linux-kernel - Re: [PATCH v8 5/5] thermal: mediatek: try again if first temp read is bogus

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Message-ID: <96e7aaf5-76ef-9356-84e2-ee1f747dafcd@linaro.org>
Date:   Wed, 25 Jan 2023 11:58:40 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Amjad Ouled-Ameur <aouledameur@...libre.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc:     linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Fabien Parent <fparent@...libre.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Rob Herring <robh@...nel.org>,
        Markus Schneider-Pargmann <msp@...libre.com>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Michael Kao <michael.kao@...iatek.com>
Subject: Re: [PATCH v8 5/5] thermal: mediatek: try again if first temp read is
 bogus

On 25/01/2023 10:50, Amjad Ouled-Ameur wrote:
> In mtk_thermal_bank_temperature, return -EAGAIN instead of 0
> on the first read of sensor that often are bogus values.
> 
> Signed-off-by: Michael Kao <michael.kao@...iatek.com>
> Signed-off-by: Hsin-Yi Wang <hsinyi@...omium.org>
> Signed-off-by: Amjad Ouled-Ameur <aouledameur@...libre.com>
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> ---
>   drivers/thermal/mtk_thermal.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/thermal/mtk_thermal.c b/drivers/thermal/mtk_thermal.c
> index b8e06f6c7c42..e7be450cd40a 100644
> --- a/drivers/thermal/mtk_thermal.c
> +++ b/drivers/thermal/mtk_thermal.c
> @@ -736,7 +736,7 @@ static int mtk_thermal_bank_temperature(struct mtk_thermal_bank *bank)
>   		 * not immediately shut down.
>   		 */
>   		if (temp > 200000)
> -			temp = 0;
> +			temp = -EAGAIN;

Did you try to add a delay between the bank init and the thermal zone 
device register (eg. 1ms) ?

May be the HW did not have time to initialize and capture a temperature 
before thermal_zone_device_register() is called (this one calls get_temp) ?

>   		if (temp > max)
>   			max = temp;
> 

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