linux-kernel - Re: Re: [PATCH] spi: pxa2xx: Add CS control clock quirk

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Message-ID: <20200213171836.GD10400@smile.fi.intel.com>
Date:   Thu, 13 Feb 2020 19:18:36 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     "Srivastava, Shobhit" <shobhit.srivastava@...el.com>
Cc:     Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        Rajat Jain <rajatja@...gle.com>,
        Daniel Mack <daniel@...que.org>,
        Haojian Zhuang <haojian.zhuang@...il.com>,
        Robert Jarzmik <robert.jarzmik@...e.fr>,
        Mark Brown <broonie@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Evan Green <evgreen@...omium.org>,
        "rajatxjain@...il.com" <rajatxjain@...il.com>,
        "evgreen@...gle.com" <evgreen@...gle.com>,
        "Muthukrishnan, Porselvan" <porselvan.muthukrishnan@...el.com>
Subject: Re: Re: [PATCH] spi: pxa2xx: Add CS control clock quirk

On Thu, Feb 13, 2020 at 04:57:24PM +0000, Srivastava, Shobhit wrote:
> > On 2/12/20 12:34 AM, Rajat Jain wrote:

...

> > I wonder is it enough to have this quick toggling only or is time or actually
> > number of clock cycles dependent? Now there is no delay between but I'm
> > thinking if it needs certain number cycles does this still work when using low
> > ssp_clk rates similar than in commit d0283eb2dbc1 ("spi:
> > pxa2xx: Add output control for multiple Intel LPSS chip selects").
> > 
> > I'm thinking can this be done only once after resume and may other LPSS
> > blocks need the same? I.e. should this be done in drivers/mfd/intel-lpss.c?

> This behavior is seen after S0ix resume, but it is not seen after S3 resume.

I already commented in the other thread about this.

Have you checked what's going on in intel_lpss_suspend() and
intel_lpss_resume() for your case?

Is intel_lpss_prepare() called during S0ix exit?

> I am thinking that it happens because we are not enabling the SSP after resume. 
> It is deferred until we need to send data. By enabling the SSP in resume, I don’t see the issue.
> For S3, I think BIOS re-enables the SSP in resume flow.

-- 
With Best Regards,
Andy Shevchenko