On Tue, 26 Sep 2023, Siddharth Vadapalli wrote:
> The PCI driver invokes the PHY APIs using the ks_pcie_enable_phy()
> function. The PHY in this case is the Serdes. It is possible that the
> PCI instance is configured for 2 lane operation across two different
> Serdes instances, using 1 lane of each Serdes. In such a configuration,
> if the reference clock for one Serdes is provided by the other Serdes,
> it results in a race condition. After the Serdes providing the reference
> clock is initialized by the PCI driver by invoking its PHY APIs, it is
> not guaranteed that this Serdes remains powered on long enough for the
> PHY APIs based initialization of the dependent Serdes. In such cases,
> the PLL of the dependent Serdes fails to lock due to the absence of the
> reference clock from the former Serdes which has been powered off by the
> PM Core.
>
> Fix this by obtaining reference to the PHYs before invoking the PHY
> initialization APIs and releasing reference after the initialization is
> complete.
>
> Fixes: 49229238ab47 ("PCI: keystone: Cleanup PHY handling")
> Signed-off-by: Siddharth Vadapalli <s-vadapalli@xxxxxx>
> ---
>
> NOTE: This patch is based on linux-next tagged next-20230925.
>
> v1:
> https://lore.kernel.org/r/20230926054200.963803-1-s-vadapalli@xxxxxx/
>
> Changes since v1:
> - Add code to release reference(s) to the phy(s) when
> ks_pcie_enable_phy(ks_pcie) fails.
>
> Regards,
> Siddharth.
>
> drivers/pci/controller/dwc/pci-keystone.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pci-keystone.c b/drivers/pci/controller/dwc/pci-keystone.c
> index 49aea6ce3e87..e4d43306a7e3 100644
> --- a/drivers/pci/controller/dwc/pci-keystone.c
> +++ b/drivers/pci/controller/dwc/pci-keystone.c
> @@ -1218,12 +1218,24 @@ static int __init ks_pcie_probe(struct platform_device *pdev)
> goto err_link;
> }
>
> + /* Obtain reference(s) to the phy(s) */
> + for (i = 0; i < num_lanes; i++)
> + phy_pm_runtime_get_sync(ks_pcie->phy[i]);
> +
> ret = ks_pcie_enable_phy(ks_pcie);
You could do the put loop here before checking ret to avoid duplicating
the put loop.
> if (ret) {
> dev_err(dev, "failed to enable phy\n");
> + /* Release reference(s) to the phy(s) */
> + for (i = 0; i < num_lanes; i++)
> + phy_pm_runtime_put_sync(ks_pcie->phy[i]);
> +
> goto err_link;
> }
>
> + /* Release reference(s) to the phy(s) */
> + for (i = 0; i < num_lanes; i++)
> + phy_pm_runtime_put_sync(ks_pcie->phy[i]);
> +
> platform_set_drvdata(pdev, ks_pcie);
> pm_runtime_enable(dev);
> ret = pm_runtime_get_sync(dev);
>
--
i.
