[PATCH] ARM: i.MX: Disable OTG controller during startup

[Sascha Hauer <s.hauer@pengutronix.de>]

When booting from USB it's sometimes observed that the USB stack on
the remote host gets confused. This happens when we adjust the PLLs
the USB controller is hanging on. The ROM just leaves the USB controller
enabled when it passes control to the bootloader, so make sure we
disable it before doing any critical clock operations.

This is currently done for i.MX51, i.MX53 and i.MX6, but a similar thing
can happen on other i.MXes aswell.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 arch/arm/mach-imx/imx51.c            |  3 +++
 arch/arm/mach-imx/imx53.c            |  3 +++
 arch/arm/mach-imx/imx6.c             |  3 +++
 arch/arm/mach-imx/include/mach/usb.h | 23 +++++++++++++++++++++++
 4 files changed, 32 insertions(+)

diff --git a/arch/arm/mach-imx/imx51.c b/arch/arm/mach-imx/imx51.c
index ec8cdd868b..494ec72aa0 100644
--- a/arch/arm/mach-imx/imx51.c
+++ b/arch/arm/mach-imx/imx51.c
@@ -22,6 +22,7 @@
 #include <mach/clock-imx51_53.h>
 #include <mach/generic.h>
 #include <mach/reset-reason.h>
+#include <mach/usb.h>
 
 #define IIM_SREV 0x24
 
@@ -140,6 +141,8 @@ void imx51_init_lowlevel(unsigned int cpufreq_mhz)
 	u32 r;
 	int rev = imx51_silicon_revision();
 
+	imx_disable_otg_controller(IOMEM(MX51_OTG_BASE_ADDR));
+
 	imx5_init_lowlevel();
 
 	/* disable write combine for TO 2 and lower revs */
diff --git a/arch/arm/mach-imx/imx53.c b/arch/arm/mach-imx/imx53.c
index b22929f749..f535de2fe5 100644
--- a/arch/arm/mach-imx/imx53.c
+++ b/arch/arm/mach-imx/imx53.c
@@ -22,6 +22,7 @@
 #include <mach/clock-imx51_53.h>
 #include <mach/generic.h>
 #include <mach/reset-reason.h>
+#include <mach/usb.h>
 
 #define SI_REV 0x48
 
@@ -88,6 +89,8 @@ void imx53_init_lowlevel_early(unsigned int cpufreq_mhz)
 	void __iomem *ccm = (void __iomem *)MX53_CCM_BASE_ADDR;
 	u32 r, cbcdr, cbcmr;
 
+	imx_disable_otg_controller(IOMEM(MX53_OTG_BASE_ADDR));
+
 	imx5_init_lowlevel();
 
 	/*
diff --git a/arch/arm/mach-imx/imx6.c b/arch/arm/mach-imx/imx6.c
index 3d95c9e374..1bd0914a0f 100644
--- a/arch/arm/mach-imx/imx6.c
+++ b/arch/arm/mach-imx/imx6.c
@@ -24,6 +24,7 @@
 #include <mach/imx6-anadig.h>
 #include <mach/imx6-regs.h>
 #include <mach/generic.h>
+#include <mach/usb.h>
 #include <asm/mmu.h>
 #include <asm/cache-l2x0.h>
 
@@ -52,6 +53,8 @@ static void imx6_init_lowlevel(void)
 	uint32_t periph_sel_2;
 	uint32_t reg;
 
+	imx_disable_otg_controller(IOMEM(MX6_OTG_BASE_ADDR));
+
 	/*
 	 * Set all MPROTx to be non-bufferable, trusted for R/W,
 	 * not forced to user-mode.
diff --git a/arch/arm/mach-imx/include/mach/usb.h b/arch/arm/mach-imx/include/mach/usb.h
index 85528d77e6..0188dd49f6 100644
--- a/arch/arm/mach-imx/include/mach/usb.h
+++ b/arch/arm/mach-imx/include/mach/usb.h
@@ -14,4 +14,27 @@
 int imx6_usb_phy2_disable_oc(void);
 int imx6_usb_phy2_enable(void);
 
+#define USBCMD	0x140
+#define USB_CMD_RUN_STOP	0x00000001
+
+/*
+ * imx_disable_otg_controller - disable the USB OTG controller
+ * @base: The base address of the controller
+ *
+ * When booting from USB the ROM just leaves the controller enabled. This can
+ * have bad side effects when for example we change PLL frequencies. In this
+ * case it is seen that the hub the board is connected to gets confused and USB
+ * is no longer working properly on the remote host. This function disables the
+ * OTG controller. It should be called before the clocks the controller hangs on
+ * is fiddled with.
+ */
+static inline void imx_disable_otg_controller(void __iomem *base)
+{
+	u32 r;
+
+	r = readl(base + USBCMD);
+	r &= ~USB_CMD_RUN_STOP;
+	writel(r, base + USBCMD);
+}
+
 #endif /* __MACH_USB_H_*/
-- 
2.18.0


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