Re: [PATCH v2 3/3] PCI/ASPM: add sysfs attributes for controlling ASPM

[Heiner Kallweit <hkallweit1@gmail.com>]

On 22.08.2019 21:15, Heiner Kallweit wrote:
> On 22.08.2019 15:05, Greg KH wrote:
>> On Wed, Aug 21, 2019 at 08:18:41PM +0200, Heiner Kallweit wrote:
>>> Background of this extension is a problem with the r8169 network driver.
>>> Several combinations of board chipsets and network chip versions have
>>> problems if ASPM is enabled, therefore we have to disable ASPM per default.
>>> However especially on notebooks ASPM can provide significant power-saving,
>>> therefore we want to give users the option to enable ASPM. With the new sysfs
>>> attributes users can control which ASPM link-states are enabled/disabled.
>>>
>>> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
>>> ---
>>> v2:
>>> - use a dedicated sysfs attribute per link state
>>> - allow separate control of ASPM and PCI PM L1 sub-states
>>> ---
>>>  Documentation/ABI/testing/sysfs-bus-pci |  13 ++
>>>  drivers/pci/pci.h                       |   8 +-
>>>  drivers/pci/pcie/aspm.c                 | 263 +++++++++++++++++++++++-
>>>  3 files changed, 276 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
>>> index 8bfee557e..38b565c30 100644
>>> --- a/Documentation/ABI/testing/sysfs-bus-pci
>>> +++ b/Documentation/ABI/testing/sysfs-bus-pci
>>> @@ -347,3 +347,16 @@ Description:
>>>  		If the device has any Peer-to-Peer memory registered, this
>>>  	        file contains a '1' if the memory has been published for
>>>  		use outside the driver that owns the device.
>>> +
>>> +What		/sys/bus/pci/devices/.../power/aspm_l0s
>>> +What		/sys/bus/pci/devices/.../power/aspm_l1
>>> +What		/sys/bus/pci/devices/.../power/aspm_l1_1
>>> +What		/sys/bus/pci/devices/.../power/aspm_l1_2
>>> +What		/sys/bus/pci/devices/.../power/aspm_l1_1_pcipm
>>> +What		/sys/bus/pci/devices/.../power/aspm_l1_2_pcipm
>>> +What		/sys/bus/pci/devices/.../power/aspm_clkpm
>>
>> Wait, there already is a "power" subdirectory for all devices in the
>> system, are you adding another one, or files to that already-created
>> directory?
>>
> This is the standard "power" directory dynamically created by
> dpm_sysfs_add().
> 
>>> +date:		August 2019
>>> +Contact:	Heiner Kallweit <hkallweit1@gmail.com>
>>> +Description:	If ASPM is supported for an endpoint, then these files
>>> +		can be used to disable or enable the individual
>>> +		power management states.
