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

[Kevin Hilman <khilman@deeprootsystems.com>]

Niilo Minkkinen <ext-niilo.1.minkkinen@nokia.com> writes:

> 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 ...

Next access of MUSB isn't until the driver starts, and even then,
there should be a clk_get(), clk_enable() before any other access to
the MUSB regs.

Kevin

> 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
>
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