linux-kernel - Re: [PATCH 08/12] drm/udl: Drop unneeded alignment

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Date:   Mon, 5 Sep 2022 10:40:58 +0200
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/12] drm/udl: Drop unneeded alignment

Hi

Am 16.08.22 um 17:36 schrieb Takashi Iwai:
> The alignment of damaged area was needed for the original udlfb driver
> that tried to trim the superfluous copies between front and backend
> buffers and handle data in long int.  It's not the case for udl DRM
> driver, hence we can omit the whole unneeded alignment, as well as the
> dead code.
> 
> Signed-off-by: Takashi Iwai <tiwai@...e.de>
> ---
>   drivers/gpu/drm/udl/udl_modeset.c  | 34 ++++++-------------------
>   drivers/gpu/drm/udl/udl_transfer.c | 40 ------------------------------
>   2 files changed, 8 insertions(+), 66 deletions(-)
> 
> diff --git a/drivers/gpu/drm/udl/udl_modeset.c b/drivers/gpu/drm/udl/udl_modeset.c
> index c34d564773a3..bca31c890108 100644
> --- a/drivers/gpu/drm/udl/udl_modeset.c
> +++ b/drivers/gpu/drm/udl/udl_modeset.c
> @@ -243,28 +243,6 @@ static long udl_log_cpp(unsigned int cpp)
>   	return __ffs(cpp);
>   }
>   
> -static int udl_aligned_damage_clip(struct drm_rect *clip, int x, int y,
> -				   int width, int height)
> -{
> -	int x1, x2;
> -
> -	if (WARN_ON_ONCE(x < 0) ||
> -	    WARN_ON_ONCE(y < 0) ||
> -	    WARN_ON_ONCE(width < 0) ||
> -	    WARN_ON_ONCE(height < 0))
> -		return -EINVAL;
> -
> -	x1 = ALIGN_DOWN(x, sizeof(unsigned long));
> -	x2 = ALIGN(width + (x - x1), sizeof(unsigned long)) + x1;
> -
> -	clip->x1 = x1;
> -	clip->y1 = y;
> -	clip->x2 = x2;
> -	clip->y2 = y + height;
> -
> -	return 0;
> -}
> -
>   static int udl_handle_damage(struct drm_framebuffer *fb,
>   			     const struct iosys_map *map,
>   			     int x, int y, int width, int height)
> @@ -277,15 +255,19 @@ static int udl_handle_damage(struct drm_framebuffer *fb,
>   	struct drm_rect clip;
>   	int log_bpp;
>   
> +	if (width <= 0 || height <= 0)
> +		return 0;
> +

That shouldn't happen.

>   	ret = udl_log_cpp(fb->format->cpp[0]);
>   	if (ret < 0)
>   		return ret;
>   	log_bpp = ret;
>   
> -	ret = udl_aligned_damage_clip(&clip, x, y, width, height);
> -	if (ret)
> -		return ret;
> -	else if ((clip.x2 > fb->width) || (clip.y2 > fb->height))
> +	clip.x1 = x;
> +	clip.y1 = y;
> +	clip.x2 = x + width;
> +	clip.y2 = y + height;

drm_rect_init() please.

> +	if (clip.x2 > fb->width || clip.y2 > fb->height)

That's another thing that should not happen. The damage clips in the 
plane state is what you what to copy. The DRM helpers ensure that these 
various plane, fb and clip coordinates add up.

Best regards
Thomas

>   		return -EINVAL;
>   
>   	ret = drm_gem_fb_begin_cpu_access(fb, DMA_FROM_DEVICE);
> diff --git a/drivers/gpu/drm/udl/udl_transfer.c b/drivers/gpu/drm/udl/udl_transfer.c
> index 176ef2a6a731..a431208dda85 100644
> --- a/drivers/gpu/drm/udl/udl_transfer.c
> +++ b/drivers/gpu/drm/udl/udl_transfer.c
> @@ -25,46 +25,6 @@
>   #define MIN_RAW_PIX_BYTES	2
>   #define MIN_RAW_CMD_BYTES	(RAW_HEADER_BYTES + MIN_RAW_PIX_BYTES)
>   
> -/*
> - * Trims identical data from front and back of line
> - * Sets new front buffer address and width
> - * And returns byte count of identical pixels
> - * Assumes CPU natural alignment (unsigned long)
> - * for back and front buffer ptrs and width
> - */
> -#if 0
> -static int udl_trim_hline(const u8 *bback, const u8 **bfront, int *width_bytes)
> -{
> -	int j, k;
> -	const unsigned long *back = (const unsigned long *) bback;
> -	const unsigned long *front = (const unsigned long *) *bfront;
> -	const int width = *width_bytes / sizeof(unsigned long);
> -	int identical = width;
> -	int start = width;
> -	int end = width;
> -
> -	for (j = 0; j < width; j++) {
> -		if (back[j] != front[j]) {
> -			start = j;
> -			break;
> -		}
> -	}
> -
> -	for (k = width - 1; k > j; k--) {
> -		if (back[k] != front[k]) {
> -			end = k+1;
> -			break;
> -		}
> -	}
> -
> -	identical = start + (width - end);
> -	*bfront = (u8 *) &front[start];
> -	*width_bytes = (end - start) * sizeof(unsigned long);
> -
> -	return identical * sizeof(unsigned long);
> -}
> -#endif
> -
>   static inline u16 pixel32_to_be16(const uint32_t pixel)
>   {
>   	return (((pixel >> 3) & 0x001f) |

-- 
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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