11.03.2021 01:17, Nicolin Chen пишет: > On Wed, Mar 10, 2021 at 11:22:57PM +0300, Dmitry Osipenko wrote: >> 10.03.2021 22:13, Dmitry Osipenko пишет: >>> I found that this patch introduced a serious regression on Tegra30 using >>> today's linux-next. Tegra30 has two 3d h/w blocks connected in SLI and >>> only one of the blocks is now attached to IOMMU domain, meaning that GPU >>> is unusable now. All 3d, 2d and display devices share the same "DRM" >>> group on Tegra30. >>> >>> Nicolin, please let me know if have any suggestions. I may take a closer >>> look a day later, for now I'll just revert this patch locally. Thanks in >>> advance. >>> >> >> Actually, this was easy to fix: >> >> diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c >> index 97eb62f667d2..639d5ceab60b 100644 >> --- a/drivers/iommu/tegra-smmu.c >> +++ b/drivers/iommu/tegra-smmu.c >> @@ -853,8 +853,6 @@ static struct iommu_device >> *tegra_smmu_probe_device(struct device *dev) >> >> if (err < 0) >> return ERR_PTR(err); >> - >> - break; > > Hmm..I don't understand why this "break" causes problems on Tegra30. > The older versions that used _find()+configure() had it also, e.g.: > https://elixir.bootlin.com/linux/v5.9.16/source/drivers/iommu/tegra-smmu.c#L760 > > Dmitry, do you have any idea? > The older variant of tegra_smmu_attach_dev() didn't use fwspec [1], that makes the difference. In other words, the older variant of tegra_smmu_probe_device() was already buggy, but the bug was masked by the tegra_smmu_attach_dev() that didn't use the fwspec. [1] https://elixir.bootlin.com/linux/v5.10.22/source/drivers/iommu/tegra-smmu.c#L476
