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Re: [PATCH v4 05/10] drm/ttm: Add vmap/vunmap to TTM and TTM GEM helpers

Am 15.10.20 um 19:52 schrieb Thomas Zimmermann:

Hi

On Thu, 15 Oct 2020 18:49:09 +0200 Daniel Vetter <daniel@xxxxxxxx> wrote:


On Thu, Oct 15, 2020 at 04:08:13PM +0200, Christian König wrote:

Am 15.10.20 um 14:38 schrieb Thomas Zimmermann:

The new functions ttm_bo_{vmap,vunmap}() map and unmap a TTM BO in
kernel address space. The mapping's address is returned as struct
dma_buf_map. Each function is a simplified version of TTM's existing
kmap code. Both functions respect the memory's location ani/or
writecombine flags.

On top TTM's functions, GEM TTM helpers got drm_gem_ttm_{vmap,vunmap}(),
two helpers that convert a GEM object into the TTM BO and forward the
call to TTM's vmap/vunmap. These helpers can be dropped into the rsp
GEM object callbacks.

v4:
        * drop ttm_kmap_obj_to_dma_buf() in favor of vmap helpers
(Daniel, Christian)

Bunch of minor comments below, but over all look very solid to me.

Yeah I think just duplicating the ttm bo map stuff for vmap is indeed the
cleanest. And then we can maybe push the combinatorial monster into
vmwgfx, which I think is the only user after this series. Or perhaps a
dedicated set of helpers to map an invidual page (again using the
dma_buf_map stuff).

 From a quick look, I'd say it should be possible to have the same interface
for kmap/kunmap as for vmap/vunmap (i.e., parameters are bo and dma-buf-map).
All mapping state can be deduced from this. And struct ttm_bo_kmap_obj can be
killed off entirely.


Yes, that would be rather nice to have.

Thanks,
Christian.



Best regards
Thomas


I'll let Christian with the details, but at a high level this is
definitely

Acked-by: Daniel Vetter <daniel.vetter@xxxxxxxx>

Thanks a lot for doing all this.
-Daniel


Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
---
   drivers/gpu/drm/drm_gem_ttm_helper.c | 38 +++++++++++++++
   drivers/gpu/drm/ttm/ttm_bo_util.c    | 72 ++++++++++++++++++++++++++++
   include/drm/drm_gem_ttm_helper.h     |  6 +++
   include/drm/ttm/ttm_bo_api.h         | 28 +++++++++++
   include/linux/dma-buf-map.h          | 20 ++++++++
   5 files changed, 164 insertions(+)

diff --git a/drivers/gpu/drm/drm_gem_ttm_helper.c
b/drivers/gpu/drm/drm_gem_ttm_helper.c index 0e4fb9ba43ad..db4c14d78a30
100644 --- a/drivers/gpu/drm/drm_gem_ttm_helper.c
+++ b/drivers/gpu/drm/drm_gem_ttm_helper.c
@@ -49,6 +49,44 @@ void drm_gem_ttm_print_info(struct drm_printer *p,
unsigned int indent, }
   EXPORT_SYMBOL(drm_gem_ttm_print_info);
+/**
+ * drm_gem_ttm_vmap() - vmap &ttm_buffer_object
+ * @gem: GEM object.
+ * @map: [out] returns the dma-buf mapping.
+ *
+ * Maps a GEM object with ttm_bo_vmap(). This function can be used as
+ * &drm_gem_object_funcs.vmap callback.
+ *
+ * Returns:
+ * 0 on success, or a negative errno code otherwise.
+ */
+int drm_gem_ttm_vmap(struct drm_gem_object *gem,
+                    struct dma_buf_map *map)
+{
+       struct ttm_buffer_object *bo = drm_gem_ttm_of_gem(gem);
+
+       return ttm_bo_vmap(bo, map);
+
+}
+EXPORT_SYMBOL(drm_gem_ttm_vmap);
+
+/**
+ * drm_gem_ttm_vunmap() - vunmap &ttm_buffer_object
+ * @gem: GEM object.
+ * @map: dma-buf mapping.
+ *
+ * Unmaps a GEM object with ttm_bo_vunmap(). This function can be used
as
+ * &drm_gem_object_funcs.vmap callback.
+ */
+void drm_gem_ttm_vunmap(struct drm_gem_object *gem,
+                       struct dma_buf_map *map)
+{
+       struct ttm_buffer_object *bo = drm_gem_ttm_of_gem(gem);
+
+       ttm_bo_vunmap(bo, map);
+}
+EXPORT_SYMBOL(drm_gem_ttm_vunmap);
+
   /**
    * drm_gem_ttm_mmap() - mmap &ttm_buffer_object
    * @gem: GEM object.
diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c
b/drivers/gpu/drm/ttm/ttm_bo_util.c index bdee4df1f3f2..80c42c774c7d
100644 --- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -32,6 +32,7 @@
   #include <drm/ttm/ttm_bo_driver.h>
   #include <drm/ttm/ttm_placement.h>
   #include <drm/drm_vma_manager.h>
+#include <linux/dma-buf-map.h>
   #include <linux/io.h>
   #include <linux/highmem.h>
   #include <linux/wait.h>
@@ -526,6 +527,77 @@ void ttm_bo_kunmap(struct ttm_bo_kmap_obj *map)
   }
   EXPORT_SYMBOL(ttm_bo_kunmap);
+int ttm_bo_vmap(struct ttm_buffer_object *bo, struct dma_buf_map *map)
+{
+       struct ttm_resource *mem = &bo->mem;
+       int ret;
+
+       ret = ttm_mem_io_reserve(bo->bdev, mem);
+       if (ret)
+               return ret;
+
+       if (mem->bus.is_iomem) {
+               void __iomem *vaddr_iomem;
+               unsigned long size = bo->num_pages << PAGE_SHIFT;

