Re: [PATCH v4 07/10] PCI: PCI: Add pcie_is_link_active() to determine if the PCIe link is active

[Krishna Chaitanya Chundru]

On 2/25/2025 3:24 PM, Lukas Wunner wrote:
> On Tue, Feb 25, 2025 at 03:04:04PM +0530, Krishna Chaitanya Chundru wrote:
> > Introduce a common API to check if the PCIe link is active, replacing
> > duplicate code in multiple locations.
> [...]
> > --- a/drivers/pci/hotplug/pciehp_hpc.c
> > +++ b/drivers/pci/hotplug/pciehp_hpc.c
> > @@ -234,18 +234,7 @@ static void pcie_write_cmd_nowait(struct controller *ctrl, u16 cmd, u16 mask)
> >    */
> >   int pciehp_check_link_active(struct controller *ctrl)
> >   {
> > -	struct pci_dev *pdev = ctrl_dev(ctrl);
> > -	u16 lnk_status;
> > -	int ret;
> > -
> > -	ret = pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status);
> > -	if (ret == PCIBIOS_DEVICE_NOT_FOUND || PCI_POSSIBLE_ERROR(lnk_status))
> > -		return -ENODEV;
> > -
> > -	ret = !!(lnk_status & PCI_EXP_LNKSTA_DLLLA);
> > -	ctrl_dbg(ctrl, "%s: lnk_status = %x\n", __func__, lnk_status);
> > -
> > -	return ret;
> > +	return pcie_is_link_active(ctrl_dev(ctrl));
> >   }
>
> Please replace all call sites of pciehp_check_link_active() with a call
> to the new function.
ack
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -4923,8 +4922,7 @@ int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type)
> >   		if (!dev->link_active_reporting)
> >   			return -ENOTTY;
> >   
> > -		pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &status);
> > -		if (!(status & PCI_EXP_LNKSTA_DLLLA))
> > +		if (pcie_is_link_active(dev))
> >   			return -ENOTTY;
>
> Missing negation.
ack
> > +/**
> > + * pcie_is_link_active() - Checks if the link is active or not
> > + * @pdev: PCI device to query
> > + *
> > + * Check whether the link is active or not.
> > + *
> > + * If the config read returns error then return -ENODEV.
> > + */
> > +int pcie_is_link_active(struct pci_dev *pdev)
>
> Why not return bool?
pciehp_check_link_active is expecting int to make sure this new function
not disturbing the hotplug driver I added return type as int, I can 
change it to bool if it fine with hotplug drivers.
> I don't quite like the function name because in English the correct word
> order is subject - predicate - object, i.e. pcie_link_is_active() or
> even shorter, pcie_link_active().
ack
> > @@ -2094,6 +2095,10 @@ pci_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs,
> >   {
> >   	return -ENOSPC;
> >   }
> > +
> > +static inline int pcie_is_link_active(struct pci_dev *dev)
> > +{ return -ENODEV; }
> > +
> >   #endif /* CONFIG_PCI */
>
> Is the empty inline really necessary?  What breaks if you leave it out?
ack I will remove it.

- Krishna Chaitanya.
> Thanks,
>
> Lukas