On 4/11/22 16:46, Robin Murphy wrote:
Refactor the confusing logic to make it both clearer and more robust. If the host1x parent device does have an IOMMU domain then iommu_present() is redundantly true, while otherwise for the 32-bit DMA mask case it still doesn't say whether the IOMMU driver actually knows about the DRM device or not.
Signed-off-by: Robin Murphy robin.murphy@arm.com
v2: Fix logic for older SoCs and clarify.
drivers/gpu/drm/tegra/drm.c | 28 ++++++++++++++++++++-------- 1 file changed, 20 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c index 9464f522e257..4f2bdab31064 100644 --- a/drivers/gpu/drm/tegra/drm.c +++ b/drivers/gpu/drm/tegra/drm.c @@ -1092,6 +1092,19 @@ static bool host1x_drm_wants_iommu(struct host1x_device *dev) struct host1x *host1x = dev_get_drvdata(dev->dev.parent); struct iommu_domain *domain;
- /* For starters, this is moot if no IOMMU is available */
- if (!device_iommu_mapped(&dev->dev))
return false;- /*
* Tegra20 and Tegra30 don't support addressing memory beyond the* 32-bit boundary, so the regular GATHER opcodes will always be* sufficient and whether or not the host1x is attached to an IOMMU* doesn't matter.*/- if (host1x_get_dma_mask(host1x) <= DMA_BIT_MASK(32))
return true;- /*
- If the Tegra DRM clients are backed by an IOMMU, push buffers are
- likely to be allocated beyond the 32-bit boundary if sufficient
@@ -1122,14 +1135,13 @@ static bool host1x_drm_wants_iommu(struct host1x_device *dev) domain = iommu_get_domain_for_dev(dev->dev.parent);
/*
* Tegra20 and Tegra30 don't support addressing memory beyond the* 32-bit boundary, so the regular GATHER opcodes will always be* sufficient and whether or not the host1x is attached to an IOMMU* doesn't matter.
* At the moment, the exact type of domain doesn't actually matter.* Only for 64-bit kernels might this be a managed DMA API domain, and* then only on newer SoCs using arm-smmu, since tegra-smmu doesn't* support default domains at all, and since those SoCs are the same* ones with extended GATHER support, even if it's a passthrough domain* it can still work out OK.
- if (!domain && host1x_get_dma_mask(host1x) <= DMA_BIT_MASK(32))
return true;- return domain != NULL;
}
@@ -1149,7 +1161,7 @@ static int host1x_drm_probe(struct host1x_device *dev) goto put; }
- if (host1x_drm_wants_iommu(dev) && iommu_present(&platform_bus_type)) {
- if (host1x_drm_wants_iommu(dev)) { tegra->domain = iommu_domain_alloc(&platform_bus_type); if (!tegra->domain) { err = -ENOMEM;
Robin, thank you for the updated version. The patch looks okay to me.
Reviewed-by: Dmitry Osipenko dmitry.osipenko@collabora.com
A bit later I'll also will give it a test, just to be sure because we had problems with that function in the past.