linux-kernel - Re: [PATCH 3/5] PCI: Extract link retraining from pcie_aspm_configure_common

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Date:   Wed, 26 Oct 2016 14:42:46 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     linux-pci@...r.kernel.org
Cc:     bhelgaas@...gle.com, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] PCI: Extract link retraining from
 pcie_aspm_configure_common_clock()

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

> Signed-off-by: Alex Williamson <alex.williamson@...hat.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,
>