linux-kernel - Re: [PATCH v4] hwmon: (k10temp) Enable AMD3255 Proc to show negative temperature

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Message-ID: <d21d005d-569d-6105-e89c-7e6a7e84c701@roeck-us.net>
Date:   Thu, 27 Jul 2023 10:17:25 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Baskaran Kannan <Baski.Kannan@....com>, babu.moger@....com,
        Mario.Limonciello@....com, clemens@...isch.de, jdelvare@...e.com,
        linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] hwmon: (k10temp) Enable AMD3255 Proc to show negative
 temperature

On 7/27/23 09:21, 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.
> 
> A flag 'disp_negative' is added 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>
> ---
> V4: Changed probe from model number to model id.
> V3: https://lore.kernel.org/all/20230619165413.806450-1-Baski.Kannan@amd.com/
> 
>   drivers/hwmon/k10temp.c | 16 ++++++++++++++--
>   1 file changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hwmon/k10temp.c b/drivers/hwmon/k10temp.c
> index 7b177b9fbb09..18c4deae82ba 100644
> --- a/drivers/hwmon/k10temp.c
> +++ b/drivers/hwmon/k10temp.c
> @@ -77,6 +77,12 @@ static DEFINE_MUTEX(nb_smu_ind_mutex);
>   #define ZEN_CUR_TEMP_RANGE_SEL_MASK		BIT(19)
>   #define ZEN_CUR_TEMP_TJ_SEL_MASK		GENMASK(17, 16)
>   
> +/* AMD's Industrial processor 3255 supports temperature from -40 deg to 105 deg Celsius.
> + * Use the model name to identify 3255 CPUs and set a flag to display negative temperature.
> + * Do not round off to zero for negative Tctl or Tdie values if the flag is set
> + */

This is not the networking subsystem. Please use standard multi-line comments.
Never mind, applied after fixing the comment style.

Guenter

> +#define AMD_I3255_STR				"3255"
> +
>   struct k10temp_data {
>   	struct pci_dev *pdev;
>   	void (*read_htcreg)(struct pci_dev *pdev, u32 *regval);
> @@ -86,6 +92,7 @@ struct k10temp_data {
>   	u32 show_temp;
>   	bool is_zen;
>   	u32 ccd_offset;
> +	bool disp_negative;
>   };
>   
>   #define TCTL_BIT	0
> @@ -204,12 +211,12 @@ 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 +412,11 @@ 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 &&
> +	    strstr(boot_cpu_data.x86_model_id, AMD_I3255_STR)) {
> +		data->disp_negative = true;
> +	}
> +
>   	if (boot_cpu_data.x86 == 0x15 &&
>   	    ((boot_cpu_data.x86_model & 0xf0) == 0x60 ||
>   	     (boot_cpu_data.x86_model & 0xf0) == 0x70)) {