Re: [PATCH] drm/rockchip: Check iommu itself instead of it's parent for device_is_available

[Robin Murphy]

On 2021-06-27 09:47, Andy Yan wrote:
When iommu itself is disabled in dts, we should
fallback to non-iommu buffer, check iommu parent
is meanless here.
Signed-off-by: Andy Yan <andy....@rock-chips.com>
---

  drivers/gpu/drm/rockchip/rockchip_drm_drv.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c 
b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
index 212bd87c0c4a..0d20c8cc1ffa 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
@@ -366,7 +366,7 @@ static int rockchip_drm_platform_of_probe(struct device 
*dev)
                }
  
  		iommu = of_parse_phandle(port->parent, "iommus", 0);
-               if (!iommu || !of_device_is_available(iommu->parent)) {
+               if (!iommu || !of_device_is_available(iommu)) {

Just wondering, could you use device_iommu_mapped() to avoid poking at 
the DT at all here, or is it that you need to check remote graph 
endpoints whose struct device may not be ready yet?

Robin.

                        DRM_DEV_DEBUG(dev,
                                      "no iommu attached for %pOF, using non-iommu 
buffers\n",
                                      port->parent);