>>> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
>>> index 3f126f808..e51c91f38 100644
>>> --- a/drivers/pci/pci.h
>>> +++ b/drivers/pci/pci.h
>>> @@ -525,17 +525,13 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev);
>>>  void pcie_aspm_exit_link_state(struct pci_dev *pdev);
>>>  void pcie_aspm_pm_state_change(struct pci_dev *pdev);
>>>  void pcie_aspm_powersave_config_link(struct pci_dev *pdev);
>>> +void pcie_aspm_create_sysfs_dev_files(struct pci_dev *pdev);
>>> +void pcie_aspm_remove_sysfs_dev_files(struct pci_dev *pdev);
>>>  #else
>>>  static inline void pcie_aspm_init_link_state(struct pci_dev *pdev) { }
>>>  static inline void pcie_aspm_exit_link_state(struct pci_dev *pdev) { }
>>>  static inline void pcie_aspm_pm_state_change(struct pci_dev *pdev) { }
>>>  static inline void pcie_aspm_powersave_config_link(struct pci_dev *pdev) { }
>>> -#endif
>>> -
>>> -#ifdef CONFIG_PCIEASPM_DEBUG
>>> -void pcie_aspm_create_sysfs_dev_files(struct pci_dev *pdev);
>>> -void pcie_aspm_remove_sysfs_dev_files(struct pci_dev *pdev);
>>> -#else
>>>  static inline void pcie_aspm_create_sysfs_dev_files(struct pci_dev *pdev) { }
>>>  static inline void pcie_aspm_remove_sysfs_dev_files(struct pci_dev *pdev) { }
>>>  #endif
>>> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
>>> index 149b876c9..e7dfcd1bd 100644
>>> --- a/drivers/pci/pcie/aspm.c
>>> +++ b/drivers/pci/pcie/aspm.c
>>> @@ -1275,38 +1275,297 @@ static ssize_t clk_ctl_store(struct device *dev,
>>>  
>>>  static DEVICE_ATTR_RW(link_state);
>>>  static DEVICE_ATTR_RW(clk_ctl);
>>> +#endif
>>> +
>>> +static const char power_group[] = "power";
>>> +
>>> +static struct pcie_link_state *aspm_get_parent_link(struct pci_dev *pdev)
>>> +{
>>> +	struct pci_dev *parent = pdev->bus->self;
>>> +
>>> +	if (pdev->has_secondary_link)
>>> +		parent = pdev;
>>> +
>>> +	return parent ? parent->link_state : NULL;
>>> +}
>>> +
>>> +static bool pcie_check_valid_aspm_endpoint(struct pci_dev *pdev)
>>> +{
>>> +	struct pcie_link_state *link;
>>> +
>>> +	if (pci_pcie_type(pdev) != PCI_EXP_TYPE_ENDPOINT)
>>> +		return false;
>>> +
>>> +	link = aspm_get_parent_link(pdev);
>>> +
>>> +	return link && link->aspm_capable;
>>> +}
>>> +
>>> +static ssize_t aspm_attr_show_common(struct device *dev,
>>> +				     struct device_attribute *attr,
>>> +				     char *buf, int state)
>>> +{
>>> +	struct pci_dev *pdev = to_pci_dev(dev);
>>> +	struct pcie_link_state *link;
>>> +	int val;
>>> +
>>> +	link = aspm_get_parent_link(pdev);
>>> +	if (!link)
>>> +		return -EOPNOTSUPP;
>>> +
>>> +	mutex_lock(&aspm_lock);
>>> +	val = !!(link->aspm_enabled & state);
>>> +	mutex_unlock(&aspm_lock);
>>> +
>>> +	return snprintf(buf, PAGE_SIZE, "%d\n", val);
>>
>> For sysfs files, you never need to use snprintf() as you "know" the size
>> of the buffer is big, and you are just printing out a single number.  So
>> that can be cleaned up in all of these attribute files.
>>
>>> +}
>>> +
>>> +static ssize_t aspm_l0s_show(struct device *dev,
>>> +			     struct device_attribute *attr, char *buf)
>>> +{
>>> +	return aspm_attr_show_common(dev, attr, buf, ASPM_STATE_L0S);
