drm/msm: add support for "stolen" mem

Add support to use the VRAM carveout (if specified in dtb) for fbdev
scanout buffer.  This allows drm/msm to take over a bootloader splash-
screen, and avoids corruption on screen that results if the kernel uses
memory that is still being scanned out for itself.

Signed-off-by: Rob Clark <robdclark@gmail.com>

4 files changed, 66 insertions, 11 deletions

diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
index b250610e6393..0c38f34066e5 100644
--- a/drivers/gpu/drm/msm/msm_drv.c
+++ b/drivers/gpu/drm/msm/msm_drv.c
@@ -182,21 +182,57 @@ static int get_mdp_ver(struct platform_device *pdev)
         return 4;
 }
 
+#include <linux/of_address.h>
+
 static int msm_init_vram(struct drm_device *dev)
 {
         struct msm_drm_private *priv = dev->dev_private;
+        unsigned long size = 0;
+        int ret = 0;
+
+#ifdef CONFIG_OF
+        /* In the device-tree world, we could have a 'memory-region'
+         * phandle, which gives us a link to our "vram".  Allocating
+         * is all nicely abstracted behind the dma api, but we need
+         * to know the entire size to allocate it all in one go. There
+         * are two cases:
+         *  1) device with no IOMMU, in which case we need exclusive
+         *     access to a VRAM carveout big enough for all gpu
+         *     buffers
+         *  2) device with IOMMU, but where the bootloader puts up
+         *     a splash screen.  In this case, the VRAM carveout
+         *     need only be large enough for fbdev fb.  But we need
+         *     exclusive access to the buffer to avoid the kernel
+         *     using those pages for other purposes (which appears
+         *     as corruption on screen before we have a chance to
+         *     load and do initial modeset)
+         */
+        struct device_node *node;
+
+        node = of_parse_phandle(dev->dev->of_node, "memory-region", 0);
+        if (node) {
+                struct resource r;
+                ret = of_address_to_resource(node, 0, &r);
+                if (ret)
+                        return ret;
+                size = r.end - r.start;
+                DRM_INFO("using VRAM carveout: %lx@%08x\n", size, r.start);
+        } else
+#endif
 
         /* if we have no IOMMU, then we need to use carveout allocator.
          * Grab the entire CMA chunk carved out in early startup in
          * mach-msm:
          */
         if (!iommu_present(&platform_bus_type)) {
+                DRM_INFO("using %s VRAM carveout\n", vram);
+                size = memparse(vram, NULL);
+        }
+
+        if (size) {
                 DEFINE_DMA_ATTRS(attrs);
-                unsigned long size;
                 void *p;
 
-                DBG("using %s VRAM carveout", vram);
-                size = memparse(vram, NULL);
                 priv->vram.size = size;
 
                 drm_mm_init(&priv->vram.mm, 0, (size >> PAGE_SHIFT) - 1);
@@ -220,7 +256,7 @@ static int msm_init_vram(struct drm_device *dev)
                                 (uint32_t)(priv->vram.paddr + size));
         }
 
-        return 0;
+        return ret;
 }
 
 static int msm_load(struct drm_device *dev, unsigned long flags)
diff --git a/drivers/gpu/drm/msm/msm_fbdev.c b/drivers/gpu/drm/msm/msm_fbdev.c
index df60f65728ff..95f6532df02d 100644
--- a/drivers/gpu/drm/msm/msm_fbdev.c
+++ b/drivers/gpu/drm/msm/msm_fbdev.c
@@ -110,7 +110,8 @@ static int msm_fbdev_create(struct drm_fb_helper *helper,
         size = mode_cmd.pitches[0] * mode_cmd.height;
         DBG("allocating %d bytes for fb %d", size, dev->primary->index);
         mutex_lock(&dev->struct_mutex);
-        fbdev->bo = msm_gem_new(dev, size, MSM_BO_SCANOUT | MSM_BO_WC);
+        fbdev->bo = msm_gem_new(dev, size, MSM_BO_SCANOUT |
+                        MSM_BO_WC | MSM_BO_STOLEN);
         mutex_unlock(&dev->struct_mutex);
         if (IS_ERR(fbdev->bo)) {
                 ret = PTR_ERR(fbdev->bo);
diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index 49dea4fb55ac..479d8af72bcb 100644
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -32,6 +32,12 @@ static dma_addr_t physaddr(struct drm_gem_object *obj)
                         priv->vram.paddr;
 }
 