Please use uint64_t here and make sure to cast bo->num_pages before
shifting.

We have an unit tests of allocating a 8GB BO and that should work on a
32bit machine as well :)


+
+               if (mem->bus.addr)
+                       vaddr_iomem = (void *)(((u8 *)mem->bus.addr));
+               else if (mem->placement & TTM_PL_FLAG_WC)

I've just nuked the TTM_PL_FLAG_WC flag in drm-misc-next. There is a new
mem->bus.caching enum as replacement.


+                       vaddr_iomem = ioremap_wc(mem->bus.offset,
size);
+               else
+                       vaddr_iomem = ioremap(mem->bus.offset, size);
+
+               if (!vaddr_iomem)
+                       return -ENOMEM;
+
+               dma_buf_map_set_vaddr_iomem(map, vaddr_iomem);
+
+       } else {
+               struct ttm_operation_ctx ctx = {
+                       .interruptible = false,
+                       .no_wait_gpu = false
+               };
+               struct ttm_tt *ttm = bo->ttm;
+               pgprot_t prot;
+               void *vaddr;
+
+               BUG_ON(!ttm);

I think we can drop this, populate will just crash badly anyway.


+
+               ret = ttm_tt_populate(bo->bdev, ttm, &ctx);
+               if (ret)
+                       return ret;
+
+               /*
+                * We need to use vmap to get the desired page
protection
+                * or to make the buffer object look contiguous.
+                */
+               prot = ttm_io_prot(mem->placement, PAGE_KERNEL);

The calling convention has changed on drm-misc-next as well, but should be
trivial to adapt.

Regards,
Christian.


