Date:   Fri, 28 Jun 2019 10:55:14 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Wu Hao <hao.wu@...el.com>
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 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.

>         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.

>     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.

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 ?

> 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.

> +
> +	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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