linux-kernel - Re: [PATCH v2 0/3] ARM: OMAP3: Fix McBSP2/3 hwmod setup for sidetone

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Date:	Mon, 18 Apr 2016 16:51:53 -0700
From:	Tony Lindgren <tony@...mide.com>
To:	Peter Ujfalusi <peter.ujfalusi@...com>
Cc:	Paul Walmsley <paul@...an.com>, jarkko.nikula@...mer.com,
	t-kristo@...com, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v2 0/3] ARM: OMAP3: Fix McBSP2/3 hwmod setup for sidetone

* Peter Ujfalusi <peter.ujfalusi@...com> [160415 12:52]:
> On 04/15/2016 06:16 PM, Tony Lindgren wrote:
> >> We can hack this around by adding HWMOD_NO_IDLEST to the sidetone hwmod I
> >> guess. As the sidetone does not have PRCM level control - it is part of McBSP.
> > 
> > Heh if they are using the same register bits for two separate modules,
> > then that's a bug for sure :) I think the sidetone module only has the
> > clock gating bit in the ST_SYSCONFIG.
> 
> Yes, the sidetone only has clock gating bit in ST_SYSCONFIG, but the hwmod has
> the prcm section which is identical of the corresponding McBSP hwmod prcm section.
> 
> Since we have only one MCBSP2_ICLK and only one bit in PRCM registers for it,
> this is a bug in the hwmod data for sure. Only the mcbsp hwmod should have
> prcm section and the sidetone hwmod is not needed IMO:
> It is a bug to have sidetone enabled when McBSP is not enabled and configured
> properly. The sidetone can not work w/o proper McBSP configuration.
> 
> If we were to keep both hwmods and add new set of pm_runtime calls for the
> mcbsp.sidetone, it will only increase/decrease the mcbsp_iclk enable count. It
> must never enable the clock itself since that is a bug in the SW.

OK makes sense. I'd prefer to keep it to match the hardware for the modules.

> > Then all these modules just sit on the L4 interconnet at
> > separate targets, including the clockdomain.
> 
> The McBSPi core and it's sidetone is in the same clock domain as the sidetone
> is using the McBSPi interface clock. It is kind of a leech ;)

Well they still are able to use the McBSP interface clock independently
AFAIK :)

Tony