linux-kernel - Re: [PATCH V2] ASoC: fsl_ssi: refine ipg clock usage in this module

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Message-ID: <20140912085446.GA8844@pengutronix.de>
Date:	Fri, 12 Sep 2014 10:54:46 +0200
From:	Markus Pargmann <mpa@...gutronix.de>
To:	Shengjiu Wang <shengjiu.wang@...escale.com>
Cc:	Nicolin Chen <nicoleotsuka@...il.com>, timur@...i.org,
	Li.Xiubo@...escale.com, lgirdwood@...il.com, broonie@...nel.org,
	perex@...ex.cz, tiwai@...e.de, alsa-devel@...a-project.org,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] ASoC: fsl_ssi: refine ipg clock usage in this module

On Fri, Sep 12, 2014 at 03:14:28PM +0800, Shengjiu Wang wrote:
> On Fri, Sep 12, 2014 at 08:17:06AM +0200, Markus Pargmann wrote:
> > Hi,
> > 
> > On Fri, Sep 12, 2014 at 10:01:12AM +0800, Shengjiu Wang wrote:
> > > On Thu, Sep 11, 2014 at 03:57:37PM -0700, Nicolin Chen wrote:
> > > > On Thu, Sep 11, 2014 at 01:38:29PM +0800, Shengjiu Wang wrote:
> > > > > Move the ipg clock enable and disable operation to startup and shutdown,
> > > > > that is only enable ipg clock when ssi is working. Keep clock is disabled
> > > > > when ssi is in idle.
> > > > > otherwise, _fsl_ssi_set_dai_fmt function need to be called in probe,
> > > > > so add ipg clock control for it.
> > > > 
> > > > It seems to be no objection so far against my last suggestion to
> > > > use regmap's mmio_clk() for named ipg clk only. So you may still
> > > > consider about that.
> > > >
> > > I think mmio_clk() can be put to another patch. and this patch only for clk_enable()
> > > and clk_disable() operation.
> > 
> > I would also prefer Nicolin's suggestion using regmap's mmio clk. I
> > think it may be better to not add this particular patch at all and just
> > go with the mmio_clk patch. It should be easy enough to just add the
> > clock names to the devicetrees. That way we can avoid all those clock
> > enable/disable function calls.
> >
> I considered if use Nicolin's suggestion, I still need ot add those
> enable/disable function calls, because I want to remove the enable/disable
> function call in fsl_ssi_imx_probe, then I need to add enable/disable 
> function call in _fsl_ssi_set_dai_fmt(), which is called in fsl_ssi_probe().
> _fsl_ssi_set_dai_fmt() need to access the registers.

I think Nicolin's suggestion was to check for a clock named "ipg". If it
exists, you can simply use devm_regmap_init_mmio_clk(). Otherwise you
could fallback to the old behaviour and get the first clock and enable
it without disabling it after the probe function.

After that, you could add the clock-names property to the devicetrees
and have the same result.

> 
> > >  
> > > > Anyway, I'd like to do thing in parallel. So I just simply tested
> > > > it on my side and its works fine, it may still need to be tested
> > > > by others though.
> > > > 
> > > > Nicolina
> > > 
> > > Hi Markus
> > > 
> > > could you please review it, and share your comments?
> > 
> > I think the clock enabling for AC97 is missing in your patch.
> > 
> I add clock enable in fsl_ssi_startup(), I think it is enough for AC97, does it?

No. We export ac97 read/write ops for the whole AC97 stuff. These may be
used outside of the usual startup/shutdown which is done for substreams.
It may work to have the ipg clock enabled in
fsl_ssi_ac97_read/fsl_ssi_ac97_write.

Best regards,

Markus

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