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

["Nilawar, Badal" <badal.nilawar@intel.com>]

On 07-09-2024 16:48, Raag Jadav wrote:
> On Fri, Sep 06, 2024 at 04:33:12PM +0530, Nilawar, Badal wrote:
>> On 06-09-2024 11:56, Anshuman Gupta wrote:
>>> On 2024-09-05 at 22:18:17 +0300, Raag Jadav wrote:
>>>> 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.
>>> IMO lets prefer the style which was used in this entire file,
>>> that is more readable along with other attributes.
>>> Idea behind switch was scalable attribute for future.
>>> It is something related to individual preference therefore
>>>    let's prefer the symmetry with other hwmon attributes.
>> I agree with this, but even if this approach is used file-wide, there were
>> concerns about using a switch case for a single case while implementing the
>> fan_input attribute.
>> https://patchwork.freedesktop.org/patch/607642/?series=136036&rev=4"
>> So I suggested to implement temp_input the way fan_input is implemented, at
>> least we should follow this approach to maintain symmetry with new
>> attributes. But in case if there is agreement to use file wide approach then
>> please follow that approach for fan_input as well.
> 
> Let's try to keep it simple and use whatever works for the case.
> I'm sure the driver is much easier to maintain with a few less lines.
Let's not break symmetry, whichever approach is being followed please 
maintain it file wide.

Regards,
Badal
> 
> Raag