ACK: [PATCH] drm/fb_cma_helper: Implement fb_mmap callback

Stefan Bader stefan.bader at canonical.com
Thu Aug 3 13:38:45 UTC 2017


On 03.08.2017 12:17, Paolo Pisati wrote:
> From: Robin Murphy <robin.murphy at arm.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1708417
> 
> In the absence of an fb_mmap callback, the fbdev code falls back to a
> naive implementation which relies upon the DMA address being the same
> as the physical address, and the buffer being physically contiguous
> from there. Whilst this often holds for standard CMA allocations via
> the platform's regular DMA ops, if the allocation is provided by an
> IOMMU then such assumptions can fall apart spectacularly.
> 
> To resolve this, reroute the fb_mmap call to the appropriate DMA API
> implementation, as per the other cma_helper calls.
> 
> Signed-off-by: Robin Murphy <robin.murphy at arm.com>
> Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> Link: http://patchwork.freedesktop.org/patch/msgid/8fd95ac1440e0f01daad6d4380be3a4c8fa61055.1465301219.git.robin.murphy@arm.com
> (cherry picked from commit ce0c5757681052eb8965209129f28362c3a4d8a7)
> Signed-off-by: Paolo Pisati <paolo.pisati at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>

> ---

Limited to specific subtree where it is testable.

>  drivers/gpu/drm/drm_fb_cma_helper.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c b/drivers/gpu/drm/drm_fb_cma_helper.c
> index 6349d0c..033f846 100644
> --- a/drivers/gpu/drm/drm_fb_cma_helper.c
> +++ b/drivers/gpu/drm/drm_fb_cma_helper.c
> @@ -23,6 +23,7 @@
>  #include <drm/drm_crtc_helper.h>
>  #include <drm/drm_gem_cma_helper.h>
>  #include <drm/drm_fb_cma_helper.h>
> +#include <linux/dma-mapping.h>
>  #include <linux/module.h>
>  
>  struct drm_fb_cma {
> @@ -220,6 +221,12 @@ int drm_fb_cma_debugfs_show(struct seq_file *m, void *arg)
>  EXPORT_SYMBOL_GPL(drm_fb_cma_debugfs_show);
>  #endif
>  
> +static int drm_fb_cma_mmap(struct fb_info *info, struct vm_area_struct *vma)
> +{
> +	return dma_mmap_writecombine(info->device, vma, info->screen_base,
> +				     info->fix.smem_start, info->fix.smem_len);
> +}
> +
>  static struct fb_ops drm_fbdev_cma_ops = {
>  	.owner		= THIS_MODULE,
>  	.fb_fillrect	= drm_fb_helper_sys_fillrect,
> @@ -230,6 +237,7 @@ static struct fb_ops drm_fbdev_cma_ops = {
>  	.fb_blank	= drm_fb_helper_blank,
>  	.fb_pan_display	= drm_fb_helper_pan_display,
>  	.fb_setcmap	= drm_fb_helper_setcmap,
> +	.fb_mmap	= drm_fb_cma_mmap,
>  };
>  
>  static int drm_fbdev_cma_create(struct drm_fb_helper *helper,
> 


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