+static bool use_pages(struct drm_gem_object *obj)
+{
+        struct msm_gem_object *msm_obj = to_msm_bo(obj);
+        return !msm_obj->vram_node;
+}
+
 /* allocate pages from VRAM carveout, used when no IOMMU: */
 static struct page **get_pages_vram(struct drm_gem_object *obj,
                 int npages)
@@ -72,7 +78,7 @@ static struct page **get_pages(struct drm_gem_object *obj)
                 struct page **p;
                 int npages = obj->size >> PAGE_SHIFT;
 
-                if (iommu_present(&platform_bus_type))
+                if (use_pages(obj))
                         p = drm_gem_get_pages(obj);
                 else
                         p = get_pages_vram(obj, npages);
@@ -116,7 +122,7 @@ static void put_pages(struct drm_gem_object *obj)
                 sg_free_table(msm_obj->sgt);
                 kfree(msm_obj->sgt);
 
-                if (iommu_present(&platform_bus_type))
+                if (use_pages(obj))
                         drm_gem_put_pages(obj, msm_obj->pages, true, false);
                 else {
                         drm_mm_remove_node(msm_obj->vram_node);
@@ -580,6 +586,7 @@ static int msm_gem_new_impl(struct drm_device *dev,
         struct msm_drm_private *priv = dev->dev_private;
         struct msm_gem_object *msm_obj;
         unsigned sz;
+        bool use_vram = false;
 
         switch (flags & MSM_BO_CACHE_MASK) {
         case MSM_BO_UNCACHED:
@@ -592,15 +599,23 @@ static int msm_gem_new_impl(struct drm_device *dev,
                 return -EINVAL;
         }
 
-        sz = sizeof(*msm_obj);
         if (!iommu_present(&platform_bus_type))
+                use_vram = true;
+        else if ((flags & MSM_BO_STOLEN) && priv->vram.size)
+                use_vram = true;
+
+        if (WARN_ON(use_vram && !priv->vram.size))
+                return -EINVAL;
+
+        sz = sizeof(*msm_obj);
+        if (use_vram)
                 sz += sizeof(struct drm_mm_node);
 
         msm_obj = kzalloc(sz, GFP_KERNEL);
         if (!msm_obj)
                 return -ENOMEM;
 
-        if (!iommu_present(&platform_bus_type))
+        if (use_vram)
                 msm_obj->vram_node = (void *)&msm_obj[1];
 
         msm_obj->flags = flags;
@@ -630,7 +645,7 @@ struct drm_gem_object *msm_gem_new(struct drm_device *dev,
         if (ret)
                 goto fail;
 
-        if (iommu_present(&platform_bus_type)) {
+        if (use_pages(obj)) {
                 ret = drm_gem_object_init(dev, obj, size);
                 if (ret)
                         goto fail;
diff --git a/drivers/gpu/drm/msm/msm_gem.h b/drivers/gpu/drm/msm/msm_gem.h
index 8fbbd0594c46..85d481e29276 100644
--- a/drivers/gpu/drm/msm/msm_gem.h
+++ b/drivers/gpu/drm/msm/msm_gem.h
@@ -21,6 +21,9 @@
 #include <linux/reservation.h>
 #include "msm_drv.h"
 
+/* Additional internal-use only BO flags: */
+#define MSM_BO_STOLEN        0x10000000    /* try to use stolen/splash memory */
+
 struct msm_gem_object {
         struct drm_gem_object base;
 
@@ -59,7 +62,7 @@ struct msm_gem_object {
         struct reservation_object _resv;
 
         /* For physically contiguous buffers.  Used when we don't have
-         * an IOMMU.
+         * an IOMMU.  Also used for stolen/splashscreen buffer.
          */
         struct drm_mm_node *vram_node;
 };