Re: [PATCH] rtc: snvs: improve timeout handling in snvs_rtc_enable()

Re: [PATCH] rtc: snvs: improve timeout handling in snvs_rtc_enable()

[Lothar Waßmann]

Shawn Guo writes:
> On Sat, Aug 18, 2012 at 10:10:08AM +0200, Lothar Waßmann wrote:
> > If snvs_rtc_enable() happens to be descheduled for a period longer
> > than the timout period, a timeout may be indicated even if the RTC
> > status has changed meanwhile. Force a status read at the end of the
> > timeout period to prevent bogus timeout errors.
> > 
> > 
> > Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
> > ---
> >  drivers/rtc/rtc-snvs.c |   22 +++++++++++++---------
> >  1 files changed, 13 insertions(+), 9 deletions(-)
> > 
> >  Compile tested only due to lack of HW.
> 
> Tested-by: Shawn Guo <shawn.guo@linaro.org>
> 
> A small nitpick below.
> 
> > 
> > diff --git a/drivers/rtc/rtc-snvs.c b/drivers/rtc/rtc-snvs.c
> > index 912f116..dc921b2 100644
> > --- a/drivers/rtc/rtc-snvs.c
> > +++ b/drivers/rtc/rtc-snvs.c
> > @@ -81,6 +81,13 @@ static void rtc_write_sync_lp(void __iomem *ioaddr)
> >  	}
> >  }
> >  
> > +static int snvs_rtc_enable_done(int enable, void __iomem *addr)
> 
> Can we rename parameter "addr" to "ioaddr" and put it before "enable",
> also change "enable" to bool?
> 
OK. The resulting assembler code of the patch below is identical to
the previous version of this patch.


Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
Tested-by: Shawn Guo <shawn.guo@linaro.org>
---
 drivers/rtc/rtc-snvs.c |   22 +++++++++++++---------
 1 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/drivers/rtc/rtc-snvs.c b/drivers/rtc/rtc-snvs.c
index 912f116..a757cb9 100644
--- a/drivers/rtc/rtc-snvs.c
+++ b/drivers/rtc/rtc-snvs.c
@@ -81,6 +81,13 @@ static void rtc_write_sync_lp(void __iomem *ioaddr)
 	}
 }
 
+static int snvs_rtc_enable_done(void __iomem *ioaddr, bool enable)
+{
+	u32 lpcr = readl(ioaddr + SNVS_LPCR);
+
+	return enable ^ !(lpcr & SNVS_LPCR_SRTC_ENV);
+}
+
 static int snvs_rtc_enable(struct snvs_rtc_data *data, bool enable)
 {
 	unsigned long timeout = jiffies + msecs_to_jiffies(1);
@@ -99,18 +106,15 @@ static int snvs_rtc_enable(struct snvs_rtc_data *data, bool enable)
 	spin_unlock_irqrestore(&data->lock, flags);
 
 	while (1) {
-		lpcr = readl(data->ioaddr + SNVS_LPCR);
+		if (snvs_rtc_enable_done(data->ioaddr, enable))
+			break;
 
-		if (enable) {
-			if (lpcr & SNVS_LPCR_SRTC_ENV)
-				break;
-		} else {
-			if (!(lpcr & SNVS_LPCR_SRTC_ENV))
+		if (time_after(jiffies, timeout)) {
+			if (snvs_rtc_enable_done(data->ioaddr, enable))
 				break;
+			else
+				return -ETIMEDOUT;
 		}
-
-		if (time_after(jiffies, timeout))
-			return -ETIMEDOUT;
 	}
 
 	return 0;

[rtc-linux] Re: [PATCH] rtc: snvs: improve timeout handling in snvs_rtc_enable()

[Alexandre Belloni]

