On Mon, May 10, 2021 at 11:03 PM Christoph Hellwig [off-list ref] wrote:

quoted

+#ifdef CONFIG_DMA_RESTRICTED_POOL
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/of_fdt.h>
+#include <linux/of_reserved_mem.h>
+#include <linux/slab.h>
+#endif

I don't think any of this belongs into swiotlb.c.  Marking
swiotlb_init_io_tlb_mem non-static and having all this code in a separate
file is probably a better idea.

Will do in the next version.

quoted

+#ifdef CONFIG_DMA_RESTRICTED_POOL
+static int rmem_swiotlb_device_init(struct reserved_mem *rmem,
+                                 struct device *dev)
+{
+     struct io_tlb_mem *mem = rmem->priv;
+     unsigned long nslabs = rmem->size >> IO_TLB_SHIFT;
+
+     if (dev->dma_io_tlb_mem)
+             return 0;
+
+     /* Since multiple devices can share the same pool, the private data,
+      * io_tlb_mem struct, will be initialized by the first device attached
+      * to it.
+      */

This is not the normal kernel comment style.

Will fix this in the next version.

quoted

+#ifdef CONFIG_ARM
+             if (!PageHighMem(pfn_to_page(PHYS_PFN(rmem->base)))) {
+                     kfree(mem);
+                     return -EINVAL;
+             }
+#endif /* CONFIG_ARM */

And this is weird.  Why would ARM have such a restriction?  And if we have
such rstrictions it absolutely belongs into an arch helper.

Now I think the CONFIG_ARM can just be removed?
The goal here is to make sure we're using linear map and can safely
use phys_to_dma/dma_to_phys.

quoted

+             swiotlb_init_io_tlb_mem(mem, rmem->base, nslabs, false);
+
+             rmem->priv = mem;
+
+#ifdef CONFIG_DEBUG_FS
+             if (!debugfs_dir)
+                     debugfs_dir = debugfs_create_dir("swiotlb", NULL);
+
+             swiotlb_create_debugfs(mem, rmem->name, debugfs_dir);

Doesn't the debugfs_create_dir belong into swiotlb_create_debugfs?  Also
please use IS_ENABLEd or a stub to avoid ifdefs like this.

Will move it into swiotlb_create_debugfs and use IS_ENABLED in the next version.