Date:	Wed, 6 Apr 2011 11:31:39 +0200
From:	Andreas Herrmann <herrmann.der.user@...glemail.com>
To:	Guenter Roeck <guenter.roeck@...csson.com>
Cc:	Jean Delvare <khali@...ux-fr.org>,
	Thomas Renninger <trenn@...e.de>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] hwmon: Add driver for AMD family 15h processor power
 information

On Tue, Apr 05, 2011 at 01:12:38PM -0700, Guenter Roeck wrote:
> On Tue, Apr 05, 2011 at 10:45:36AM -0400, Andreas Herrmann wrote:
> > From: Andreas Herrmann <andreas.herrmann3@....com>
> > 
> > This CPU family provides NB register values to gather following
> > TDP information
> > 
> > * ProcessorPwrWatts: Specifies in Watts the maximum amount of power
> >   the processor can support.
> > * CurrPwrWatts: Specifies in Watts the current amount of power being
> >   consumed by the processor.
> > 
> > This driver provides
> > 
> > * power1_cap (ProcessorPwrWatts)
> 
> Hi Andreas,
> 
> What does the CPU do if ProcessorPwrWatts is reached ? Does it start to limit 
> power consumption, ie does it enforce the limit ?

No.

> If not you might want to use power1_max instead.

Ok, so I picked the wrong attribute. Will correct this.

> > * power1_input (CurrPwrWatts)
> > 
> > Changes from v1::
> >  - removed deprecated code line,
> >  - fixed comment,
> >  - report power only once per socket (Power information is provided
> >    for the entire package. On multi-node processors it should only be
> >    reported on internal node 0.)
> > 
> > Signed-off-by: Andreas Herrmann <andreas.herrmann3@....com>
> > ---
> >  drivers/hwmon/Kconfig      |   10 ++
> >  drivers/hwmon/Makefile     |    1 +
> >  drivers/hwmon/f15h_power.c |  216 ++++++++++++++++++++++++++++++++++++++++++++
> 
> Please also add Documentation/hwmon/f15h_power.

Ok.

> >  3 files changed, 227 insertions(+), 0 deletions(-)
> >  create mode 100644 drivers/hwmon/f15h_power.c
> > 
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index 8e84b31..0268623 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -249,6 +249,16 @@ config SENSORS_K10TEMP
> >  	  This driver can also be built as a module.  If so, the module
> >  	  will be called k10temp.
> >  
> > +config SENSORS_F15H_POWER
> > +	tristate "AMD Family 15h processor power"
> > +	depends on X86 && PCI
> > +	help
> > +	  If you say yes here you get support for processor power
> > +	  information of your AMD family 15h CPU.
> > +
> > +	  This driver can also be built as a module.  If so, the module
> > +	  will be called f15hpower.
> 
> 	f15h_power

Good catch.

> > +
> >  config SENSORS_ASB100
> >  	tristate "Asus ASB100 Bach"
> >  	depends on X86 && I2C && EXPERIMENTAL
> > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> > index dde02d9..e554b88 100644
> > --- a/drivers/hwmon/Makefile
> > +++ b/drivers/hwmon/Makefile
> > @@ -62,6 +62,7 @@ obj-$(CONFIG_SENSORS_JC42)	+= jc42.o
> >  obj-$(CONFIG_SENSORS_JZ4740)	+= jz4740-hwmon.o
> >  obj-$(CONFIG_SENSORS_K8TEMP)	+= k8temp.o
> >  obj-$(CONFIG_SENSORS_K10TEMP)	+= k10temp.o
> > +obj-$(CONFIG_SENSORS_F15H_POWER) += f15h_power.o
> >  obj-$(CONFIG_SENSORS_LIS3LV02D) += lis3lv02d.o hp_accel.o
> >  obj-$(CONFIG_SENSORS_LIS3_SPI)	+= lis3lv02d.o lis3lv02d_spi.o
> >  obj-$(CONFIG_SENSORS_LIS3_I2C)	+= lis3lv02d.o lis3lv02d_i2c.o
> > diff --git a/drivers/hwmon/f15h_power.c b/drivers/hwmon/f15h_power.c
> > new file mode 100644
> > index 0000000..40e3cbd
> > --- /dev/null
> > +++ b/drivers/hwmon/f15h_power.c
> > @@ -0,0 +1,216 @@
> > +/*
> > + * f15h_power.c - AMD Family 15h processor power monitoring
> > + *
> > + * Copyright (c) 2011 Advanced Micro Devices, Inc.
> > + * Author: Andreas Herrmann <andreas.herrmann3@....com>
> > + *
> > + *
> > + * This driver is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License; either
> > + * version 2 of the License, or (at your option) any later version.
> > + *
> > + * This driver is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> > + * See the GNU General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU General Public License
> > + * along with this driver; if not, see <http://www.gnu.org/licenses/>.
> > + */
> > +
> > +#include <linux/err.h>
> > +#include <linux/hwmon.h>
> > +#include <linux/hwmon-sysfs.h>
> > +#include <linux/init.h>
> > +#include <linux/module.h>
> > +#include <linux/pci.h>
> > +#include <linux/bitops.h>
> > +#include <asm/processor.h>
> > +
> > +MODULE_DESCRIPTION("AMD Family 15h CPU processor power monitor");
> > +MODULE_AUTHOR("Andreas Herrmann <andreas.herrmann3@....com>");
> > +MODULE_LICENSE("GPL");
> > +
> > +/* D18F3 */
> > +#define REG_NORTHBRIDGE_CAP		0xe8
> > +
> > +/* D18F4 */
> > +#define REG_PROCESSOR_TDP		0x1b8
> > +
> > +/* D18F5 */
> > +#define REG_TDP_RUNNING_AVERAGE		0xe0
> > +#define REG_TDP_LIMIT3			0xe8
> > +
> > +static ssize_t show_power(struct device *dev,
> > +			  struct device_attribute *attr, char *buf)
> > +{
> > +	u32 val, btdp, tdpl, tdp2w, arange;
> > +	s32 acap;
> > +	u64 ctdp;
> > +	struct pci_dev *f4 = to_pci_dev(dev);
> > +	struct pci_dev *f5;
> > +
> > +	pci_read_config_dword(f4, REG_PROCESSOR_TDP, &val);
> > +	btdp = (val >> 16) & 0xffff;
> > +
> > +	f5 = pci_get_slot(f4->bus, PCI_DEVFN(PCI_SLOT(f4->devfn), 5));
> > +	if (!f5) {
> > +		dev_err(dev, "no function 5 available on this slot\n");
> > +		return 0;
> > +	}
> 
> Unless this is a temporary error condition, you should check if this function
> exists in the probe function, and not create a sysfs entry if it doesn't.
> 
> If it is a temporary error which needs a runtime check, you should return 
> a negative value to indicate that there was an error.