Hi Shawn, Lothar,

On 18/08/2012 at 15:14:04 +0200, Lothar Wa=C3=9Fmann wrote :
> Shawn Guo writes:
> > On Sat, Aug 18, 2012 at 10:10:08AM +0200, Lothar Wa=C3=9Fmann wrote:
> > > If snvs_rtc_enable() happens to be descheduled for a period longer
> > > than the timout period, a timeout may be indicated even if the RTC
> > > status has changed meanwhile. Force a status read at the end of the
> > > timeout period to prevent bogus timeout errors.
> > >=20
> > >=20
> > > Signed-off-by: Lothar Wa=C3=9Fmann <LW@KARO-electronics.de>
> > > ---
> > >  drivers/rtc/rtc-snvs.c |   22 +++++++++++++---------
> > >  1 files changed, 13 insertions(+), 9 deletions(-)
> > >=20
> > >  Compile tested only due to lack of HW.
> >=20
> > Tested-by: Shawn Guo <shawn.guo@linaro.org>
> >=20

It seems that patch never made it mainline. Can you check if it is still
needed?


> > A small nitpick below.
> >=20
> > >=20
> > > diff --git a/drivers/rtc/rtc-snvs.c b/drivers/rtc/rtc-snvs.c
> > > index 912f116..dc921b2 100644
> > > --- a/drivers/rtc/rtc-snvs.c
> > > +++ b/drivers/rtc/rtc-snvs.c
> > > @@ -81,6 +81,13 @@ static void rtc_write_sync_lp(void __iomem *ioaddr=
)
> > >  	}
> > >  }
> > > =20
> > > +static int snvs_rtc_enable_done(int enable, void __iomem *addr)
> >=20
> > Can we rename parameter "addr" to "ioaddr" and put it before "enable",
> > also change "enable" to bool?
> >=20
> OK. The resulting assembler code of the patch below is identical to
> the previous version of this patch.
>=20
>=20
> Signed-off-by: Lothar Wa=C3=9Fmann <LW@KARO-electronics.de>
> Tested-by: Shawn Guo <shawn.guo@linaro.org>
> ---
>  drivers/rtc/rtc-snvs.c |   22 +++++++++++++---------
>  1 files changed, 13 insertions(+), 9 deletions(-)
>=20
> diff --git a/drivers/rtc/rtc-snvs.c b/drivers/rtc/rtc-snvs.c
> index 912f116..a757cb9 100644
> --- a/drivers/rtc/rtc-snvs.c
> +++ b/drivers/rtc/rtc-snvs.c
> @@ -81,6 +81,13 @@ static void rtc_write_sync_lp(void __iomem *ioaddr)
>  	}
>  }
> =20
> +static int snvs_rtc_enable_done(void __iomem *ioaddr, bool enable)
> +{
> +	u32 lpcr =3D readl(ioaddr + SNVS_LPCR);
> +
> +	return enable ^ !(lpcr & SNVS_LPCR_SRTC_ENV);
> +}
> +
>  static int snvs_rtc_enable(struct snvs_rtc_data *data, bool enable)
>  {
>  	unsigned long timeout =3D jiffies + msecs_to_jiffies(1);
> @@ -99,18 +106,15 @@ static int snvs_rtc_enable(struct snvs_rtc_data *dat=
a, bool enable)
>  	spin_unlock_irqrestore(&data->lock, flags);
> =20
>  	while (1) {
> -		lpcr =3D readl(data->ioaddr + SNVS_LPCR);
> +		if (snvs_rtc_enable_done(data->ioaddr, enable))
> +			break;
> =20
> -		if (enable) {
> -			if (lpcr & SNVS_LPCR_SRTC_ENV)
> -				break;
> -		} else {
> -			if (!(lpcr & SNVS_LPCR_SRTC_ENV))
> +		if (time_after(jiffies, timeout)) {
> +			if (snvs_rtc_enable_done(data->ioaddr, enable))
>  				break;
> +			else
> +				return -ETIMEDOUT;
>  		}
> -
> -		if (time_after(jiffies, timeout))
> -			return -ETIMEDOUT;
>  	}
> =20
>  	return 0;

--=20
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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