drm/tegra: Add IOMMU support

When an IOMMU device is available on the platform bus, allocate an IOMMU
domain and attach the display controllers to it. The display controllers
can then scan out non-contiguous buffers by mapping them through the
IOMMU.

Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/dc.c

@@ -9,6 +9,7 @@
 
 #include <linux/clk.h>
 #include <linux/debugfs.h>
+#include <linux/iommu.h>
 #include <linux/reset.h>
 
 #include <soc/tegra/pmc.h>
@@ -1290,6 +1291,17 @@ static int tegra_dc_init(struct host1x_client *client)
 	struct tegra_drm *tegra = drm->dev_private;
 	int err;
 
+	if (tegra->domain) {
+		err = iommu_attach_device(tegra->domain, dc->dev);
+		if (err < 0) {
+			dev_err(dc->dev, "failed to attach to domain: %d\n",
+				err);
+			return err;
+		}
+
+		dc->domain = tegra->domain;
+	}
+
 	drm_crtc_init(drm, &dc->base, &tegra_crtc_funcs);
 	drm_mode_crtc_set_gamma_size(&dc->base, 256);
 	drm_crtc_helper_add(&dc->base, &tegra_crtc_helper_funcs);
@@ -1347,6 +1359,11 @@ static int tegra_dc_exit(struct host1x_client *client)
 		return err;
 	}
 
+	if (dc->domain) {
+		iommu_detach_device(dc->domain, dc->dev);
+		dc->domain = NULL;
+	}
+
 	return 0;
 }
 

drivers/gpu/drm/tegra/drm.c

@@ -8,6 +8,7 @@
  */
 
 #include <linux/host1x.h>
+#include <linux/iommu.h>
 
 #include "drm.h"
 #include "gem.h"
@@ -33,6 +34,17 @@ static int tegra_drm_load(struct drm_device *drm, unsigned long flags)
 	if (!tegra)
 		return -ENOMEM;
 
+	if (iommu_present(&platform_bus_type)) {
+		tegra->domain = iommu_domain_alloc(&platform_bus_type);
+		if (IS_ERR(tegra->domain)) {
+			err = PTR_ERR(tegra->domain);
+			goto free;
+		}
+
+		DRM_DEBUG("IOMMU context initialized\n");
+		drm_mm_init(&tegra->mm, 0, SZ_2G);
+	}
+
 	mutex_init(&tegra->clients_lock);
 	INIT_LIST_HEAD(&tegra->clients);
 	drm->dev_private = tegra;
@@ -76,13 +88,20 @@ static int tegra_drm_load(struct drm_device *drm, unsigned long flags)
 	tegra_drm_fb_free(drm);
 config:
 	drm_mode_config_cleanup(drm);
+
+	if (tegra->domain) {
+		iommu_domain_free(tegra->domain);
+		drm_mm_takedown(&tegra->mm);
+	}
+free:
 	kfree(tegra);
 	return err;
 }
 
 static int tegra_drm_unload(struct drm_device *drm)
 {
 	struct host1x_device *device = to_host1x_device(drm->dev);
+	struct tegra_drm *tegra = drm->dev_private;
 	int err;
 
 	drm_kms_helper_poll_fini(drm);
@@ -94,6 +113,11 @@ static int tegra_drm_unload(struct drm_device *drm)
 	if (err < 0)
 		return err;
 
+	if (tegra->domain) {
+		iommu_domain_free(tegra->domain);
+		drm_mm_takedown(&tegra->mm);
+	}
+
 	return 0;
 }
 

drivers/gpu/drm/tegra/drm.h

@@ -39,6 +39,9 @@ struct tegra_fbdev {
 struct tegra_drm {
 	struct drm_device *drm;
 
+	struct iommu_domain *domain;
+	struct drm_mm mm;
+
 	struct mutex clients_lock;
 	struct list_head clients;
 
@@ -121,6 +124,8 @@ struct tegra_dc {
 	struct drm_pending_vblank_event *event;
 
 	const struct tegra_dc_soc_info *soc;
+
+	struct iommu_domain *domain;
 };
 
 static inline struct tegra_dc *

drivers/gpu/drm/tegra/fb.c

@@ -65,8 +65,12 @@ static void tegra_fb_destroy(struct drm_framebuffer *framebuffer)
 	for (i = 0; i < fb->num_planes; i++) {
 		struct tegra_bo *bo = fb->planes[i];
 
-		if (bo)
+		if (bo) {
+			if (bo->pages && bo->vaddr)
+				vunmap(bo->vaddr);
+
 			drm_gem_object_unreference_unlocked(&bo->gem);
+		}
 	}
 
 	drm_framebuffer_cleanup(framebuffer);
@@ -254,6 +258,16 @@ static int tegra_fbdev_probe(struct drm_fb_helper *helper,
 	offset = info->var.xoffset * bytes_per_pixel +
 		 info->var.yoffset * fb->pitches[0];
 
+	if (bo->pages) {
+		bo->vaddr = vmap(bo->pages, bo->num_pages, VM_MAP,
+				 pgprot_writecombine(PAGE_KERNEL));
+		if (!bo->vaddr) {
+			dev_err(drm->dev, "failed to vmap() framebuffer\n");
+			err = -ENOMEM;
+			goto destroy;
+		}
+	}
+
 	drm->mode_config.fb_base = (resource_size_t)bo->paddr;
 	info->screen_base = (void __iomem *)bo->vaddr + offset;
 	info->screen_size = size;