Date:   Sat, 29 Jun 2019 08:33:08 +0800
From:   Wu Hao <hao.wu@...el.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     mdf@...nel.org, linux-fpga@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        linux-hwmon@...r.kernel.org, jdelvare@...e.com, atull@...nel.org,
        gregkh@...uxfoundation.org, Luwei Kang <luwei.kang@...el.com>,
        Xu Yilun <yilun.xu@...el.com>
Subject: Re: [PATCH v4 3/3] fpga: dfl: fme: add power management support

On Fri, Jun 28, 2019 at 10:55:14AM -0700, Guenter Roeck wrote:
> On Thu, Jun 27, 2019 at 12:53:38PM +0800, Wu Hao wrote:
> > This patch adds support for power management private feature under
> > FPGA Management Engine (FME). This private feature driver registers
> > a hwmon for power (power1_input), thresholds information, e.g.
> > (power1_max / crit / max_alarm / crit_alarm) and also read-only sysfs
> > interfaces for other power management information. For configuration,
> > user could write threshold values via above power1_max / crit sysfs
> > interface under hwmon too.
> > 
> > Signed-off-by: Luwei Kang <luwei.kang@...el.com>
> > Signed-off-by: Xu Yilun <yilun.xu@...el.com>
> > Signed-off-by: Wu Hao <hao.wu@...el.com>
> > ---
> > v2: create a dfl_fme_power hwmon to expose power sysfs interfaces.
> >     move all sysfs interfaces under hwmon
> >         consumed          --> hwmon power1_input
> >         threshold1        --> hwmon power1_cap
> >         threshold2        --> hwmon power1_crit
> >         threshold1_status --> hwmon power1_cap_status
> >         threshold2_status --> hwmon power1_crit_status
> >         xeon_limit        --> hwmon power1_xeon_limit
> >         fpga_limit        --> hwmon power1_fpga_limit
> 
> How do those limits differ from the other limits ?
> We do have powerX_cap and powerX_cap_max, and from the context
> it appears that you could possibly at least use power1_cap_max
> (and power1_cap instead of power1_max) instead of
> power1_fpga_limit.

Thanks a lot for the review and comments.

Actually xeon/fpga_limit are introduced for different purpose. It shows
the power limit of CPU and FPGA, that may be useful in some integrated
solution, e.g. CPU and FPGA shares power. We should never these
interfaces as throttling thresholds.

> 
> >         ltr               --> hwmon power1_ltr
> > v3: rename some hwmon sysfs interfaces to follow hwmon ABI.
> > 	power1_cap         --> power1_max
> > 	power1_cap_status  --> power1_max_alarm
> > 	power1_crit_status --> power1_crit_alarm
> 
> power1_cap is standard ABI, and since the value is enforced by HW,
> it should be usable.

As you see, in thermal management, threshold1 and threshold2 are
mapped to temp1_max_alarm and temp1_crit_alarm. So we feel that if
it will be friendly to user that we keep using max_alarm and crit_alarm
in power management for threshold1 and threshold2 too.

Do you think if we can keep this, or it's better to switch back to
power1_cap?


