Re: [PATCH v1] drm/i915/hwmon: expose package temperature

[Raag Jadav <raag.jadav@intel.com>]

On Thu, Sep 05, 2024 at 07:39:31PM +0530, Anshuman Gupta wrote:
> On 2024-09-05 at 11:55:23 +0300, Raag Jadav wrote:
> > On Thu, Sep 05, 2024 at 11:56:15AM +0530, Nilawar, Badal wrote:
> > > 
> > > 
> > > On 28-08-2024 10:15, Raag Jadav wrote:
> > > > Add hwmon support for temp1_input attribute, which will expose package
> > > > temperature in millidegree Celsius. With this in place we can monitor
> > > > package temperature using lm-sensors tool.
> > > > 
> > > > $ sensors
> > > > i915-pci-0300
> > > > Adapter: PCI adapter
> > > > in0:         990.00 mV
> > > > fan1:        1260 RPM
> > > > temp1:        +45.0°C
> > > > power1:           N/A  (max =  35.00 W)
> > > > energy1:      12.62 kJ
> > > > 
> > > > Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/11276
> > > > Signed-off-by: Raag Jadav <raag.jadav@intel.com>
> > > > ---
> > > >   .../ABI/testing/sysfs-driver-intel-i915-hwmon |  8 ++++
> > > >   drivers/gpu/drm/i915/i915_hwmon.c             | 39 +++++++++++++++++++
> > > >   drivers/gpu/drm/i915/intel_mchbar_regs.h      |  4 ++
> > > >   3 files changed, 51 insertions(+)
> > > > 
> > > > diff --git a/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon b/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
> > > > index be4141a7522f..a885e5316d02 100644
> > > > --- a/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
> > > > +++ b/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
> > > > @@ -83,3 +83,11 @@ Contact:	intel-gfx@lists.freedesktop.org
> > > >   Description:	RO. Fan speed of device in RPM.
> > > >   		Only supported for particular Intel i915 graphics platforms.
> > > > +
> > > > +What:		/sys/bus/pci/drivers/i915/.../hwmon/hwmon<i>/temp1_input
> > > > +Date:		November 2024
> > > > +KernelVersion:	6.12
> > > > +Contact:	intel-gfx@lists.freedesktop.org
> > > > +Description:	RO. GPU package temperature in millidegree Celsius.
> > > > +
> > > > +		Only supported for particular Intel i915 graphics platforms.
> > > > diff --git a/drivers/gpu/drm/i915/i915_hwmon.c b/drivers/gpu/drm/i915/i915_hwmon.c
> > > > index 17d30f6b84b0..9f1a2300510b 100644
> > > > --- a/drivers/gpu/drm/i915/i915_hwmon.c
> > > > +++ b/drivers/gpu/drm/i915/i915_hwmon.c
> > > > @@ -7,6 +7,7 @@
> > > >   #include <linux/hwmon-sysfs.h>
> > > >   #include <linux/jiffies.h>
> > > >   #include <linux/types.h>
> > > > +#include <linux/units.h>
> > > >   #include "i915_drv.h"
> > > >   #include "i915_hwmon.h"
> > > > @@ -32,6 +33,7 @@
> > > >   struct hwm_reg {
> > > >   	i915_reg_t gt_perf_status;
> > > > +	i915_reg_t pkg_temp;
> > > >   	i915_reg_t pkg_power_sku_unit;
> > > >   	i915_reg_t pkg_power_sku;
> > > >   	i915_reg_t pkg_rapl_limit;
> > > > @@ -280,6 +282,7 @@ static const struct attribute_group *hwm_groups[] = {
> > > >   };
> > > >   static const struct hwmon_channel_info * const hwm_info[] = {
> > > > +	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
> > > >   	HWMON_CHANNEL_INFO(in, HWMON_I_INPUT),
> > > >   	HWMON_CHANNEL_INFO(power, HWMON_P_MAX | HWMON_P_RATED_MAX | HWMON_P_CRIT),
> > > >   	HWMON_CHANNEL_INFO(energy, HWMON_E_INPUT),
> > > > @@ -310,6 +313,36 @@ static int hwm_pcode_write_i1(struct drm_i915_private *i915, u32 uval)
> > > >   				  POWER_SETUP_SUBCOMMAND_WRITE_I1, 0, uval);
> > > >   }
> > > > +static umode_t
> > > > +hwm_temp_is_visible(const struct hwm_drvdata *ddat, u32 attr)
> > > > +{
> > > > +	struct i915_hwmon *hwmon = ddat->hwmon;
> > > > +
> > > > +	if (attr == hwmon_temp_input && i915_mmio_reg_valid(hwmon->rg.pkg_temp))
> > > > +		return 0444;
> > > > +
> > > > +	return 0;
> > > > +}
> > > > +
> > > > +static int
> > > > +hwm_temp_read(struct hwm_drvdata *ddat, u32 attr, long *val)
> > > > +{
> > > > +	struct i915_hwmon *hwmon = ddat->hwmon;
> > > > +	intel_wakeref_t wakeref;
> > > > +	u32 reg_val;
> > > > +
> > > > +	if (attr == hwmon_temp_input) {
> > > > +		with_intel_runtime_pm(ddat->uncore->rpm, wakeref)
> > > > +			reg_val = intel_uncore_read(ddat->uncore, hwmon->rg.pkg_temp);
> > > > +
> > > > +		/* HW register value is in degrees, convert to millidegrees. */
> > > > +		*val = REG_FIELD_GET(TEMP_MASK, reg_val) * MILLIDEGREE_PER_DEGREE;
> > > > +		return 0;
> > > > +	}
> > > > +
> > > > +	return -EOPNOTSUPP;
> > > > +}
> > > Let's try to have synergy between previous attribute, such as hwm_fan_input,
> > > and this one.
> > 
> > This one's simple enough to be inline IMHO.
> > Besides, it's already in synergy with hwm_in_read() which has similar
> > implementation.
> Agree this is pretty simple to have an any helper but IMO it would have been cleaner to have a switch
> like hwm_in_read() to return -EOPNOTSUPP in default case. i think that was reason switch case was 
> used in entire file.

Extending on the simplicity argument above, if() makes more sense for a single case.

Raag