linux-kernel - Re: [PATCH] PCI: altera: Poll for link training status after retraining the link

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Date:   Thu, 18 Aug 2016 15:19:00 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Ley Foon Tan <lftan@...era.com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, Ley Foon Tan <lftan.linux@...il.com>
Subject: Re: [PATCH] PCI: altera: Poll for link training status after
 retraining the link

On Mon, Aug 15, 2016 at 02:06:02PM +0800, Ley Foon Tan wrote:
> Poll for link training status is cleared before poll for link up status.
> This can help to get the reliable link up status, especially when PCIe
> is in Gen 3 speed.
> 
> Signed-off-by: Ley Foon Tan <lftan@...era.com>

Applied to pci/host-altera for v4.9, thanks!

> ---
>  drivers/pci/host/pcie-altera.c | 45 ++++++++++++++++++++++++++++++++++--------
>  1 file changed, 37 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/pci/host/pcie-altera.c b/drivers/pci/host/pcie-altera.c
> index 2b78376..58eef99 100644
> --- a/drivers/pci/host/pcie-altera.c
> +++ b/drivers/pci/host/pcie-altera.c
> @@ -61,7 +61,8 @@
>  #define TLP_LOOP			500
>  #define RP_DEVFN			0
>  
> -#define LINK_UP_TIMEOUT			5000
> +#define LINK_UP_TIMEOUT			HZ
> +#define LINK_RETRAIN_TIMEOUT		HZ
>  
>  #define INTX_NUM			4
>  
> @@ -99,11 +100,44 @@ static bool altera_pcie_link_is_up(struct altera_pcie *pcie)
>  	return !!((cra_readl(pcie, RP_LTSSM) & RP_LTSSM_MASK) == LTSSM_L0);
>  }
>  
> +static void altera_wait_link_retrain(struct pci_dev *dev)
> +{
> +	u16 reg16;
> +	unsigned long start_jiffies;
> +	struct altera_pcie *pcie = dev->bus->sysdata;
> +
> +	/* Wait for link training end. */
> +	start_jiffies = jiffies;
> +	for (;;) {
> +		pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &reg16);
> +		if (!(reg16 & PCI_EXP_LNKSTA_LT))
> +			break;
> +
> +		if (time_after(jiffies, start_jiffies + LINK_RETRAIN_TIMEOUT)) {
> +			dev_err(&pcie->pdev->dev, "link retrain timeout\n");
> +			break;
> +		}
> +		udelay(100);
> +	}
> +
> +	/* Wait for link is up */
> +	start_jiffies = jiffies;
> +	for (;;) {
> +		if (altera_pcie_link_is_up(pcie))
> +			break;
> +
> +		if (time_after(jiffies, start_jiffies + LINK_UP_TIMEOUT)) {
> +			dev_err(&pcie->pdev->dev, "link up timeout\n");
> +			break;
> +		}
> +		udelay(100);
> +	}
> +}
> +
>  static void altera_pcie_retrain(struct pci_dev *dev)
>  {
>  	u16 linkcap, linkstat;
>  	struct altera_pcie *pcie = dev->bus->sysdata;
> -	int timeout =  0;
>  
>  	if (!altera_pcie_link_is_up(pcie))
>  		return;
> @@ -121,12 +155,7 @@ static void altera_pcie_retrain(struct pci_dev *dev)
>  	if ((linkstat & PCI_EXP_LNKSTA_CLS) == PCI_EXP_LNKSTA_CLS_2_5GB) {
>  		pcie_capability_set_word(dev, PCI_EXP_LNKCTL,
>  					 PCI_EXP_LNKCTL_RL);
> -		while (!altera_pcie_link_is_up(pcie)) {
> -			timeout++;
> -			if (timeout > LINK_UP_TIMEOUT)
> -				break;
> -			udelay(5);
> -		}
> +		altera_wait_link_retrain(dev);
>  	}
>  }
>  DECLARE_PCI_FIXUP_EARLY(0x1172, PCI_ANY_ID, altera_pcie_retrain);
> -- 
> 1.8.2.1
> 
> --
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