RE: [PATCH v4] Export PBEC Data register into sysfs

["Daisuke Kobayashi (Fujitsu)" <kobayashi.da-06@fujitsu.com>]

Dear reviews.

Could you please take a look at the patch when you have time?
Thank you for your time and consideration.

Kobayashi Daisuke wrote:
> Subject: [PATCH v4] Export PBEC Data register into sysfs
> 
> This proposal aims to add a feature that outputs PCIe device power
> consumption information to sysfs.
> 
> Add support for PBEC (Power Budgeting Extended Capability) output to the
> PCIe driver. PBEC is defined in the PCIe specification(PCIe r6.0, sec 7.8.1) and
> is a standard method for obtaining device power consumption information.
> 
> PCIe devices can significantly impact the overall power consumption of a
> system. However, obtaining PCIe device power consumption information has
> traditionally been difficult.
> 
> The PBEC Data register changes depending on the value of the PBEC Data
> Select register. To obtain all PBEC Data register values defined in the device,
> obtain the value of the PBEC Data register while changing the value of the
> PBEC Data Select register.
> 
> Signed-off-by: "Kobayashi,Daisuke" <kobayashi.da-06@fujitsu.com>
> ---
>  Documentation/ABI/testing/sysfs-bus-pci | 17 +++++++++++++++
>  drivers/pci/pci-sysfs.c                 | 28
> +++++++++++++++++++++++++
>  2 files changed, 45 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-pci
> b/Documentation/ABI/testing/sysfs-bus-pci
> index ecf47559f495..be1911d948ef 100644
> --- a/Documentation/ABI/testing/sysfs-bus-pci
> +++ b/Documentation/ABI/testing/sysfs-bus-pci
> @@ -500,3 +500,20 @@ Description:
>  		console drivers from the device.  Raw users of pci-sysfs
>  		resourceN attributes must be terminated prior to resizing.
>  		Success of the resizing operation is not guaranteed.
> +
> +What:		/sys/bus/pci/devices/.../power_budget
> +Date:		September 2024
> +Contact:	Kobayashi Daisuke <kobayashi.da-06@fujitsu.com>
> +Description:
> +		This file provides information about the PCIe power budget
> +		for the device. It is a read-only file that outputs the values
> +		of the Power Budgeting Data Register for each power state as
> a
> +		series of 32-bit hexadecimal values. Each line represents a
> +		single Power Budgeting Data register entry, containing the
> +		power budget for a specific power state.
> +
> +		The specific interpretation of these values depends on the
> +		device and the PCIe specification. Refer to the PCIe
> +		specification for detailed information about the Power
> +		Budgeting Data register, including the encoding	of power
> +		states and the interpretation of Base Power and Data Scale.
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index
> 2321fdfefd7d..c52814a33597 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -182,6 +182,33 @@ static ssize_t resource_show(struct device *dev, struct
> device_attribute *attr,  }  static DEVICE_ATTR_RO(resource);
> 
> +static ssize_t power_budget_show(struct device *dev, struct
> device_attribute *attr,
> +			 char *buf)
> +{
> +	struct pci_dev *pci_dev = to_pci_dev(dev);
> +	size_t len = 0;
> +	int i, pos;
> +	u32 data;
> +
> +	pos = pci_find_ext_capability(pci_dev, PCI_EXT_CAP_ID_PWR);
> +	if (!pos)
> +		return -EINVAL;
> +
> +	for (i = 0; i < 0xff; i++) {
> +		pci_write_config_byte(pci_dev, pos + PCI_PWR_DSR, (u8)i);
> +		pci_read_config_dword(pci_dev, pos + PCI_PWR_DATA,
> &data);
> +		if (!data) {
> +			if (len == 0)
> +				return -EINVAL;
> +			break;
> +		}
> +		len += sysfs_emit_at(buf, len, "%04x\n", data);
> +	}
> +
> +	return len;
> +}
> +static DEVICE_ATTR_RO(power_budget);
> +
>  static ssize_t max_link_speed_show(struct device *dev,
>  				   struct device_attribute *attr, char *buf)
> { @@ -629,6 +656,7 @@ static struct attribute *pcie_dev_attrs[] = {
>  	&dev_attr_current_link_width.attr,
>  	&dev_attr_max_link_width.attr,
>  	&dev_attr_max_link_speed.attr,
> +	&dev_attr_power_budget.attr,
>  	NULL,
>  };
> 
> --
> 2.45.0