Re: [PATCH] OMAP3: PM: reset USB OTG module on boot

[Niilo Minkkinen <ext-niilo.1.minkkinen@nokia.com>]

On Wed, 2009-06-24 at 02:27 +0200, ext Kevin Hilman wrote:
> Rather than simply setting force-idle mode on boot, do a reset of the
> OTG module.  This really ensures that any bootloader/bootstrap code
> that leaves it active will not prevent future retention.  After reset,
> OTG module will be in force-idle, force-standby mode.
> 
> In addition, ensure that the iclk is enabled before attempting a write
> to the module SYSCONFIG register.
> 
> Problem reported by Mike Chan <mikechan@google.com>
> 
> Tested-by: Mike Chan <mikechan@google.com>
> Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
> ---
> If no comments/issues, this will be applied to PM branch and
> backported to pm-2.6.29.
> 
>  arch/arm/mach-omap2/usb-musb.c |   21 ++++++++++++++++++---
>  1 files changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/mach-omap2/usb-musb.c b/arch/arm/mach-omap2/usb-musb.c
> index d85296d..85731b8 100644
> --- a/arch/arm/mach-omap2/usb-musb.c
> +++ b/arch/arm/mach-omap2/usb-musb.c
> @@ -32,12 +32,27 @@
>  #include <mach/usb.h>
>  
>  #define OTG_SYSCONFIG	(OMAP34XX_HSUSB_OTG_BASE + 0x404)
> +#define OTG_SYSC_SOFTRESET BIT(1)
>  
>  static void __init usb_musb_pm_init(void)
>  {
> -	/* Ensure force-idle mode for OTG controller */
> -	if (cpu_is_omap34xx())
> -		omap_writel(0, OTG_SYSCONFIG);
> +	struct clk *iclk;
> +
> +	if (!cpu_is_omap34xx())
> +		return;
> +
> +	iclk = clk_get(NULL, "hsotgusb_ick");
> +	if (WARN_ON(!iclk))
> +		return;
> +
> +	clk_enable(iclk);
> +
> +	/* Reset OTG controller.  After reset, it will be in
> +	 * force-idle, force-standby mode. */
> +	omap_writel(OTG_SYSC_SOFTRESET, OTG_SYSCONFIG);

Do you think, this is safe to do w/o waiting reset to be finished
like :  ?

+       omap_writel( SOFTRST, OTG_SYSCONFIG );  /* acquire RESET */
+       start = jiffies;
+       timeout = start + msecs_to_jiffies(10); /* max 10 ms */
+       while (!time_after(jiffies, timeout)) /* wait until RESET OK */
+               if ( omap_readl(OTG_SYSSTATUS) & RESETDONE )
+                       break;

SOFTRST & RESETDONE already defined in omap2430.h

> +
> +	clk_disable(iclk);
> +	clk_put(iclk);
>  }
>  
>  #ifdef CONFIG_USB_MUSB_SOC