diff mbox series

[13/18] iommu/tegra: Add IOMMU_DOMAIN_DMA support

Message ID cd11bc7851dbe46db6d14821a942678047331913.1597931876.git.robin.murphy@arm.com
State New
Headers show
Series None | expand

Commit Message

Robin Murphy Aug. 20, 2020, 3:08 p.m. UTC 
Now that arch/arm is wired up for default domains and iommu-dma,
implement the corresponding driver-side support for DMA domains.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---
 drivers/iommu/tegra-smmu.c | 37 +++++++++++++++++++++----------------
 1 file changed, 21 insertions(+), 16 deletions(-)

Comments

Thierry Reding Aug. 27, 2020, 3:45 p.m. UTC | #1 
On Thu, Aug 20, 2020 at 04:08:32PM +0100, Robin Murphy wrote:
> Now that arch/arm is wired up for default domains and iommu-dma,
> implement the corresponding driver-side support for DMA domains.
> 
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
>  drivers/iommu/tegra-smmu.c | 37 +++++++++++++++++++++----------------
>  1 file changed, 21 insertions(+), 16 deletions(-)

We can't do that yet because it will currently still break for use-cases
such as display where we don't properly set up identity mappings during
boot. The result is that the dma-iommu code will enable translations
before the driver gets a chance to set up any mappings and if the
display controller was left on by the bootloader, scanning out a splash
screen, this causes faults between the point where dma-iommu is being
set up for the display controller and where the display controller
starts mapping its own buffers (rather than the ones mapped by the
bootloader).

That said, I do have a series that I've been carrying around for longer
than I've wanted that does exactly this for Tegra SMMU and I'd prefer if
you could drop this particular change from your series so that I can
keep working on resolving the identity mapping issues first.

Thierry
diff mbox series

Patch

diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c
index 124c8848ab7e..8e276eac84d9 100644
--- a/drivers/iommu/tegra-smmu.c
+++ b/drivers/iommu/tegra-smmu.c
@@ -5,6 +5,7 @@ 
 
 #include <linux/bitops.h>
 #include <linux/debugfs.h>
+#include <linux/dma-iommu.h>
 #include <linux/err.h>
 #include <linux/iommu.h>
 #include <linux/kernel.h>
@@ -278,7 +279,7 @@  static struct iommu_domain *tegra_smmu_domain_alloc(unsigned type)
 {
 	struct tegra_smmu_as *as;
 
-	if (type != IOMMU_DOMAIN_UNMANAGED)
+	if (type != IOMMU_DOMAIN_UNMANAGED && type != IOMMU_DOMAIN_DMA)
 		return NULL;
 
 	as = kzalloc(sizeof(*as), GFP_KERNEL);
@@ -288,25 +289,19 @@  static struct iommu_domain *tegra_smmu_domain_alloc(unsigned type)
 	as->attr = SMMU_PD_READABLE | SMMU_PD_WRITABLE | SMMU_PD_NONSECURE;
 
 	as->pd = alloc_page(GFP_KERNEL | __GFP_DMA | __GFP_ZERO);
-	if (!as->pd) {
-		kfree(as);
-		return NULL;
-	}
+	if (!as->pd)
+		goto out_free_as;
 
 	as->count = kcalloc(SMMU_NUM_PDE, sizeof(u32), GFP_KERNEL);
-	if (!as->count) {
-		__free_page(as->pd);
-		kfree(as);
-		return NULL;
-	}
+	if (!as->count)
+		goto out_free_all;
 
 	as->pts = kcalloc(SMMU_NUM_PDE, sizeof(*as->pts), GFP_KERNEL);
-	if (!as->pts) {
-		kfree(as->count);
-		__free_page(as->pd);
-		kfree(as);
-		return NULL;
-	}
+	if (!as->pts)
+		goto out_free_all;
+
+	if (type == IOMMU_DOMAIN_DMA && iommu_get_dma_cookie(&as->domain))
+		goto out_free_all;
 
 	/* setup aperture */
 	as->domain.geometry.aperture_start = 0;
@@ -314,12 +309,22 @@  static struct iommu_domain *tegra_smmu_domain_alloc(unsigned type)
 	as->domain.geometry.force_aperture = true;
 
 	return &as->domain;
+
+out_free_all:
+	kfree(as->pts);
+	kfree(as->count);
+	__free_page(as->pd);
+out_free_as:
+	kfree(as);
+	return NULL;
 }
 
 static void tegra_smmu_domain_free(struct iommu_domain *domain)
 {
 	struct tegra_smmu_as *as = to_smmu_as(domain);
 
+	iommu_put_dma_cookie(domain);
+
 	/* TODO: free page directory and page tables */
 
 	WARN_ON_ONCE(as->use_count);