Re: [PATCH 2/6] drm/ttm: Store the bo_kmap_type in struct iosys_map

["Christian König" <christian.koenig@amd.com>]

Am 14.06.24 um 15:21 schrieb Thomas Zimmermann:
> For each instances of struct iosys_map set up by ttm_bo_vmap(), store
> the type of allocation in the instance. Use this information to unmap
> the memory in ttm_bo_vunmap(). This change simplifies the unmap code
> and puts the complicated logic entirely into the map code.

I'm not sure that's a good idea.

The mapping information should already be available in the resource and 
storing it in the iosys_map structures duplicates that information.

So we might run into the issue that the resource has changed and so we 
need a different approach now, but the iosys_map will say that we should 
unmap things for example.

Regards,
Christian.

>
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> ---
>   drivers/gpu/drm/ttm/ttm_bo_util.c | 46 +++++++++++++++++++++----------
>   1 file changed, 31 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
> index 0b3f4267130c4..a9df0deff2deb 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo_util.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
> @@ -36,6 +36,7 @@
>   #include <drm/ttm/ttm_tt.h>
>   
>   #include <drm/drm_cache.h>
> +#include <drm/drm_device.h>
>   
>   struct ttm_transfer_obj {
>   	struct ttm_buffer_object base;
> @@ -479,24 +480,29 @@ int ttm_bo_vmap(struct ttm_buffer_object *bo, struct iosys_map *map)
>   
>   	if (mem->bus.is_iomem) {
>   		void __iomem *vaddr_iomem;
> +		u16 alloc_flags;
>   
> -		if (mem->bus.addr)
> +		if (mem->bus.addr) {
>   			vaddr_iomem = (void __iomem *)mem->bus.addr;
> -		else if (mem->bus.caching == ttm_write_combined)
> -			vaddr_iomem = ioremap_wc(mem->bus.offset,
> -						 bo->base.size);
> +			alloc_flags = ttm_bo_map_premapped;
> +		} else if (mem->bus.caching == ttm_write_combined) {
> +			vaddr_iomem = ioremap_wc(mem->bus.offset, bo->base.size);
> +			alloc_flags = ttm_bo_map_iomap;
>   #ifdef CONFIG_X86
> -		else if (mem->bus.caching == ttm_cached)
> -			vaddr_iomem = ioremap_cache(mem->bus.offset,
> -						  bo->base.size);
> +		} else if (mem->bus.caching == ttm_cached) {
> +			vaddr_iomem = ioremap_cache(mem->bus.offset, bo->base.size);
> +			alloc_flags = ttm_bo_map_iomap;
>   #endif
> -		else
> +		} else {
>   			vaddr_iomem = ioremap(mem->bus.offset, bo->base.size);
> +			alloc_flags = ttm_bo_map_iomap;
> +		}
>   
>   		if (!vaddr_iomem)
>   			return -ENOMEM;
>   
>   		iosys_map_set_vaddr_iomem(map, vaddr_iomem);
> +		map->alloc_flags = alloc_flags;
>   
>   	} else {
>   		struct ttm_operation_ctx ctx = {
> @@ -506,6 +512,7 @@ int ttm_bo_vmap(struct ttm_buffer_object *bo, struct iosys_map *map)
>   		struct ttm_tt *ttm = bo->ttm;
>   		pgprot_t prot;
>   		void *vaddr;
> +		u16 alloc_flags;
>   
>   		ret = ttm_tt_populate(bo->bdev, ttm, &ctx);
>   		if (ret)
> @@ -519,8 +526,10 @@ int ttm_bo_vmap(struct ttm_buffer_object *bo, struct iosys_map *map)
>   		vaddr = vmap(ttm->pages, ttm->num_pages, 0, prot);
>   		if (!vaddr)
>   			return -ENOMEM;
> +		alloc_flags = ttm_bo_map_vmap;
>   
>   		iosys_map_set_vaddr(map, vaddr);
> +		map->alloc_flags = alloc_flags;
>   	}
>   
>   	return 0;
> @@ -537,20 +546,27 @@ EXPORT_SYMBOL(ttm_bo_vmap);
>    */
>   void ttm_bo_vunmap(struct ttm_buffer_object *bo, struct iosys_map *map)
>   {
> -	struct ttm_resource *mem = bo->resource;
> -
>   	dma_resv_assert_held(bo->base.resv);
>   
>   	if (iosys_map_is_null(map))
>   		return;
>   
> -	if (!map->is_iomem)
> -		vunmap(map->vaddr);
> -	else if (!mem->bus.addr)
> +	switch (map->alloc_flags) {
> +	case ttm_bo_map_iomap:
>   		iounmap(map->vaddr_iomem);
> -	iosys_map_clear(map);
> -
> +		break;
> +	case ttm_bo_map_vmap:
> +		vunmap(map->vaddr);
> +		break;
> +	case ttm_bo_map_premapped:
> +		break;
> +	default:
> +		drm_err(bo->base.dev, "Unsupported alloc_flags 0x%x\n", map->alloc_flags);
> +		return;
> +	}
>   	ttm_mem_io_free(bo->bdev, bo->resource);
> +
> +	iosys_map_clear(map);
>   }
>   EXPORT_SYMBOL(ttm_bo_vunmap);
>