Re: [PATCH v6 2/5] PCI: qcom: Add retry logic for link to be stable in L1ss

Bjorn Helgaas
2022-09-09T19:50:09Z

On Fri, Sep 09, 2022 at 02:14:41PM +0530, Krishna chaitanya chundru wrote:
> Some specific devices are taking time to settle the link in L1ss.
> So added a retry logic before returning from the suspend op.

"L1ss" is not a state. If you mean "L1.1" or "L1.2", say that. Also
in code comments below.

s/So added a/Add/

What are these specific devices? Is this a qcom controller defect?
An endpoint defect that should be addressed via some kind of generic
quirk?

> Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
> ---
> drivers/pci/controller/dwc/pcie-qcom.c | 36 +++++++++++++++++++++++-----------
> 1 file changed, 25 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 6e04d0d..15c2067 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -1809,26 +1809,40 @@ static int qcom_pcie_probe(struct platform_device *pdev)
> static int __maybe_unused qcom_pcie_pm_suspend(struct qcom_pcie *pcie)
> {
> u32 val;
> + ktime_t timeout, start;
> struct dw_pcie *pci = pcie->pci;
> struct device *dev = pci->dev;
>
> if (!pcie->cfg->supports_system_suspend)
> return 0;
>
> - /* if the link is not active turn off clocks */
> - if (!dw_pcie_link_up(pci)) {
> - dev_info(dev, "Link is not active\n");
> - goto suspend;
> - }
> + start = ktime_get();
> + /* Wait max 200 ms */
> + timeout = ktime_add_ms(start, 200);
>
> - /* if the link is not in l1ss don't turn off clocks */
> - val = readl(pcie->parf + PCIE20_PARF_PM_STTS);
> - if (!(val & PCIE20_PARF_PM_STTS_LINKST_IN_L1SUB)) {
> - dev_warn(dev, "Link is not in L1ss\n");
> - return 0;
> + while (1) {
> +
> + if (!dw_pcie_link_up(pci)) {
> + dev_warn(dev, "Link is not active\n");
> + break;
> + }
> +
> + /* if the link is not in l1ss don't turn off clocks */
> + val = readl(pcie->parf + PCIE20_PARF_PM_STTS);
> + if ((val & PCIE20_PARF_PM_STTS_LINKST_IN_L1SUB)) {
> + dev_dbg(dev, "Link enters L1ss after %d ms\n",
> + ktime_to_ms(ktime_get() - start));
> + break;
> + }
> +
> + if (ktime_after(ktime_get(), timeout)) {
> + dev_warn(dev, "Link is not in L1ss\n");
> + return 0;
> + }
> +
> + udelay(1000);
> }
>
> -suspend:
> if (pcie->cfg->ops->suspend)
> pcie->cfg->ops->suspend(pcie);
>
> --
> 2.7.4
>