Merge branch 'stable/for-linus-5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb

Pull swiotlb updates from Konrad Rzeszutek Wilk:
 "Expands the SWIOTLB to have debugfs support (along with bug-fixes),
  and a tiny fix"

* 'stable/for-linus-5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb:
  swiotlb: drop pointless static qualifier in swiotlb_create_debugfs()
  swiotlb: checking whether swiotlb buffer is full with io_tlb_used
  swiotlb: add debugfs to track swiotlb buffer usage
  swiotlb: fix comment on swiotlb_bounce()

kernel/dma/swiotlb.c

@@ -34,6 +34,9 @@
 #include <linux/scatterlist.h>
 #include <linux/mem_encrypt.h>
 #include <linux/set_memory.h>
+#ifdef CONFIG_DEBUG_FS
+#include <linux/debugfs.h>
+#endif
 
 #include <asm/io.h>
 #include <asm/dma.h>
@@ -72,6 +75,11 @@ phys_addr_t io_tlb_start, io_tlb_end;
  */
 static unsigned long io_tlb_nslabs;
 
+/*
+ * The number of used IO TLB block
+ */
+static unsigned long io_tlb_used;
+
 /*
  * This is a free list describing the number of free entries available from
  * each index
@@ -385,7 +393,7 @@ void __init swiotlb_exit(void)
 }
 
 /*
- * Bounce: copy the swiotlb buffer back to the original dma location
+ * Bounce: copy the swiotlb buffer from or back to the original dma location
  */
 static void swiotlb_bounce(phys_addr_t orig_addr, phys_addr_t tlb_addr,
 			   size_t size, enum dma_data_direction dir)
@@ -475,6 +483,10 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
 	 * request and allocate a buffer from that IO TLB pool.
 	 */
 	spin_lock_irqsave(&io_tlb_lock, flags);
+
+	if (unlikely(nslots > io_tlb_nslabs - io_tlb_used))
+		goto not_found;
+
 	index = ALIGN(io_tlb_index, stride);
 	if (index >= io_tlb_nslabs)
 		index = 0;
@@ -524,6 +536,7 @@ not_found:
 		dev_warn(hwdev, "swiotlb buffer is full (sz: %zd bytes)\n", size);
 	return DMA_MAPPING_ERROR;
 found:
+	io_tlb_used += nslots;
 	spin_unlock_irqrestore(&io_tlb_lock, flags);
 
 	/*
@@ -584,6 +597,8 @@ void swiotlb_tbl_unmap_single(struct device *hwdev, phys_addr_t tlb_addr,
 		 */
 		for (i = index - 1; (OFFSET(i, IO_TLB_SEGSIZE) != IO_TLB_SEGSIZE -1) && io_tlb_list[i]; i--)
 			io_tlb_list[i] = ++count;
+
+		io_tlb_used -= nslots;
 	}
 	spin_unlock_irqrestore(&io_tlb_lock, flags);
 }
@@ -650,3 +665,36 @@ bool swiotlb_map(struct device *dev, phys_addr_t *phys, dma_addr_t *dma_addr,
 
 	return true;
 }
+
+#ifdef CONFIG_DEBUG_FS
+
+static int __init swiotlb_create_debugfs(void)
+{
+	struct dentry *d_swiotlb_usage;
+	struct dentry *ent;
+
+	d_swiotlb_usage = debugfs_create_dir("swiotlb", NULL);
+
+	if (!d_swiotlb_usage)
+		return -ENOMEM;
+
+	ent = debugfs_create_ulong("io_tlb_nslabs", 0400,
+				   d_swiotlb_usage, &io_tlb_nslabs);
+	if (!ent)
+		goto fail;
+
+	ent = debugfs_create_ulong("io_tlb_used", 0400,
+				   d_swiotlb_usage, &io_tlb_used);
+	if (!ent)
+		goto fail;
+
+	return 0;
+
+fail:
+	debugfs_remove_recursive(d_swiotlb_usage);
+	return -ENOMEM;
+}
+
+late_initcall(swiotlb_create_debugfs);
+
+#endif