Am 03.03.21 um 09:49 schrieb Thomas
Zimmermann:
Hi
Am 01.03.21 um 23:43 schrieb Oak Zeng:
If tbo.mem.bus.caching is cached, buffer is intended to be mapped
as cached from CPU. Map it with ioremap_cache.
Just a question for my understanding: This is on-device memory? Accessing device memory is usually slow. If that memory can be mapped with CPU caching enabled, access will roughly be as fast as for system memory?
There is still a penalty associated with accessing it from the CPU, but it is much faster (both lower latency as well as throughput) as traditional device memory accessed over PCIe.
Regards,
Christian.
Best regards
Thomas
This wasn't necessary before as device memory was never mapped
as cached from CPU side. It becomes necessary for aldebaran as
device memory is mapped cached from CPU.
Signed-off-by: Oak Zeng <Oak.Zeng@xxxxxxx>
Reviewed-by: Christian Konig <Christian.Koenig@xxxxxxx>
---
drivers/gpu/drm/ttm/ttm_bo_util.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
index 031e581..8c65a13 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -91,6 +91,8 @@ static int ttm_resource_ioremap(struct ttm_device *bdev,
if (mem->bus.caching == ttm_write_combined)
addr = ioremap_wc(mem->bus.offset, bus_size);
+ else if (mem->bus.caching == ttm_cached)
+ addr = ioremap_cache(mem->bus.offset, bus_size);
else
addr = ioremap(mem->bus.offset, bus_size);
if (!addr) {
@@ -372,6 +374,9 @@ static int ttm_bo_ioremap(struct ttm_buffer_object *bo,
if (mem->bus.caching == ttm_write_combined)
map->virtual = ioremap_wc(bo->mem.bus.offset + offset,
size);
+ else if (mem->bus.caching == ttm_cached)
+ map->virtual = ioremap_cache(bo->mem.bus.offset + offset,
+ size);
else
map->virtual = ioremap(bo->mem.bus.offset + offset,
size);
@@ -490,6 +495,9 @@ int ttm_bo_vmap(struct ttm_buffer_object *bo, struct dma_buf_map *map)
else if (mem->bus.caching == ttm_write_combined)
vaddr_iomem = ioremap_wc(mem->bus.offset,
bo->base.size);
+ else if (mem->bus.caching == ttm_cached)
+ vaddr_iomem = ioremap_cache(mem->bus.offset,
+ bo->base.size);
else
vaddr_iomem = ioremap(mem->bus.offset, bo->base.size);
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