From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Murphy Subject: Re: [PATCH] drm/fb_cma_helper: Implement fb_mmap callback Date: Tue, 7 Jun 2016 16:03:40 +0100 Message-ID: <5756E24C.7070402@arm.com> References: <8fd95ac1440e0f01daad6d4380be3a4c8fa61055.1465301219.git.robin.murphy@arm.com> <20160607144305.GC3363@phenom.ffwll.local> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20160607144305.GC3363@phenom.ffwll.local> Sender: linux-kernel-owner@vger.kernel.org To: airlied@linux.ie, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, liviu.dudau@arm.com List-Id: dri-devel@lists.freedesktop.org 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 >> Signed-off-by: Robin Murphy >> --- >> >> 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 :) 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 >> #include >> #include >> +#include >> #include >> >> #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 >> >