linux-kernel - Re: [PATCH 5/6] hwmon: (k10temp) Define helper function to read CCD temp

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Message-ID: <485dbd08-7616-09e3-c9eb-de0a1f78572b@amd.com>
Date:   Wed, 17 May 2023 10:09:12 -0400
From:   Yazen Ghannam <yazen.ghannam@....com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     yazen.ghannam@....com, x86@...nel.org,
        linux-kernel@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        markgross@...nel.org, hdegoede@...hat.com,
        Shyam-sundar.S-k@....com, linux-edac@...r.kernel.org,
        clemens@...isch.de, jdelvare@...e.com, linux-hwmon@...r.kernel.org,
        mario.limonciello@....com, babu.moger@....com
Subject: Re: [PATCH 5/6] hwmon: (k10temp) Define helper function to read CCD
 temp

On 5/17/23 8:30 AM, Guenter Roeck wrote:
> On Tue, May 16, 2023 at 03:24:29PM -0500, Yazen Ghannam wrote:
>> The CCD temperature register is read in two places. These reads are done
>> using an AMD SMN access, and a number of parameters are needed for the
>> operation.
>>
>> Move the SMN access and parameter gathering into a helper function in
>> order to simply the code flow. This also has a benefit of centralizing
>> the hardware register access in a single place in case fixes or special
>> decoding is required.
>>
>> Signed-off-by: Yazen Ghannam <yazen.ghannam@....com>
>> ---
>>  drivers/hwmon/k10temp.c | 19 ++++++++++++++-----
>>  1 file changed, 14 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/hwmon/k10temp.c b/drivers/hwmon/k10temp.c
>> index 6ea1fa62b7c1..06af1fe38af7 100644
>> --- a/drivers/hwmon/k10temp.c
>> +++ b/drivers/hwmon/k10temp.c
>> @@ -150,6 +150,18 @@ static void read_tempreg_nb_zen(struct pci_dev *pdev, u32 *regval)
>>  		*regval = 0;
>>  }
>>  
>> +static int read_ccd_temp_reg(struct k10temp_data *data, int ccd, u32 *regval)
>> +{
>> +	u16 node_id = amd_pci_dev_to_node_id(data->pdev);
>> +	u32 tmp;
>> +
>> +	if (amd_smn_read(node_id, ZEN_CCD_TEMP(data->ccd_offset, ccd), &tmp))
>> +		return -EINVAL;
> 
> As mentioned before, this is not appropriate. The error code
> from amd_smn_read() should be returned.
>

Okay, will do.

>> +
>> +	*regval = tmp;
> 
> This seems pointless. Why not just pass regval as parameter
> to amd_smn_read() ?
> 
> This function should be reduced to
> 
> 	return amd_smn_read(node_id, ZEN_CCD_TEMP(data->ccd_offset, ccd), regval));
> 

Yes, will do. I think I got carried away with the "don't save invalid
value" idea. But this isn't necessary if the caller checks the return
code and avoids using the value.

>> +	return 0;
>> +}
>> +
>>  static long get_raw_temp(struct k10temp_data *data)
>>  {
>>  	u32 regval;
>> @@ -214,9 +226,7 @@ static int k10temp_read_temp(struct device *dev, u32 attr, int channel,
>>  				*val = 0;
>>  			break;
>>  		case 2 ... 13:		/* Tccd{1-12} */
>> -			if (amd_smn_read(amd_pci_dev_to_node_id(data->pdev),
>> -					 ZEN_CCD_TEMP(data->ccd_offset, channel - 2),
>> -					 &regval))
>> +			if (read_ccd_temp_reg(data, channel - 2, &regval))
>>  				return -EINVAL;
> 
> Now this is really wrong, no matter what. Why bother replacing the
> error code in read_ccd_temp_reg() only to replace it again ?
>

Understood. Will fix like the other places.

Thanks,
Yazen