[PATCH 3.2 24/24] Bluetooth: ath3k: workaround the compatibility issue with xHCI controller

[Ben Hutchings <ben@decadent.org.uk>]

3.2.68-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Adam Lee <adam.lee@canonical.com>

commit c561a5753dd631920c4459a067d22679b3d110d6 upstream.

BugLink: https://bugs.launchpad.net/bugs/1400215

ath3k devices fail to load firmwares on xHCI buses, but work well on
EHCI, this might be a compatibility issue between xHCI and ath3k chips.
As my testing result, those chips will work on xHCI buses again with
this patch.

This workaround is from Qualcomm, they also did some workarounds in
Windows driver.

Signed-off-by: Adam Lee <adam.lee@canonical.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 drivers/bluetooth/ath3k.c | 8 ++++++++
 1 file changed, 8 insertions(+)

--- a/drivers/bluetooth/ath3k.c
+++ b/drivers/bluetooth/ath3k.c
@@ -172,6 +172,8 @@ static struct usb_device_id ath3k_blist_
 #define USB_REQ_DFU_DNLOAD	1
 #define BULK_SIZE		4096
 #define FW_HDR_SIZE		20
+#define TIMEGAP_USEC_MIN	50
+#define TIMEGAP_USEC_MAX	100
 
 static int ath3k_load_firmware(struct usb_device *udev,
 				const struct firmware *firmware)
@@ -202,6 +204,9 @@ static int ath3k_load_firmware(struct us
 	count -= 20;
 
 	while (count) {
+		/* workaround the compatibility issue with xHCI controller*/
+		usleep_range(TIMEGAP_USEC_MIN, TIMEGAP_USEC_MAX);
+
 		size = min_t(uint, count, BULK_SIZE);
 		pipe = usb_sndbulkpipe(udev, 0x02);
 		memcpy(send_buf, firmware->data + sent, size);
@@ -278,6 +283,9 @@ static int ath3k_load_fwfile(struct usb_
 	count -= size;
 
 	while (count) {
+		/* workaround the compatibility issue with xHCI controller*/
+		usleep_range(TIMEGAP_USEC_MIN, TIMEGAP_USEC_MAX);
+
 		size = min_t(uint, count, BULK_SIZE);
 		pipe = usb_sndbulkpipe(udev, 0x02);