> 
> >     update sysfs doc for above sysfs interface changes.
> >     replace scnprintf with sprintf in sysfs interface.
> > v4: use HWMON_CHANNEL_INFO.
> >     update date in sysfs doc.
> > ---
> >  Documentation/ABI/testing/sysfs-platform-dfl-fme |  67 +++++++
> >  drivers/fpga/dfl-fme-main.c                      | 221 +++++++++++++++++++++++
> >  2 files changed, 288 insertions(+)
> > 
> > diff --git a/Documentation/ABI/testing/sysfs-platform-dfl-fme b/Documentation/ABI/testing/sysfs-platform-dfl-fme
> > index 2cd17dc..a669548 100644
> > --- a/Documentation/ABI/testing/sysfs-platform-dfl-fme
> > +++ b/Documentation/ABI/testing/sysfs-platform-dfl-fme
> > @@ -127,6 +127,7 @@ Contact:	Wu Hao <hao.wu@...el.com>
> >  Description:	Read-Only. Read this file to get the name of hwmon device, it
> >  		supports values:
> >  		    'dfl_fme_thermal' - thermal hwmon device name
> > +		    'dfl_fme_power'   - power hwmon device name
> >  
> >  What:		/sys/bus/platform/devices/dfl-fme.0/hwmon/hwmonX/temp1_input
> >  Date:		June 2019
> > @@ -183,3 +184,69 @@ Description:	Read-Only. Read this file to get the policy of hardware threshold1
> >  		(see 'temp1_max'). It only supports two values (policies):
> >  		    0 - AP2 state (90% throttling)
> >  		    1 - AP1 state (50% throttling)
> > +
> > +What:		/sys/bus/platform/devices/dfl-fme.0/hwmon/hwmonX/power1_input
> > +Date:		June 2019
> > +KernelVersion:	5.3
> > +Contact:	Wu Hao <hao.wu@...el.com>
> > +Description:	Read-Only. It returns current FPGA power consumption in uW.
> > +
> > +What:		/sys/bus/platform/devices/dfl-fme.0/hwmon/hwmonX/power1_max
> > +Date:		June 2019
> > +KernelVersion:	5.3
> > +Contact:	Wu Hao <hao.wu@...el.com>
> > +Description:	Read-Write. Read this file to get current hardware power
> > +		threshold1 in uW. If power consumption rises at or above
> > +		this threshold, hardware starts 50% throttling.
> > +		Write this file to set current hardware power threshold1 in uW.
> > +		As hardware only accepts values in Watts, so input value will
> > +		be round down per Watts (< 1 watts part will be discarded).
> > +		Write fails with -EINVAL if input parsing fails or input isn't
> > +		in the valid range (0 - 127000000 uW).
> > +
> > +What:		/sys/bus/platform/devices/dfl-fme.0/hwmon/hwmonX/power1_crit
> > +Date:		June 2019
> > +KernelVersion:	5.3
> > +Contact:	Wu Hao <hao.wu@...el.com>
> > +Description:	Read-Write. Read this file to get current hardware power
> > +		threshold2 in uW. If power consumption rises at or above
> > +		this threshold, hardware starts 90% throttling.
> > +		Write this file to set current hardware power threshold2 in uW.
> > +		As hardware only accepts values in Watts, so input value will
> > +		be round down per Watts (< 1 watts part will be discarded).
> > +		Write fails with -EINVAL if input parsing fails or input isn't
> > +		in the valid range (0 - 127000000 uW).
> > +
> > +What:		/sys/bus/platform/devices/dfl-fme.0/hwmon/hwmonX/power1_max_alarm
> > +Date:		June 2019
> > +KernelVersion:	5.3
> > +Contact:	Wu Hao <hao.wu@...el.com>
> > +Description:	Read-only. It returns 1 if power consumption is currently at or
> > +		above hardware threshold1 (see 'power1_max'), otherwise 0.
> > +
> > +What:		/sys/bus/platform/devices/dfl-fme.0/hwmon/hwmonX/power1_crit_alarm
> > +Date:		June 2019
> > +KernelVersion:	5.3
> > +Contact:	Wu Hao <hao.wu@...el.com>
> > +Description:	Read-only. It returns 1 if power consumption is currently at or
> > +		above hardware threshold2 (see 'power1_crit'), otherwise 0.
> > +
> > +What:		/sys/bus/platform/devices/dfl-fme.0/hwmon/hwmonX/power1_xeon_limit
> > +Date:		June 2019
> > +KernelVersion:	5.3
> > +Contact:	Wu Hao <hao.wu@...el.com>
> > +Description:	Read-Only. It returns power limit for XEON in uW.
> > +
> > +What:		/sys/bus/platform/devices/dfl-fme.0/hwmon/hwmonX/power1_fpga_limit
> > +Date:		June 2019
> > +KernelVersion:	5.3
> > +Contact:	Wu Hao <hao.wu@...el.com>
> > +Description:	Read-Only. It returns power limit for FPGA in uW.
> > +
> > +What:		/sys/bus/platform/devices/dfl-fme.0/hwmon/hwmonX/power1_ltr
> > +Date:		June 2019
> > +KernelVersion:	5.3
> > +Contact:	Wu Hao <hao.wu@...el.com>
> > +Description:	Read-only. Read this file to get current Latency Tolerance
> > +		Reporting (ltr) value. This ltr impacts the CPU low power
> > +		state in integrated solution.
> 
> Does that attribute add any value without any kind of unit or an explanation
> of its meaning ? What is userspace supposed to do with that information ?
> Without context, it is just a meaningless number.

