BACKPORT: swiotlb: remove swiotlb_nr_tbl

All callers just use it to check if swiotlb is active at all, for which
they can just use is_swiotlb_active.  In the longer run drivers need
to stop using is_swiotlb_active as well, but let's do the simple step
first.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
(cherry picked from commit 2cbc2776ef)
[willdeacon@: Fixed up additional users in DRM drivers]
Signed-off-by: Will Deacon <willdeacon@google.com>
Bug: 190591509
Change-Id: I3bd4c17695f0224ae68509d0e51cb5bdc455277a

drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c

@@ -1357,7 +1357,7 @@ static int amdgpu_ttm_tt_populate(struct ttm_bo_device *bdev,
 	}
 
 #ifdef CONFIG_SWIOTLB
-	if (adev->need_swiotlb && swiotlb_nr_tbl()) {
+	if (adev->need_swiotlb && is_swiotlb_active()) {
 		return ttm_dma_populate(&gtt->ttm, adev->dev, ctx);
 	}
 #endif
@@ -1401,7 +1401,7 @@ static void amdgpu_ttm_tt_unpopulate(struct ttm_bo_device *bdev, struct ttm_tt *
 	adev = amdgpu_ttm_adev(bdev);
 
 #ifdef CONFIG_SWIOTLB
-	if (adev->need_swiotlb && swiotlb_nr_tbl()) {
+	if (adev->need_swiotlb && is_swiotlb_active()) {
 		ttm_dma_unpopulate(&gtt->ttm, adev->dev);
 		return;
 	}
@@ -2589,7 +2589,7 @@ int amdgpu_ttm_debugfs_init(struct amdgpu_device *adev)
 	count = ARRAY_SIZE(amdgpu_ttm_debugfs_list);
 
 #ifdef CONFIG_SWIOTLB
-	if (!(adev->need_swiotlb && swiotlb_nr_tbl()))
+	if (!(adev->need_swiotlb && is_swiotlb_active()))
 		--count;
 #endif
 

drivers/gpu/drm/i915/gem/i915_gem_internal.c

@@ -42,7 +42,7 @@ static int i915_gem_object_get_pages_internal(struct drm_i915_gem_object *obj)
 
 	max_order = MAX_ORDER;
 #ifdef CONFIG_SWIOTLB
-	if (swiotlb_nr_tbl()) {
+	if (is_swiotlb_active()) {
 		unsigned int max_segment;
 
 		max_segment = swiotlb_max_segment();

drivers/gpu/drm/nouveau/nouveau_bo.c

@@ -1328,7 +1328,7 @@ nouveau_ttm_tt_populate(struct ttm_bo_device *bdev,
 #endif
 
 #if IS_ENABLED(CONFIG_SWIOTLB) && IS_ENABLED(CONFIG_X86)
-	if (swiotlb_nr_tbl()) {
+	if (is_swiotlb_active()) {
 		return ttm_dma_populate((void *)ttm, dev, ctx);
 	}
 #endif
@@ -1358,7 +1358,7 @@ nouveau_ttm_tt_unpopulate(struct ttm_bo_device *bdev,
 #endif
 
 #if IS_ENABLED(CONFIG_SWIOTLB) && IS_ENABLED(CONFIG_X86)
-	if (swiotlb_nr_tbl()) {
+	if (is_swiotlb_active()) {
 		ttm_dma_unpopulate((void *)ttm, dev);
 		return;
 	}

drivers/gpu/drm/radeon/radeon_ttm.c

@@ -658,7 +658,7 @@ static int radeon_ttm_tt_populate(struct ttm_bo_device *bdev,
 #endif
 
 #ifdef CONFIG_SWIOTLB
-	if (rdev->need_swiotlb && swiotlb_nr_tbl()) {
+	if (rdev->need_swiotlb && is_swiotlb_active()) {
 		return ttm_dma_populate(&gtt->ttm, rdev->dev, ctx);
 	}
 #endif
@@ -689,7 +689,7 @@ static void radeon_ttm_tt_unpopulate(struct ttm_bo_device *bdev, struct ttm_tt *
 #endif
 
 #ifdef CONFIG_SWIOTLB
-	if (rdev->need_swiotlb && swiotlb_nr_tbl()) {
+	if (rdev->need_swiotlb && is_swiotlb_active()) {
 		ttm_dma_unpopulate(&gtt->ttm, rdev->dev);
 		return;
 	}
@@ -1100,7 +1100,7 @@ static int radeon_ttm_debugfs_init(struct radeon_device *rdev)
 	count = ARRAY_SIZE(radeon_ttm_debugfs_list);
 
 #ifdef CONFIG_SWIOTLB
-	if (!(rdev->need_swiotlb && swiotlb_nr_tbl()))
+	if (!(rdev->need_swiotlb && is_swiotlb_active()))
 		--count;
 #endif
 

drivers/pci/xen-pcifront.c

@@ -693,7 +693,7 @@ static int pcifront_connect_and_init_dma(struct pcifront_device *pdev)
 
 	spin_unlock(&pcifront_dev_lock);
 
-	if (!err && !swiotlb_nr_tbl()) {
+	if (!err && !is_swiotlb_active()) {
 		err = pci_xen_swiotlb_init_late();
 		if (err)
 			dev_err(&pdev->xdev->dev, "Could not setup SWIOTLB!\n");

include/linux/swiotlb.h

@@ -37,7 +37,6 @@ enum swiotlb_force {
 
 extern void swiotlb_init(int verbose);
 int swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose);
-extern unsigned long swiotlb_nr_tbl(void);
 unsigned long swiotlb_size_or_default(void);
 extern int swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs);
 extern int swiotlb_late_init_with_default_size(size_t default_size);

kernel/dma/swiotlb.c

@@ -94,12 +94,6 @@ setup_io_tlb_npages(char *str)
 }
 early_param("swiotlb", setup_io_tlb_npages);
 
-unsigned long swiotlb_nr_tbl(void)
-{
-	return io_tlb_default_mem ? io_tlb_default_mem->nslabs : 0;
-}
-EXPORT_SYMBOL_GPL(swiotlb_nr_tbl);
-
 unsigned int swiotlb_max_segment(void)
 {
 	return io_tlb_default_mem ? max_segment : 0;
@@ -653,6 +647,7 @@ bool is_swiotlb_active(void)
 {
 	return io_tlb_default_mem != NULL;
 }
+EXPORT_SYMBOL_GPL(is_swiotlb_active);
 
 #ifdef CONFIG_DEBUG_FS