linux-kernel - Re: [PATCH v2 1/6] phy: qcom-qmp: Enable pipe_clk before checking USB3 PHY

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Date:   Thu, 22 Mar 2018 11:43:01 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Kishon Vijay Abraham I <kishon@...com>,
        Manu Gautam <mgautam@...eaurora.org>
Cc:     linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        linux-arm-msm@...r.kernel.org,
        Manu Gautam <mgautam@...eaurora.org>,
        Vivek Gautam <vivek.gautam@...eaurora.org>,
        Varadarajan Narayanan <varada@...eaurora.org>,
        smuthayy <smuthayy@...eaurora.org>,
        Wei Yongjun <weiyongjun1@...wei.com>,
        Fengguang Wu <fengguang.wu@...el.com>
Subject: Re: [PATCH v2 1/6] phy: qcom-qmp: Enable pipe_clk before checking USB3
 PHY_STATUS

Quoting Manu Gautam (2018-03-22 01:50:41)
> QMP PHY for USB mode requires pipe_clk for calibration and PLL lock
> to take place. This lock is output from PHY to GCC clock_ctl and then

s/lock/clock/

> fed back to QMP PHY and is output from PHY only after PHY is reset
> and initialized, hence it can't be enabled too early in initialization
> sequence.
> 
> Signed-off-by: Manu Gautam <mgautam@...eaurora.org>
> ---
>  drivers/phy/qualcomm/phy-qcom-qmp.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp.c b/drivers/phy/qualcomm/phy-qcom-qmp.c
> index 6470c5d..73aa282 100644
> --- a/drivers/phy/qualcomm/phy-qcom-qmp.c
> +++ b/drivers/phy/qualcomm/phy-qcom-qmp.c
> @@ -797,8 +797,13 @@ static int qcom_qmp_phy_poweron(struct phy *phy)
>  {
>         struct qmp_phy *qphy = phy_get_drvdata(phy);
>         struct qcom_qmp *qmp = qphy->qmp;
> +       const struct qmp_phy_cfg *cfg = qmp->cfg;
>         int ret;
>  
> +       /* Not needed for USB3 PHY as pipe_clk is enabled from phy_init */
> +       if (cfg->type == PHY_TYPE_USB3)
> +               return 0;

Would be nice to not even assign phy_poweron when the PHY is USB3 type.

> +
>         ret = clk_prepare_enable(qphy->pipe_clk);
>         if (ret)
>                 dev_err(qmp->dev, "pipe_clk enable failed, err=%d\n", ret);
> @@ -1008,6 +1013,19 @@ static int qcom_qmp_phy_init(struct phy *phy)
>         status = pcs + cfg->regs[QPHY_PCS_READY_STATUS];
>         mask = cfg->mask_pcs_ready;
>  
> +       /* USB3 PHY requires pipe_clk for PLL lock and calibration */
> +       if (cfg->type == PHY_TYPE_USB3) {
> +               ret = clk_prepare_enable(qphy->pipe_clk);
> +               if (ret)
> +                       dev_err(qmp->dev, "pipe_clk enable err=%d\n", ret);
> +               /*
> +                * Ignore this error as pipe_clk might take some time to get
> +                * enabled. In any case following check for PHY PLL lock would
> +                * timeout below if there is a fatal error and clock is not fed
> +                * to PHY
> +                */
> +

This is odd. If clk_enable() fails then we don't keep parent clks (or
the clk that's being operated on) up refcounted and enabled. How is that
going to work?