I should add more description here, will fix it in the next version.

> 
> Also, it appears that the information is supposed to be passed to power
> management via the set_latency_tolerance() callback. If so, it would be
> reported there. Would it possibly make more sense to use that interface ?

If I remember correctly set_latency_tolerance is used to communicate a tolerance
to device, but actually this is a read-only value, to indicate latency tolerance
requirement for memory access from FPGA device, as you know FPGA could be
programmed for different workloads, and different workloads may have different
latency requirements, if workloads in FPGA don't have any need for immediate
memory access, then it would be safe for deeper sleep state of system memory.

> 
> > diff --git a/drivers/fpga/dfl-fme-main.c b/drivers/fpga/dfl-fme-main.c
> > index 59ff9f1..9225b68 100644
> > --- a/drivers/fpga/dfl-fme-main.c
> > +++ b/drivers/fpga/dfl-fme-main.c
> > @@ -400,6 +400,223 @@ static void fme_thermal_mgmt_uinit(struct platform_device *pdev,
> >  	.uinit = fme_thermal_mgmt_uinit,
> >  };
> >  
> > +#define FME_PWR_STATUS		0x8
> > +#define FME_LATENCY_TOLERANCE	BIT_ULL(18)
> > +#define PWR_CONSUMED		GENMASK_ULL(17, 0)
> > +
> > +#define FME_PWR_THRESHOLD	0x10
> > +#define PWR_THRESHOLD1		GENMASK_ULL(6, 0)	/* in Watts */
> > +#define PWR_THRESHOLD2		GENMASK_ULL(14, 8)	/* in Watts */
> > +#define PWR_THRESHOLD_MAX	0x7f			/* in Watts */
> > +#define PWR_THRESHOLD1_STATUS	BIT_ULL(16)
> > +#define PWR_THRESHOLD2_STATUS	BIT_ULL(17)
> > +
> > +#define FME_PWR_XEON_LIMIT	0x18
> > +#define XEON_PWR_LIMIT		GENMASK_ULL(14, 0)	/* in 0.1 Watts */
> > +#define XEON_PWR_EN		BIT_ULL(15)
> > +#define FME_PWR_FPGA_LIMIT	0x20
> > +#define FPGA_PWR_LIMIT		GENMASK_ULL(14, 0)	/* in 0.1 Watts */
> > +#define FPGA_PWR_EN		BIT_ULL(15)
> > +
> > +#define PWR_THRESHOLD_MAX_IN_UW (PWR_THRESHOLD_MAX * 1000000)
> > +
> > +static int power_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
> > +			    u32 attr, int channel, long *val)
> > +{
> > +	struct dfl_feature *feature = dev_get_drvdata(dev);
> > +	u64 v;
> > +
> > +	switch (attr) {
> > +	case hwmon_power_input:
> > +		v = readq(feature->ioaddr + FME_PWR_STATUS);
> > +		*val = (long)(FIELD_GET(PWR_CONSUMED, v) * 1000000);
> > +		break;
> > +	case hwmon_power_max:
> > +		v = readq(feature->ioaddr + FME_PWR_THRESHOLD);
> > +		*val = (long)(FIELD_GET(PWR_THRESHOLD1, v) * 1000000);
> > +		break;
> > +	case hwmon_power_crit:
> > +		v = readq(feature->ioaddr + FME_PWR_THRESHOLD);
> > +		*val = (long)(FIELD_GET(PWR_THRESHOLD2, v) * 1000000);
> > +		break;
> > +	case hwmon_power_max_alarm:
> > +		v = readq(feature->ioaddr + FME_PWR_THRESHOLD);
> > +		*val = (long)FIELD_GET(PWR_THRESHOLD1_STATUS, v);
> > +		break;
> > +	case hwmon_power_crit_alarm:
> > +		v = readq(feature->ioaddr + FME_PWR_THRESHOLD);
> > +		*val = (long)FIELD_GET(PWR_THRESHOLD2_STATUS, v);
> > +		break;
> > +	default:
> > +		return -EOPNOTSUPP;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int power_hwmon_write(struct device *dev, enum hwmon_sensor_types type,
> > +			     u32 attr, int channel, long val)
> > +{
> > +	struct dfl_feature_platform_data *pdata = dev_get_platdata(dev->parent);
> > +	struct dfl_feature *feature = dev_get_drvdata(dev);
> > +	int ret = 0;
> > +	u64 v;
> > +
> > +	if (val < 0 || val > PWR_THRESHOLD_MAX_IN_UW)
> > +		return -EINVAL;
> 
> We usually use clamp_val() in such cases because there is no useful means
> for the user to know the valid range.

