map_is_null(&primary_plane_info->map[0])))
>>>>    		return -EINVAL;
>>>> -	vaddr = primary_plane_info->map[0].vaddr;
>>>> +	if (WARN_ON(!check_planes_x_bounds(crtc_state, wb_frame_info)))
>>>> +		return -EINVAL;
>>>> -	memcpy(*vaddr_out, vaddr, gem_obj->size);
>>>> +	line_width = drm_rect_width(&primary_plane_info->dst);
>>>> -	/* If there are other planes besides primary, we consider the active
>>>> -	 * planes should be in z-order and compose them associatively:
>>>> -	 * ((primary <- overlay) <- cursor)
>>>> -	 */
>>>> -	for (i = 1; i < crtc_state->num_active_planes; i++)
>>>> -		compose_plane(primary_plane_info,
>>>> -			      crtc_state->active_planes[i]->frame_info,
>>>> -			      *vaddr_out);
>>>> +	stage_buffer = kvmalloc(line_width * pixel_size, GFP_KERNEL);
>>>> +	if (!stage_buffer) {
>>>> +		DRM_ERROR("Cannot allocate memory for the output line buffer");
>>>> +		return -ENOMEM;
>>>> +	}
>>>> -	return 0;
>>>> +	output_buffer = kvmalloc(line_width * pixel_size, GFP_KERNEL);
>>>> +	if (!output_buffer) {
>>>> +		DRM_ERROR("Cannot allocate memory for intermediate line buffer");
>>>> +		ret = -ENOMEM;
>>>> +		goto free_stage_buffer;
>>>> +	}
>>>> +
>>>> +	get_format_transform_functions(crtc_state, plane_funcs);
>>>> +
>>>> +	if (wb_frame_info) {
>>>> +		wb_format = wb_frame_info->fb->format->format;
>>>> +		wb_func = get_wb_fmt_transform_function(wb_format);
>>>> +		wb_frame_info->src = primary_plane_info->src;
>>>> +		wb_frame_info->dst = primary_plane_info->dst;
>>>> +	}
>>>> +
>>>> +	blend(wb_frame_info, wb_func, crtc_state, plane_funcs, crc32,
>>>> +	      stage_buffer, output_buffer, (s64)line_width * pixel_size);
>>>> +
>>>> +	kvfree(output_buffer);
>>>> +free_stage_buffer:
>>>> +	kvfree(stage_buffer);
>>>> +
>>>> +	return ret;
>>>>    }
>>>>    /**
>>>> @@ -222,13 +230,12 @@ void vkms_composer_worker(struct work_struct *work)
>>>>    						struct vkms_crtc_state,
>>>>    						composer_work);
>>>>    	struct drm_crtc *crtc = crtc_state->base.crtc;
>>>> +	struct vkms_writeback_job *active_wb = crtc_state->active_writeback;
>>>> +	struct vkms_frame_info *wb_frame_info = &active_wb->frame_info;
>>>>    	struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
>>>> -	struct vkms_frame_info *primary_plane_info = NULL;
>>>> -	struct vkms_plane_state *act_plane = NULL;
>>>>    	bool crc_pending, wb_pending;
>>>> -	void *vaddr_out = NULL;
>>>> -	u32 crc32 = 0;
>>>>    	u64 frame_start, frame_end;
>>>> +	u32 crc32 = 0;
>>>>    	int ret;
>>>>    	spin_lock_irq(&out->composer_lock);
>>>> @@ -248,35 +255,19 @@ void vkms_composer_worker(struct work_struct *work)
>>>>    	if (!crc_pending)
>>>>    		return;
>>>> -	if (crtc_state->num_active_planes >= 1) {
>>>> -		act_plane = crtc_state->active_planes[0];
>>>> -		if (act_plane->base.base.plane->type == DRM_PLANE_TYPE_PRIMARY)
>>>> -			primary_plane_info = act_plane->frame_info;
>>>> -	}
>>>> -
>>>> -	if (!primary_plane_info)
>>>> -		return;
>>>> -
>>>>    	if (wb_pending)