Probably I'll follow Clemens' advice to ignore the theoretic case that
the device doesn't exist. (AFAIK such a scenario is only imaginable
under virtualization if only some PCI devices are passed into a
guest.)

> > +	pci_read_config_dword(f5, REG_TDP_RUNNING_AVERAGE, &val);
> > +	acap = (val >> 4) & 0x3fffff;
> > +	acap = sign_extend32(acap, 22);
> > +	arange = val & 0xf;
> > +
> > +	pci_read_config_dword(f5, REG_TDP_LIMIT3, &val);
> > +	pci_dev_put(f5);
> > +
> > +	tdpl = (val >> 16) & 0x1fff;
> > +	tdp2w = ((val & 0x3ff) << 6) | ((val >> 10) & 0x3f);
> > +	ctdp = tdpl - (s32)(acap >> (arange + 1)) + btdp;
> > +	ctdp *= tdp2w;
> > +
> > +	/*
> > +	 * Convert to microWatt
> > +	 *
> > +	 * power is in Watt provided as fixed point integer with
> > +	 * scaling factor 1/(2^16).  For conversion we use
> > +	 * (10^6)/(2^16) = 15625/(2^10)
> > +	 */
> > +	ctdp = (ctdp * 15625) >> 10;
> > +	return sprintf(buf, "%d\n", (u32) ctdp);
> 
> 	%u

Yep.

> > +}
> > +static DEVICE_ATTR(power1_input, S_IRUGO, show_power, NULL);
> > +
> > +static ssize_t show_power_cap(struct device *dev,
> > +			     struct device_attribute *attr, char *buf)
> > +{
> > +	u32 val, tdp2w;
> > +	u64 ptdp;
> > +	struct pci_dev *f4 = to_pci_dev(dev);
> > +	struct pci_dev *f5;
> > +
> > +	pci_read_config_dword(f4, REG_PROCESSOR_TDP, &val);
> > +	ptdp = val & 0xffff;
> > +
> > +	f5 = pci_get_slot(f4->bus, PCI_DEVFN(PCI_SLOT(f4->devfn), 5));
> > +	if (!f5) {
> > +		dev_err(dev, "no function 5 available on this slot\n");
> > +		return 0;
> > +	}
> > +
> Same as above - should be checked in probe function.
> 
> If it is a temporary error which needs a runtime check, you should return 
> a negative value to indicate that there was an error.
> 
> > +	pci_read_config_dword(f5, REG_TDP_LIMIT3, &val);
> > +	pci_dev_put(f5);
> > +
> > +	tdp2w = ((val & 0x3ff) << 6) | ((val >> 10) & 0x3f);
> > +	ptdp *= tdp2w;
> > +
> > +	/* result not allowed to be >= 256W */
> > +	WARN_ON(ptdp>>16 >= 256);
> > +
> Does this really ask for such drastic measures, or would dev_warn() be sufficient ?

dev_warn() should be sufficient.

