* Dong, Chuanxiao <chuanxiao.dong@xxxxxxxxx> [2011-02-24 20:25:21 +0800]: > > -----Original Message----- > > From: Marc Koschewski [mailto:marc@xxxxxxxxxxxxxxx] > > Sent: Thursday, February 24, 2011 8:23 PM > > To: Dong, Chuanxiao > > Cc: linux-mmc@xxxxxxxxxxxxxxx; cjb@xxxxxxxxxx; adrian.hunter@xxxxxxxxx; > > linus.walleij@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx > > Subject: Re: [PATCH 1/1]mmc: fix division by zero when calculate mmc erase time > > > > * Dong, Chuanxiao <chuanxiao.dong@xxxxxxxxx> [2011-02-24 20:09:59 +0800]: > > > > > > > > > > > > -----Original Message----- > > > > From: Marc Koschewski [mailto:marc@xxxxxxxxxxxxxxx] > > > > Sent: Thursday, February 24, 2011 7:38 PM > > > > To: Dong, Chuanxiao > > > > Cc: linux-mmc@xxxxxxxxxxxxxxx; cjb@xxxxxxxxxx; adrian.hunter@xxxxxxxxx; > > > > linus.walleij@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx > > > > Subject: Re: [PATCH 1/1]mmc: fix division by zero when calculate mmc erase > > time > > > > > > > > Hi, > > > > > > > > * Chuanxiao Dong <chuanxiao.dong@xxxxxxxxx> [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@xxxxxxxxx> > > > > > --- > > > > > 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 { > OK. With the clock gating framework enabled... I agree. So, what do you think? Add a new variable is better? I personally would prefer the variable over the spinlock and function call, yes. And calling the same method with the same parameters on a line and another time on the next line is generally a bad idea I think. But maybe that's kind of a 'taste', moreover. It just hit my eye when I saw it... Cheers, Marc > > Thanks > Chuanxiao > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > > -- Marc Koschewski -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
