Re: [PATCH 1/2] ARM: dts: msm8974: Hook up adsp-pil's xo clock

["Jonathan Neuschäfer" <j.neuschaefer-hi6Y0CQ0nG0@public.gmane.org>]

On Mon, Feb 20, 2017 at 09:45:04PM -0800, Bjorn Andersson wrote:
> On Mon 20 Feb 14:00 PST 2017, Andy Gross wrote:
> 
> > On Wed, Feb 15, 2017 at 05:51:56AM +0100, Jonathan Neuschäfer wrote:
> > > Without this patch (and with CONFIG_QCOM_ADSP_PIL), I get this error:
> > > 
> > > 	[    0.711529] qcom_adsp_pil adsp-pil: failed to get xo clock
> > > 	[    0.711540] remoteproc remoteproc0: releasing adsp-pil
> > > 
> > > With this patch, adsp-pil can initialize correctly.
> > > 
> > > Signed-off-by: Jonathan Neuschäfer <j.neuschaefer-hi6Y0CQ0nG0@public.gmane.org>
> 
> Reviewed-by: Bjorn Andersson <bjorn.andersson-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>

Thanks!

> The ADSP is running off a clock derived from XO, as such a vote for XO
> must be held while the ADSP is running. It's possible the all
> application CPUs hit idle after launching the ADSP, but before the ADSP
> firmware can communicate this need with the RPM, which would result in
> the votes hitting 0 and the RPM might gate the XO.
> 
> To prevent this the ADSP remoteproc driver must hold an extra vote with
> the RPM until the ADSP signals that it has cast its vote.
> 
> Unfortunately there are some issues with nested probe deferral in the
> clock framework, so we can't accurately describe the XO today and as
> we're still missing some last pieces of idle mechanism causing above
> events we can survive by faking it and using xo_board - for a little
> bit longer...

Ok, that makes sense.


Jonathan
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