Re: [PATCH 3/7] drm/mipi-dbi: Use framebuffer dma-buf helpers

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Jul 16, 2021 at 04:07:57PM +0200, Thomas Zimmermann wrote:
> Replace dma_buf_begin_cpu_access() with drm_gem_fb_begin_cpu_access();
> same for _end_cpu_access(). Remove some boiler-plate code. No functional
> changes.
> 
> There's one left-over reference to the imported attachment that we
> keep. GEM BOs with imported attachment are considered uncached and
> enables special handling within the drm_fb_swab().
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> ---
>  drivers/gpu/drm/drm_mipi_dbi.c | 20 +++++++-------------
>  1 file changed, 7 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_mipi_dbi.c b/drivers/gpu/drm/drm_mipi_dbi.c
> index 10b4e59384ae..71b646c4131f 100644
> --- a/drivers/gpu/drm/drm_mipi_dbi.c
> +++ b/drivers/gpu/drm/drm_mipi_dbi.c
> @@ -7,7 +7,6 @@
>  
>  #include <linux/debugfs.h>
>  #include <linux/delay.h>
> -#include <linux/dma-buf.h>
>  #include <linux/gpio/consumer.h>
>  #include <linux/module.h>
>  #include <linux/regulator/consumer.h>
> @@ -202,21 +201,17 @@ int mipi_dbi_buf_copy(void *dst, struct drm_framebuffer *fb,
>  {
>  	struct drm_gem_object *gem = drm_gem_fb_get_obj(fb, 0);
>  	struct drm_gem_cma_object *cma_obj = to_drm_gem_cma_obj(gem);
> -	struct dma_buf_attachment *import_attach = gem->import_attach;
>  	void *src = cma_obj->vaddr;
> -	int ret = 0;
> +	int ret;
>  
> -	if (import_attach) {
> -		ret = dma_buf_begin_cpu_access(import_attach->dmabuf,
> -					       DMA_FROM_DEVICE);
> -		if (ret)
> -			return ret;
> -	}
> +	ret = drm_gem_fb_begin_cpu_access(fb, DMA_FROM_DEVICE);
> +	if (ret)
> +		return ret;
>  
>  	switch (fb->format->format) {
>  	case DRM_FORMAT_RGB565:
>  		if (swap)
> -			drm_fb_swab(dst, src, fb, clip, !import_attach);
> +			drm_fb_swab(dst, src, fb, clip, !gem->import_attach);

I freaked out about this because for dma-buf WC vs WB is undefined, but
it's purely a perf optimization. So it's fine. Plus we're not even
bothering with the iomem vs normal memory distinction here.

Anyway, that aside, all looks good. On the series:

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>

>  		else
>  			drm_fb_memcpy(dst, src, fb, clip);
>  		break;
> @@ -229,9 +224,8 @@ int mipi_dbi_buf_copy(void *dst, struct drm_framebuffer *fb,
>  		return -EINVAL;
>  	}
>  
> -	if (import_attach)
> -		ret = dma_buf_end_cpu_access(import_attach->dmabuf,
> -					     DMA_FROM_DEVICE);
> +	drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
> +
>  	return ret;
>  }
>  EXPORT_SYMBOL(mipi_dbi_buf_copy);
> -- 
> 2.32.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch