Re: [Intel-gfx] [PATCH 1/7] drm/i915/hwmon: Add HWMON infrastructure

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

On 21-09-2022 18:14, Andi Shyti wrote:
> Hi Badal,
> 
>> +struct hwm_reg {
>> +};
>> +
>> +struct hwm_drvdata {
>> +	struct i915_hwmon *hwmon;
>> +	struct intel_uncore *uncore;
>> +	struct device *hwmon_dev;
>> +	char name[12];
>> +};
>> +
>> +struct i915_hwmon {
>> +	struct hwm_drvdata ddat;
>> +	struct mutex hwmon_lock;		/* counter overflow logic and rmw */
>> +	struct hwm_reg rg;
>> +};
>> +
>> +static const struct hwmon_channel_info *hwm_info[] = {
>> +	NULL
>> +};
>> +
>> +static umode_t
>> +hwm_is_visible(const void *drvdata, enum hwmon_sensor_types type,
>> +	       u32 attr, int channel)
>> +{
>> +	switch (type) {
>> +	default:
>> +		return 0;
>> +	}
>> +}
>> +
>> +static int
>> +hwm_read(struct device *dev, enum hwmon_sensor_types type, u32 attr,
>> +	 int channel, long *val)
>> +{
>> +	switch (type) {
>> +	default:
>> +		return -EOPNOTSUPP;
>> +	}
>> +}
>> +
>> +static int
>> +hwm_write(struct device *dev, enum hwmon_sensor_types type, u32 attr,
>> +	  int channel, long val)
>> +{
>> +	switch (type) {
>> +	default:
>> +		return -EOPNOTSUPP;
>> +	}
>> +}
>> +
>> +static const struct hwmon_ops hwm_ops = {
>> +	.is_visible = hwm_is_visible,
>> +	.read = hwm_read,
>> +	.write = hwm_write,
>> +};
>> +
>> +static const struct hwmon_chip_info hwm_chip_info = {
>> +	.ops = &hwm_ops,
>> +	.info = hwm_info,
>> +};
> 
> what's the point for splitting so much? Can't you just send the
> hwmon driver all at once? With this patch you are not actually
> doing anything useful. In my opinion this should be squashed with
> the next ones.
During discussion in cover letter of rev0 series we decided to create 
separate infrastructure patch, as we wanted to keep kconfig, i915 hwmon 
structures and new file addition in separate patch. Further feature wise 
we kept adding new patches.
> 
>> +static void
>> +hwm_get_preregistration_info(struct drm_i915_private *i915)
>> +{
>> +}
>> +
>> +void i915_hwmon_register(struct drm_i915_private *i915)
>> +{
>> +	struct device *dev = i915->drm.dev;
>> +	struct i915_hwmon *hwmon;
>> +	struct device *hwmon_dev;
>> +	struct hwm_drvdata *ddat;
>> +
>> +	/* hwmon is available only for dGfx */
>> +	if (!IS_DGFX(i915))
>> +		return;
>> +
>> +	hwmon = kzalloc(sizeof(*hwmon), GFP_KERNEL);
> 
> why don't we use devm_kzalloc?
> 
>> +	if (!hwmon)
>> +		return;
>> +
>> +	i915->hwmon = hwmon;
>> +	mutex_init(&hwmon->hwmon_lock);
>> +	ddat = &hwmon->ddat;
>> +
>> +	ddat->hwmon = hwmon;
>> +	ddat->uncore = &i915->uncore;
>> +	snprintf(ddat->name, sizeof(ddat->name), "i915");
>> +
>> +	hwm_get_preregistration_info(i915);
>> +
>> +	/*  hwmon_dev points to device hwmon<i> */
>> +	hwmon_dev = hwmon_device_register_with_info(dev, ddat->name,
>> +						    ddat,
>> +						    &hwm_chip_info,
>> +						    NULL);
>> +	if (IS_ERR(hwmon_dev)) {
>> +		mutex_destroy(&hwmon->hwmon_lock);
> 
> there is not such a big need to destroy the mutex. Destroying
> mutexes is more useful when you actually are creating/destroying
> and there is some debug need. I don't think that's the case.
> 
> With the devm_kzalloc this would be just a return.
I think we can switch to devm_kzalloc.

Regards,
Badal
> 
> Andi
> 
>> +		i915->hwmon = NULL;
>> +		kfree(hwmon);
>> +		return;
>> +	}
>> +
>> +	ddat->hwmon_dev = hwmon_dev;
>> +}
>> +
>> +void i915_hwmon_unregister(struct drm_i915_private *i915)
>> +{
>> +	struct i915_hwmon *hwmon;
>> +	struct hwm_drvdata *ddat;
>> +
>> +	hwmon = fetch_and_zero(&i915->hwmon);
>> +	if (!hwmon)
>> +		return;
>> +
>> +	ddat = &hwmon->ddat;
>> +	if (ddat->hwmon_dev)
>> +		hwmon_device_unregister(ddat->hwmon_dev);
>> +
>> +	mutex_destroy(&hwmon->hwmon_lock);
>> +	kfree(hwmon);
>> +}
>> diff --git a/drivers/gpu/drm/i915/i915_hwmon.h b/drivers/gpu/drm/i915/i915_hwmon.h
>> new file mode 100644
>> index 000000000000..7ca9cf2c34c9
>> --- /dev/null
>> +++ b/drivers/gpu/drm/i915/i915_hwmon.h
>> @@ -0,0 +1,20 @@
>> +/* SPDX-License-Identifier: MIT */
>> +
>> +/*
>> + * Copyright © 2022 Intel Corporation
>> + */
>> +
>> +#ifndef __I915_HWMON_H__
>> +#define __I915_HWMON_H__
>> +
>> +struct drm_i915_private;
>> +
>> +#if IS_REACHABLE(CONFIG_HWMON)
>> +void i915_hwmon_register(struct drm_i915_private *i915);
>> +void i915_hwmon_unregister(struct drm_i915_private *i915);
>> +#else
>> +static inline void i915_hwmon_register(struct drm_i915_private *i915) { };
>> +static inline void i915_hwmon_unregister(struct drm_i915_private *i915) { };
>> +#endif
>> +
>> +#endif /* __I915_HWMON_H__ */
>> -- 
>> 2.25.1