> > +	/* convert to microWatt */
> > +	ptdp = (ptdp * 15625) >> 10;
> > +	return sprintf(buf, "%d\n", (u32) ptdp);
> 
> 	%u



> > +}
> > +static DEVICE_ATTR(power1_cap, S_IRUGO, show_power_cap, NULL);
> > +
> > +static ssize_t show_name(struct device *dev,
> > +			 struct device_attribute *attr, char *buf)
> > +{
> > +	return sprintf(buf, "f15h_power\n");
> > +}
> > +static DEVICE_ATTR(name, S_IRUGO, show_name, NULL);
> > +
> > +static int __devinit f15h_power_is_internal_node0(struct pci_dev *f4)
> > +{
> > +	u32 val;
> > +	struct pci_dev *f3;
> > +
> > +	f3 = pci_get_slot(f4->bus, PCI_DEVFN(PCI_SLOT(f4->devfn), 3));
> > +	if (!f3) {
> > +		dev_err(&f4->dev, "no function 3 available on this slot\n");
> > +		return 0;
> 
> It is a common practice to return a negative value on errors. Why not here ?
> Also, is this really an error which asks for an error message, or just a CPU
> or system which does not support the attribute ? In the latter case, you should 
> not display an error message.

This paranoid check will be removed.

> > +	}
> > +
> > +	pci_read_config_dword(f3, REG_NORTHBRIDGE_CAP, &val);
> > +	pci_dev_put(f3);
> > +
> > +	if ((val & BIT(29)) && ((val >> 30) & 3))
> > +		return 0;
> > +
> > +	return 1;
> > +}
> > +
> > +static int __devinit f15h_power_probe(struct pci_dev *pdev,
> > +				      const struct pci_device_id *id)
> > +{
> > +	struct device *hwmon_dev;
> > +	int err = -ENODEV;
> > +
> > +	if (!f15h_power_is_internal_node0(pdev))
> > +		goto exit;
> > +
> > +	err = device_create_file(&pdev->dev, &dev_attr_power1_input);
> > +	if (err)
> > +		goto exit;
> > +	err = device_create_file(&pdev->dev, &dev_attr_power1_cap);
> > +	if (err)
> > +		goto exit_remove;
> > +
> > +	err = device_create_file(&pdev->dev, &dev_attr_name);
> > +	if (err)
> > +		goto exit_remove;
> > +
> > +	hwmon_dev = hwmon_device_register(&pdev->dev);
> > +	if (IS_ERR(hwmon_dev)) {
> > +		err = PTR_ERR(hwmon_dev);
> > +		goto exit_remove;
> > +	}
> > +	dev_set_drvdata(&pdev->dev, hwmon_dev);
> > +
> > +	return 0;
> > +
> > +exit_remove:
> > +	device_remove_file(&pdev->dev, &dev_attr_name);
> > +	device_remove_file(&pdev->dev, &dev_attr_power1_input);
> > +	device_remove_file(&pdev->dev, &dev_attr_power1_cap);
> > +exit:
> > +	return err;
> > +}
> > +
> > +static void __devexit f15h_power_remove(struct pci_dev *pdev)
> > +{
> > +	hwmon_device_unregister(dev_get_drvdata(&pdev->dev));
> > +	device_remove_file(&pdev->dev, &dev_attr_name);
> > +	device_remove_file(&pdev->dev, &dev_attr_power1_input);
> > +	device_remove_file(&pdev->dev, &dev_attr_power1_cap);
> > +	dev_set_drvdata(&pdev->dev, NULL);
> > +}
> > +
> > +static const struct pci_device_id f15h_power_id_table[] = {
> 
> checkpatch says:
> 
> WARNING: Use DEFINE_PCI_DEVICE_TABLE for struct pci_device_id
> #326: FILE: drivers/hwmon/f15h_power.c:192:
> 
> Please fix.

Ok.

> > +	{ PCI_VDEVICE(AMD, PCI_DEVICE_ID_AMD_15H_NB_LINK) },
> > +	{}
> > +};
> > +MODULE_DEVICE_TABLE(pci, f15h_power_id_table);
> > +
> > +static struct pci_driver f15h_power_driver = {
> > +	.name = "f15h_power",
> > +	.id_table = f15h_power_id_table,
> > +	.probe = f15h_power_probe,
> > +	.remove = __devexit_p(f15h_power_remove),
> > +};
> > +
> > +static int __init f15h_power_init(void)
> > +{
> > +	return pci_register_driver(&f15h_power_driver);
> > +}
> > +
> > +static void __exit f15h_power_exit(void)
> > +{
> > +	pci_unregister_driver(&f15h_power_driver);
> > +}
> > +
> > +module_init(f15h_power_init)
> > +module_exit(f15h_power_exit)


Thanks for the review.


Andreas
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