>>>> -		vaddr_out = crtc_state->active_writeback->data[0].vaddr;
>>>> +		ret = compose_active_planes(wb_frame_info, crtc_state, &crc32);
>>>> +	else
>>>> +		ret = compose_active_planes(NULL, crtc_state, &crc32);
>>>> -	ret = compose_active_planes(&vaddr_out, primary_plane_info,
>>>> -				    crtc_state);
>>>> -	if (ret) {
>>>> -		if (ret == -EINVAL && !wb_pending)
>>>> -			kvfree(vaddr_out);
>>>> +	if (ret)
>>>>    		return;
>>>> -	}
>>>> -
>>>> -	crc32 = compute_crc(vaddr_out, primary_plane_info);
>>>>    	if (wb_pending) {
>>>>    		drm_writeback_signal_completion(&out->wb_connector, 0);
>>>>    		spin_lock_irq(&out->composer_lock);
>>>>    		crtc_state->wb_pending = false;
>>>>    		spin_unlock_irq(&out->composer_lock);
>>>> -	} else {
>>>> -		kvfree(vaddr_out);
>>>>    	}
>>>>    	/*
>>>> diff --git a/drivers/gpu/drm/vkms/vkms_formats.c b/drivers/gpu/drm/vkms/vkms_formats.c
>>>> new file mode 100644
>>>> index 000000000000..0d1838d1b835
>>>> --- /dev/null
>>>> +++ b/drivers/gpu/drm/vkms/vkms_formats.c
>>>> @@ -0,0 +1,138 @@
>>>> +/* SPDX-License-Identifier: GPL-2.0+ */
>>> checkpatch complains here ^ Use `\\`
>>
>> I change it, but:
>>
>> WARNING: Improper SPDX comment style for
>> 'drivers/gpu/drm/vkms/vkms_formats.h', please use '/*' instead
>> #660: FILE: drivers/gpu/drm/vkms/vkms_formats.h:1:
>> +// SPDX-License-Identifier: GPL-2.0+
> Ok, previously checkpatch was complaining only for `vkms_format.c` but
> not for the header. I got it wrong when I pointed to the .h file too,
> sorry. I had two points in mind, but the second issue is not here, it is
> `multiple blank lines` in the next patch.
> 
> btw, you find more details about the comment style for SPDX here:
> https://www.kernel.org/doc/html/latest/process/license-rules.html#license-identifier-syntax
> 
>>
>> I keep the change to be consitent with the rest of the vkms files.
>>
>>>> +
>>>> +#include <drm/drm_rect.h>
>>>> +#include "vkms_formats.h"
>>>> +
>>>> +format_transform_func get_fmt_transform_function(u32 format)
>>>> +{
>>>> +	if (format == DRM_FORMAT_ARGB8888)
>>>> +		return &ARGB8888_to_ARGB16161616;
>>>> +	else
>>>> +		return &XRGB8888_to_ARGB16161616;
>>>> +}
>>>> +
>>>> +format_transform_func get_wb_fmt_transform_function(u32 format)
>>>> +{
>>>> +	if (format == DRM_FORMAT_ARGB8888)
>>>> +		return &convert_to_ARGB8888;
>>>> +	else
>>>> +		return &convert_to_XRGB8888;
>>>> +}
>>>> +
>>>> +static int pixel_offset(struct vkms_frame_info *frame_info, int x, int y)
>>>> +{
>>>> +	return frame_info->offset + (y * frame_info->pitch)
>>>> +				  + (x * frame_info->cpp);
>>>> +}
>>>> +
>>>> +/*
>>>> + * packed_pixels_addr - Get the pointer to pixel of a given pair of coordinates
>>>> + *
>>>> + * @frame_info: Buffer metadata
>>>> + * @x: The x(width) coordinate of the 2D buffer
>>>> + * @y: The y(Heigth) coordinate of the 2D buffer
>>>> + *
>>>> + * Takes the information stored in the frame_info, a pair of coordinates, and
>>>> + * returns the address of the first color channel.
