linux-kernel - Re: [PATCH 02/14] thermal: exynos: Propagate error value from tmu

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Date:   Mon, 16 Apr 2018 14:35:01 +0200
From:   Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     Eduardo Valentin <edubezval@...il.com>,
        Zhang Rui <rui.zhang@...el.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Kukjin Kim <kgene@...nel.org>,
        linux-samsung-soc@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH 02/14] thermal: exynos: Propagate error value from
 tmu_read()

On Monday, April 16, 2018 02:16:56 PM Daniel Lezcano wrote:
> On 16/04/2018 12:11, Bartlomiej Zolnierkiewicz wrote:
> > From: Marek Szyprowski <m.szyprowski@...sung.com>
> > 
> > tmu_read() in case of Exynos4210 might return error for out of bound
> > values. Current code ignores such value, what leads to reporting critical
> > temperature value. Add proper error code propagation to exynos_get_temp()
> > function.
> 
> For me the comment in the function exynos4210_tmu_read
> 
> /* "temp_code" should range between 75 and 175 */
> 
> ... is strange. I would double check this assertion before dealing with
> the error value.

static int exynos4210_tmu_read(struct exynos_tmu_data *data)
{
	int ret = readb(data->base + EXYNOS_TMU_REG_CURRENT_TEMP);

	/* "temp_code" should range between 75 and 175 */
	return (ret < 75 || ret > 175) ? -ENODATA : ret;
}

The value returned by Exynos4210 hardware should be > 75 && < 175 and
it is later used as the "temp_code" parameter for code_to_temp():

static int code_to_temp(struct exynos_tmu_data *data, u16 temp_code)
{
	if (data->cal_type == TYPE_ONE_POINT_TRIMMING)
		return temp_code - data->temp_error1 + EXYNOS_FIRST_POINT_TRIM;

	return (temp_code - data->temp_error1) *
		(EXYNOS_SECOND_POINT_TRIM - EXYNOS_FIRST_POINT_TRIM) /
		(data->temp_error2 - data->temp_error1) +
		EXYNOS_FIRST_POINT_TRIM;
}

so after the current fix the code finally matches the comment.

> > Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
> > CC: stable@...r.kernel.org # v4.6+
> > Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
> > ---
> >  drivers/thermal/samsung/exynos_tmu.c | 9 +++++++--
> >  1 file changed, 7 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/thermal/samsung/exynos_tmu.c b/drivers/thermal/samsung/exynos_tmu.c
> > index 986cbd0..ac83f72 100644
> > --- a/drivers/thermal/samsung/exynos_tmu.c
> > +++ b/drivers/thermal/samsung/exynos_tmu.c
> > @@ -892,6 +892,7 @@ static void exynos7_tmu_control(struct platform_device *pdev, bool on)
> >  static int exynos_get_temp(void *p, int *temp)
> >  {
> >  	struct exynos_tmu_data *data = p;
> > +	int value, ret = 0;
> >  
> >  	if (!data || !data->tmu_read || !data->enabled)
> >  		return -EINVAL;
> > @@ -899,12 +900,16 @@ static int exynos_get_temp(void *p, int *temp)
> >  	mutex_lock(&data->lock);
> >  	clk_enable(data->clk);
> >  
> > -	*temp = code_to_temp(data, data->tmu_read(data)) * MCELSIUS;
> > +	value = data->tmu_read(data);
> > +	if (value < 0)
> > +		ret = value;
> > +	else
> > +		*temp = code_to_temp(data, value) * MCELSIUS;
> >  
> >  	clk_disable(data->clk);
> >  	mutex_unlock(&data->lock);
> >  
> > -	return 0;
> > +	return ret;
> >  }
> >  
> >  #ifdef CONFIG_THERMAL_EMULATION

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics