Re: [PATCH v2 4/8] drm/ssd130x: Add support for DRM_FORMAT_R1

[Thomas Zimmermann <tzimmermann@suse.de>]

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Hi

Am 24.08.23 um 17:08 schrieb Geert Uytterhoeven:
> The native display format is monochrome light-on-dark (R1).
> Hence add support for R1, so monochrome applications not only look
> better, but also avoid the overhead of back-and-forth conversions
> between R1 and XR24.
> 
> Do not allocate the intermediate conversion buffer when it is not
> needed, and reorder the two buffer allocations to streamline operation.
> 
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
> ---
> v2:
>    - Rework on top op commit 8c3926367ac9df6c ("drm/ssd130x: Use
>      shadow-buffer helpers when managing plane's state") in drm/drm-next.
>      Hence I did not add Javier's tags given on v1.
>    - Do not allocate intermediate buffer when not needed.
> ---
>   drivers/gpu/drm/solomon/ssd130x.c | 76 +++++++++++++++++++++----------
>   1 file changed, 51 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/gpu/drm/solomon/ssd130x.c b/drivers/gpu/drm/solomon/ssd130x.c
> index 78272b1f9d5b167f..18007cb4f3de5aa1 100644
> --- a/drivers/gpu/drm/solomon/ssd130x.c
> +++ b/drivers/gpu/drm/solomon/ssd130x.c
> @@ -449,15 +449,14 @@ static int ssd130x_init(struct ssd130x_device *ssd130x)
>   
>   static int ssd130x_update_rect(struct ssd130x_device *ssd130x,
>   			       struct ssd130x_plane_state *ssd130x_state,
> +			       u8 *buf, unsigned int pitch,
>   			       struct drm_rect *rect)
>   {
>   	unsigned int x = rect->x1;
>   	unsigned int y = rect->y1;
> -	u8 *buf = ssd130x_state->buffer;
>   	u8 *data_array = ssd130x_state->data_array;
>   	unsigned int width = drm_rect_width(rect);
>   	unsigned int height = drm_rect_height(rect);
> -	unsigned int line_length = DIV_ROUND_UP(width, 8);
>   	unsigned int page_height = ssd130x->device_info->page_height;
>   	unsigned int pages = DIV_ROUND_UP(height, page_height);
>   	struct drm_device *drm = &ssd130x->drm;
> @@ -516,7 +515,7 @@ static int ssd130x_update_rect(struct ssd130x_device *ssd130x,
>   			u8 data = 0;
>   
>   			for (k = 0; k < m; k++) {
> -				u8 byte = buf[(8 * i + k) * line_length + j / 8];
> +				u8 byte = buf[(8 * i + k) * pitch + j / 8];
>   				u8 bit = (byte >> (j % 8)) & 1;
>   
>   				data |= bit << k;
> @@ -602,27 +601,51 @@ static int ssd130x_fb_blit_rect(struct drm_plane_state *state,

The handing of different formats in this function is confusing. I'd 
rather implement ssd130x_fb_blit_rect_r1 and 
ssd130x_fb_blit_rect_xrgb8888 which then handle a single format.

>   	struct ssd130x_device *ssd130x = drm_to_ssd130x(fb->dev);
>   	unsigned int page_height = ssd130x->device_info->page_height;
>   	struct ssd130x_plane_state *ssd130x_state = to_ssd130x_plane_state(state);
> -	u8 *buf = ssd130x_state->buffer;
>   	struct iosys_map dst;
>   	unsigned int dst_pitch;
>   	int ret = 0;
> +	u8 *buf;
>   
>   	/* Align y to display page boundaries */
>   	rect->y1 = round_down(rect->y1, page_height);
>   	rect->y2 = min_t(unsigned int, round_up(rect->y2, page_height), ssd130x->height);
>   
> -	dst_pitch = DIV_ROUND_UP(drm_rect_width(rect), 8);
> +	switch (fb->format->format) {
> +	case DRM_FORMAT_R1:
> +		/* Align x to byte boundaries */
> +		rect->x1 = round_down(rect->x1, 8);
> +		rect->x2 = round_up(rect->x2, 8);

Is rounding to multiples of 8 guaranteed to work? I know it did on 
VGA-compatible HW, because VGA enforces it. But is that generally the case?

