Re: [PATCH 3/5] PCI: Extract link retraining from pcie_aspm_configure_common_clock()

[Alex Williamson]

On Wed, 26 Oct 2016 12:01:28 -0600
Alex Williamson <alex.william...@redhat.com> wrote:

> Signed-off-by: Alex Williamson <alex.william...@redhat.com>
> ---
>  drivers/pci/pci.c       |   29 +++++++++++++++++++++++++++++
>  drivers/pci/pcie/aspm.c |   17 +----------------
>  include/linux/pci.h     |    1 +
>  3 files changed, 31 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 6d6cf89..4d327d4 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -4729,6 +4729,35 @@ int pcie_set_mps(struct pci_dev *dev, int mps)
>  }
>  EXPORT_SYMBOL(pcie_set_mps);
>  
> +int pcie_retrain_link(struct pci_dev *dev)
> +{
> +     int ret;
> +     u16 lnksta;
> +     unsigned long timeout;
> +
> +     /* Can only retrain from downstream ports */
> +     if (!pci_is_pcie(dev) ||
> +         (pci_pcie_type(dev) != PCI_EXP_TYPE_DOWNSTREAM &&
> +          pci_pcie_type(dev) != PCI_EXP_TYPE_ROOT_PORT))
> +             return -EINVAL;
> +
> +     ret = pcie_capability_set_word(dev, PCI_EXP_LNKCTL, PCI_EXP_LNKCTL_RL);
> +     if (ret)
> +             return ret;
> +
> +     timeout = jiffies + HZ; /* Retraining timeout */
> +     for (;;) {
> +             pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &lnksta);
> +             if (!(lnksta & PCI_EXP_LNKSTA_LT) ||
> +                 time_after(jiffies, timeout))
> +                     break;
> +             msleep(1);
> +     }
> +
> +     return (lnksta & PCI_EXP_LNKSTA_LT) ? -EBUSY : 0;
> +}
> +EXPORT_SYMBOL(pcie_retrain_link);
> +
>  int pcie_get_link(struct pci_dev *dev, enum pci_bus_speed *speed,
>                 enum pcie_link_width *width)
>  {
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index 0ec649d..482d60c 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -91,8 +91,6 @@ struct pcie_link_state {
>       [POLICY_POWERSAVE] = "powersave"
>  };
>  
> -#define LINK_RETRAIN_TIMEOUT HZ
> -
>  static int policy_to_aspm_state(struct pcie_link_state *link)
>  {
>       switch (aspm_policy) {
> @@ -222,20 +220,7 @@ static void pcie_aspm_configure_common_clock(struct 
> pcie_link_state *link)
>       pcie_capability_write_word(parent, PCI_EXP_LNKCTL, reg16);
>  
>       /* Retrain link */
> -     reg16 |= PCI_EXP_LNKCTL_RL;
> -     pcie_capability_write_word(parent, PCI_EXP_LNKCTL, reg16);
> -
> -     /* Wait for link training end. Break out after waiting for timeout */
> -     start_jiffies = jiffies;

Zero day builders remind me that I forgot to remove the declaration of
start_jiffies from this function and that it's now unused.  I'll refrain
from immediately spamming the list with a v2 for that minor change, but
note that this patch will need a respin or fixup on commit, whichever
is preferred.  Thanks,

Alex

> -     for (;;) {
> -             pcie_capability_read_word(parent, PCI_EXP_LNKSTA, &reg16);
> -             if (!(reg16 & PCI_EXP_LNKSTA_LT))
> -                     break;
> -             if (time_after(jiffies, start_jiffies + LINK_RETRAIN_TIMEOUT))
> -                     break;
> -             msleep(1);
> -     }
> -     if (!(reg16 & PCI_EXP_LNKSTA_LT))
> +     if (!pcie_retrain_link(parent))
>               return;
>  
>       /* Training failed. Restore common clock configurations */
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index fbfbb40..eb0e9be 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1024,6 +1024,7 @@ static inline int pci_is_managed(struct pci_dev *pdev)
>  int pcie_set_readrq(struct pci_dev *dev, int rq);
>  int pcie_get_mps(struct pci_dev *dev);
>  int pcie_set_mps(struct pci_dev *dev, int mps);
> +int pcie_retrain_link(struct pci_dev *dev);
>  int pcie_get_minimum_link(struct pci_dev *dev, enum pci_bus_speed *speed,
>                         enum pcie_link_width *width);
>  int pcie_get_link(struct pci_dev *dev, enum pci_bus_speed *speed,
>