[PATCH RFC 3/3] drm/i915/display: Implement fb_mmap callback function

[Nirmoy Das <nirmoy.das@intel.com>]

If stolen memory allocation fails for fbdev, the driver will
fallback to system memory. Calculation of smem_start is wrong
for such framebuffer objs if the platform comes with no gmadr or
no aperture. Solve this by adding fb_mmap callback which also gives
driver more control.

Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
---
 drivers/gpu/drm/i915/display/intel_fbdev.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_fbdev.c b/drivers/gpu/drm/i915/display/intel_fbdev.c
index 98ae3a3a986a..ed0f9e2af3ed 100644
--- a/drivers/gpu/drm/i915/display/intel_fbdev.c
+++ b/drivers/gpu/drm/i915/display/intel_fbdev.c
@@ -40,8 +40,10 @@
 #include <drm/drm_crtc.h>
 #include <drm/drm_fb_helper.h>
 #include <drm/drm_fourcc.h>
+#include <drm/drm_gem_framebuffer_helper.h>
 
 #include "gem/i915_gem_lmem.h"
+#include "gem/i915_gem_mman.h"
 
 #include "i915_drv.h"
 #include "intel_display_types.h"
@@ -120,6 +122,23 @@ static int intel_fbdev_pan_display(struct fb_var_screeninfo *var,
 	return ret;
 }
 
+#define to_intel_fbdev(x) container_of(x, struct intel_fbdev, helper)
+static int intel_fbdev_mmap(struct fb_info *info, struct vm_area_struct *vma)
+{
+	struct intel_fbdev *fbdev = to_intel_fbdev(info->par);
+	struct drm_gem_object *bo = drm_gem_fb_get_obj(&fbdev->fb->base, 0);
+	struct drm_i915_gem_object *obj = to_intel_bo(bo);
+	struct drm_device *dev = fbdev->helper.dev;
+
+	vma->vm_page_prot =
+			pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
+
+	if (obj->stolen)
+		return vm_iomap_memory(vma, info->fix.smem_start,
+				       info->fix.smem_len);
+
+	return i915_gem_object_mmap(obj, vma);
+}
 static const struct fb_ops intelfb_ops = {
 	.owner = THIS_MODULE,
 	DRM_FB_HELPER_DEFAULT_OPS,
@@ -131,6 +150,7 @@ static const struct fb_ops intelfb_ops = {
 	.fb_imageblit = drm_fb_helper_cfb_imageblit,
 	.fb_pan_display = intel_fbdev_pan_display,
 	.fb_blank = intel_fbdev_blank,
+	.fb_mmap = intel_fbdev_mmap,
 };
 
 static int intelfb_alloc(struct drm_fb_helper *helper,
-- 
2.39.0