linux-kernel - Re: [PATCH 2/2] phy: qcom-qmp-pcie: Add support for keeping refclk always on

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Message-ID: <CAA8EJpq9azRC5msZfS1V8NK4EmPN+jxh+99yGEyQ+EWkk1gROQ@mail.gmail.com>
Date:   Mon, 6 Nov 2023 14:13:43 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Krishna chaitanya chundru <quic_krichai@...cinc.com>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Vinod Koul <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        quic_vbadigan@...cinc.com, quic_ramkri@...cinc.com,
        quic_nitegupt@...cinc.com, quic_skananth@...cinc.com,
        quic_vpernami@...cinc.com, quic_parass@...cinc.com
Subject: Re: [PATCH 2/2] phy: qcom-qmp-pcie: Add support for keeping refclk
 always on

On Mon, 6 Nov 2023 at 13:53, Krishna chaitanya chundru
<quic_krichai@...cinc.com> wrote:
>
> In PCIe low power states like L1.1 or L1.2 the phy will stop
> supplying refclk to endpoint. If endpoint asserts clkreq to bring
> back link L0, then RC needs to provide refclk to endpoint.
>
> If there is some issues in platform with clkreq signal propagation
> to host and due to that host will not send refclk which results PCIe link
> down. For those platforms  phy needs to provide refclk even in low power
> states.
>
> Add a flag which indicates refclk is always supplied to endpoint.
>
> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
> ---
>  drivers/phy/qualcomm/phy-qcom-qmp-pcie.c | 21 +++++++++++++++++----
>  1 file changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> index a63ca7424974..d7e377a7d96e 100644
> --- a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> +++ b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> @@ -43,6 +43,8 @@
>  /* QPHY_PCS_STATUS bit */
>  #define PHYSTATUS                              BIT(6)
>  #define PHYSTATUS_4_20                         BIT(7)
> +/* PCS_PCIE_ENDPOINT_REFCLK_CNTRL */
> +#define EPCLK_ALWAYS_ON_EN                     BIT(6)


>
>  #define PHY_INIT_COMPLETE_TIMEOUT              10000
>
> @@ -77,6 +79,7 @@ enum qphy_reg_layout {
>         QPHY_START_CTRL,
>         QPHY_PCS_STATUS,
>         QPHY_PCS_POWER_DOWN_CONTROL,
> +       QPHY_PCS_ENDPOINT_REFCLK_CNTRL,
>         /* Keep last to ensure regs_layout arrays are properly initialized */
>         QPHY_LAYOUT_SIZE
>  };
> @@ -103,10 +106,11 @@ static const unsigned int sdm845_qhp_pciephy_regs_layout[QPHY_LAYOUT_SIZE] = {
>  };
>
>  static const unsigned int pciephy_v4_regs_layout[QPHY_LAYOUT_SIZE] = {
> -       [QPHY_SW_RESET]                 = QPHY_V4_PCS_SW_RESET,
> -       [QPHY_START_CTRL]               = QPHY_V4_PCS_START_CONTROL,
> -       [QPHY_PCS_STATUS]               = QPHY_V4_PCS_PCS_STATUS1,
> -       [QPHY_PCS_POWER_DOWN_CONTROL]   = QPHY_V4_PCS_POWER_DOWN_CONTROL,
> +       [QPHY_SW_RESET]                         = QPHY_V4_PCS_SW_RESET,
> +       [QPHY_START_CTRL]                       = QPHY_V4_PCS_START_CONTROL,
> +       [QPHY_PCS_STATUS]                       = QPHY_V4_PCS_PCS_STATUS1,
> +       [QPHY_PCS_POWER_DOWN_CONTROL]           = QPHY_V4_PCS_POWER_DOWN_CONTROL,

No unnecessary whitespace changes, please.

> +       [QPHY_PCS_ENDPOINT_REFCLK_CNTRL]        = QPHY_V4_PCS_PCIE_ENDPOINT_REFCLK_CNTRL,

Any other platform having this register?

>  };
>
>  static const unsigned int pciephy_v5_regs_layout[QPHY_LAYOUT_SIZE] = {
> @@ -2244,6 +2248,8 @@ struct qmp_pcie {
>         struct phy *phy;
>         int mode;
>
> +       bool refclk_always_on;
> +
>         struct clk_fixed_rate pipe_clk_fixed;
>  };
>
> @@ -3159,6 +3165,10 @@ static void qmp_pcie_init_registers(struct qmp_pcie *qmp, const struct qmp_phy_c
>         qmp_pcie_configure(pcs, tbls->pcs, tbls->pcs_num);
>         qmp_pcie_configure(pcs_misc, tbls->pcs_misc, tbls->pcs_misc_num);
>
> +       if (qmp->refclk_always_on && cfg->regs[QPHY_PCS_ENDPOINT_REFCLK_CNTRL])
> +               qphy_setbits(pcs_misc, cfg->regs[QPHY_PCS_ENDPOINT_REFCLK_CNTRL],
> +                            EPCLK_ALWAYS_ON_EN);
> +
>         if (cfg->lanes >= 4 && qmp->tcsr_4ln_config) {
>                 qmp_pcie_configure(serdes, cfg->serdes_4ln_tbl, cfg->serdes_4ln_num);
>                 qmp_pcie_init_port_b(qmp, tbls);
> @@ -3681,6 +3691,9 @@ static int qmp_pcie_probe(struct platform_device *pdev)
>         if (ret)
>                 goto err_node_put;
>
> +       qmp->refclk_always_on = of_property_read_bool(dev->of_node,
> +                                                     "qcom,refclk-always-on");

Error out if !cfg->regs[QPHY_PCS_ENDPOINT_REFCLK_CNTRL]).
Otherwise your DT value can be silently ignored.

> +
>         ret = phy_pipe_clk_register(qmp, np);
>         if (ret)
>                 goto err_node_put;
>
> --
> 2.42.0
>


-- 
With best wishes
Dmitry