[PATCH] drm/ttm: ioremap buffer according to TTM mem caching setting

[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?

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 at amd.com>
> Reviewed-by: Christian Konig <Christian.Koenig at amd.com>
> ---
>   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);
>   
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

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