usb: dma bounce buffer support

usb: dma bounce buffer support V4

This patch adds dma bounce buffer support to the usb core. These buffers
can be enabled with the HCD_LOCAL_MEM flag, and they make sure that all data
passed to the host controller is allocated using dma_alloc_coherent().

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 163 insertions, 23 deletions

diff --git a/drivers/usb/core/buffer.c b/drivers/usb/core/buffer.c
index 28d4972f7ad5..acd9f00a0b76 100644
--- a/drivers/usb/core/buffer.c
+++ b/drivers/usb/core/buffer.c
@@ -53,7 +53,8 @@ int hcd_buffer_create(struct usb_hcd *hcd)
         char            name[16];
         int             i, size;
 
-        if (!hcd->self.controller->dma_mask)
+        if (!hcd->self.controller->dma_mask &&
+            !(hcd->driver->flags & HCD_LOCAL_MEM))
                 return 0;
 
         for (i = 0; i < HCD_BUFFER_POOLS; i++) { 
@@ -107,7 +108,8 @@ void *hcd_buffer_alloc(
         int                     i;
 
         /* some USB hosts just use PIO */
-        if (!bus->controller->dma_mask) {
+        if (!bus->controller->dma_mask &&
+            !(hcd->driver->flags & HCD_LOCAL_MEM)) {
                 *dma = ~(dma_addr_t) 0;
                 return kmalloc(size, mem_flags);
         }
@@ -132,7 +134,8 @@ void hcd_buffer_free(
         if (!addr)
                 return;
 
-        if (!bus->controller->dma_mask) {
+        if (!bus->controller->dma_mask &&
+            !(hcd->driver->flags & HCD_LOCAL_MEM)) {
                 kfree(addr);
                 return;
         }
diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 372372116bb0..febd6b40da3b 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -35,6 +35,7 @@
 #include <linux/mutex.h>
 #include <asm/irq.h>
 #include <asm/byteorder.h>
+#include <asm/unaligned.h>
 #include <linux/platform_device.h>
 #include <linux/workqueue.h>
 
@@ -1112,48 +1113,177 @@ void usb_hcd_unlink_urb_from_ep(struct usb_hcd *hcd, struct urb *urb)
 }
 EXPORT_SYMBOL_GPL(usb_hcd_unlink_urb_from_ep);
 
