[+Ley Foon Tan]
On Mon, Oct 30, 2017 at 07:27:14PM +0530, Manikanta Maddireddy wrote:
> Tegra124, 132, 210 and 186 support 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@xxxxxxxxxx>
> ---
> V3:
> * Corrected commit log
> * Replaced jiffies with ktime
> V2:
> * no change in this patch
>
> 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 068510b40c1a..ed5e8acfdc32 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 100000
> +
> struct tegra_msi {
> struct msi_controller chip;
> DECLARE_BITMAP(used, INT_PCI_MSI_NR);
> @@ -2134,6 +2136,42 @@ 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;
> + ktime_t deadline;
> + unsigned short val;
u16
> + /* 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);
Should you not read the Link Capabilities 2 register ("Supported Speed
Vector") before programming the Link control 2 register Target Link
Speed value ?
> +
> + /* 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);
> +
> + deadline = ktime_add_us(ktime_get(), LINK_RETRAIN_TIMEOUT);
> + for (;;) {
> + pcie_capability_read_word(pci_dev, PCI_EXP_LNKSTA, &val);
> + if (!(val & PCI_EXP_LNKSTA_LT))
> + break;
> + if (ktime_after(ktime_get(), deadline))
> + break;
> + usleep_range(2000, 3000);
Ok - I hope we won't end up with every host bridge re-writing its own
link training loop because at that point in time we should think about
consolidating this.
CC'ing Ley Foon Tan since I would like to understand why the Altera
driver link retraining can't be written with the same code as this
driver - I suspect it has to do with the retraining sequence and when
the retraining is actually carried out in the host bridge probe
sequence.
> + }
> +
> + 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,
> @@ -2335,6 +2373,7 @@ 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));
> @@ -2400,6 +2439,9 @@ 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);
> +
Are you sure it is safe to change link speed after adding devices ?
Lorenzo
> if (IS_ENABLED(CONFIG_DEBUG_FS)) {
> err = tegra_pcie_debugfs_init(pcie);
> if (err < 0)
> --
> 2.1.4
>
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