Re: [PATCH 1/8] drm/ttm: remove TTM_MEMTYPE_FLAG_CMA

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Am 16.07.20 um 15:05 schrieb Thomas Zimmermann:
Hi,

this patchset could have benefited from a cover letter.

Yeah, I didn't thought it would result in such an extensive patch set.

Am 16.07.20 um 14:50 schrieb Christian König:
The original intention was to avoid CPU page table unmaps
when BOs move between the GTT and SYSTEM domain.

The problem is that this never correctly handled changes
in the caching attributes or backing pages.

Just drop this for now and simply unmap the CPU page
tables in all cases.

Signed-off-by: Christian König <christian.koenig@xxxxxxx>
---
  drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c    |  4 +--
  drivers/gpu/drm/nouveau/nouveau_bo.c       |  3 +-
  drivers/gpu/drm/radeon/radeon_ttm.c        |  2 +-
  drivers/gpu/drm/ttm/ttm_bo.c               | 34 ++++------------------
  drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c |  2 +-
  include/drm/ttm/ttm_bo_driver.h            |  1 -
  6 files changed, 11 insertions(+), 35 deletions(-)
Why's CMA cleaned up in one patch and MAPPABLE in the other 7?

There is a chance that the CMA removal fixes some bugs and needs to be back-ported. But the other 7 are pure cleanup.

Wouldn't it have been better to kill both the flags from ttm in 2
patches, then have one patch per driver and finally remove both flags
from the ttm header?

That's what I did initially. Basically I found that the TTM_MEMTYPE_FLAG_CMA flag might be the root of some problems because of the problematic implementation.

While removing it I've found that the TTM_MEMTYPE_FLAG_MAPPABLE is completely unused in TTM as well, so I removed both at the same time.

But that turned out to break drivers because they use the TTM_MEMTYPE_FLAG_MAPPABLE flag for no good reason at all :)

Anyway, I want to keep the order now since it might be a good idea to back port the CMA flag removal (but I'm not 100% sure of that).

Thanks,
Christian.


