Re: [PATCH 1/2] OMAP3 PM: move omap3 sleep to ddr

["Peter 'p2' De Schrijver" <peter.de-schrijver@nokia.com>]

On Fri, Nov 19, 2010 at 05:14:15PM +0100, ext Derrick, David wrote:
> >-----Original Message-----
> >From: Jean Pihet [mailto:jean.pihet@newoldbits.com] 
> >Sent: Friday, November 19, 2010 9:37 AM
> 
> >On Thu, Nov 18, 2010 at 7:34 PM, Jean Pihet <jean.pihet@newoldbits.com> >wrote:
> >> On Thu, Nov 18, 2010 at 7:27 PM, Tony Lindgren <tony@atomide.com> wrote:
> >>> * Jean Pihet <jean.pihet@newoldbits.com> [101118 10:06]:
> >>>> On Thu, Nov 18, 2010 at 6:52 PM, Tony Lindgren <tony@atomide.com> wrote:
> >>>>
> >>>> About the DPLL lock:
> >>>> 1) wait_sdrc_ok is only called when back from the non-OFF modes,
> >>>> 2) I checked that when running wait_sdrc_ok the CORE is already out of
> >>>> idle and the DPLL is already locked. Note: l-o code has no support for
> >>>> the voltages OFF and the external clocks OFF.
> >>>>
> >>>> What to conclude from 1) and 2)? In my test setup ot looks like
> >>>> wait_sdrc_ok is of no use, but I agree this a premature conclusion.
> >>>
> >>> Yeah we should figure out in which cases wait_sdrc_ok is needed.
> >>>
> >>> BTW, are you sure you're hitting core idle in your tests?
> >> Yes it is OK from the console messages and the counters values in
> >> /debug/pm_debug/count.
> >>
> >> Let me confirm asap with the PRCM registers dump.
> 
> >Here is what I experimented:
> >1) added a cache flush (v7_flush_kern_cache_all) just before WFI, in all >cases,
> >2) checked the real state entered in low power mode from the console
> >messages, the output of /debug/pm_debug/count and PRCM registers dump
> 
> >2) is OK, which means that the RET and OFF modes are correctly hit.
> 
> >Can I conclude from 1) that the wake-up code is not running from the
> >cache in RETention?
> 
> [Derrick, David] 
> 
> To add some context to the wait_sdrc_ok function and why it was added:
> 
> wait_sdrc_ok was added because the DLL takes 500 L3 clock cycles 
> to lock. So you do not want to go back to DDR before DLL is locked. Also, we 
> found some times DLL never locked so we introduced the DLL kick procedure to 
> force it to lock.
> 

The root cause for the DLL not locking has been found though and a
workaround implemented. So it should work now :) That still leaves the
500 L3 cycle delay though.

Cheers,

Peter.