>   
> -	ret = drm_gem_fb_begin_cpu_access(fb, DMA_FROM_DEVICE);
> -	if (ret)
> -		return ret;
> +		ret = drm_gem_fb_begin_cpu_access(fb, DMA_FROM_DEVICE);
> +		if (ret)
> +			return ret;
> +
> +		dst_pitch = fb->pitches[0];
> +		buf = vmap[0].vaddr + rect->y1 * dst_pitch + rect->x1 / 8;
> +
> +		ssd130x_update_rect(ssd130x, ssd130x_state, buf, dst_pitch,
> +				    rect);
> +
> +		drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
> +		break;
> +
> +	case DRM_FORMAT_XRGB8888:
> +		dst_pitch = DIV_ROUND_UP(drm_rect_width(rect), 8);
> +		buf = ssd130x_state->buffer;
> +
> +		ret = drm_gem_fb_begin_cpu_access(fb, DMA_FROM_DEVICE);
> +		if (ret)
> +			return ret;
>   
> -	iosys_map_set_vaddr(&dst, buf);
> -	drm_fb_xrgb8888_to_mono(&dst, &dst_pitch, vmap, fb, rect);
> +		iosys_map_set_vaddr(&dst, buf);
> +		drm_fb_xrgb8888_to_mono(&dst, &dst_pitch, vmap, fb, rect);
>   
> -	drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
> +		drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
>   
> -	ssd130x_update_rect(ssd130x, ssd130x_state, rect);
> +		ssd130x_update_rect(ssd130x, ssd130x_state, buf, dst_pitch,
> +				    rect);
> +		break;
> +	}
>   
>   	return ret;
>   }
> @@ -644,22 +667,24 @@ static int ssd130x_primary_plane_helper_atomic_check(struct drm_plane *plane,
>   	if (ret)
>   		return ret;
>   
> -	fi = drm_format_info(DRM_FORMAT_R1);
> -	if (!fi)
> -		return -EINVAL;
> +	ssd130x_state->data_array = kcalloc(ssd130x->width, pages, GFP_KERNEL);
> +	if (!ssd130x_state->data_array)
> +		return -ENOMEM;
>   
> -	pitch = drm_format_info_min_pitch(fi, 0, ssd130x->width);
> +	if (plane_state->fb->format->format != DRM_FORMAT_R1) {
> +		fi = drm_format_info(DRM_FORMAT_R1);
> +		if (!fi)
> +			return -EINVAL;
>   
> -	ssd130x_state->buffer = kcalloc(pitch, ssd130x->height, GFP_KERNEL);
> -	if (!ssd130x_state->buffer)
> -		return -ENOMEM;
> +		pitch = drm_format_info_min_pitch(fi, 0, ssd130x->width);
>   
> -	ssd130x_state->data_array = kcalloc(ssd130x->width, pages, GFP_KERNEL);
> -	if (!ssd130x_state->data_array) {
> -		kfree(ssd130x_state->buffer);
> -		/* Set to prevent a double free in .atomic_destroy_state() */
> -		ssd130x_state->buffer = NULL;
> -		return -ENOMEM;
> +		ssd130x_state->buffer = kcalloc(pitch, ssd130x->height, GFP_KERNEL);
> +		if (!ssd130x_state->buffer) {
> +			kfree(ssd130x_state->data_array);
> +			/* Set to prevent a double free in .atomic_destroy_state() */
> +			ssd130x_state->data_array = NULL;
> +			return -ENOMEM;
> +		}
>   	}
>   
>   	return 0;
> @@ -898,6 +923,7 @@ static const struct drm_mode_config_funcs ssd130x_mode_config_funcs = {
>   };
>   
>   static const uint32_t ssd130x_formats[] = {
> +	DRM_FORMAT_R1,
>   	DRM_FORMAT_XRGB8888,
>   };
>   

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

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