> From: Jon Hunter <jon-hun...@ti.com>
>
> Depending on the OMAP3 boot mode the MUSB peripheral may or may not be
> accessible when the kernel starts.
>
> The OMAP3 can boot from several devices including USB. The sequence of the
> devices the OMAP will attempt to boot from is configured via the sys_boot
> pins on the device. If USB is one of the devices the OMAP boot ROM attempts
> to boot from on power-on, then the interface clock to the MUSB peripheral will
> be enabled by the boot ROM and the MUSB peripheral will be accessible when the
> kernel boots. However, if USB is not one of the devices OMAP will attempt to
> boot from then the interface clock is not enabled and the MUSB peripheral will
> not be accessible on start-up.
>
> If the MUSB peripheral is not accessible when the kernel boots, then the
> kernel will crash when attempting to access the OTG_SYSCONFIG in the function
> musb_platform_init(). The actual cause of the crash is the write to the
> OTG_SYSCONFIG register in the function usb_musb_pm_init() to reset the MUSB
> peripheral which occurs prior to calling musb_platform_init(). The function
> usb_musb_pm_init() does not check to see if the interface clock for the MUSB
> peripheral is enabled before writing to MUSB register. This write access does
> not generate a data-abort at this point, but because this write does not
> complete all future accesses to the MUSB controller will generate data-aborts
> regardless of whether the interface clock has been enabled at a later stage.
> The only way I have found to recover from this is resetting the device.
> My understanding is that the interconnect works in this way to prevent a bad
> access locking up the system.
>
> This patch crudely ensures the interface clock for the MUSB in the function
> usb_musb_pm_init() is enabled. This patch also ensures that the interface
> clock is disabled after the reset is complete. My reasoning for always
> disabling the clock rather than maintaing its state is:
>
> 1). If the MUSB peripheral is not being used then the interface clock should
> be disabled.
> 2). The musb_set_clock() function uses a static variable called "clk_on" to
> determine if the MUSB interface clock is on or off. On boot-up clk_on will be
> 0 and so this function assumes that the clock is off by default which may not
> be the case in the current code.
>
> I have also added a while-loop to wait for the reset of the MUSB module to
> complete before this function exits and the interface clock it disabled.
>
> Signed-off-by: Jon Hunter <jon-hun...@ti.com>
For what it's worth,
Tested-by: Anand Gadiyar <gadi...@ti.com>
on a 3430SDP.
> ---
> arch/arm/mach-omap2/usb-musb.c | 30 ++++++++++++++++++++++++++++--
> 1 files changed, 28 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/mach-omap2/usb-musb.c b/arch/arm/mach-omap2/usb-musb.c
> index 3efa19c..7cfe9bb 100644
> --- a/arch/arm/mach-omap2/usb-musb.c
> +++ b/arch/arm/mach-omap2/usb-musb.c
> @@ -32,25 +32,51 @@
> #include <mach/irqs.h>
> #include <mach/mux.h>
> #include <mach/usb.h>
> +#include "cm.h"
>
> #define OTG_SYSCONFIG 0x404
> #define OTG_SYSC_SOFTRESET BIT(1)
> +#define OTG_SYSSTATUS 0x408
> +#define OTG_SYSS_RESETDONE BIT(0)
>
> static void __init usb_musb_pm_init(void)
> {
> - void __iomem *otg_base;
> + void __iomem *cm_base, *otg_base;
> + unsigned int cm_iclken_core;
>
> if (!cpu_is_omap34xx())
> return;
>
> + cm_base = ioremap(OMAP3430_CM_BASE, SZ_4K);
> + if (WARN_ON(!cm_base))
> + return;
> +
> otg_base = ioremap(OMAP34XX_HSUSB_OTG_BASE, SZ_4K);
> - if (WARN_ON(!otg_base))
> + if (WARN_ON(!otg_base)) {
> + iounmap(cm_base);
> return;
> + }
> +
> + /* Ensure the inferface clock for MUSB is enabled */
> + cm_iclken_core = __raw_readl(OMAP34XX_CM_REGADDR(CORE_MOD,
> + CM_ICLKEN1));
> + __raw_writel((cm_iclken_core |
> + (1 << OMAP3430_EN_HSOTGUSB_SHIFT)),
> + OMAP34XX_CM_REGADDR(CORE_MOD, CM_ICLKEN1));
>
> /* Reset OTG controller. After reset, it will be in
> * force-idle, force-standby mode. */
> __raw_writel(OTG_SYSC_SOFTRESET, otg_base + OTG_SYSCONFIG);
>
> + while (!(OTG_SYSS_RESETDONE & __raw_readl(otg_base + OTG_SYSSTATUS)))
> + cpu_relax();
> +
> + /* Ensure the interface clock for MUSB is disabled */
> + __raw_writel((cm_iclken_core &
> + ~(1 << OMAP3430_EN_HSOTGUSB_SHIFT)),
> + OMAP34XX_CM_REGADDR(CORE_MOD, CM_ICLKEN1));
> +
> + iounmap(cm_base);
> iounmap(otg_base);
> }
>
> --
> 1.6.0.4
>
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