[PATCH v2 1/3] usb: ehci: add freescale imx28 special write register method

[Peter Chen]

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

Signed-off-by: Peter Chen <peter.chen at freescale.com>
Acked-by: Alan Stern <stern at rowland.harvard.edu>
---

Changes for v2:
Add Acked-by from Alan Stern

 drivers/usb/host/ehci.h |   13 +++++++++++++
 1 files changed, 13 insertions(+), 0 deletions(-)

diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h
index e8f41c5..535aa8b 100644
--- a/drivers/usb/host/ehci.h
+++ b/drivers/usb/host/ehci.h
@@ -225,6 +225,7 @@ struct ehci_hcd {			/* one per controller */
 	unsigned		has_synopsys_hc_bug:1; /* Synopsys HC */
 	unsigned		frame_index_bug:1; /* MosChip (AKA NetMos) */
 	unsigned		need_oc_pp_cycle:1; /* MPC834X port power */
+	unsigned		imx28_write_fix:1; /* For Freescale i.MX28 */
 
 	/* required for usb32 quirk */
 	#define OHCI_CTRL_HCFS          (3 << 6)
@@ -728,6 +729,13 @@ static inline unsigned int ehci_readl(const struct ehci_hcd *ehci,
 #endif
 }
 
+#ifdef CONFIG_SOC_IMX28
+static inline void imx28_ehci_writel(u32 val32, volatile u32 *addr)
+{
+	__asm__ ("swp %0, %0, [%1]" : : "r"(val32), "r"(addr));
+}
+#endif
+
 static inline void ehci_writel(const struct ehci_hcd *ehci,
 		const unsigned int val, __u32 __iomem *regs)
 {
@@ -735,6 +743,11 @@ static inline void ehci_writel(const struct ehci_hcd *ehci,
 	ehci_big_endian_mmio(ehci) ?
 		writel_be(val, regs) :
 		writel(val, regs);
+#elif defined(CONFIG_SOC_IMX28)
+	if (ehci->imx28_write_fix)
+		imx28_ehci_writel(val, regs);
+	else
+		writel(val, regs);
 #else
 	writel(val, regs);
 #endif
-- 
1.7.1