[PATCH 3/5] drm: Add infrastructure for vmap operations of I/O memory
Thomas Zimmermann
tzimmermann at suse.de
Wed Jul 29 13:41:46 UTC 2020
Most platforms allow for accessing framebuffer I/O memory with regular
load and store operations. Some platforms, such as sparc64, require
the use of special instructions instead.
This patch adds vmap_iomem to struct drm_gem_object_funcs. The new
interface drm_client_buffer_vmap_iomem() gives DRM clients access to the
I/O memory buffer. The semantics of struct drm_gem_objcet_funcs.vmap
change slightly. It used to return system or I/O memory. Now it is
expected to return memory addresses that can be accessed with regular
load and store operations. So nothing changes for existing implementations
of GEM objects. If the GEM object also implements vmap_iomem, a call
to vmap shall only return system memory, even if I/O memory could be
accessed with loads and stores.
The existing interface drm_client_buffer_vmap() shall only return memory
as given by drm_gem_vmap ((i.e., that is accessible via regular load and
store). The new interface drm_client_buffer_vmap_iomem() shall only
return I/O memory.
DRM clients must map buffers by calling drm_client_buffer_vmap_iomem()
and drm_client_buffer_vmap() to get the buffer in I/O or system memory.
Each function returns NULL if the buffer is in the other memory area.
Depending on the type of the returned memory, clients must access the
framebuffer with the appropriate operations.
Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
---
drivers/gpu/drm/drm_client.c | 52 ++++++++++++++++++++++++++++++++--
drivers/gpu/drm/drm_gem.c | 19 +++++++++++++
drivers/gpu/drm/drm_internal.h | 1 +
include/drm/drm_client.h | 8 +++++-
include/drm/drm_gem.h | 17 +++++++++--
5 files changed, 91 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
index 495f47d23d87..b5bbe089a41e 100644
--- a/drivers/gpu/drm/drm_client.c
+++ b/drivers/gpu/drm/drm_client.c
@@ -327,6 +327,46 @@ void *drm_client_buffer_vmap(struct drm_client_buffer *buffer)
}
EXPORT_SYMBOL(drm_client_buffer_vmap);
+/**
+ * drm_client_buffer_vmap_iomem - Map DRM client buffer into address space
+ * @buffer: DRM client buffer
+ *
+ * This function maps a client buffer into kernel address space. If the
+ * buffer is already mapped, it returns the mapping's address.
+ *
+ * Client buffer mappings are not ref'counted. Each call to
+ * drm_client_buffer_vmap() should be followed by a call to
+ * drm_client_buffer_vunmap(); or the client buffer should be mapped
+ * throughout its lifetime.
+ *
+ * Returns:
+ * The mapped memory's address
+ */
+void __iomem *drm_client_buffer_vmap_iomem(struct drm_client_buffer *buffer)
+{
+ void __iomem *vaddr_iomem;
+
+ if (buffer->vaddr_iomem)
+ return buffer->vaddr_iomem;
+
+ /*
+ * FIXME: The dependency on GEM here isn't required, we could
+ * convert the driver handle to a dma-buf instead and use the
+ * backend-agnostic dma-buf vmap support instead. This would
+ * require that the handle2fd prime ioctl is reworked to pull the
+ * fd_install step out of the driver backend hooks, to make that
+ * final step optional for internal users.
