drm/tegra: fb: Implement ->fb_mmap() callback

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.ziswiler@toradex.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Tested-by: Stefan Agner <stefan@agner.ch>
Tested-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Reported-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

1 files changed, 16 insertions, 0 deletions

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 @@ unreference:
 }
 
 #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,