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

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Jun 07, 2016 at 04:03:40PM +0100, Robin Murphy wrote:
> On 07/06/16 15:43, 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.
> 
> Yeah, drm-misc sounds appropriate so if you're happy to pick it up, please
> feel free :)

Applied, thanks.
-Daniel

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