+               vaddr = vmap(ttm->pages, bo->num_pages, 0, prot);
+               if (!vaddr)
+                       return -ENOMEM;
+
+               dma_buf_map_set_vaddr(map, vaddr);
+       }
+
+       return 0;
+}
+EXPORT_SYMBOL(ttm_bo_vmap);
+
+void ttm_bo_vunmap(struct ttm_buffer_object *bo, struct dma_buf_map
*map) +{
+       if (dma_buf_map_is_null(map))
+               return;
+
+       if (map->is_iomem)
+               iounmap(map->vaddr_iomem);
+       else
+               vunmap(map->vaddr);
+       dma_buf_map_clear(map);
+
+       ttm_mem_io_free(bo->bdev, &bo->mem);
+}
+EXPORT_SYMBOL(ttm_bo_vunmap);
+
   static int ttm_bo_wait_free_node(struct ttm_buffer_object *bo,
                                 bool dst_use_tt)
   {
diff --git a/include/drm/drm_gem_ttm_helper.h
b/include/drm/drm_gem_ttm_helper.h index 118cef76f84f..7c6d874910b8
100644 --- a/include/drm/drm_gem_ttm_helper.h
+++ b/include/drm/drm_gem_ttm_helper.h
@@ -10,11 +10,17 @@
   #include <drm/ttm/ttm_bo_api.h>
   #include <drm/ttm/ttm_bo_driver.h>
+struct dma_buf_map;
+
   #define drm_gem_ttm_of_gem(gem_obj) \
        container_of(gem_obj, struct ttm_buffer_object, base)
   void drm_gem_ttm_print_info(struct drm_printer *p, unsigned int
indent, const struct drm_gem_object *gem);
+int drm_gem_ttm_vmap(struct drm_gem_object *gem,
+                    struct dma_buf_map *map);
+void drm_gem_ttm_vunmap(struct drm_gem_object *gem,
+                       struct dma_buf_map *map);
   int drm_gem_ttm_mmap(struct drm_gem_object *gem,
                     struct vm_area_struct *vma);
diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index 37102e45e496..2c59a785374c 100644
--- a/include/drm/ttm/ttm_bo_api.h
+++ b/include/drm/ttm/ttm_bo_api.h
@@ -48,6 +48,8 @@ struct ttm_bo_global;
   struct ttm_bo_device;
+struct dma_buf_map;
+
   struct drm_mm_node;
   struct ttm_placement;
@@ -494,6 +496,32 @@ int ttm_bo_kmap(struct ttm_buffer_object *bo,
unsigned long start_page, */
   void ttm_bo_kunmap(struct ttm_bo_kmap_obj *map);
+/**
+ * ttm_bo_vmap
+ *
+ * @bo: The buffer object.
+ * @map: pointer to a struct dma_buf_map representing the map.
+ *
+ * Sets up a kernel virtual mapping, using ioremap or vmap to the
+ * data in the buffer object. The parameter @map returns the virtual
+ * address as struct dma_buf_map. Unmap the buffer with
ttm_bo_vunmap().
+ *
+ * Returns
+ * -ENOMEM: Out of memory.
+ * -EINVAL: Invalid range.
+ */
+int ttm_bo_vmap(struct ttm_buffer_object *bo, struct dma_buf_map *map);
+
+/**
+ * ttm_bo_vunmap
+ *
+ * @bo: The buffer object.
+ * @map: Object describing the map to unmap.
+ *
+ * Unmaps a kernel map set up by ttm_bo_vmap().
+ */
+void ttm_bo_vunmap(struct ttm_buffer_object *bo, struct dma_buf_map
*map); +
   /**
    * ttm_bo_mmap_obj - mmap memory backed by a ttm buffer object.
    *
diff --git a/include/linux/dma-buf-map.h b/include/linux/dma-buf-map.h
index fd1aba545fdf..2e8bbecb5091 100644
--- a/include/linux/dma-buf-map.h
+++ b/include/linux/dma-buf-map.h
@@ -45,6 +45,12 @@
    *
    *   dma_buf_map_set_vaddr(&map. 0xdeadbeaf);
    *
+ * To set an address in I/O memory, use dma_buf_map_set_vaddr_iomem().
+ *
+ * .. code-block:: c
+ *
+ *     dma_buf_map_set_vaddr_iomem(&map. 0xdeadbeaf);
+ *
    * Test if a mapping is valid with either dma_buf_map_is_set() or
    * dma_buf_map_is_null().
    *
@@ -118,6 +124,20 @@ static inline void dma_buf_map_set_vaddr(struct
dma_buf_map *map, void *vaddr) map->is_iomem = false;
   }
+/**
+ * dma_buf_map_set_vaddr_iomem - Sets a dma-buf mapping structure to
an address in I/O memory
+ * @map:               The dma-buf mapping structure
+ * @vaddr_iomem:       An I/O-memory address
+ *
+ * Sets the address and the I/O-memory flag.
+ */
+static inline void dma_buf_map_set_vaddr_iomem(struct dma_buf_map *map,
+                                              void __iomem
*vaddr_iomem) +{
+       map->vaddr_iomem = vaddr_iomem;
+       map->is_iomem = true;
+}
+
   /**
    * dma_buf_map_is_equal - Compares two dma-buf mapping structures for
equality
    * @lhs:     The dma-buf mapping structure

 

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