Re: [PATCH v3] sdhci: Advertise 2.0v supply on SDIO host interface

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Thu, 2018-01-11 at 09:57 +0200, Adrian Hunter wrote:
> On 10/01/18 22:06, Ulf Hansson wrote:
> > On 10 January 2018 at 19:04, Andy Shevchenko
> > <andriy.shevchenko@linux.intel.com> wrote:
> > > On Wed, 2018-01-10 at 18:01 +0100, Ulf Hansson wrote:
> > > > On 10 January 2018 at 16:32, Andy Shevchenko
> > > > <andriy.shevchenko@linux.intel.com> wrote:
> > > > > On Intel Edison the Broadcom WiFi card, which is connected to
> > > > > SDIO,
> > > > > requires 2.0v, while the host, according to Intel Merrifield
> > > > > TRM,
> > > > > supports 1.8v supply only.
> > > > > +       /*
> > > > > +        * Without a regulator, SDHCI does not support 2.0v
> > > > > but we
> > > > > get
> > > > > +        * here because we advertised 2.0v support for
> > > > > compatibility
> > > > > +        * with the SDIO card's OCR. Map it to 1.8v for the
> > > > > purpose
> > > > > of
> > > > > +        * turning on the power.
> > > > > +        */
> > > > > +       if (IS_ERR(host->mmc->supply.vmmc) && vdd ==
> > > > > ilog2(MMC_VDD_20_21))
> > > > > +               vdd = ilog2(MMC_VDD_165_195);
> > > > 
> > > > Why not instead extend the range in sdhci_set_power_noreg() to
> > > > also
> > > > check for MMC_VDD_20_21?
> > > > 
> > > > Or is there a problem with that?
> > > 
> > > Do we have any grounds to do this in generic code?
> > > 
> > > Moreover, if we check for 2.0v what should we do in generic code?
> > > For my understanding
> > > 
> > > case _20_21:
> > >  pwr = _180;
> > 
> > Yeah, why is that a problem?
> 
> Shouldn't be a problem.  Just add a comment:
> 
> 		/*
> 		 * Without a regulator, SDHCI does not support 2.0v so
> we only
> 		 * get here if the driver deliberately added the 2.0v
> range to
> 		 * ocr_avail. Map it to 1.8V for the purpose of turning
> on the
> 		 * power.
> 		 */
> 		case MMC_VDD_20_21:
> 			pwr = SDHCI_POWER_180;
> 			break;

OK.
I will send v4 soon after giving some testing.

> > What does other variants do in this regards?
> 
> Use regulators or 3V I expect.

Yep, correct.

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy