linux-kernel - Re: [RFC] hwmon: (fam15h_power) Add bit masking for tdp

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Date:	Wed, 27 Jan 2016 14:45:38 +0800
From:	Huang Rui <ray.huang@....com>
To:	Gi-Oh Kim <gi-oh.kim@...fitbricks.com>
CC:	Guenter Roeck <linux@...ck-us.net>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Borislav Petkov <bp@...en8.de>
Subject: Re: [RFC] hwmon: (fam15h_power) Add bit masking for tdp_limit

On Tue, Jan 26, 2016 at 11:57:35AM +0100, Gi-Oh Kim wrote:
> 
> 
> On 26.01.2016 03:25, Huang Rui wrote:
> >On Mon, Jan 25, 2016 at 07:41:07PM +0800, Gioh Kim wrote:

> Thanks for your reply.
> I'm not completely sure that the reserved bits are always zero.
> Are they always zero?
> Or do we need bit-masking like following?
> 

Reserved bits aren't always zero. But here they are reserved for
ApmTdpLimit expansion.

Yes, we would better add bit-masking here. :-)

> -------------- 8< -----------------
> Subject: [PATCH] hwmon: (fam15h_power) Add bit masking for tdp_limit
> 
> Add bit masking to read ApmTdpLimit precisely
> 
> Signed-off-by: Gioh Kim <gi-oh.kim@...fitbricks.com>
> ---
>  drivers/hwmon/fam15h_power.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/hwmon/fam15h_power.c b/drivers/hwmon/fam15h_power.c
> index f77eb97..edbcf6c 100644
> --- a/drivers/hwmon/fam15h_power.c
> +++ b/drivers/hwmon/fam15h_power.c
> @@ -90,7 +90,11 @@ static ssize_t show_power(struct device *dev,
>      pci_bus_read_config_dword(f4->bus, PCI_DEVFN(PCI_SLOT(f4->devfn), 5),
>                    REG_TDP_LIMIT3, &val);
> 
> -    tdp_limit = val >> 16;
> +    if (boot_cpu_data.x86_model >= 0x60)
> +        tdp_limit = val >> 16;

You need add CPU family check and a comment to mention bit field
change. This updates since family 15h and model 60h.

if (boot_cpu_data.x86 == 0x15 && boot_cpu_data.x86_model >= 0x60)

Thanks,
Rui