linux-kernel - Re: [PATCH 2/3] hwmon: Driver for OMAP3 temperature sensor

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Date:	Sun, 28 Dec 2014 00:24:47 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Pavel Machek <pavel@....cz>
Cc:	Sebastian Reichel <sre@...nel.org>,
	Pali Rohar <pali.rohar@...il.com>,
	Jean Delvare <jdelvare@...e.de>,
	Tony Lindgren <tony@...mide.com>,
	Benoît Cousson <bcousson@...libre.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-omap@...r.kernel.org, lm-sensors@...sensors.org,
	devicetree@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>
Subject: Re: [PATCH 2/3] hwmon: Driver for OMAP3 temperature sensor

On Sat, Dec 27, 2014 at 11:35:16PM +0100, Pavel Machek wrote:
> On Sat 2014-12-27 20:58:25, Pavel Machek wrote:
> > On Fri 2014-12-26 13:34:53, Sebastian Reichel wrote:
> > > OMAP34xx and OMAP36xx processors contain a register in the syscon area,
> > > which can be used to determine the SoCs temperature. This patch provides
> > > a DT based driver for the temperature sensor based on an older driver
> > > written by Peter De Schrijver for the Nokia N900 and N9.
> > > 
> > > Signed-off-by: Sebastian Reichel <sre@...nel.org>
> > > ---
> > >  drivers/hwmon/Kconfig      |   8 ++
> > >  drivers/hwmon/Makefile     |   1 +
> > >  drivers/hwmon/omap3-temp.c | 307 +++++++++++++++++++++++++++++++++++++++++++++
> > >  3 files changed, 316 insertions(+)
> > >  create mode 100644 drivers/hwmon/omap3-temp.c
> > 
> > When it hangs, it loops here:
> > 
> > do {
> > regmap_read(data->syscon, SYSCON_TEMP_REG,&temp_sensor_reg);
> > if ((temp_sensor_reg & eocz_mask) == level)
> >    return true;
> > printk("=");
> > }
> > while (ktime_us_delta(expire, ktime_get()) > 0);
> 
> And this fixes the hang, and makes level handling more readable.
> 
> Fix the timeout code, now it actually works. Driver still fails after
> a while.
> 
> Signed-off-by: Pavel Machek <pavel@....cz>
> 
> diff --git a/drivers/hwmon/omap3-temp.c b/drivers/hwmon/omap3-temp.c
> index 8a69604..1b8c768 100644
> --- a/drivers/hwmon/omap3-temp.c
> +++ b/drivers/hwmon/omap3-temp.c
> @@ -130,9 +130,7 @@ static inline bool wait_for_eocz(struct omap3_temp_data *data,
>  	ktime_t timeout, expire;
>  	u32 temp_sensor_reg, eocz_mask;
>  
>  	eocz_mask = BIT(data->hwdata->eocz_bit);
> -	level &= 1;
> -	level *= eocz_mask;
>  
>  	expire = ktime_add_ns(ktime_get(), max_delay);
>  	timeout = ktime_set(0, min_delay);
> @@ -140,9 +141,9 @@ static inline bool wait_for_eocz(struct omap3_temp_data *data,
>  	schedule_hrtimeout(&timeout, HRTIMER_MODE_REL);
>  	do {
>  		regmap_read(data->syscon, SYSCON_TEMP_REG, &temp_sensor_reg);
> -		if ((temp_sensor_reg & eocz_mask) == level)
> +		if (!!(temp_sensor_reg & eocz_mask) == level)
>  			return true;
> -	} while (ktime_us_delta(expire, ktime_get()) > 0);
> +	} while (ktime_after(expire, ktime_get()));
>  
Does this have to be a hard loop, without sleep ? I am a bit concerned that it
may loop for more than a ms.

Other than that, I assume we'll see an updated version with the coding style
issues and hang-up problems fixed.

Thanks,
Guenter
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