summaryrefslogtreecommitdiff
path: root/drivers/usb
diff options
context:
space:
mode:
authorRoger Quadros <rogerq@ti.com>2016-09-13 11:16:03 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-09-13 17:25:35 +0200
commitb44bbc46a8bbcd9c6bb1d167ca3f78d3aa5ee41d (patch)
tree9aaf9cc2763417f3a79527a9422bc93648b3cbec /drivers/usb
parent9cdd8e11c2a2f4b7553823240dc16a35ffa243e9 (diff)
usb: core: setup dma_pfn_offset for USB devices and, interfaces
If dma_pfn_offset is not inherited correctly from the host controller, it might result in sub-optimal configuration as bounce buffer limit might be set to less than optimal level. Consider the mass storage device case. USB storage driver creates a scsi host for the mass storage interface in drivers/usb/storage/usb.c The scsi host parent device is nothing but the the USB interface device. Now, __scsi_init_queue() calls scsi_calculate_bounce_limit() to find out and set the block layer bounce limit. scsi_calculate_bounce_limit() uses dma_max_pfn(host_dev) to get the bounce_limit. host_dev is nothing but the device representing the mass storage interface. If that device doesn't have the right dma_pfn_offset, then dma_max_pfn() is messed up and the bounce buffer limit is wrong. e.g. On Keystone 2 systems, dma_max_pfn() is 0x87FFFF and dma_mask_pfn is 0xFFFFF. Consider a mass storage use case: Without this patch, usb scsi host device (usb-storage) will get a dma_pfn_offset of 0 resulting in a dma_max_pfn() of 0xFFFFF within the scsi layer (scsi_calculate_bounce_limit()). This will result in bounce buffers being unnecessarily used. Hint: On 32-bit ARM platforms dma_max_pfn() = dma_mask_pfn + dma_pfn_offset Signed-off-by: Roger Quadros <rogerq@ti.com> Acked-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb')
-rw-r--r--drivers/usb/core/message.c5
-rw-r--r--drivers/usb/core/usb.c11
2 files changed, 16 insertions, 0 deletions
diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index 5ab5c1a81462..3a4707746157 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -1859,7 +1859,12 @@ free_interfaces:
intf->dev.bus = &usb_bus_type;
intf->dev.type = &usb_if_device_type;
intf->dev.groups = usb_interface_groups;
+ /*
+ * Please refer to usb_alloc_dev() to see why we set
+ * dma_mask and dma_pfn_offset.
+ */
intf->dev.dma_mask = dev->dev.dma_mask;
+ intf->dev.dma_pfn_offset = dev->dev.dma_pfn_offset;
INIT_WORK(&intf->reset_ws, __usb_queue_reset_device);
intf->minor = -1;
device_initialize(&intf->dev);
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index 5e80697ef952..592151461017 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -440,7 +440,18 @@ struct usb_device *usb_alloc_dev(struct usb_device *parent,
dev->dev.bus = &usb_bus_type;
dev->dev.type = &usb_device_type;
dev->dev.groups = usb_device_groups;
+ /*
+ * Fake a dma_mask/offset for the USB device:
+ * We cannot really use the dma-mapping API (dma_alloc_* and
+ * dma_map_*) for USB devices but instead need to use
+ * usb_alloc_coherent and pass data in 'urb's, but some subsystems
+ * manually look into the mask/offset pair to determine whether
+ * they need bounce buffers.
+ * Note: calling dma_set_mask() on a USB device would set the
+ * mask for the entire HCD, so don't do that.
+ */
dev->dev.dma_mask = bus->controller->dma_mask;
+ dev->dev.dma_pfn_offset = bus->controller->dma_pfn_offset;
set_dev_node(&dev->dev, dev_to_node(bus->controller));
dev->state = USB_STATE_ATTACHED;
dev->lpm_disable_count = 1;