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>

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_ttm.c

@@ -321,7 +321,7 @@ nouveau_ttm_init(struct nouveau_drm *drm)
 	}
 
 #if IS_ENABLED(CONFIG_SWIOTLB) && IS_ENABLED(CONFIG_X86)
-	need_swiotlb = !!swiotlb_nr_tbl();
+	need_swiotlb = is_swiotlb_active();
 #endif
 
 	ret = ttm_bo_device_init(&drm->ttm.bdev, &nouveau_bo_driver,

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;
@@ -652,6 +646,7 @@ bool is_swiotlb_active(void)
 {
 	return io_tlb_default_mem != NULL;
 }
+EXPORT_SYMBOL_GPL(is_swiotlb_active);
 
 #ifdef CONFIG_DEBUG_FS