[V2,03/12] PCI: tegra: Retrain link for Gen2 speed

Tegra124, 132, 210 and 186 supports Gen2 link speed. After the link is up
in Gen1, set target link speed as Gen2 and retrain link. Link switches to
Gen2 speed if Gen2 capable end point is connected, else link stays in Gen1.

Signed-off-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
---
V2:
* Fixed alignment issue

 drivers/pci/host/pci-tegra.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

On 30.10.2017 06:18, Manikanta Maddireddy wrote:
> Tegra124, 132, 210 and 186 supports Gen2 link speed. After the link is up

s/supports/support/

> in Gen1, set target link speed as Gen2 and retrain link. Link switches to
> Gen2 speed if Gen2 capable end point is connected, else link stays in Gen1.
>
> Signed-off-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
> ---
> V2:
> * Fixed alignment issue
>
>  drivers/pci/host/pci-tegra.c | 42 ++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 42 insertions(+)
>
> diff --git a/drivers/pci/host/pci-tegra.c b/drivers/pci/host/pci-tegra.c
> index 2c64eb6cc3cc..9f6d331c3571 100644
> --- a/drivers/pci/host/pci-tegra.c
> +++ b/drivers/pci/host/pci-tegra.c
> @@ -232,6 +232,8 @@
>  #define PADS_REFCLK_CFG_PREDI_SHIFT		8  /* 11:8 */
>  #define PADS_REFCLK_CFG_DRVI_SHIFT		12 /* 15:12 */
>
> +#define LINK_RETRAIN_TIMEOUT HZ

I guess this originates in the pcie-altera driver or some common 
ancestor, but it doesn't make much sense to me why this is bound to HZ. 
It seems to me it should be just some constant.

> +
>  struct tegra_msi {
>  	struct msi_controller chip;
>  	DECLARE_BITMAP(used, INT_PCI_MSI_NR);
> @@ -2133,6 +2135,42 @@ static void tegra_pcie_enable_ports(struct tegra_pcie *pcie)
>  	}
>  }
>
> +static void tegra_pcie_change_link_speed(struct tegra_pcie *pcie,
> +					 struct pci_dev *pci_dev)
> +{
> +	struct device *dev = pcie->dev;
> +	unsigned long start_jiffies;
> +	unsigned short val;
> +
> +	/* Skip if the current device is not a root port */
> +	if (pci_pcie_type(pci_dev) != PCI_EXP_TYPE_ROOT_PORT)
> +		return;
> +
> +	pcie_capability_read_word(pci_dev, PCI_EXP_LNKCTL2, &val);
> +	val &= ~PCI_EXP_LNKSTA_CLS;
> +	val |= PCI_EXP_LNKSTA_CLS_5_0GB;
> +	pcie_capability_write_word(pci_dev, PCI_EXP_LNKCTL2, val);
> +
> +	/* Retrain the link */
> +	pcie_capability_read_word(pci_dev, PCI_EXP_LNKCTL, &val);
> +	val |= PCI_EXP_LNKCTL_RL;
> +	pcie_capability_write_word(pci_dev, PCI_EXP_LNKCTL, val);
> +
> +	start_jiffies = jiffies;
> +	for (;;) {
> +		pcie_capability_read_word(pci_dev, PCI_EXP_LNKSTA, &val);
> +		if (!(val & PCI_EXP_LNKSTA_LT))
> +			break;
> +		if (time_after(jiffies, start_jiffies + LINK_RETRAIN_TIMEOUT))
> +			break;
> +		usleep_range(2000, 3000);
> +	}

Please use the ktime series of functions instead of using jiffies 
directly. E.g.

ktime_t deadline = ktime_add_us(ktime_get(), LINK_RETRAIN_TIMEOUT);
if (ktime_after(ktime_get(), deadline))
	break;

(and replace LINK_RETRAIN_TIMEOUT with a timeout in microseconds)

You can take a look at the macros in linux/iopoll.h which do this but 
for iomem access.

> +
> +	if (val & PCI_EXP_LNKSTA_LT)
> +		dev_err(dev, "link retrain of PCIe slot %u failed\n",
> +			PCI_SLOT(pci_dev->devfn));
> +}
> +
>  static const struct tegra_pcie_soc tegra20_pcie = {
>  	.num_ports = 2,
>  	.msi_base_shift = 0,
> @@ -2334,6 +2372,7 @@ static int tegra_pcie_probe(struct platform_device *pdev)
>  	struct pci_host_bridge *host;
>  	struct tegra_pcie *pcie;
>  	struct pci_bus *child;
> +	struct pci_dev *pci_dev = NULL;
>  	int err;
>
>  	host = devm_pci_alloc_host_bridge(dev, sizeof(*pcie));
> @@ -2399,6 +2438,9 @@ static int tegra_pcie_probe(struct platform_device *pdev)
>
>  	pci_bus_add_devices(host->bus);
>
> +	for_each_pci_dev(pci_dev)
> +		tegra_pcie_change_link_speed(pcie, pci_dev);
> +
>  	if (IS_ENABLED(CONFIG_DEBUG_FS)) {
>  		err = tegra_pcie_debugfs_init(pcie);
>  		if (err < 0)
>