Sure. Will fix this in the next version. Thanks for the comments.

Thanks
Hao

> 
> > +
> > +	val = val / 1000000;
> > +
> > +	mutex_lock(&pdata->lock);
> > +
> > +	switch (attr) {
> > +	case hwmon_power_max:
> > +		v = readq(feature->ioaddr + FME_PWR_THRESHOLD);
> > +		v &= ~PWR_THRESHOLD1;
> > +		v |= FIELD_PREP(PWR_THRESHOLD1, val);
> > +		writeq(v, feature->ioaddr + FME_PWR_THRESHOLD);
> > +		break;
> > +	case hwmon_power_crit:
> > +		v = readq(feature->ioaddr + FME_PWR_THRESHOLD);
> > +		v &= ~PWR_THRESHOLD2;
> > +		v |= FIELD_PREP(PWR_THRESHOLD2, val);
> > +		writeq(v, feature->ioaddr + FME_PWR_THRESHOLD);
> > +		break;
> > +	default:
> > +		ret = -EOPNOTSUPP;
> > +		break;
> > +	}
> > +
> > +	mutex_unlock(&pdata->lock);
> > +
> > +	return ret;
> > +}
> > +
> > +static umode_t power_hwmon_attrs_visible(const void *drvdata,
> > +					 enum hwmon_sensor_types type,
> > +					 u32 attr, int channel)
> > +{
> > +	switch (attr) {
> > +	case hwmon_power_input:
> > +	case hwmon_power_max_alarm:
> > +	case hwmon_power_crit_alarm:
> > +		return 0444;
> > +	case hwmon_power_max:
> > +	case hwmon_power_crit:
> > +		return 0644;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct hwmon_ops power_hwmon_ops = {
> > +	.is_visible = power_hwmon_attrs_visible,
> > +	.read = power_hwmon_read,
> > +	.write = power_hwmon_write,
> > +};
> > +
> > +static const struct hwmon_channel_info *power_hwmon_info[] = {
> > +	HWMON_CHANNEL_INFO(power, HWMON_P_INPUT |
> > +				  HWMON_P_MAX   | HWMON_P_MAX_ALARM |
> > +				  HWMON_P_CRIT  | HWMON_P_CRIT_ALARM),
> > +	NULL
> > +};
> > +
> > +static const struct hwmon_chip_info power_hwmon_chip_info = {
> > +	.ops = &power_hwmon_ops,
> > +	.info = power_hwmon_info,
> > +};
> > +
> > +static ssize_t power1_xeon_limit_show(struct device *dev,
> > +				      struct device_attribute *attr, char *buf)
> > +{
> > +	struct dfl_feature *feature = dev_get_drvdata(dev);
> > +	u16 xeon_limit = 0;
> > +	u64 v;
> > +
> > +	v = readq(feature->ioaddr + FME_PWR_XEON_LIMIT);
> > +
> > +	if (FIELD_GET(XEON_PWR_EN, v))
> > +		xeon_limit = FIELD_GET(XEON_PWR_LIMIT, v);
> > +
> > +	return sprintf(buf, "%u\n", xeon_limit * 100000);
> > +}
> > +
> > +static ssize_t power1_fpga_limit_show(struct device *dev,
> > +				      struct device_attribute *attr, char *buf)
> > +{
> > +	struct dfl_feature *feature = dev_get_drvdata(dev);
> > +	u16 fpga_limit = 0;
> > +	u64 v;
> > +
