linux-kernel - Re: [PATCH 3/3] hwmon: (coretemp) Use a model-specific bitmask to read registers

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Message-ID: <20240415011946.GA12551@ranerica-svr.sc.intel.com>
Date: Sun, 14 Apr 2024 18:19:46 -0700
From: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To: "Zhang, Rui" <rui.zhang@...el.com>
Cc: "linux@...ck-us.net" <linux@...ck-us.net>,
	"Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
	"jdelvare@...e.com" <jdelvare@...e.com>,
	"srinivas.pandruvada@...ux.intel.com" <srinivas.pandruvada@...ux.intel.com>,
	"lukasz.luba@....com" <lukasz.luba@....com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
	"daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Neri, Ricardo" <ricardo.neri@...el.com>
Subject: Re: [PATCH 3/3] hwmon: (coretemp) Use a model-specific bitmask to
 read registers

On Sun, Apr 07, 2024 at 08:24:40AM +0000, Zhang, Rui wrote:
> On Fri, 2024-04-05 at 18:04 -0700, Ricardo Neri wrote:
> > The Intel Software Development manual defines states the temperature
> 
> I failed to parse this, is the above "states" redundant?

Sorry Rui! I missed this repy.

Ah, the commit message is wrong. I will do s/defines//

> 
> [...]
> 
> > digital readout as the bits [22:16] of the
> > IA32_[PACKAGE]_THERM_STATUS
> > registers. In recent processor, however, the range is [23:16]. Use a
> > model-specific bitmask to extract the temperature readout correctly.
> > 
> > diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
> > index 616bd1a5b864..5632e1b1dfb1 100644
> > --- a/drivers/hwmon/coretemp.c
> > +++ b/drivers/hwmon/coretemp.c
> > @@ -17,6 +17,7 @@
> >  #include <linux/sysfs.h>
> >  #include <linux/hwmon-sysfs.h>
> >  #include <linux/err.h>
> > +#include <linux/intel_tcc.h>
> >  #include <linux/mutex.h>
> >  #include <linux/list.h>
> >  #include <linux/platform_device.h>
> > @@ -404,6 +405,8 @@ static ssize_t show_temp(struct device *dev,
> >         tjmax = get_tjmax(tdata, dev);
> >         /* Check whether the time interval has elapsed */
> >         if (time_after(jiffies, tdata->last_updated + HZ)) {
> > +               u32 mask =
> > intel_tcc_get_temp_mask(is_pkg_temp_data(tdata));
> > +
> >                 rdmsr_on_cpu(tdata->cpu, tdata->status_reg, &eax,
> > &edx);
> >                 /*
> >                  * Ignore the valid bit. In all observed cases the
> > register
> > @@ -411,7 +414,7 @@ static ssize_t show_temp(struct device *dev,
> >                  * Return it instead of reporting an error which
> > doesn't
> >                  * really help at all.
> >                  */
> > -               tdata->temp = tjmax - ((eax >> 16) & 0x7f) * 1000;
> > +               tdata->temp = tjmax - ((eax >> 16) & mask) * 1000;
> >                 tdata->last_updated = jiffies;
> >         }
> > 
> Besides this one, we can also convert to use intel_tcc_get_tjmax() in
> get_tjmax().

I thought about this, but realized that the bitmask of TjMax is always
[23:16]; no need for a model check. If anything, intel_tcc_get_tjmax()
would remove some duplicated code. But coretemp.c would need to depend
on INTEL_TCC, which seems to be a non-starter.