Hi Mikko, Thierry,
While setting up my Jetson TK1 using the mainline kernel I discovered that the HDMI output
didn't work.
After some more debugging I discovered that this commit 404bfb78daf3bedafb0bfab24947059575cbea3d
(gpu: host1x: Add IOMMU support) was the culprit.
As far as I understand it host1x_probe() calls iommu_attach_device(), which in turn tries to
find the 'iommus' property in the DT. But the hdmi@54280000 device has no such property and so
iommu_attach_device() returns -ENODEV and the host1x_probe fails.
After making this extremely ugly patch it all works again:
diff --git a/drivers/gpu/host1x/dev.c b/drivers/gpu/host1x/dev.c
index 2c58a390123a..683f3a5f382a 100644
--- a/drivers/gpu/host1x/dev.c
+++ b/drivers/gpu/host1x/dev.c
@@ -186,6 +186,11 @@ static int host1x_probe(struct platform_device *pdev)
return -ENOMEM;
err = iommu_attach_device(host->domain, &pdev->dev);
+ if (err == -ENODEV) {
+ iommu_domain_free(host->domain);
+ host->domain = NULL;
+ goto no_mmu;
+ }
if (err)
goto fail_free_domain;
@@ -197,7 +202,7 @@ static int host1x_probe(struct platform_device *pdev)
geometry->aperture_end >> order);
host->iova_end = geometry->aperture_end;
}
-
+no_mmu:
err = host1x_channel_list_init(&host->channel_list,
host->info->nb_channels);
if (err) {
My plan is to use my Jetson TK1 to upstream the Tegra CEC driver that I wrote, but
a working HDMI output would help a lot :-)
I'm not sure if my analysis of the cause is correct, but if someone can take a look
then I would appreciate that!
Regards,
Hans
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