linux-kernel - Re: [PATCH 3/7] mmc: sdhci: fix SDHCI_QUIRK2_CLOCK_DIV_ZERO

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Date:   Wed, 15 Apr 2020 18:03:02 +0200
From:   Michał Mirosław <mirq-linux@...e.qmqm.pl>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Suneel Garapati <suneel.garapati@...inx.com>,
        Kevin Liu <kliu5@...vell.com>,
        Michal Simek <michal.simek@...inx.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org
Subject: Re: [PATCH 3/7] mmc: sdhci: fix SDHCI_QUIRK2_CLOCK_DIV_ZERO_BROKEN

On Wed, Apr 15, 2020 at 04:06:02PM +0300, Adrian Hunter wrote:
> On 2/04/20 2:54 pm, Michał Mirosław wrote:
> > Fix returned clock rate for SDHCI_QUIRK2_CLOCK_DIV_ZERO_BROKEN case.
> 
> Does this change anything, because it looks the same to me?

The value of real_div is fixed this way. With previous code after
applying the quirk you would have real_div = 1 instead of real_div = 2.

Best Regards,
Michał Mirosław

> 
> > 
> > Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
> > Cc: stable@...nel.vger.org
> > Fixes: d1955c3a9a1d ("mmc: sdhci: add quirk SDHCI_QUIRK_CLOCK_DIV_ZERO_BROKEN")
> > ---
> >  drivers/mmc/host/sdhci.c | 10 +++++-----
> >  1 file changed, 5 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> > index b2dc4f1cfa5c..a043bf5e3565 100644
> > --- a/drivers/mmc/host/sdhci.c
> > +++ b/drivers/mmc/host/sdhci.c
> > @@ -1807,9 +1807,12 @@ u16 sdhci_calc_clk(struct sdhci_host *host, unsigned int clock,
> >  
> >  		if (!host->clk_mul || switch_base_clk) {
> >  			/* Version 3.00 divisors must be a multiple of 2. */
> > -			if (host->max_clk <= clock)
> > +			if (host->max_clk <= clock) {
> >  				div = 1;
> > -			else {
> > +				if ((host->quirks2 & SDHCI_QUIRK2_CLOCK_DIV_ZERO_BROKEN)
> > +					&& host->max_clk <= 25000000)
> > +					div = 2;
> > +			} else {
> >  				for (div = 2; div < SDHCI_MAX_DIV_SPEC_300;
> >  				     div += 2) {
> >  					if ((host->max_clk / div) <= clock)
> > @@ -1818,9 +1821,6 @@ u16 sdhci_calc_clk(struct sdhci_host *host, unsigned int clock,
> >  			}
> >  			real_div = div;
> >  			div >>= 1;
> > -			if ((host->quirks2 & SDHCI_QUIRK2_CLOCK_DIV_ZERO_BROKEN)
> > -				&& !div && host->max_clk <= 25000000)
> > -				div = 1;
> >  		}
> >  	} else {
> >  		/* Version 2.00 divisors must be a power of 2. */
> > 
>