Best regards
Thomas

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 9c0f12f74af9..44fa8bc49d18 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -93,7 +93,7 @@ static int amdgpu_init_mem_type(struct ttm_bo_device *bdev, uint32_t type,
  		man->func = &amdgpu_gtt_mgr_func;
  		man->available_caching = TTM_PL_MASK_CACHING;
  		man->default_caching = TTM_PL_FLAG_CACHED;
-		man->flags = TTM_MEMTYPE_FLAG_MAPPABLE | TTM_MEMTYPE_FLAG_CMA;
+		man->flags = TTM_MEMTYPE_FLAG_MAPPABLE;
  		break;
  	case TTM_PL_VRAM:
  		/* "On-card" video ram */
@@ -108,7 +108,7 @@ static int amdgpu_init_mem_type(struct ttm_bo_device *bdev, uint32_t type,
  	case AMDGPU_PL_OA:
  		/* On-chip GDS memory*/
  		man->func = &ttm_bo_manager_func;
-		man->flags = TTM_MEMTYPE_FLAG_FIXED | TTM_MEMTYPE_FLAG_CMA;
+		man->flags = TTM_MEMTYPE_FLAG_FIXED;
  		man->available_caching = TTM_PL_FLAG_UNCACHED;
  		man->default_caching = TTM_PL_FLAG_UNCACHED;
  		break;
diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
index a1037478fa3f..7883341f8c83 100644
--- a/drivers/gpu/drm/nouveau/nouveau_bo.c
+++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
@@ -695,8 +695,7 @@ nouveau_bo_init_mem_type(struct ttm_bo_device *bdev, uint32_t type,
  				TTM_PL_FLAG_WC;
  			man->default_caching = TTM_PL_FLAG_WC;
  		} else {
-			man->flags = TTM_MEMTYPE_FLAG_MAPPABLE |
-				     TTM_MEMTYPE_FLAG_CMA;
+			man->flags = TTM_MEMTYPE_FLAG_MAPPABLE;
  			man->available_caching = TTM_PL_MASK_CACHING;
  			man->default_caching = TTM_PL_FLAG_CACHED;
  		}
diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
index 73085523fad7..54af06df865b 100644
--- a/drivers/gpu/drm/radeon/radeon_ttm.c
+++ b/drivers/gpu/drm/radeon/radeon_ttm.c
@@ -84,7 +84,7 @@ static int radeon_init_mem_type(struct ttm_bo_device *bdev, uint32_t type,
  		man->func = &ttm_bo_manager_func;
  		man->available_caching = TTM_PL_MASK_CACHING;
  		man->default_caching = TTM_PL_FLAG_CACHED;
-		man->flags = TTM_MEMTYPE_FLAG_MAPPABLE | TTM_MEMTYPE_FLAG_CMA;
+		man->flags = TTM_MEMTYPE_FLAG_MAPPABLE;
  #if IS_ENABLED(CONFIG_AGP)
  		if (rdev->flags & RADEON_IS_AGP) {
  			if (!rdev->ddev->agp) {
diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 8b9e7f62bea7..0768a054a916 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -272,20 +272,15 @@ static int ttm_bo_handle_move_mem(struct ttm_buffer_object *bo,
  				  struct ttm_operation_ctx *ctx)
  {
  	struct ttm_bo_device *bdev = bo->bdev;
-	bool old_is_pci = ttm_mem_reg_is_pci(bdev, &bo->mem);
-	bool new_is_pci = ttm_mem_reg_is_pci(bdev, mem);
  	struct ttm_mem_type_manager *old_man = &bdev->man[bo->mem.mem_type];
  	struct ttm_mem_type_manager *new_man = &bdev->man[mem->mem_type];
-	int ret = 0;
+	int ret;
- if (old_is_pci || new_is_pci ||
-	    ((mem->placement & bo->mem.placement & TTM_PL_MASK_CACHING) == 0)) {
-		ret = ttm_mem_io_lock(old_man, true);
-		if (unlikely(ret != 0))
-			goto out_err;
-		ttm_bo_unmap_virtual_locked(bo);
-		ttm_mem_io_unlock(old_man);
-	}
+	ret = ttm_mem_io_lock(old_man, true);
+	if (unlikely(ret != 0))
+		goto out_err;
+	ttm_bo_unmap_virtual_locked(bo);
+	ttm_mem_io_unlock(old_man);
/*
  	 * Create and bind a ttm if required.
@@ -1698,23 +1693,6 @@ EXPORT_SYMBOL(ttm_bo_device_init);
   * buffer object vm functions.
   */
-bool ttm_mem_reg_is_pci(struct ttm_bo_device *bdev, struct ttm_mem_reg *mem)
-{
-	struct ttm_mem_type_manager *man = &bdev->man[mem->mem_type];
-
-	if (!(man->flags & TTM_MEMTYPE_FLAG_FIXED)) {
-		if (mem->mem_type == TTM_PL_SYSTEM)
-			return false;
-
-		if (man->flags & TTM_MEMTYPE_FLAG_CMA)
-			return false;
-
-		if (mem->placement & TTM_PL_FLAG_CACHED)
-			return false;
-	}
-	return true;
-}
-
  void ttm_bo_unmap_virtual_locked(struct ttm_buffer_object *bo)
  {
  	struct ttm_bo_device *bdev = bo->bdev;
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
index bfd0c54ec30a..6bea7548aee0 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
@@ -762,7 +762,7 @@ static int vmw_init_mem_type(struct ttm_bo_device *bdev, uint32_t type,
  		 *  slots as well as the bo size.
  		 */
  		man->func = &vmw_gmrid_manager_func;
-		man->flags = TTM_MEMTYPE_FLAG_CMA | TTM_MEMTYPE_FLAG_MAPPABLE;
+		man->flags = TTM_MEMTYPE_FLAG_MAPPABLE;
  		man->available_caching = TTM_PL_FLAG_CACHED;
  		man->default_caching = TTM_PL_FLAG_CACHED;
  		break;
diff --git a/include/drm/ttm/ttm_bo_driver.h b/include/drm/ttm/ttm_bo_driver.h
index 45522e4fbd6b..71b195e78c7c 100644
--- a/include/drm/ttm/ttm_bo_driver.h
+++ b/include/drm/ttm/ttm_bo_driver.h
@@ -47,7 +47,6 @@
#define TTM_MEMTYPE_FLAG_FIXED (1 << 0) /* Fixed (on-card) PCI memory */
  #define TTM_MEMTYPE_FLAG_MAPPABLE      (1 << 1)	/* Memory mappable */
-#define TTM_MEMTYPE_FLAG_CMA           (1 << 3)	/* Can't map aperture */
struct ttm_mem_type_manager;

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