-static void map_urb_for_dma(struct usb_hcd *hcd, struct urb *urb)
+/*
+ * Some usb host controllers can only perform dma using a small SRAM area.
+ * The usb core itself is however optimized for host controllers that can dma
+ * using regular system memory - like pci devices doing bus mastering.
+ *
+ * To support host controllers with limited dma capabilites we provide dma
+ * bounce buffers. This feature can be enabled using the HCD_LOCAL_MEM flag.
+ * For this to work properly the host controller code must first use the
+ * function dma_declare_coherent_memory() to point out which memory area
+ * that should be used for dma allocations.
+ *
+ * The HCD_LOCAL_MEM flag then tells the usb code to allocate all data for
+ * dma using dma_alloc_coherent() which in turn allocates from the memory
+ * area pointed out with dma_declare_coherent_memory().
+ *
+ * So, to summarize...
+ *
+ * - We need "local" memory, canonical example being
+ *   a small SRAM on a discrete controller being the
+ *   only memory that the controller can read ...
+ *   (a) "normal" kernel memory is no good, and
+ *   (b) there's not enough to share
+ *
+ * - The only *portable* hook for such stuff in the
+ *   DMA framework is dma_declare_coherent_memory()
+ *
+ * - So we use that, even though the primary requirement
+ *   is that the memory be "local" (hence addressible
+ *   by that device), not "coherent".
+ *
+ */
+
+static int hcd_alloc_coherent(struct usb_bus *bus,
+                              gfp_t mem_flags, dma_addr_t *dma_handle,
+                              void **vaddr_handle, size_t size,
+                              enum dma_data_direction dir)
+{
+        unsigned char *vaddr;
+
+        vaddr = hcd_buffer_alloc(bus, size + sizeof(vaddr),
+                                 mem_flags, dma_handle);
+        if (!vaddr)
+                return -ENOMEM;
+
+        /*
+         * Store the virtual address of the buffer at the end
+         * of the allocated dma buffer. The size of the buffer
+         * may be uneven so use unaligned functions instead
+         * of just rounding up. It makes sense to optimize for
+         * memory footprint over access speed since the amount
+         * of memory available for dma may be limited.
+         */
+        put_unaligned((unsigned long)*vaddr_handle,
+                      (unsigned long *)(vaddr + size));
+
+        if (dir == DMA_TO_DEVICE)
+                memcpy(vaddr, *vaddr_handle, size);
+
+        *vaddr_handle = vaddr;
+        return 0;
+}
+
+static void hcd_free_coherent(struct usb_bus *bus, dma_addr_t *dma_handle,
+                              void **vaddr_handle, size_t size,
+                              enum dma_data_direction dir)
+{
+        unsigned char *vaddr = *vaddr_handle;
+
+        vaddr = (void *)get_unaligned((unsigned long *)(vaddr + size));
+
+        if (dir == DMA_FROM_DEVICE)
+                memcpy(vaddr, *vaddr_handle, size);
+
+        hcd_buffer_free(bus, size + sizeof(vaddr), *vaddr_handle, *dma_handle);
+
+        *vaddr_handle = vaddr;
+        *dma_handle = 0;
+}
+
+static int map_urb_for_dma(struct usb_hcd *hcd, struct urb *urb,
+                           gfp_t mem_flags)
 {
+        enum dma_data_direction dir;
+        int ret = 0;
+
         /* Map the URB's buffers for DMA access.
          * Lower level HCD code should use *_dma exclusively,
          * unless it uses pio or talks to another transport.
          */
-        if (hcd->self.uses_dma && !is_root_hub(urb->dev)) {
-                if (usb_endpoint_xfer_control(&urb->ep->desc)
-                        && !(urb->transfer_flags & URB_NO_SETUP_DMA_MAP))
-                        urb->setup_dma = dma_map_single (
+        if (is_root_hub(urb->dev))
+                return 0;
+
+        if (usb_endpoint_xfer_control(&urb->ep->desc)
+            && !(urb->transfer_flags & URB_NO_SETUP_DMA_MAP)) {
+                if (hcd->self.uses_dma)
+                        urb->setup_dma = dma_map_single(
                                         hcd->self.controller,
                                         urb->setup_packet,
-                                        sizeof (struct usb_ctrlrequest),
+                                        sizeof(struct usb_ctrlrequest),
                                         DMA_TO_DEVICE);
-                if (urb->transfer_buffer_length != 0
-                        && !(urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP))
+                else if (hcd->driver->flags & HCD_LOCAL_MEM)
+                        ret = hcd_alloc_coherent(
+                                        urb->dev->bus, mem_flags,
+                                        &urb->setup_dma,
+                                        (void **)&urb->setup_packet,
+                                        sizeof(struct usb_ctrlrequest),
+                                        DMA_TO_DEVICE);
+        }
+
+        dir = usb_urb_dir_in(urb) ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
+        if (ret == 0 && urb->transfer_buffer_length != 0
+            && !(urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP)) {
+                if (hcd->self.uses_dma)
                         urb->transfer_dma = dma_map_single (
                                         hcd->self.controller,
                                         urb->transfer_buffer,
                                         urb->transfer_buffer_length,
-                                        usb_urb_dir_in(urb)
-                                            ? DMA_FROM_DEVICE
-                                            : DMA_TO_DEVICE);
+                                        dir);
+                else if (hcd->driver->flags & HCD_LOCAL_MEM) {
+                        ret = hcd_alloc_coherent(
+                                        urb->dev->bus, mem_flags,
+                                        &urb->transfer_dma,
+                                        &urb->transfer_buffer,
+                                        urb->transfer_buffer_length,
+                                        dir);
+
+                        if (ret && usb_endpoint_xfer_control(&urb->ep->desc)
+                            && !(urb->transfer_flags & URB_NO_SETUP_DMA_MAP))
+                                hcd_free_coherent(urb->dev->bus,
+                                        &urb->setup_dma,
+                                        (void **)&urb->setup_packet,
+                                        sizeof(struct usb_ctrlrequest),
+                                        DMA_TO_DEVICE);
+                }
         }
+        return ret;
 }
 
