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.vet...@ffwll.ch> Signed-off-by: Robin Murphy <robin.mur...@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. 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
