[PATCH 1/1]mmc: fix division by zero when calculate mmc erase time

[PATCH 1/1]mmc: fix division by zero when calculate mmc erase time

[Chuanxiao Dong]

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);
 
 		erase_timeout = timeout_us / 1000;
 
-- 
1.6.6.1

Re: [PATCH 1/1]mmc: fix division by zero when calculate mmc erase time

[Marc Koschewski]

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?

Cheers,
Marc

>  
>  		erase_timeout = timeout_us / 1000;
>  
> -- 
> 1.6.6.1
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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> 
> 

-- 
Marc Koschewski

RE: [PATCH 1/1]mmc: fix division by zero when calculate mmc erase time

[Dong, Chuanxiao]

> -----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.

Thanks
Chuanxiao

Re: [PATCH 1/1]mmc: fix division by zero when calculate mmc erase time

[Marc Koschewski]

* 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
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
> 
> 

-- 
Marc Koschewski

RE: [PATCH 1/1]mmc: fix division by zero when calculate mmc erase time

[Dong, Chuanxiao]

> -----Original Message-----
> From: Marc Koschewski [mailto:marc@osknowledge.org]
> Sent: Thursday, February 24, 2011 8:23 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
> 
> * 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 {
OK. With the clock gating framework enabled... I agree. So, what do you think? Add a new variable is better?

Thanks
Chuanxiao

Re: [PATCH 1/1]mmc: fix division by zero when calculate mmc erase time

[Marc Koschewski]

* Dong, Chuanxiao <chuanxiao.dong@intel.com> [2011-02-24 20:25:21 +0800]:

> > -----Original Message-----
> > From: Marc Koschewski [mailto:marc@osknowledge.org]
> > Sent: Thursday, February 24, 2011 8:23 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
> > 
> > * 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 {
> 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@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
> 
> 

-- 
Marc Koschewski

Re: [PATCH 1/1]mmc: fix division by zero when calculate mmc erase time

[Linus Walleij]

2011/2/24 Chuanxiao Dong <chuanxiao.dong@intel.com>:
> 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>

Acked-by: Linus Walleij <linus.walleij@linaro.org>

Actually I think these divide-by zero bugs were there before since clock
0 is perfectly legal, we just didn't trigger them before.

Yours,
Linus Walleij