Re: [cip-dev] [PATCH 4.19.y-cip 02/10] thermal: rcar_gen3_thermal: Remove temperature bound

From: "Pavel Machek" <pavel@ucw.cz>
To: Biju Das <biju.das.jz@bp.renesas.com>
Cc: cip-dev@lists.cip-project.org,
	Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>,
	Pavel Machek <pavel@denx.de>,
	Chris Paterson <chris.paterson2@renesas.com>,
	Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp.renesas.com>
Subject: Re: [cip-dev] [PATCH 4.19.y-cip 02/10] thermal: rcar_gen3_thermal: Remove temperature bound
Date: Wed, 26 Aug 2020 09:21:32 +0200	[thread overview]
Message-ID: <20200826072132.GA7244@amd> (raw)
In-Reply-To: <20200825132156.7839-3-biju.das.jz@bp.renesas.com>

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On Tue 2020-08-25 14:21:48, Biju Das wrote:
> From: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> 
> commit 0f510a2457cbbba18a98492bab1bf540be57ebd1 upstream.
> 
> The hardware manual states that the operation of the sensor is not
> guaranteed with temperatures above 125°C, not that the readings are
> invalid. Remove the bound check and try to deliver temperature readings
> even if we are outside the guaranteed operation range.

I'm tempted to ask "how was this tested?" :-).

Sometimes sensors have glitches producing very high values in normal
temperatures, and it such case clamping can be useful, but I'll assume
your sensor works ok.

Best regards,
								Pavel

> +++ b/drivers/thermal/rcar_gen3_thermal.c
> @@ -182,9 +182,7 @@ static int rcar_gen3_thermal_get_temp(void *devdata, int *temp)
>  				tsc->coef.a2);
>  	mcelsius = FIXPT_TO_MCELSIUS(val);
>  
> -	/* Make sure we are inside specifications */
> -	if ((mcelsius < MCELSIUS(-40)) || (mcelsius > MCELSIUS(125)))
> -		return -EIO;
> +	/* Guaranteed operating range is -40C to 125C. */
>  
>  	/* Round value to device granularity setting */
>  	*temp = rcar_gen3_thermal_round(mcelsius);

-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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