Re: [PATCH 21/22] drm/tegra: Don't use IOMMU on Tegra20

On 06/01/2017 11:36 AM, Dmitry Osipenko wrote:

On 23.05.2017 03:16, Dmitry Osipenko wrote:

quoted

There is no IOMMU on Tegra20, instead a GART would be picked as an IOMMU
provider.

Signed-off-by: Dmitry Osipenko <redacted>
---
  drivers/gpu/drm/tegra/drm.c | 5 ++++-
  drivers/gpu/host1x/dev.c    | 5 ++++-
  2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
index 17416e1c219a..ac8f76d9475f 100644
--- a/drivers/gpu/drm/tegra/drm.c
+++ b/drivers/gpu/drm/tegra/drm.c

@@ -15,6 +15,8 @@
  #include <drm/drm_atomic.h>
  #include <drm/drm_atomic_helper.h>
  
+#include <soc/tegra/fuse.h>
+
  #include "drm.h"
  #include "gem.h"
  

@@ -131,7 +133,8 @@ static int tegra_drm_load(struct drm_device *drm, unsigned long flags)
  	if (!tegra)
  		return -ENOMEM;
  
-	if (iommu_present(&platform_bus_type)) {
+	if (iommu_present(&platform_bus_type) &&
+	    tegra_get_chip_id() != TEGRA20) {
  		u64 carveout_start, carveout_end, gem_start, gem_end;
  		struct iommu_domain_geometry *geometry;
  		unsigned long order;

diff --git a/drivers/gpu/host1x/dev.c b/drivers/gpu/host1x/dev.c
index 5c1c711a21af..56b7e6d51894 100644
--- a/drivers/gpu/host1x/dev.c
+++ b/drivers/gpu/host1x/dev.c

@@ -25,6 +25,8 @@
  #include <linux/of.h>
  #include <linux/slab.h>
  
+#include <soc/tegra/fuse.h>
+
  #define CREATE_TRACE_POINTS
  #include <trace/events/host1x.h>
  #undef CREATE_TRACE_POINTS

@@ -177,7 +179,8 @@ static int host1x_probe(struct platform_device *pdev)
  		return err;
  	}
  
-	if (iommu_present(&platform_bus_type)) {
+	if (iommu_present(&platform_bus_type) &&
+	    tegra_get_chip_id() != TEGRA20) {
  		struct iommu_domain_geometry *geometry;
  		unsigned long order;
  

Nicolas noticed that this breaks driver module compilation, as the
`tegra_get_chip_id` is not an exported symbol. I'll consider alternatives to
symbol exporting and will fix it in the new revision of the patch.

My recommendation is of_machine_is_compatible()

Cheers,
Mikko