linux-kernel - Re: [PATCH v3 1/6] phy: qcom-qmp: Enable pipe_clk before checking USB3 PHY

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Date:   Tue, 27 Mar 2018 12:21:18 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     Manu Gautam <mgautam@...eaurora.org>,
        Kishon Vijay Abraham I <kishon@...com>
Cc:     linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        linux-arm-msm@...r.kernel.org,
        Varadarajan Narayanan <varada@...eaurora.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Wei Yongjun <weiyongjun1@...wei.com>,
        Fengguang Wu <fengguang.wu@...el.com>
Subject: Re: [PATCH v3 1/6] phy: qcom-qmp: Enable pipe_clk before checking
 USB3 PHY_STATUS

Hi Manu,


On 3/23/2018 11:41 AM, Manu Gautam wrote:
> QMP PHY for USB mode requires pipe_clk for calibration and PLL lock
> to take place.

AFAIK, that's not true. The pipe clock is the *output* of the PLL, and 
it's should not
be needed for PLL calibration and locking. The PLL locking happens when 
the phy is
configured and powered on.
Atleast that's what the PIPE spec also says.

            CLK
              |
              |
              Y
    ----------------
   |      PLL        |--------> PCLK (this is pipe clock 125/250/... MHz 
corresponding to the data width)
    ----------------

That's the reason we were enabling it after the PLL was locked.

> This clock is output from PHY to GCC clock_ctl and then
> fed back to QMP PHY and is available 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 | 33 ++++++++++++++++++++++++++++++++-
>   1 file changed, 32 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp.c b/drivers/phy/qualcomm/phy-qcom-qmp.c
> index 6470c5d..5d8df6a 100644
> --- a/drivers/phy/qualcomm/phy-qcom-qmp.c
> +++ b/drivers/phy/qualcomm/phy-qcom-qmp.c
> @@ -1008,6 +1008,19 @@ 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.
> +	 * Enable it from here for USB. For UFS/PCIE, it gets enabled
> +	 * from poweron.
> +	 */
> +	if (cfg->type == PHY_TYPE_USB3) {
> +		ret = clk_prepare_enable(qphy->pipe_clk);

As mentioned before AFAIU, pipe clock is just an output coming out of 
the PHY's PLL
and we shouldn't try to enable pipe clock before PHY even gets initialized.
We should may just try to first fix the unbalanced pipe clock 
enable/disable problem.

Moreover, lets take care of all USB, PCIe and DP phys when we want to 
enable/disbale
pipe clock as all of them use this clock.

Best regards
Vivek

> +		if (ret) {
> +			dev_err(qmp->dev, "pipe_clk enable err=%d\n", ret);
> +			goto err_clk_enable;
> +		}
> +	}
> +
>   	ret = readl_poll_timeout(status, val, !(val & mask), 1,
>   				 PHY_INIT_COMPLETE_TIMEOUT);
>   	if (ret) {
> @@ -1019,6 +1032,9 @@ static int qcom_qmp_phy_init(struct phy *phy)
>   	return ret;
>   
>   err_pcs_ready:
> +	if (cfg->type == PHY_TYPE_USB3)
> +		clk_disable_unprepare(qphy->pipe_clk);
> +err_clk_enable:
>   	if (cfg->has_lane_rst)
>   		reset_control_assert(qphy->lane_rst);
>   err_lane_rst:
> @@ -1288,10 +1304,19 @@ static int phy_pipe_clk_register(struct qcom_qmp *qmp, struct device_node *np)
>   	.owner		= THIS_MODULE,
>   };
>   
> +/* USB PHY doesn't require power_on op */
> +static const struct phy_ops qcom_qmp_usb_phy_gen_ops = {
> +	.init		= qcom_qmp_phy_init,
> +	.exit		= qcom_qmp_phy_exit,
> +	.set_mode	= qcom_qmp_phy_set_mode,
> +	.owner		= THIS_MODULE,
> +};
> +
>   static
>   int qcom_qmp_phy_create(struct device *dev, struct device_node *np, int id)
>   {
>   	struct qcom_qmp *qmp = dev_get_drvdata(dev);
> +	const struct phy_ops *ops;
>   	struct phy *generic_phy;
>   	struct qmp_phy *qphy;
>   	char prop_name[MAX_PROP_NAME];
> @@ -1354,7 +1379,13 @@ int qcom_qmp_phy_create(struct device *dev, struct device_node *np, int id)
>   		}
>   	}
>   
> -	generic_phy = devm_phy_create(dev, np, &qcom_qmp_phy_gen_ops);
> +	/* USB PHY doesn't use power_on op */
> +	if (qmp->cfg->type == PHY_TYPE_USB3)
> +		ops = &qcom_qmp_usb_phy_gen_ops;
> +	else
> +		ops = &qcom_qmp_phy_gen_ops;
> +
> +	generic_phy = devm_phy_create(dev, np, ops);
>   	if (IS_ERR(generic_phy)) {
>   		ret = PTR_ERR(generic_phy);
>   		dev_err(dev, "failed to create qphy %d\n", ret);