RE: [PATCH v1] PCI: qcom: Add system PM support

Prasad Malisetty (Temp)
2021-12-29T10:59:03Z

Hi Dmitry,

Thanks for the review and comments.

Please find the response inline.

Thanks
-Prasad

-----Original Message-----
From: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Sent: Thursday, December 23, 2021 8:44 PM
To: Prasad Malisetty <quic_c_pmaliset@quicinc.com>
Cc: agross@kernel.org; bjorn.andersson@linaro.org; lorenzo.pieralisi@arm.com; robh@kernel.org; kw@linux.com; bhelgaas@google.com; linux-pci@vger.kernel.org; linux-arm-msm@vger.kernel.org; linux-kernel@vger.kernel.org; quic_vbadigan <quic_vbadigan@quicinc.com>; Rama Krishna (QUIC) <quic_ramkri@quicinc.com>; manivannan.sadhasivam@linaro.org; swboyd@chromium.org; quic_pmaliset <quic_pmaliset@quicinc.com>
Subject: Re: [PATCH v1] PCI: qcom: Add system PM support

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On Wed, 22 Dec 2021 at 19:08, Prasad Malisetty <quic_c_pmaliset@quicinc.com> wrote:
>
> From: Prasad Malisetty <quic_pmaliset@quicinc.com>
>
> Add suspend_noirq and resume_noirq callbacks to handle System suspend
> and resume in dwc pcie controller driver.
>
> When system suspends, send PME turnoff message to enter link into L2
> state. Along with powerdown the PHY, disable pipe clock, switch
> gcc_pcie_1_pipe_clk_src to XO if mux is supported and disable the pcie
> clocks, regulators.

The GDSC stays on, if I'm not mistaken. Is this an expected behaviour for the suspend procedure?

>> No, GDSC will be disabled as part of system suspend. We are switching gcc_pcie_1_clk_src to XO as GDSC should be enable in resume path.

Also as a side note, the qcom-pcie driver supports a variety of SoCs from different generations. Which platforms were really tested?
Judging from your patch I suppose that you did not test this on any non-recent platform.

>> We have tested on SC7280 SoC which is recently added.

> When system resumes, PCIe link will be re-established and setup rc
> settings.
>
> Signed-off-by: Prasad Malisetty <quic_pmaliset@quicinc.com>
> ---
> drivers/pci/controller/dwc/pcie-qcom.c | 103
> +++++++++++++++++++++++++++++++++
> 1 file changed, 103 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c
> b/drivers/pci/controller/dwc/pcie-qcom.c
> index c19cd506..24dcf5a 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -73,6 +73,8 @@
>
> #define PCIE20_PARF_Q2A_FLUSH 0x1AC
>
> +#define PCIE20_PARF_PM_STTS 0x24
> +
> #define PCIE20_MISC_CONTROL_1_REG 0x8BC
> #define DBI_RO_WR_EN 1
>
> @@ -1616,6 +1618,107 @@ static int qcom_pcie_probe(struct platform_device *pdev)
> return ret;
> }
>
> +static int qcom_pcie_send_pme_turnoff_msg(struct qcom_pcie *pcie) {
> + int ret = 0;
> + u32 val = 0, poll_val = 0;
> + uint64_t l23_rdy_poll_timeout = 100000;
> + struct dw_pcie *pci = pcie->pci;
> + struct device *dev = pci->dev;
> +
> + val = readl(pcie->elbi + PCIE20_ELBI_SYS_CTRL);
> + val |= BIT(4);
> + writel(val, pcie->elbi + PCIE20_ELBI_SYS_CTRL);
> +
> + ret = readl_poll_timeout((pcie->parf + PCIE20_PARF_PM_STTS), poll_val,
> + (poll_val & BIT(5)), 10000, l23_rdy_poll_timeout);
> + if (!ret)
> + dev_dbg(dev, "PCIe: PM_Enter_L23 is received\n");
> + else
> + dev_err(dev, "PM_Enter_L23 is NOT received.PARF_PM_STTS 0x%x\n",
> + readl_relaxed(pcie->parf +
> + PCIE20_PARF_PM_STTS));
> +
> + return ret;
> +}
> +
> +static void qcom_pcie_host_disable(struct qcom_pcie *pcie) {
> + struct qcom_pcie_resources_2_7_0 *res = &pcie->res.v2_7_0;
> +
> + /*Assert the reset of endpoint */
> + qcom_ep_reset_assert(pcie);
> +
> + /* Put PHY into POWER DOWN state */
> + phy_power_off(pcie->phy);
> +
> + writel(1, pcie->parf + PCIE20_PARF_PHY_CTRL);
> +
> + /* Disable pipe clock */
> + pcie->ops->post_deinit(pcie);
> +
> + /* Change GCC_PCIE_1_PIPE_MUXR register to 0x2 for XO as parent */
> + if (pcie->pipe_clk_need_muxing)
> + clk_set_parent(res->pipe_clk_src, res->ref_clk_src);
> +
> + /* Disable PCIe clocks and regulators*/
> + pcie->ops->deinit(pcie);
> +}
> +
> +static int __maybe_unused qcom_pcie_pm_suspend_noirq(struct device
> +*dev) {
> + int ret = 0;
> + struct qcom_pcie *pcie = dev_get_drvdata(dev);
> + struct dw_pcie *pci = pcie->pci;
> +
> + if (!dw_pcie_link_up(pci)) {
> + dev_err(dev, "Power has been turned off already\n");
> + return ret;
> + }
> +
> + /* Send PME turnoff msg */
> + ret = qcom_pcie_send_pme_turnoff_msg(pcie);
> + if (ret)
> + return ret;
> +
> + /* Power down the PHY, disable clock and regulators */
> + qcom_pcie_host_disable(pcie);
> +
> + dev_info(dev, "PM: PCI is suspended\n");
> + return ret;
> +}
> +
> +/* Resume the PCIe link */
> +static int __maybe_unused qcom_pcie_pm_resume_noirq(struct device
> +*dev) {
> + int ret = 0;
> + struct qcom_pcie *pcie = dev_get_drvdata(dev);
> + struct dw_pcie *pci = pcie->pci;
> + struct pcie_port *pp = &pci->pp;
> +
> + dev_info(dev, "PM: Resuming\n");
> +
> + /* Initialize PCIe host */
> + ret = qcom_pcie_host_init(pp);
> + if (ret)
> + dev_err(dev, "cannot initialize host\n");
> +
> + dw_pcie_iatu_detect(pci);
> + dw_pcie_setup_rc(pp);
> +
> + /* Start the PCIe link */
> + qcom_pcie_start_link(pci);
> +
> + ret = dw_pcie_wait_for_link(pci);
> + if (ret)
> + dev_err(dev, "Link never came up, Resume failed\n");
> +
> + return ret;
> +}
> +
> +static const struct dev_pm_ops qcom_pcie_pm_ops = {
> + SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(qcom_pcie_pm_suspend_noirq,
> +qcom_pcie_pm_resume_noirq) };
> +
> static const struct of_device_id qcom_pcie_match[] = {
> { .compatible = "qcom,pcie-apq8084", .data = &apq8084_cfg },
> { .compatible = "qcom,pcie-ipq8064", .data = &ipq8064_cfg },
> --
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