>>> +}
>>> +
>>> +static ssize_t aspm_l1_show(struct device *dev,
>>> +			    struct device_attribute *attr, char *buf)
>>> +{
>>> +	return aspm_attr_show_common(dev, attr, buf, ASPM_STATE_L1);
>>> +}
>>> +
>>> +static ssize_t aspm_l1_1_show(struct device *dev,
>>> +			      struct device_attribute *attr, char *buf)
>>> +{
>>> +	return aspm_attr_show_common(dev, attr, buf, ASPM_STATE_L1_1);
>>> +}
>>> +
>>> +static ssize_t aspm_l1_2_show(struct device *dev,
>>> +			      struct device_attribute *attr, char *buf)
>>> +{
>>> +	return aspm_attr_show_common(dev, attr, buf, ASPM_STATE_L1_2);
>>> +}
>>> +
>>> +static ssize_t aspm_l1_1_pcipm_show(struct device *dev,
>>> +				    struct device_attribute *attr, char *buf)
>>> +{
>>> +	return aspm_attr_show_common(dev, attr, buf, ASPM_STATE_L1_1_PCIPM);
>>> +}
>>> +
>>> +static ssize_t aspm_l1_2_pcipm_show(struct device *dev,
>>> +				    struct device_attribute *attr, char *buf)
>>> +{
>>> +	return aspm_attr_show_common(dev, attr, buf, ASPM_STATE_L1_2_PCIPM);
>>> +}
>>> +
>>> +static ssize_t aspm_attr_store_common(struct device *dev,
>>> +				      struct device_attribute *attr,
>>> +				      const char *buf, size_t len, int state)
>>> +{
>>> +	struct pci_dev *pdev = to_pci_dev(dev);
>>> +	struct pcie_link_state *link;
>>> +	bool state_enable;
>>> +
>>> +	if (aspm_disabled)
>>> +		return -EPERM;
>>> +
>>> +	link = aspm_get_parent_link(pdev);
>>> +	if (!link)
>>> +		return -EOPNOTSUPP;
>>> +
>>> +	if (!(link->aspm_capable & state))
>>> +		return -EOPNOTSUPP;
>>> +
>>> +	if (strtobool(buf, &state_enable) < 0)
>>> +		return -EINVAL;
>>> +
>>> +	down_read(&pci_bus_sem);
>>> +	mutex_lock(&aspm_lock);
>>> +
>>> +	if (state_enable)
>>> +		link->aspm_disable &= ~state;
>>> +	else
>>> +		link->aspm_disable |= state;
>>> +
>>> +	if (link->aspm_disable & ASPM_STATE_L1)
>>> +		link->aspm_disable |= ASPM_STATE_L1SS;
>>> +
>>> +	pcie_config_aspm_link(link, policy_to_aspm_state(link));
>>
>> This function can't fail?
>>
> It has no return value.
> 
>>> +
>>> +	mutex_unlock(&aspm_lock);
>>> +	up_read(&pci_bus_sem);
>>> +
>>> +	return len;
>>> +}
>>> +
>>> +static ssize_t aspm_l0s_store(struct device *dev,
>>> +			      struct device_attribute *attr,
>>> +			      const char *buf, size_t len)
>>> +{
>>> +	return aspm_attr_store_common(dev, attr, buf, len, ASPM_STATE_L0S);
>>> +}
>>> +
>>> +static ssize_t aspm_l1_store(struct device *dev,
>>> +			     struct device_attribute *attr,
>>> +			     const char *buf, size_t len)
>>> +{
>>> +	return aspm_attr_store_common(dev, attr, buf, len, ASPM_STATE_L1);
>>> +}
>>> +
>>> +static ssize_t aspm_l1_1_store(struct device *dev,
>>> +			       struct device_attribute *attr,
>>> +			       const char *buf, size_t len)
>>> +{
>>> +	return aspm_attr_store_common(dev, attr, buf, len, ASPM_STATE_L1_1);
>>> +}
>>> +
>>> +static ssize_t aspm_l1_2_store(struct device *dev,
>>> +			       struct device_attribute *attr,
>>> +			       const char *buf, size_t len)
>>> +{
>>> +	return aspm_attr_store_common(dev, attr, buf, len, ASPM_STATE_L1_2);
>>> +}
>>> +
>>> +static ssize_t aspm_l1_1_pcipm_store(struct device *dev,
