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Date: Tue, 4 Jun 2024 13:00:08 -0400 (EDT)
From: Nicolas Pitre <npitre@baylibre.com>
To: Julien Panis <jpanis@baylibre.com>
cc: "Rafael J. Wysocki" <rafael@kernel.org>, 
    Daniel Lezcano <daniel.lezcano@linaro.org>, 
    Zhang Rui <rui.zhang@intel.com>, Lukasz Luba <lukasz.luba@arm.com>, 
    Matthias Brugger <matthias.bgg@gmail.com>, 
    AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>, 
    linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, 
    linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org
Subject: Re: [PATCH v2] thermal/drivers/mediatek/lvts_thermal: Return error
 in case of invalid efuse data
In-Reply-To: <20240604-mtk-thermal-calib-check-v2-1-8f258254051d@baylibre.com>
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References: <20240604-mtk-thermal-calib-check-v2-1-8f258254051d@baylibre.com>
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On Tue, 4 Jun 2024, Julien Panis wrote:

> This patch prevents from registering thermal entries and letting the
> driver misbehave if efuse data is invalid. A device is not properly
> calibrated if the golden temperature is zero.
> 
> Fixes: f5f633b18234 ("thermal/drivers/mediatek: Add the Low Voltage Thermal Sensor driver")
> Signed-off-by: Julien Panis <jpanis@baylibre.com>

Reviewed-by: Nicolas Pitre <npitre@baylibre.com>

> ---
> Guard against invalid calibration data, following this discussion:
> https://lore.kernel.org/all/ad047631-16b8-42ce-8a8d-1429e6af4517@collabora.com/
> ---
> Changes in v2:
> - Add Fixes tag.
> - Link to v1: https://lore.kernel.org/r/20240603-mtk-thermal-calib-check-v1-1-5d6bf040414c@baylibre.com
> ---
>  drivers/thermal/mediatek/lvts_thermal.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/thermal/mediatek/lvts_thermal.c b/drivers/thermal/mediatek/lvts_thermal.c
> index 0bb3a495b56e..185d5a32711f 100644
> --- a/drivers/thermal/mediatek/lvts_thermal.c
> +++ b/drivers/thermal/mediatek/lvts_thermal.c
> @@ -769,7 +769,11 @@ static int lvts_golden_temp_init(struct device *dev, u8 *calib,
>  	 */
>  	gt = (((u32 *)calib)[0] >> lvts_data->gt_calib_bit_offset) & 0xff;
>  
> -	if (gt && gt < LVTS_GOLDEN_TEMP_MAX)
> +	/* A zero value for gt means that device has invalid efuse data */
> +	if (!gt)
> +		return -ENODATA;
> +
> +	if (gt < LVTS_GOLDEN_TEMP_MAX)
>  		golden_temp = gt;
>  
>  	golden_temp_offset = golden_temp * 500 + lvts_data->temp_offset;
> 
> ---
> base-commit: 632483ea8004edfadd035de36e1ab2c7c4f53158
> change-id: 20240603-mtk-thermal-calib-check-ba2ec24a1c32
> 
> Best regards,
> -- 
> Julien Panis <jpanis@baylibre.com>
> 
>