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 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

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