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

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Date:   Fri, 19 Aug 2016 15:55:35 +0800
From:   Ley Foon Tan <lftan@...era.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-pci <linux-pci@...r.kernel.org>
Subject: Re: [PATCH] PCI: altera: Poll for link training status after
 retraining the link

On Fri, Aug 19, 2016 at 4:19 AM, Bjorn Helgaas <helgaas@...nel.org> wrote:
> 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!

Thanks, Bjorn.

>
>> ---
>>  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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