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

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Date:   Mon, 16 Apr 2018 15:02:50 +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 02:54:01 PM Daniel Lezcano wrote:
> On 16/04/2018 14:49, Bartlomiej Zolnierkiewicz wrote:
> > On Monday, April 16, 2018 02:41:48 PM Daniel Lezcano wrote:
> >> On 16/04/2018 14:35, Bartlomiej Zolnierkiewicz wrote:
> >>> 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;
> >>> }
> >>>
> >>
> >> But I don't get why it *should* ?
> > 
> > Because of hardware design.
> > 
> >> Shouldn't be the same with the 4412, it seems having the same sensor, no?
> > 
> > Probably same limitations apply to all SoCs (Exynos4412 has very similar
> > sensor) but the driver currently lacks the needed checks for them (it is
> > on TODO but other things have higher priority).
> 
> 
> I understand. Why the other boards are not reporting a critical value?

->tmu_read methods for other SoCs currently lack hardware limitations
checking so they don't return negative values (which before fix was passed
to code_to_temp() unchecked and was mapped to critical temperature value).

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