> > +	v = readq(feature->ioaddr + FME_PWR_FPGA_LIMIT);
> > +
> > +	if (FIELD_GET(FPGA_PWR_EN, v))
> > +		fpga_limit = FIELD_GET(FPGA_PWR_LIMIT, v);
> > +
> > +	return sprintf(buf, "%u\n", fpga_limit * 100000);
> > +}
> > +
> > +static ssize_t power1_ltr_show(struct device *dev,
> > +			       struct device_attribute *attr, char *buf)
> > +{
> > +	struct dfl_feature *feature = dev_get_drvdata(dev);
> > +	u64 v;
> > +
> > +	v = readq(feature->ioaddr + FME_PWR_STATUS);
> > +
> > +	return sprintf(buf, "%u\n",
> > +		       (unsigned int)FIELD_GET(FME_LATENCY_TOLERANCE, v));
> > +}
> > +
> > +static DEVICE_ATTR_RO(power1_xeon_limit);
> > +static DEVICE_ATTR_RO(power1_fpga_limit);
> > +static DEVICE_ATTR_RO(power1_ltr);
> > +
> > +static struct attribute *power_extra_attrs[] = {
> > +	&dev_attr_power1_xeon_limit.attr,
> > +	&dev_attr_power1_fpga_limit.attr,
> > +	&dev_attr_power1_ltr.attr,
> > +	NULL
> > +};
> > +
> > +ATTRIBUTE_GROUPS(power_extra);
> > +
> > +static int fme_power_mgmt_init(struct platform_device *pdev,
> > +			       struct dfl_feature *feature)
> > +{
> > +	struct device *hwmon;
> > +
> > +	dev_dbg(&pdev->dev, "FME Power Management Init.\n");
> > +
> > +	hwmon = devm_hwmon_device_register_with_info(&pdev->dev,
> > +						     "dfl_fme_power", feature,
> > +						     &power_hwmon_chip_info,
> > +						     power_extra_groups);
> > +	if (IS_ERR(hwmon)) {
> > +		dev_err(&pdev->dev, "Fail to register power hwmon\n");
> > +		return PTR_ERR(hwmon);
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static void fme_power_mgmt_uinit(struct platform_device *pdev,
> > +				 struct dfl_feature *feature)
> > +{
> > +	dev_dbg(&pdev->dev, "FME Power Management UInit.\n");
> > +}
> > +
> > +static const struct dfl_feature_id fme_power_mgmt_id_table[] = {
> > +	{.id = FME_FEATURE_ID_POWER_MGMT,},
> > +	{0,}
> > +};
> > +
> > +static const struct dfl_feature_ops fme_power_mgmt_ops = {
> > +	.init = fme_power_mgmt_init,
> > +	.uinit = fme_power_mgmt_uinit,
> > +};
> > +
> >  static struct dfl_feature_driver fme_feature_drvs[] = {
> >  	{
> >  		.id_table = fme_hdr_id_table,
> > @@ -418,6 +635,10 @@ static void fme_thermal_mgmt_uinit(struct platform_device *pdev,
> >  		.ops = &fme_thermal_mgmt_ops,
> >  	},
> >  	{
> > +		.id_table = fme_power_mgmt_id_table,
> > +		.ops = &fme_power_mgmt_ops,
> > +	},
> > +	{
> >  		.ops = NULL,
> >  	},
> >  };
> > -- 
> > 1.8.3.1
> > 

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