From: Thierry Reding <tred...@nvidia.com>

This fixes hangs with legacy applications that use the mmap() syscall on
the fbdev device to map framebuffer memory. The fbdev implementation for
mmap() creates a mapping that conflicts with DRM usage and causes a hang
when the memory is accessed through the mapping.

Reported-by: Marcel Ziswiler <marcel.ziswi...@toradex.com>
Signed-off-by: Thierry Reding <tred...@nvidia.com>
---
 drivers/gpu/drm/tegra/fb.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/gpu/drm/tegra/fb.c b/drivers/gpu/drm/tegra/fb.c
index 001cb77e2f59..0786159edef3 100644
--- a/drivers/gpu/drm/tegra/fb.c
+++ b/drivers/gpu/drm/tegra/fb.c
@@ -224,12 +224,28 @@ struct drm_framebuffer *tegra_fb_create(struct drm_device 
*drm,
 }
 
 #ifdef CONFIG_DRM_FBDEV_EMULATION
+static int tegra_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
+{
+       struct drm_fb_helper *helper = info->par;
+       struct tegra_bo *bo;
+       int err;
+
+       bo = tegra_fb_get_plane(helper->fb, 0);
+
+       err = drm_gem_mmap_obj(&bo->gem, bo->gem.size, vma);
+       if (err < 0)
+               return err;
+
+       return __tegra_gem_mmap(&bo->gem, vma);
+}
+
 static struct fb_ops tegra_fb_ops = {
        .owner = THIS_MODULE,
        DRM_FB_HELPER_DEFAULT_OPS,
        .fb_fillrect = drm_fb_helper_sys_fillrect,
        .fb_copyarea = drm_fb_helper_sys_copyarea,
        .fb_imageblit = drm_fb_helper_sys_imageblit,
+       .fb_mmap = tegra_fb_mmap,
 };
 
 static int tegra_fbdev_probe(struct drm_fb_helper *helper,
-- 
2.15.1

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