>>> +				     struct device_attribute *attr,
>>> +				     const char *buf, size_t len)
>>> +{
>>> +	return aspm_attr_store_common(dev, attr, buf, len,
>>> +				      ASPM_STATE_L1_1_PCIPM);
>>> +}
>>> +
>>> +static ssize_t aspm_l1_2_pcipm_store(struct device *dev,
>>> +				     struct device_attribute *attr,
>>> +				     const char *buf, size_t len)
>>> +{
>>> +	return aspm_attr_store_common(dev, attr, buf, len,
>>> +				      ASPM_STATE_L1_2_PCIPM);
>>> +}
>>> +
>>> +static ssize_t aspm_clkpm_show(struct device *dev,
>>> +			       struct device_attribute *attr, char *buf)
>>> +{
>>> +	struct pci_dev *pdev = to_pci_dev(dev);
>>> +	struct pcie_link_state *link;
>>> +	int val;
>>> +
>>> +	link = aspm_get_parent_link(pdev);
>>> +	if (!link)
>>> +		return -EOPNOTSUPP;
>>> +
>>> +	mutex_lock(&aspm_lock);
>>> +	val = link->clkpm_enabled;
>>> +	mutex_unlock(&aspm_lock);
>>> +
>>> +	return snprintf(buf, PAGE_SIZE, "%d\n", val);
>>> +}
>>> +
>>> +static ssize_t aspm_clkpm_store(struct device *dev,
>>> +				struct device_attribute *attr,
>>> +				const char *buf, size_t len)
>>> +{
>>> +	struct pci_dev *pdev = to_pci_dev(dev);
>>> +	struct pcie_link_state *link;
>>> +	bool state_enable;
>>> +
>>> +	if (aspm_disabled)
>>> +		return -EPERM;
>>> +
>>> +	link = aspm_get_parent_link(pdev);
>>> +	if (!link)
>>> +		return -EOPNOTSUPP;
>>> +
>>> +	if (!link->clkpm_capable)
>>> +		return -EOPNOTSUPP;
>>> +
>>> +	if (strtobool(buf, &state_enable) < 0)
>>> +		return -EINVAL;
>>> +
>>> +	down_read(&pci_bus_sem);
>>> +	mutex_lock(&aspm_lock);
>>> +
>>> +	link->clkpm_disable = !state_enable;
>>> +	pcie_set_clkpm(link, policy_to_clkpm_state(link));
>>> +
>>> +	mutex_unlock(&aspm_lock);
>>> +	up_read(&pci_bus_sem);
>>> +
>>> +	return len;
>>> +}
>>> +
>>> +static DEVICE_ATTR_RW(aspm_l0s);
>>> +static DEVICE_ATTR_RW(aspm_l1);
>>> +static DEVICE_ATTR_RW(aspm_l1_1);
>>> +static DEVICE_ATTR_RW(aspm_l1_2);
>>> +static DEVICE_ATTR_RW(aspm_l1_1_pcipm);
>>> +static DEVICE_ATTR_RW(aspm_l1_2_pcipm);
>>> +static DEVICE_ATTR_RW(aspm_clkpm);
>>>  
>>> -static char power_group[] = "power";
>>>  void pcie_aspm_create_sysfs_dev_files(struct pci_dev *pdev)
>>>  {
>>>  	struct pcie_link_state *link_state = pdev->link_state;
>>>  
>>> +	if (pcie_check_valid_aspm_endpoint(pdev)) {
>>> +		sysfs_add_file_to_group(&pdev->dev.kobj,
>>> +			&dev_attr_aspm_l0s.attr, power_group);
>>> +		sysfs_add_file_to_group(&pdev->dev.kobj,
>>> +			&dev_attr_aspm_l1.attr, power_group);
>>> +		sysfs_add_file_to_group(&pdev->dev.kobj,
>>> +			&dev_attr_aspm_l1_1.attr, power_group);
>>> +		sysfs_add_file_to_group(&pdev->dev.kobj,
>>> +			&dev_attr_aspm_l1_2.attr, power_group);
>>> +		sysfs_add_file_to_group(&pdev->dev.kobj,
>>> +			&dev_attr_aspm_l1_1_pcipm.attr, power_group);
>>> +		sysfs_add_file_to_group(&pdev->dev.kobj,
>>> +			&dev_attr_aspm_l1_2_pcipm.attr, power_group);
>>> +		sysfs_add_file_to_group(&pdev->dev.kobj,
>>> +			&dev_attr_aspm_clkpm.attr, power_group);
>>
>> Huh?  First of, if you are ever in a driver, and you have to call a
>> sysfs_* function, you know something is wrong.
