[3.5.y.z extended stable] Patch "usb: ehci: add freescale imx28 special write register method" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    usb: ehci: add freescale imx28 special write register method

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 9c522ad19069b36ffdee12ceeeb7c0d8ed9a78e9 Mon Sep 17 00:00:00 2001
From: Peter Chen <peter.chen at freescale.com>
Date: Fri, 10 Jan 2014 13:51:26 +0800
Subject: usb: ehci: add freescale imx28 special write register method

commit feffe09f510c475df082546815f9e4a573f6a233 upstream.

According to Freescale imx28 Errata, "ENGR119653 USB: ARM to USB
register error issue", All USB register write operations must
use the ARM SWP instruction. So, we implement a special ehci_write
for imx28.

Discussion for it at below:
http://marc.info/?l=linux-usb&m=137996395529294&w=2

Without this patcheset, imx28 works unstable at high AHB bus loading.
If the bus loading is not high, the imx28 usb can work well at the most
of time. There is a IC errata for this problem, usually, we consider
IC errata is a problem not a new feature, and this workaround is needed
for that, so we need to add them to stable tree 3.11+.

Cc: robert.hodaszi at digi.com
Signed-off-by: Peter Chen <peter.chen at freescale.com>
Acked-by: Alan Stern <stern at rowland.harvard.edu>
Signed-off-by: Marc Kleine-Budde <mkl at pengutronix.de>
Tested-by: Marc Kleine-Budde <mkl at pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
[ luis: backported to 3.5: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/usb/host/ehci.h | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h
index 2694ed6..b272634 100644
--- a/drivers/usb/host/ehci.h
+++ b/drivers/usb/host/ehci.h
@@ -149,6 +149,7 @@ struct ehci_hcd {			/* one per controller */
 	unsigned		use_dummy_qh:1;	/* AMD Frame List table quirk*/
 	unsigned		has_synopsys_hc_bug:1; /* Synopsys HC */
 	unsigned		frame_index_bug:1; /* MosChip (AKA NetMos) */
+	unsigned		imx28_write_fix:1; /* For Freescale i.MX28 */

 	/* required for usb32 quirk */
 	#define OHCI_CTRL_HCFS          (3 << 6)
@@ -656,6 +657,18 @@ static inline unsigned int ehci_readl(const struct ehci_hcd *ehci,
 #endif
 }

+#ifdef CONFIG_SOC_IMX28
+static inline void imx28_ehci_writel(const unsigned int val,
+		volatile __u32 __iomem *addr)
+{
+	__asm__ ("swp %0, %0, [%1]" : : "r"(val), "r"(addr));
+}
+#else
+static inline void imx28_ehci_writel(const unsigned int val,
+		volatile __u32 __iomem *addr)
+{
+}
+#endif
 static inline void ehci_writel(const struct ehci_hcd *ehci,
 		const unsigned int val, __u32 __iomem *regs)
 {
@@ -664,7 +677,10 @@ static inline void ehci_writel(const struct ehci_hcd *ehci,
 		writel_be(val, regs) :
 		writel(val, regs);
 #else
-	writel(val, regs);
+	if (ehci->imx28_write_fix)
+		imx28_ehci_writel(val, regs);
+	else
+		writel(val, regs);
 #endif
 }

--
1.9.1