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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <f61f548b-0007-404e-9c9d-d84a2a657983@roeck-us.net>
Date:   Wed, 17 May 2023 05:30:52 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Yazen Ghannam <yazen.ghannam@....com>
Cc:     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 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.

> +
> +	*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));

> +	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 ?

>  
>  			*val = (regval & ZEN_CCD_TEMP_MASK) * 125 - 49000;
> @@ -376,8 +386,7 @@ static void k10temp_get_ccd_support(struct pci_dev *pdev,
>  	int i;
>  
>  	for (i = 0; i < limit; i++) {
> -		if (amd_smn_read(amd_pci_dev_to_node_id(pdev),
> -				 ZEN_CCD_TEMP(data->ccd_offset, i), &regval))
> +		if (read_ccd_temp_reg(data, i, &regval))
>  			continue;
>  
>  		if (regval & ZEN_CCD_TEMP_VALID)
> -- 
> 2.34.1
>