ARM: 5966/1: at91_udc HW glitch

Add some delay to avoid reading CSR TXCOUNT too early after
updating it.

For more info about this HW glitch see:
http://lists.arm.linux.org.uk/lurker/message/20090325.150843.f515c02f.en.html
http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20100129/10ba0f8b/attachment.el
http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20100203/09cdb3b4/attachment.el
http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20100203/08b5b249/attachment.el

First applied: "Fix soft lockup in at91 udc driver"
http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=5965

Signed-off-by: Anti Sullin <anti.sullin@artecdesign.ee>
Signed-off-by: Harro Haan <hrhaan@gmail.com>
Acked-by: Remy Bohmer <linux@bohmer.net>
Acked-by: Andrew Victor <linux@maxim.org.za>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 7 insertions, 0 deletions

diff --git a/drivers/usb/gadget/at91_udc.c b/drivers/usb/gadget/at91_udc.c
index 12ac9cd32a07..b3bd22ef82ba 100644
--- a/drivers/usb/gadget/at91_udc.c
+++ b/drivers/usb/gadget/at91_udc.c
@@ -366,6 +366,13 @@ rescan:
         if (is_done)
                 done(ep, req, 0);
         else if (ep->is_pingpong) {
+                /*
+                 * One dummy read to delay the code because of a HW glitch:
+                 * CSR returns bad RXCOUNT when read too soon after updating
+                 * RX_DATA_BK flags.
+                 */
+                csr = __raw_readl(creg);
+
                 bufferspace -= count;
                 buf += count;
                 goto rescan;