Re: [PATCH v8 7/7] thermal/drivers/loongson2: Add Loongson-2K0300 support

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [Medium] thermal/drivers/loongson2: missing MFD_SYSCON dependency in Kconfig
- [Medium] thermal: loongson2: missing ADC delay in ls2k0300_thermal_hw_init()
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commit 10dff186e720aacd669123374d9a7f0a467f16da
Author: Binbin Zhou <zhoubinbin@loongson.cn>

thermal/drivers/loongson2: Add Loongson-2K0300 support

This commit adds thermal sensor support for the Loongson-2K0300 SoC, reading
calibration offsets from the CHIP ID syscon registers and falling back to an
old-fuse slope when the calibrated temperature falls outside the valid range.

> diff --git a/drivers/thermal/loongson2_thermal.c b/drivers/thermal/loongson2_thermal.c
> index d83aaa588c485..0a9d039c9ab8c 100644
> --- a/drivers/thermal/loongson2_thermal.c
> +++ b/drivers/thermal/loongson2_thermal.c

[ ... ]

> @@ -83,6 +118,101 @@ static int loongson2_thermal_set_trips(struct thermal_zone_device *tz, int low,
>  	return 0;
>  }
>  
> +static int ls2k0300_thermal_adc_to_temp_mc(struct loongson2_thermal_data *data, int slope)
> +{
> +	int raw_adc;
> +
> +	raw_adc = FIELD_GET(LOONGSON2_THSENS_OUT_11B_MASK,
> +			    readl(data->ctrl_reg + LOONGSON2_THSENS_OUT_REG));
> +
> +	return (raw_adc + data->calib_offset) * slope - LS2K0300_TEMP_OFFSET;
> +}

[ ... ]

> +static void ls2k0300_thermal_detect_old_fuse(struct device *dev,
> +					     struct loongson2_thermal_data *data)
> +{
> +	int temp;
> +
> +	temp = ls2k0300_thermal_adc_to_temp_mc(data, LS2K0300_TEMP_SLOPE);
> +
> +	if (temp < LOONGSON2_LOWEST_VALID_TEMP ||
> +	    temp > LOONGSON2_HIGHEST_VALID_TEMP) {
> +		dev_warn(dev, "calibrated temperature %d mC out of range [%d, %d], using old fuse formula",
> +			 temp, LOONGSON2_LOWEST_VALID_TEMP, LOONGSON2_HIGHEST_VALID_TEMP);
> +		data->flags = LS2K0300_UNCALIBRATED_FLAG;
> +		data->calib_offset = 0;
> +	}
> +}

[ ... ]

> +static int ls2k0300_thermal_hw_init(struct platform_device *pdev,
> +				    struct loongson2_thermal_data *data)
> +{
> +	struct device *dev = &pdev->dev;
> +	int ret;
> +
> +	data->regmap_cfg = syscon_regmap_lookup_by_phandle(dev->of_node, "loongson,chipid");
> +	if (IS_ERR(data->regmap_cfg))
> +		return PTR_ERR(data->regmap_cfg);

[Severity: Medium]
In drivers/thermal/loongson2_thermal.c, ls2k0300_thermal_hw_init()
unconditionally calls syscon_regmap_lookup_by_phandle(). When
CONFIG_MFD_SYSCON is not enabled, the stub in include/linux/mfd/syscon.h
returns ERR_PTR(-ENOTSUPP), causing loongson2_thermal_probe() to fail at
runtime on Loongson-2K0300.

Neither LOONGSON2_THERMAL in drivers/thermal/Kconfig nor LOONGARCH in
arch/loongarch/Kconfig selects or depends on MFD_SYSCON:

drivers/thermal/Kconfig:
    config LOONGSON2_THERMAL
        tristate "Loongson-2 SoC series thermal driver"
        depends on LOONGARCH || COMPILE_TEST
        depends on OF

Should LOONGSON2_THERMAL select MFD_SYSCON in Kconfig?

> +
> +	ret = ls2k0300_thermal_read_calib(data);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "failed to read calibration data");
> +
> +	writel(LS2K0300_THSENS_INIT_MASK, data->ctrl_reg + LS2K0300_THSENS_CFG_REG);
> +
> +	ls2k0300_thermal_detect_old_fuse(dev, data);

[Severity: Medium]
As reported by Sashiko on v7 [1], in drivers/thermal/loongson2_thermal.c,
ls2k0300_thermal_hw_init() writes LS2K0300_THSENS_INIT_MASK to
LS2K0300_THSENS_CFG_REG and immediately calls
ls2k0300_thermal_detect_old_fuse() without waiting for the sensor ADC to
finish its initial conversion.

If the sensor was not already enabled prior to probe,
ls2k0300_thermal_detect_old_fuse() -> ls2k0300_thermal_adc_to_temp_mc() can
read a reset or stale value of 0 from LOONGSON2_THSENS_OUT_REG. With
raw_adc == 0, any calibration offset of 622 or less produces a temperature
below LOONGSON2_LOWEST_VALID_TEMP (-40000 mC), permanently setting
LS2K0300_UNCALIBRATED_FLAG and clearing data->calib_offset.

Should there be a delay or readiness check after writing
LS2K0300_THSENS_CFG_REG before reading LOONGSON2_THSENS_OUT_REG?

[1] https://lore.kernel.org/r/93002842dcf01ec651a9711075f5967026b95987.1791512067.git.zhoubinbin@loongson.cn

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/cover.1793690276.git.zhoubinbin@loongson.cn?part=7