+ */
+ vaddr_iomem = drm_gem_vmap_iomem(buffer->gem);
+ if (IS_ERR(vaddr_iomem))
+ return vaddr_iomem;
+
+ buffer->vaddr_iomem = vaddr_iomem;
+
+ return vaddr_iomem;
+}
+EXPORT_SYMBOL(drm_client_buffer_vmap_iomem);
+
/**
* drm_client_buffer_vunmap - Unmap DRM client buffer
* @buffer: DRM client buffer
@@ -337,8 +377,16 @@ EXPORT_SYMBOL(drm_client_buffer_vmap);
*/
void drm_client_buffer_vunmap(struct drm_client_buffer *buffer)
{
- drm_gem_vunmap(buffer->gem, buffer->vaddr);
- buffer->vaddr = NULL;
+ drm_WARN_ON(buffer->client->dev, buffer->vaddr && buffer->vaddr_iomem);
+
+ if (buffer->vaddr) {
+ drm_gem_vunmap(buffer->gem, buffer->vaddr);
+ buffer->vaddr = NULL;
+ }
+ if (buffer->vaddr_iomem) {
+ drm_gem_vunmap(buffer->gem, (void *)buffer->vaddr_iomem);
+ buffer->vaddr_iomem = NULL;
+ }
}
EXPORT_SYMBOL(drm_client_buffer_vunmap);
diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index a57f5379fc08..a001be8c0965 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -1227,6 +1227,25 @@ void *drm_gem_vmap(struct drm_gem_object *obj)
vaddr = obj->funcs->vmap(obj);
else if (obj->dev->driver->gem_prime_vmap)
vaddr = obj->dev->driver->gem_prime_vmap(obj);
+ else if (obj->funcs && obj->funcs->vmap_iomem)
+ vaddr = NULL; /* requires mapping as I/O memory */
+ else
+ vaddr = ERR_PTR(-EOPNOTSUPP);
+
+ if (!vaddr)
+ vaddr = ERR_PTR(-ENOMEM);
+
+ return vaddr;
+}
+
+void __iomem *drm_gem_vmap_iomem(struct drm_gem_object *obj)
+{
+ void __iomem *vaddr;
+
+ if (obj->funcs && obj->funcs->vmap_iomem)
+ vaddr = obj->funcs->vmap_iomem(obj);
+ else if (obj->funcs && obj->funcs->vmap)
+ vaddr = NULL; /* requires mapping as system memory */
else
vaddr = ERR_PTR(-EOPNOTSUPP);
diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
index 8e01caaf95cc..aa1a3d4f9223 100644
--- a/drivers/gpu/drm/drm_internal.h
+++ b/drivers/gpu/drm/drm_internal.h
@@ -187,6 +187,7 @@ void drm_gem_print_info(struct drm_printer *p, unsigned int indent,
int drm_gem_pin(struct drm_gem_object *obj);
void drm_gem_unpin(struct drm_gem_object *obj);
void *drm_gem_vmap(struct drm_gem_object *obj);
+void __iomem *drm_gem_vmap_iomem(struct drm_gem_object *obj);
void drm_gem_vunmap(struct drm_gem_object *obj, void *vaddr);
/* drm_debugfs.c drm_debugfs_crc.c */
diff --git a/include/drm/drm_client.h b/include/drm/drm_client.h
index 7aaea665bfc2..94aa075ee4b6 100644
--- a/include/drm/drm_client.h
+++ b/include/drm/drm_client.h
@@ -141,10 +141,15 @@ struct drm_client_buffer {
struct drm_gem_object *gem;
/**
- * @vaddr: Virtual address for the buffer
+ * @vaddr: Virtual address for the buffer in system memory
*/
void *vaddr;
+ /**
+ * @vaddr: Virtual address for the buffer in I/O memory
+ */
+ void *vaddr_iomem;
+
/**
* @fb: DRM framebuffer
*/
@@ -156,6 +161,7 @@ drm_client_framebuffer_create(struct drm_client_dev *client, u32 width, u32 heig
void drm_client_framebuffer_delete(struct drm_client_buffer *buffer);
int drm_client_framebuffer_flush(struct drm_client_buffer *buffer, struct drm_rect *rect);
void *drm_client_buffer_vmap(struct drm_client_buffer *buffer);
+void __iomem *drm_client_buffer_vmap_iomem(struct drm_client_buffer *buffer);
void drm_client_buffer_vunmap(struct drm_client_buffer *buffer);
int drm_client_modeset_create(struct drm_client_dev *client);
diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
index 337a48321705..bc735ff522a8 100644
--- a/include/drm/drm_gem.h
+++ b/include/drm/drm_gem.h
@@ -134,17 +134,28 @@ struct drm_gem_object_funcs {
* @vmap:
*
* Returns a virtual address for the buffer. Used by the
- * drm_gem_dmabuf_vmap() helper.
+ * drm_gem_dmabuf_vmap() helper. If the buffer is not
+ * located in system memory, the function returns NULL.
*
* This callback is optional.
*/
void *(*vmap)(struct drm_gem_object *obj);
+ /**
+ * @vmap_iomem:
+ *
+ * Returns a virtual address for the buffer. If the buffer is not
+ * located in I/O memory, the function returns NULL.
+ *
+ * This callback is optional.
+ */
+ void __iomem *(*vmap_iomem)(struct drm_gem_object *obj);
+
/**
* @vunmap:
*
- * Releases the address previously returned by @vmap. Used by the
- * drm_gem_dmabuf_vunmap() helper.
+ * Releases the address previously returned by @vmap or @vmap_iomem.
+ * Used by the drm_gem_dmabuf_vunmap() helper.
*
* This callback is optional.
*/
--
2.27.0
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