linux-kernel - Re: [PATCH v6] ARM: imx: Add basic imx6q thermal driver

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Date:	Wed, 27 Jun 2012 15:48:49 +0200
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Robert Lee <rob.lee@...aro.org>
Cc:	kernel@...gutronix.de, shawn.guo@...aro.org,
	linux@....linux.org.uk, richard.zhao@...escale.com,
	dirk.behme@...bosch.com, amit.kachhap@...aro.org,
	amit.kucheria@...aro.org, lenb@...nel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linaro-dev@...ts.linaro.org, patches@...aro.org
Subject: Re: [PATCH v6] ARM: imx: Add basic imx6q thermal driver

On Tue, Jun 26, 2012 at 11:51:55PM -0500, Robert Lee wrote:
> +static inline int anatop_get_temp(int *temp, struct thermal_zone_device *tzdev)
> +{
> +	unsigned int n_meas;
> +	unsigned int reg;
> +	struct imx_anatop_tsdata *sd;
> +
> +	sd = &((struct imx_anatop_thdata *)tzdev->devdata)->sensor_data;
> +
> +
> +	do {
> +		/*
> +		 * Every time we measure the temperature, we will power on the
> +		 * temperature sensor, enable measurements, take a reading,
> +		 * disable measurements, power off the temperature sensor.
> +		 */
> +		sd->handle_suspend = false;
> +
> +		anatop_write_reg(sd->anatopmfd, HW_ANADIG_TEMPSENSE0, 0,
> +			BM_ANADIG_TEMPSENSE0_POWER_DOWN);
> +		anatop_write_reg(sd->anatopmfd, HW_ANADIG_TEMPSENSE0,
> +			BM_ANADIG_TEMPSENSE0_MEASURE_TEMP,
> +			BM_ANADIG_TEMPSENSE0_MEASURE_TEMP);
> +		/*
> +		 * According to the anatop temp sensor designers, it may require
> +		 * up to ~17us to complete a measurement (imx6q).
> +		 * But this timing isn't checked on every part nor is it
> +		 * specified in the datasheet,	so sleeping at least 1ms should
> +		 * provide plenty of time.  Sleeping longer than 1ms is ok so no
> +		 * need for usleep_range */
> +		msleep(1);
> +
> +		reg = anatop_read_reg(sd->anatopmfd, HW_ANADIG_TEMPSENSE0);
> +
> +		anatop_write_reg(sd->anatopmfd, HW_ANADIG_TEMPSENSE0, 0,
> +			BM_ANADIG_TEMPSENSE0_MEASURE_TEMP);
> +		anatop_write_reg(sd->anatopmfd, HW_ANADIG_TEMPSENSE0,
> +			BM_ANADIG_TEMPSENSE0_POWER_DOWN,
> +			BM_ANADIG_TEMPSENSE0_POWER_DOWN);
> +
> +	/* if we had a suspend and resume event, we will re-take the reading */
> +	} while (sd->handle_suspend);

[...]

> +static int anatop_thermal_suspend(struct platform_device *pdev,
> +					pm_message_t state)
> +{
> +	struct imx_anatop_thdata *dd = platform_get_drvdata(pdev);
> +	struct imx_anatop_tsdata *sd = &dd->sensor_data;
> +
> +	/* power off the sensor during suspend */
> +	anatop_write_reg(sd->anatopmfd, HW_ANADIG_TEMPSENSE0, 0,
> +		BM_ANADIG_TEMPSENSE0_MEASURE_TEMP);
> +
> +	anatop_write_reg(sd->anatopmfd, HW_ANADIG_TEMPSENSE0,
> +		BM_ANADIG_TEMPSENSE0_POWER_DOWN,
> +		BM_ANADIG_TEMPSENSE0_POWER_DOWN);
> +	return 0;
> +}
> +
> +static int anatop_thermal_resume(struct platform_device *pdev)
> +{
> +	struct imx_anatop_thdata *dd = platform_get_drvdata(pdev);
> +	struct imx_anatop_tsdata *sd = &dd->sensor_data;
> +
> +	sd->handle_suspend = true;
> +	return 0;
> +}

I don't know how to handle this properly or if it's really needed, but
the usage of this handle_suspend variable really looks suspicious. I've
never seen a driver looping around a while-suspended-in-between. Someone
else should have a look over this.

Sascha

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