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drm/gem-vram: Support pinning buffers to current location

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Pinning a buffer prevents it from being moved to a different memory
location. For some operations, such as buffer updates, it is not
important where the buffer is located. Setting the pin function's
pl_flag argument to 0 will pin the buffer to whereever it is stored.

v2:
	* document pin flags in PRIME pin helper

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190613073041.29350-2-tzimmermann@suse.de
This commit is contained in:
Thomas Zimmermann 2019-06-13 09:30:33 +02:00
parent bb5ce9a017
commit a6c3464f69
1 changed files with 16 additions and 4 deletions
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18
drivers/gpu/drm/drm_gem_vram_helper.c
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@ -224,7 +224,9 @@ EXPORT_SYMBOL(drm_gem_vram_offset);
*
* Pinning a buffer object ensures that it is not evicted from
* a memory region. A pinned buffer object has to be unpinned before
* it can be pinned to another region.
* it can be pinned to another region. If the pl_flag argument is 0,
* the buffer is pinned at its current location (video RAM or system
* memory).
*
* Returns:
* 0 on success, or
@ -242,7 +244,9 @@ int drm_gem_vram_pin(struct drm_gem_vram_object *gbo, unsigned long pl_flag)
if (gbo->pin_count)
goto out;
if (pl_flag)
drm_gem_vram_placement(gbo, pl_flag);
for (i = 0; i < gbo->placement.num_placement; ++i)
gbo->placements[i].flags |= TTM_PL_FLAG_NO_EVICT;
@ -691,7 +695,15 @@ int drm_gem_vram_driver_gem_prime_pin(struct drm_gem_object *gem)
{
struct drm_gem_vram_object *gbo = drm_gem_vram_of_gem(gem);
return drm_gem_vram_pin(gbo, DRM_GEM_VRAM_PL_FLAG_VRAM);
/* Fbdev console emulation is the use case of these PRIME
* helpers. This may involve updating a hardware buffer from
* a shadow FB. We pin the buffer to it's current location
* (either video RAM or system memory) to prevent it from
* being relocated during the update operation. If you require
* the buffer to be pinned to VRAM, implement a callback that
* sets the flags accordingly.
*/
return drm_gem_vram_pin(gbo, 0);
}
EXPORT_SYMBOL(drm_gem_vram_driver_gem_prime_pin);
@ -723,7 +735,7 @@ void *drm_gem_vram_driver_gem_prime_vmap(struct drm_gem_object *gem)
int ret;
void *base;
ret = drm_gem_vram_pin(gbo, DRM_GEM_VRAM_PL_FLAG_VRAM);
ret = drm_gem_vram_pin(gbo, 0);
if (ret)
return NULL;
base = drm_gem_vram_kmap(gbo, true, NULL);