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

[liviu.dudau@arm.com]

On Tue, Jun 07, 2016 at 04:43:05PM +0200, Daniel Vetter wrote:
> On Tue, Jun 07, 2016 at 01:18:09PM +0100, Robin Murphy wrote:
> > 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.
> > 
> > Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> > Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> > ---
> > 
> > Resending rebased to 4.7-rc1 with Daniel's ack. I know Russell raised
> > some concerns about the general way fb_cma_helper uses fb_info[1], but
> > AFAICS that's a longstanding separate problem orthogonal to this patch.
> 
> Do you want me to pull this in through drm-misc, or will this land through
> some driver tree? Note that I'll do -misc pulls about every week, so if
> you don't send your pull this week I'd like to pull it in to avoid
> hilarity^W needless conflicts.
> -Daniel

Hi Daniel,

This patch is for drm core, so no driver can carry it (?).

Please pull it into your drm-misc.

Best regards,
Liviu

> 
> > 
> > Robin.
> > 
> > [1]:http://thread.gmane.org/gmane.comp.video.dri.devel/149288
> > 
> >  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 172cafe11c71..a25afc068d3f 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>
> >  
> >  #define DEFAULT_FBDEFIO_DELAY_MS 50
> > @@ -297,6 +298,12 @@ 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,
> > @@ -307,6 +314,7 @@ 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_deferred_io_mmap(struct fb_info *info,
> > -- 
> > 2.8.1.dirty
> > 
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
> 

-- 
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