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

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

On Wed, 2009-06-24 at 15:21 +0200, ext Kevin Hilman wrote:
> Niilo Minkkinen <ext-niilo.1.minkkinen@nokia.com> writes:
> 
> > 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;
> 
> I thought about waiting for reset, but I decided that it wasn't
> necessary to wait since I wasn't going to write any other values
> after.  Why hold up the boot process when nothing else will be
> writing?
> 
> Kevin
> 

Sure you are right.
Thing I don't know, how near is the next access to musb ...
In my tests, this wait hasn't take even 1 ms (in units of jiffies), so I
don't know duration of it.
My comment anyhow can be think as a face-up.

-niilo-

> > SOFTRST & RESETDONE already defined in omap2430.h
> >
> >> +
> >> +	clk_disable(iclk);
> >> +	clk_put(iclk);
> >>  }
> >>  
> >>  #ifdef CONFIG_USB_MUSB_SOC