drm/simpledrm: Add support for system memory framebuffers

Simple framebuffers can be set up in system memory, which cannot be
requested and/or I/O remapped using the I/O resource helpers. Add a
separate code path that obtains system memory framebuffers from the
reserved memory region referenced in the memory-region property.

Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230120173103.4002342-6-thierry.reding@gmail.com

diff --git a/drivers/gpu/drm/tiny/simpledrm.c b/drivers/gpu/drm/tiny/simpledrm.c
index c1ed6dd..2acc0eb 100644 (file)
--- a/drivers/gpu/drm/tiny/simpledrm.c
+++ b/drivers/gpu/drm/tiny/simpledrm.c
@@ -3,6 +3,7 @@
 #include <linux/clk.h>
 #include <linux/of_clk.h>
 #include <linux/minmax.h>
+#include <linux/of_address.h>
 #include <linux/platform_data/simplefb.h>
 #include <linux/platform_device.h>
 #include <linux/regulator/consumer.h>
@@ -184,6 +185,31 @@ simplefb_get_format_of(struct drm_device *dev, struct device_node *of_node)
        return simplefb_get_validated_format(dev, format);
 }
 
+static struct resource *
+simplefb_get_memory_of(struct drm_device *dev, struct device_node *of_node)
+{
+       struct device_node *np;
+       struct resource *res;
+       int err;
+
+       np = of_parse_phandle(of_node, "memory-region", 0);
+       if (!np)
+               return NULL;
+
+       res = devm_kzalloc(dev->dev, sizeof(*res), GFP_KERNEL);
+       if (!res)
+               return ERR_PTR(-ENOMEM);
+
+       err = of_address_to_resource(np, 0, res);
+       if (err)
+               return ERR_PTR(err);
+
+       if (of_get_property(of_node, "reg", NULL))
+               drm_warn(dev, "preferring \"memory-region\" over \"reg\" property\n");
+
+       return res;
+}
+
 /*
  * Simple Framebuffer device
  */
@@ -604,8 +630,7 @@ static struct simpledrm_device *simpledrm_device_create(struct drm_driver *drv,
        struct drm_device *dev;
        int width, height, stride;
        const struct drm_format_info *format;
-       struct resource *res, *mem;
-       void __iomem *screen_base;
+       struct resource *res, *mem = NULL;
        struct drm_plane *primary_plane;
        struct drm_crtc *crtc;
        struct drm_encoder *encoder;
@@ -657,6 +682,9 @@ static struct simpledrm_device *simpledrm_device_create(struct drm_driver *drv,
                format = simplefb_get_format_of(dev, of_node);
                if (IS_ERR(format))
                        return ERR_CAST(format);
+               mem = simplefb_get_memory_of(dev, of_node);
+               if (IS_ERR(mem))
+                       return ERR_CAST(mem);
        } else {
                drm_err(dev, "no simplefb configuration found\n");
                return ERR_PTR(-ENODEV);
@@ -679,32 +707,55 @@ static struct simpledrm_device *simpledrm_device_create(struct drm_driver *drv,
         * Memory management
         */
 
-       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-       if (!res)
-               return ERR_PTR(-EINVAL);
+       if (mem) {
+               void *screen_base;
 
-       ret = devm_aperture_acquire_from_firmware(dev, res->start, resource_size(res));
-       if (ret) {
-               drm_err(dev, "could not acquire memory range %pr: error %d\n", res, ret);
-               return ERR_PTR(ret);
-       }
+               ret = devm_aperture_acquire_from_firmware(dev, mem->start, resource_size(mem));
+               if (ret) {
+                       drm_err(dev, "could not acquire memory range %pr: %d\n", mem, ret);
+                       return ERR_PTR(ret);
+               }
 
-       mem = devm_request_mem_region(&pdev->dev, res->start, resource_size(res), drv->name);
-       if (!mem) {
-               /*
-                * We cannot make this fatal. Sometimes this comes from magic
-                * spaces our resource handlers simply don't know about. Use
-                * the I/O-memory resource as-is and try to map that instead.
-                */
-               drm_warn(dev, "could not acquire memory region %pr\n", res);
-               mem = res;
-       }
+               drm_dbg(dev, "using system memory framebuffer at %pr\n", mem);
 
-       screen_base = devm_ioremap_wc(&pdev->dev, mem->start, resource_size(mem));
-       if (!screen_base)
-               return ERR_PTR(-ENOMEM);
+               screen_base = devm_memremap(dev->dev, mem->start, resource_size(mem), MEMREMAP_WC);
+               if (!screen_base)
+                       return ERR_PTR(-ENOMEM);
+
+               iosys_map_set_vaddr(&sdev->screen_base, screen_base);
+       } else {
+               void __iomem *screen_base;
+
+               res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+               if (!res)
+                       return ERR_PTR(-EINVAL);
 
-       iosys_map_set_vaddr_iomem(&sdev->screen_base, screen_base);
+               ret = devm_aperture_acquire_from_firmware(dev, res->start, resource_size(res));
+               if (ret) {
+                       drm_err(dev, "could not acquire memory range %pr: %d\n", &res, ret);
+                       return ERR_PTR(ret);
+               }
+
+               drm_dbg(dev, "using I/O memory framebuffer at %pr\n", res);
+
+               mem = devm_request_mem_region(&pdev->dev, res->start, resource_size(res),
+                                             drv->name);
+               if (!mem) {
+                       /*
+                        * We cannot make this fatal. Sometimes this comes from magic
+                        * spaces our resource handlers simply don't know about. Use
+                        * the I/O-memory resource as-is and try to map that instead.
+                        */
+                       drm_warn(dev, "could not acquire memory region %pr\n", res);
+                       mem = res;
+               }
+
+               screen_base = devm_ioremap_wc(&pdev->dev, mem->start, resource_size(mem));
+               if (!screen_base)
+                       return ERR_PTR(-ENOMEM);
+
+               iosys_map_set_vaddr_iomem(&sdev->screen_base, screen_base);
+       }
 
        /*
         * Modesetting