 static void unmap_urb_for_dma(struct usb_hcd *hcd, struct urb *urb)
 {
-        if (hcd->self.uses_dma && !is_root_hub(urb->dev)) {
-                if (usb_endpoint_xfer_control(&urb->ep->desc)
-                        && !(urb->transfer_flags & URB_NO_SETUP_DMA_MAP))
+        enum dma_data_direction dir;
+
+        if (is_root_hub(urb->dev))
+                return;
+
+        if (usb_endpoint_xfer_control(&urb->ep->desc)
+            && !(urb->transfer_flags & URB_NO_SETUP_DMA_MAP)) {
+                if (hcd->self.uses_dma)
                         dma_unmap_single(hcd->self.controller, urb->setup_dma,
                                         sizeof(struct usb_ctrlrequest),
                                         DMA_TO_DEVICE);
-                if (urb->transfer_buffer_length != 0
-                        && !(urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP))
+                else if (hcd->driver->flags & HCD_LOCAL_MEM)
+                        hcd_free_coherent(urb->dev->bus, &urb->setup_dma,
+                                        (void **)&urb->setup_packet,
+                                        sizeof(struct usb_ctrlrequest),
+                                        DMA_TO_DEVICE);
+        }
+
+        dir = usb_urb_dir_in(urb) ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
+        if (urb->transfer_buffer_length != 0
+            && !(urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP)) {
+                if (hcd->self.uses_dma)
                         dma_unmap_single(hcd->self.controller,
                                         urb->transfer_dma,
                                         urb->transfer_buffer_length,
-                                        usb_urb_dir_in(urb)
-                                            ? DMA_FROM_DEVICE
-                                            : DMA_TO_DEVICE);
+                                        dir);
+                else if (hcd->driver->flags & HCD_LOCAL_MEM)
+                        hcd_free_coherent(urb->dev->bus, &urb->transfer_dma,
+                                        &urb->transfer_buffer,
+                                        urb->transfer_buffer_length,
+                                        dir);
         }
 }
 
@@ -1185,7 +1315,12 @@ int usb_hcd_submit_urb (struct urb *urb, gfp_t mem_flags)
          * URBs must be submitted in process context with interrupts
          * enabled.
          */
-        map_urb_for_dma(hcd, urb);
+        status = map_urb_for_dma(hcd, urb, mem_flags);
+        if (unlikely(status)) {
+                usbmon_urb_submit_error(&hcd->self, urb, status);
+                goto error;
+        }
+
         if (is_root_hub(urb->dev))
                 status = rh_urb_enqueue(hcd, urb);
         else
@@ -1194,6 +1329,7 @@ int usb_hcd_submit_urb (struct urb *urb, gfp_t mem_flags)
         if (unlikely(status)) {
                 usbmon_urb_submit_error(&hcd->self, urb, status);
                 unmap_urb_for_dma(hcd, urb);
+ error:
                 urb->hcpriv = NULL;
                 INIT_LIST_HEAD(&urb->urb_list);
                 atomic_dec(&urb->use_count);
diff --git a/drivers/usb/core/hcd.h b/drivers/usb/core/hcd.h
index 080298ad5990..0095641c51fa 100644
--- a/drivers/usb/core/hcd.h
+++ b/drivers/usb/core/hcd.h
@@ -165,6 +165,7 @@ struct hc_driver {
 
         int     flags;
 #define HCD_MEMORY      0x0001          /* HC regs use memory (else I/O) */
+#define HCD_LOCAL_MEM   0x0002          /* HC needs local memory */
 #define HCD_USB11       0x0010          /* USB 1.1 */
 #define HCD_USB2        0x0020          /* USB 2.0 */