linux-kernel - Re: [PATCH] pwm: mc33xs2410: add support for temperature sensors

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Message-ID: <1bd48694-9760-4e6b-9138-4651d42ff032@roeck-us.net>
Date: Mon, 12 May 2025 06:04:33 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: dimitri.fedrau@...bherr.com, Uwe Kleine-König
 <ukleinek@...nel.org>, Jean Delvare <jdelvare@...e.com>
Cc: linux-pwm@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-hwmon@...r.kernel.org, Dimitri Fedrau <dima.fedrau@...il.com>
Subject: Re: [PATCH] pwm: mc33xs2410: add support for temperature sensors

On 5/12/25 04:26, Dimitri Fedrau via B4 Relay wrote:
> From: Dimitri Fedrau <dimitri.fedrau@...bherr.com>
> 
> The MC33XS2410 provides temperature sensors for the central die temperature
> and the four outputs. Additionally a common temperature warning threshold
> can be configured for the outputs. Add hwmon support for the sensors.
> 
> Signed-off-by: Dimitri Fedrau <dimitri.fedrau@...bherr.com>
> ---

> +
> +static int mc33xs2410_hwmon_read_out_status(struct spi_device *spi,
> +					    int channel, u16 *val)
> +{
> +	int ret;
> +
> +	ret = mc33xs2410_read_reg_diag(spi, MC33XS2410_OUT_STA(channel), val);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Bits latches high */
> +	return mc33xs2410_read_reg_diag(spi, MC33XS2410_OUT_STA(channel), val);

Is that double read of the same register needed ? If so, you'll probably
need a lock to prevent it from being executed from multiple threads at the
same time.

The comment "Bit latches high" doesn't really mean anything to me and doesn't
explain why the register needs to be read twice.

Thanks,
Guenter