Re: [PATCH v7 4/5] PCI/ASPM: Add sysfs attributes for controlling ASPM link states

[Bjorn Helgaas <helgaas@kernel.org>]

On Sat, Oct 05, 2019 at 02:07:56PM +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>

> +static ssize_t aspm_attr_show_common(struct device *dev,
> +				     struct device_attribute *attr,
> +				     char *buf, u8 state)
> +{
> +	struct pci_dev *pdev = to_pci_dev(dev);
> +	struct pcie_link_state *link;
> +	bool enabled;
> +
> +	link = pcie_aspm_get_link(pdev);
> +
> +	mutex_lock(&aspm_lock);
> +	enabled = link->aspm_enabled & state;
> +	mutex_unlock(&aspm_lock);

Not sure the mutex is needed; do you have a reason, or is it just
copied from existing code?  If the latter, we can just wait to see
what Rafael says.

> +	return sprintf(buf, "%d\n", enabled ? 1 : 0);
> +}