>>>> + * This function assumes the channels are packed together, i.e. a color channel
>>>> + * comes immediately after another in the memory. And therefore, this function
>>>> + * doesn't work for YUV with chroma subsampling (e.g. YUV420 and NV21).
>>>> + */
>>>> +static void *packed_pixels_addr(struct vkms_frame_info *frame_info, int x, int y)
>>>> +{
>>>> +	int offset = pixel_offset(frame_info, x, y);
>>>> +
>>>> +	return (u8 *)frame_info->map[0].vaddr + offset;
>>>> +}
>>>> +
>>>> +static void *get_packed_src_addr(struct vkms_frame_info *frame_info, int y)
>>>> +{
>>>> +	int x_src = frame_info->src.x1 >> 16;
>>>> +	int y_src = y - frame_info->dst.y1 + (frame_info->src.y1 >> 16);
>>>> +
>>>> +	return packed_pixels_addr(frame_info, x_src, y_src);
>>>> +}
>>>> +
>>>> +void ARGB8888_to_ARGB16161616(struct vkms_frame_info *frame_info, int y,
>>>> +			      struct line_buffer *stage_buffer)
>>>> +{
>>>> +	u8 *src_pixels = get_packed_src_addr(frame_info, y);
>>>> +	int x, x_limit = drm_rect_width(&frame_info->dst);
>>>> +
>>>> +	for (x = 0; x < x_limit; x++, src_pixels += 4) {
>>>> +		/*
>>>> +		 * Organizes the channels in their respective positions and converts
>>>> +		 * the 8 bits channel to 16.
>>>> +		 * 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.
>>>> +		 * And a similar idea applies to others RGB color conversions.
>>>> +		 */
>>>> +		stage_buffer[x].a = (u16)src_pixels[3] * 257;
>>>> +		stage_buffer[x].r = (u16)src_pixels[2] * 257;
>>>> +		stage_buffer[x].g = (u16)src_pixels[1] * 257;
>>>> +		stage_buffer[x].b = (u16)src_pixels[0] * 257;
>>>> +	}
>>>> +}
>>>> +
>>>> +void XRGB8888_to_ARGB16161616(struct vkms_frame_info *frame_info, int y,
>>>> +			      struct line_buffer *stage_buffer)
>>>> +{
>>>> +	u8 *src_pixels = get_packed_src_addr(frame_info, y);
>>>> +	int x, x_limit = drm_rect_width(&frame_info->dst);
>>>> +
>>>> +	for (x = 0; x < x_limit; x++, src_pixels += 4) {
>>>> +		stage_buffer[x].a = (u16)0xffff;
>>>> +		stage_buffer[x].r = (u16)src_pixels[2] * 257;
>>>> +		stage_buffer[x].g = (u16)src_pixels[1] * 257;
>>>> +		stage_buffer[x].b = (u16)src_pixels[0] * 257;
>>>> +	}
>>>> +}
>>>> +
>>>> +/*
>>>> + * The following  functions take an line of ARGB16161616 pixels from the
>>>> + * src_buffer, convert them to a specific format, and store them in the
>>>> + * destination.
>>>> + *
>>>> + * They are used in the `compose_active_planes` to convert and store a line
>>>> + * from the src_buffer to the writeback buffer.
