drm/panfrost: Support cache-coherent integrations

When the GPU's ACE-Lite interface is fully wired up and capable of
snooping CPU caches, it may be described as "dma-coherent" in
devicetree, which will already inform the DMA layer not to perform
unnecessary cache maintenance. However, we still need to ensure that
the GPU uses the appropriate cacheable outer-shareable attributes in
order to generate the requisite snoop signals, and that CPU mappings
don't create a mismatch by using a non-cacheable type either.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Tested-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/7024ce18c1cb1a226e918037d49175571db0b436.1600780574.git.robin.murphy@arm.com

drivers/gpu/drm/panfrost/panfrost_device.h

@@ -88,6 +88,7 @@ struct panfrost_device {
 	/* pm_domains for devices with more than one. */
 	struct device *pm_domain_devs[MAX_PM_DOMAINS];
 	struct device_link *pm_domain_links[MAX_PM_DOMAINS];
+	bool coherent;
 
 	struct panfrost_features features;
 	const struct panfrost_compatible *comp;

drivers/gpu/drm/panfrost/panfrost_drv.c

@@ -587,6 +587,8 @@ static int panfrost_probe(struct platform_device *pdev)
 	if (!pfdev->comp)
 		return -ENODEV;
 
+	pfdev->coherent = device_get_dma_attr(&pdev->dev) == DEV_DMA_COHERENT;
+
 	/* Allocate and initialze the DRM device. */
 	ddev = drm_dev_alloc(&panfrost_drm_driver, &pdev->dev);
 	if (IS_ERR(ddev))

drivers/gpu/drm/panfrost/panfrost_gem.c

@@ -220,6 +220,7 @@ static const struct drm_gem_object_funcs panfrost_gem_funcs = {
  */
 struct drm_gem_object *panfrost_gem_create_object(struct drm_device *dev, size_t size)
 {
+	struct panfrost_device *pfdev = dev->dev_private;
 	struct panfrost_gem_object *obj;
 
 	obj = kzalloc(sizeof(*obj), GFP_KERNEL);
@@ -229,6 +230,7 @@ struct drm_gem_object *panfrost_gem_create_object(struct drm_device *dev, size_t
 	INIT_LIST_HEAD(&obj->mappings.list);
 	mutex_init(&obj->mappings.lock);
 	obj->base.base.funcs = &panfrost_gem_funcs;
+	obj->base.map_cached = pfdev->coherent;
 
 	return &obj->base.base;
 }

drivers/gpu/drm/panfrost/panfrost_mmu.c

@@ -371,6 +371,7 @@ int panfrost_mmu_pgtable_alloc(struct panfrost_file_priv *priv)
 		.pgsize_bitmap	= SZ_4K | SZ_2M,
 		.ias		= FIELD_GET(0xff, pfdev->features.mmu_features),
 		.oas		= FIELD_GET(0xff00, pfdev->features.mmu_features),
+		.coherent_walk	= pfdev->coherent,
 		.tlb		= &mmu_tlb_ops,
 		.iommu_dev	= pfdev->dev,
 	};