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From: Guenter Roeck <linux@roeck-us.net>
To: Lars Povlsen <lars.povlsen@microchip.com>
Cc: Jean Delvare <jdelvare@suse.com>,
	Microchip Linux Driver Support <UNGLinuxDriver@microchip.com>,
	linux-hwmon@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] hwmon: sparx5: Fix initial reading of temperature
Date: Thu, 3 Sep 2020 06:52:09 -0700	[thread overview]
Message-ID: <8ca270c9-5561-3176-61cf-7a9fbee10d1f@roeck-us.net> (raw)
In-Reply-To: <20200903134704.8949-1-lars.povlsen@microchip.com>

On 9/3/20 6:47 AM, Lars Povlsen wrote:
> If the temperature is read before the internal calibration is
> completed, the driver returns -EIO. Instead it should return -EAGAIN
> to encourage repeating the operation.
> 
> Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com>
> ---
>  drivers/hwmon/sparx5-temp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hwmon/sparx5-temp.c b/drivers/hwmon/sparx5-temp.c
> index 1a2b1026b026..98be48e3a22a 100644
> --- a/drivers/hwmon/sparx5-temp.c
> +++ b/drivers/hwmon/sparx5-temp.c
> @@ -56,7 +56,7 @@ static int s5_read(struct device *dev, enum hwmon_sensor_types type,
>  	case hwmon_temp_input:
>  		stat = readl_relaxed(hwmon->base + TEMP_STAT);
>  		if (!(stat & TEMP_STAT_VALID))
> -			return -EIO;
> +			return -EAGAIN;

The problem is that this may result in a hard loop and effectively hang the system,
or at least the calling process. It may be better to return -ENODATA in this situation.

Guenter

>  		value = stat & TEMP_STAT_TEMP;
>  		/*
>  		 * From register documentation:
> --
> 2.27.0
> 

WARNING: multiple messages have this Message-ID (diff)
From: Guenter Roeck <linux@roeck-us.net>
To: Lars Povlsen <lars.povlsen@microchip.com>
Cc: linux-hwmon@vger.kernel.org, Jean Delvare <jdelvare@suse.com>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Microchip Linux Driver Support <UNGLinuxDriver@microchip.com>
Subject: Re: [PATCH] hwmon: sparx5: Fix initial reading of temperature
Date: Thu, 3 Sep 2020 06:52:09 -0700	[thread overview]
Message-ID: <8ca270c9-5561-3176-61cf-7a9fbee10d1f@roeck-us.net> (raw)
In-Reply-To: <20200903134704.8949-1-lars.povlsen@microchip.com>

On 9/3/20 6:47 AM, Lars Povlsen wrote:
> If the temperature is read before the internal calibration is
> completed, the driver returns -EIO. Instead it should return -EAGAIN
> to encourage repeating the operation.
> 
> Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com>
> ---
>  drivers/hwmon/sparx5-temp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hwmon/sparx5-temp.c b/drivers/hwmon/sparx5-temp.c
> index 1a2b1026b026..98be48e3a22a 100644
> --- a/drivers/hwmon/sparx5-temp.c
> +++ b/drivers/hwmon/sparx5-temp.c
> @@ -56,7 +56,7 @@ static int s5_read(struct device *dev, enum hwmon_sensor_types type,
>  	case hwmon_temp_input:
>  		stat = readl_relaxed(hwmon->base + TEMP_STAT);
>  		if (!(stat & TEMP_STAT_VALID))
> -			return -EIO;
> +			return -EAGAIN;

The problem is that this may result in a hard loop and effectively hang the system,
or at least the calling process. It may be better to return -ENODATA in this situation.

Guenter

>  		value = stat & TEMP_STAT_TEMP;
>  		/*
>  		 * From register documentation:
> --
> 2.27.0
> 

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  reply	other threads:[~2020-09-03 14:18 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-03 13:47 [PATCH] hwmon: sparx5: Fix initial reading of temperature Lars Povlsen
2020-09-03 13:47 ` Lars Povlsen
2020-09-03 13:52 ` Guenter Roeck [this message]
2020-09-03 13:52   ` Guenter Roeck
2020-09-04  8:33   ` Lars Povlsen
2020-09-04  8:33     ` Lars Povlsen
2020-09-04 14:08     ` Guenter Roeck
2020-09-04 14:08       ` Guenter Roeck
2020-09-04 16:40 ` Guenter Roeck
2020-09-04 16:40   ` Guenter Roeck

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