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SubjectRe: [PATCH 1/1]mmc: fix division by zero when calculate mmc erase time
* Dong, Chuanxiao <chuanxiao.dong@intel.com> [2011-02-24 20:09:59 +0800]:

>
>
> > -----Original Message-----
> > From: Marc Koschewski [mailto:marc@osknowledge.org]
> > Sent: Thursday, February 24, 2011 7:38 PM
> > To: Dong, Chuanxiao
> > Cc: linux-mmc@vger.kernel.org; cjb@laptop.org; adrian.hunter@nokia.com;
> > linus.walleij@linaro.org; linux-kernel@vger.kernel.org
> > Subject: Re: [PATCH 1/1]mmc: fix division by zero when calculate mmc erase time
> >
> > Hi,
> >
> > * Chuanxiao Dong <chuanxiao.dong@intel.com> [2011-02-24 19:18:01 +0800]:
> >
> > > Since if clock gating feature is enabled, the clock frequency may be zero when
> > > host clock is gated. In such scenario, mmc_set_mmc_erase_timeout() may have a
> > > division by zero bug.
> > >
> > > So this patch used mmc_host_clk_rate() to fix this.
> > >
> > > Signed-off-by: Chuanxiao Dong <chuanxiao.dong@intel.com>
> > > ---
> > > drivers/mmc/core/core.c | 10 ++++++++--
> > > 1 files changed, 8 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> > > index 34a7e8c..12d0eb8 100644
> > > --- a/drivers/mmc/core/core.c
> > > +++ b/drivers/mmc/core/core.c
> > > @@ -1201,8 +1201,14 @@ static void mmc_set_mmc_erase_timeout(struct
> > mmc_card *card,
> > > * less but not that much less, so fudge it by multiplying by 2.
> > > */
> > > timeout_clks <<= 1;
> > > - timeout_us += (timeout_clks * 1000) /
> > > - (card->host->ios.clock / 1000);
> > > +
> > > + /*
> > > + * at this moment, host controller maybe clock gated, so make
> > > + * sure we can get a correct host clock freq.
> > > + */
> > > + if (mmc_host_clk_rate(card->host))
> > > + timeout_us += (timeout_clks * 1000) /
> > > + (mmc_host_clk_rate(card->host) / 1000);
> >
> > Why don't you just reuse mmc_host_clk_rate()'s result instead of calling it twice?
> This is a incline function and just return host->ios.clock. Reuse mmc_host_clk_rate()'s result need to add a new variable to save the value.

It's not inline on trunk and it spinlocks.

drivers/mmc/core/host.c:195

194 */
195 unsigned int mmc_host_clk_rate(struct mmc_host *host)
196 {
Cheers,
Marc

>
> Thanks
> Chuanxiao
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>

--
Marc Koschewski


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