>>
>> Why are you dynamically adding files to a group?  These should all be
>> statically allocated and then at creation time you can dynamically
>> determine if you need to show them or not.  Use the is_visable callback
>> for that.
>>
> 
> The "power" group is dynamically created by the base driver core
> (dpm_sysfs_add). Not sure how the ASPM sysfs files could be statically
> allocated. We could add an attribute group to the "pci" bus_type,
> but this doesn't feel right.
> What we could do to make it simpler:
> Create an attribute group and then use sysfs_merge_group().
> But I see no way not to use sysfs_xxx functions. Also functions
> like device_add_groups() are just very simple wrappers around sysfs_
> functions.
> 
> Alternatively we could not use the existing "power" group but create
> our own group with device_add_group(). But I don't see that we gain much.
> 
After a little bit more checking:
We could statically add an attribute group to pci_dev_attr_groups,
similar to pcie_dev_attr_group.

>>> +	}
>>> +
>>>  	if (!link_state)
>>>  		return;
>>>  
>>> +#ifdef CONFIG_PCIEASPM_DEBUG
>>>  	if (link_state->aspm_support)
>>>  		sysfs_add_file_to_group(&pdev->dev.kobj,
>>>  			&dev_attr_link_state.attr, power_group);
>>>  	if (link_state->clkpm_capable)
>>>  		sysfs_add_file_to_group(&pdev->dev.kobj,
>>>  			&dev_attr_clk_ctl.attr, power_group);
>>
>> Same here.
>>
>>> +#endif
>>>  }
>>>  
>>>  void pcie_aspm_remove_sysfs_dev_files(struct pci_dev *pdev)
>>>  {
>>>  	struct pcie_link_state *link_state = pdev->link_state;
>>>  
>>> +	if (pcie_check_valid_aspm_endpoint(pdev)) {
>>> +		sysfs_remove_file_from_group(&pdev->dev.kobj,
>>> +			&dev_attr_aspm_l0s.attr, power_group);
>>> +		sysfs_remove_file_from_group(&pdev->dev.kobj,
>>> +			&dev_attr_aspm_l1.attr, power_group);
>>> +		sysfs_remove_file_from_group(&pdev->dev.kobj,
>>> +			&dev_attr_aspm_l1_1.attr, power_group);
>>> +		sysfs_remove_file_from_group(&pdev->dev.kobj,
>>> +			&dev_attr_aspm_l1_2.attr, power_group);
>>> +		sysfs_remove_file_from_group(&pdev->dev.kobj,
>>> +			&dev_attr_aspm_l1_1_pcipm.attr, power_group);
>>> +		sysfs_remove_file_from_group(&pdev->dev.kobj,
>>> +			&dev_attr_aspm_l1_2_pcipm.attr, power_group);
>>> +		sysfs_remove_file_from_group(&pdev->dev.kobj,
>>> +			&dev_attr_aspm_clkpm.attr, power_group);
>>
>> And then you never have to do this type of messy logic at all.
>>
>> Ick.
>>
>>> +	}
>>> +
>>>  	if (!link_state)
>>>  		return;
>>>  
>>> +#ifdef CONFIG_PCIEASPM_DEBUG
>>>  	if (link_state->aspm_support)
>>>  		sysfs_remove_file_from_group(&pdev->dev.kobj,
>>>  			&dev_attr_link_state.attr, power_group);
>>>  	if (link_state->clkpm_capable)
>>>  		sysfs_remove_file_from_group(&pdev->dev.kobj,
>>>  			&dev_attr_clk_ctl.attr, power_group);
>>
>> And you get to drop this nonsense as well.
>>
> Right, with the new attributes CONFIG_PCIEASPM_DEBUG and all
> related stuff could be removed most likely.
> 
>> thanks,
>>
>> greg k-h
>>
> 
> Heiner
>