>>>> + */
>>>> +void convert_to_ARGB8888(struct vkms_frame_info *frame_info,
>>>> +			 int y, struct line_buffer *src_buffer)
>>>> +{
>>>> +	int x, x_dst = frame_info->dst.x1;
>>>> +	u8 *dst_pixels = packed_pixels_addr(frame_info, x_dst, y);
>>>> +	int x_limit = drm_rect_width(&frame_info->dst);
>>>> +
>>>> +	for (x = 0; x < x_limit; x++, dst_pixels += 4) {
>>>> +		/*
>>>> +		 * This sequence below is important because the format's byte order is
>>>> +		 * in little-endian. In the case of the ARGB8888 the memory is
>>>> +		 * organized this way:
>>>> +		 *
>>>> +		 * | Addr     | = blue channel
>>>> +		 * | Addr + 1 | = green channel
>>>> +		 * | Addr + 2 | = Red channel
>>>> +		 * | Addr + 3 | = Alpha channel
>>>> +		 */
>>>> +		dst_pixels[3] = DIV_ROUND_UP(src_buffer[x].a, 257);
>>>> +		dst_pixels[2] = DIV_ROUND_UP(src_buffer[x].r, 257);
>>>> +		dst_pixels[1] = DIV_ROUND_UP(src_buffer[x].g, 257);
>>>> +		dst_pixels[0] = DIV_ROUND_UP(src_buffer[x].b, 257);
>>>> +	}
>>>> +}
>>>> +
>>>> +void convert_to_XRGB8888(struct vkms_frame_info *frame_info,
>>>> +			 int y, struct line_buffer *src_buffer)
>>>> +{
>>>> +	int x, x_dst = frame_info->dst.x1;
>>>> +	u8 *dst_pixels = packed_pixels_addr(frame_info, x_dst, y);
>>>> +	int x_limit = drm_rect_width(&frame_info->dst);
>>>> +
>>>> +	for (x = 0; x < x_limit; x++, dst_pixels += 4) {
>>>> +		dst_pixels[3] = (u8)0xff;
>>>> +		dst_pixels[2] = DIV_ROUND_UP(src_buffer[x].r, 257);
>>>> +		dst_pixels[1] = DIV_ROUND_UP(src_buffer[x].g, 257);
>>>> +		dst_pixels[0] = DIV_ROUND_UP(src_buffer[x].b, 257);
>>>> +	}
>>>> +}
>>>> diff --git a/drivers/gpu/drm/vkms/vkms_formats.h b/drivers/gpu/drm/vkms/vkms_formats.h
>>>> new file mode 100644
>>>> index 000000000000..817e8b2124ae
>>>> --- /dev/null
>>>> +++ b/drivers/gpu/drm/vkms/vkms_formats.h
>>>> @@ -0,0 +1,31 @@
>>>> +/* SPDX-License-Identifier: GPL-2.0+ */
>>> and here ^
>>>
>>>> +
>>>> +#ifndef _VKMS_FORMATS_H_
>>>> +#define _VKMS_FORMATS_H_
>>>> +
>>>> +#include "vkms_drv.h"
>>>> +
>>>> +struct line_buffer {
>>>> +	u16 a, r, g, b;
>>>> +};
>>>> +
>>>> +void ARGB8888_to_ARGB16161616(struct vkms_frame_info *frame_info, int y,
>>>> +			      struct line_buffer *stage_buffer);
>>>> +
>>>> +void XRGB8888_to_ARGB16161616(struct vkms_frame_info *frame_info, int y,
>>>> +			      struct line_buffer *stage_buffer);
>>>> +
>>>> +void convert_to_ARGB8888(struct vkms_frame_info *frame_info, int y,
>>>> +			 struct line_buffer *src_buffer);
>>>> +
>>>> +void convert_to_XRGB8888(struct vkms_frame_info *frame_info, int y,
>>>> +			 struct line_buffer *src_buffer);
>>>> +
>>>> +typedef void (*format_transform_func)(struct vkms_frame_info *frame_info, int y,
>>>> +				      struct line_buffer *buffer);
>>>> +
>>>> +format_transform_func get_fmt_transform_function(u32 format);
>>>> +
>>>> +format_transform_func get_wb_fmt_transform_function(u32 format);
>>>> +
>>>> +#endif /* _VKMS_FORMATS_H_ */
>>>> -- 
>>>> 2.30.2
>>>>


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