linux-kernel - Re: [PATCH v3] hwmon: (k10temp) Enable AMD3255 Proc to show negative temperature

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Date:   Mon, 19 Jun 2023 10:07:17 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Baskaran Kannan <Baski.Kannan@....com>, Mario.Limonciello@....com,
        babu.moger@....com, clemens@...isch.de, jdelvare@...e.com,
        linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] hwmon: (k10temp) Enable AMD3255 Proc to show negative
 temperature

On 6/19/23 09:54, Baskaran Kannan wrote:
> Industrial processor i3255 supports temperatures -40 deg celcius
> to 105 deg Celcius. The current implementation of k10temp_read_temp
> rounds off any negative
> temperatures to '0'. To fix this, the following changes have been made.
> Added a flag 'disp_negative' to struct k10temp_data to support
> AMD i3255 processors. Flag 'disp_negative' is set if 3255 processor
> is found during k10temp_probe.  Flag 'disp_negative' is used to determine
> whether to round off negative temperatures to '0' in k10temp_read_temp.
> 
> Signed-off-by: Baskaran Kannan <Baski.Kannan@....com>

Now you have made changes you were not asked to make, extended the flag
to cover a range of processors instead of just i3255, and did not provide
a change log nor a comment in the code describing why processors with
certain model numbers should display negative temperatures.

Guenter

> ---
>   drivers/hwmon/k10temp.c | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hwmon/k10temp.c b/drivers/hwmon/k10temp.c
> index 7b177b9fbb09..2613420d43ff 100644
> --- a/drivers/hwmon/k10temp.c
> +++ b/drivers/hwmon/k10temp.c
> @@ -86,6 +86,7 @@ struct k10temp_data {
>   	u32 show_temp;
>   	bool is_zen;
>   	u32 ccd_offset;
> +	bool disp_negative;
>   };
>   
>   #define TCTL_BIT	0
> @@ -204,12 +205,12 @@ static int k10temp_read_temp(struct device *dev, u32 attr, int channel,
>   		switch (channel) {
>   		case 0:		/* Tctl */
>   			*val = get_raw_temp(data);
> -			if (*val < 0)
> +			if (*val < 0 && !data->disp_negative)
>   				*val = 0;
>   			break;
>   		case 1:		/* Tdie */
>   			*val = get_raw_temp(data) - data->temp_offset;
> -			if (*val < 0)
> +			if (*val < 0 && !data->disp_negative)
>   				*val = 0;
>   			break;
>   		case 2 ... 13:		/* Tccd{1-12} */
> @@ -405,6 +406,9 @@ static int k10temp_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>   	data->pdev = pdev;
>   	data->show_temp |= BIT(TCTL_BIT);	/* Always show Tctl */
>   
> +	if (boot_cpu_data.x86 == 0x17 && boot_cpu_data.x86_model < 0x8)
> +		data->disp_negative = true;
> +
>   	if (boot_cpu_data.x86 == 0x15 &&
>   	    ((boot_cpu_data.x86_model & 0xf0) == 0x60 ||
>   	     (boot_cpu_data.x86_model & 0xf0) == 0x70)) {