Re: [PATCH RFC 1/5] phy: qcom-qmp: add support for pipe clock muxing

[Dmitry Baryshkov <dmitry.baryshkov@linaro.org>]

On 21/04/2022 13:20, Johan Hovold wrote:
> Some QMP PHYs need to remux to their pipe clock input to the pipe clock
> output generated by the PHY before powering on the PHY and restore the
> default source during power down.
> 
> Add support for an optional pipe clock mux which will be reparented to
> the generated pipe clock before powering on the PHY and restored to the
> default reference source on power off.
> 
> Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
> ---
>   drivers/phy/qualcomm/phy-qcom-qmp.c | 71 ++++++++++++++++++++++++++---
>   1 file changed, 65 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp.c b/drivers/phy/qualcomm/phy-qcom-qmp.c
> index 7d2d1ab061f7..bc6db9670291 100644
> --- a/drivers/phy/qualcomm/phy-qcom-qmp.c
> +++ b/drivers/phy/qualcomm/phy-qcom-qmp.c
> @@ -3292,6 +3292,8 @@ struct qmp_phy_combo_cfg {
>    * @rx2: iomapped memory space for second lane's rx (in dual lane PHYs)
>    * @pcs_misc: iomapped memory space for lane's pcs_misc
>    * @pipe_clk: pipe clock
> + * @pipemux_clk: pipe clock source mux
> + * @piperef_clk: pipe clock default reference source
>    * @index: lane index
>    * @qmp: QMP phy to which this lane belongs
>    * @lane_rst: lane's reset controller
> @@ -3311,6 +3313,8 @@ struct qmp_phy {
>   	void __iomem *rx2;
>   	void __iomem *pcs_misc;
>   	struct clk *pipe_clk;
> +	struct clk *pipemux_clk;
> +	struct clk *piperef_clk;
>   	unsigned int index;
>   	struct qcom_qmp *qmp;
>   	struct reset_control *lane_rst;
> @@ -3346,6 +3350,7 @@ struct qcom_qmp {
>   	void __iomem *dp_com;
>   
>   	struct clk_bulk_data *clks;
> +	struct clk *pipe_clksrc;

Please move this to qmp_phy too.

>   	struct reset_control **resets;
>   	struct regulator_bulk_data *vregs;
>   
> @@ -5355,6 +5360,42 @@ static int qcom_qmp_phy_init(struct phy *phy)
>   	return 0;
>   }
>   
> +static int qcom_qmp_phy_pipe_clk_enable(struct qmp_phy *qphy)
> +{
> +	struct qcom_qmp *qmp = qphy->qmp;
> +	int ret;
> +
> +	ret = clk_set_parent(qphy->pipemux_clk, qmp->pipe_clksrc);
> +	if (ret)
> +		dev_err(qmp->dev, "failed to reparent pipe clock: %d\n", ret);
> +
> +
> +	ret = clk_prepare_enable(qphy->pipe_clk);
> +	if (ret) {
> +		dev_err(qmp->dev, "failed to enable pipe clock: %d\n", ret);
> +		goto err_restore_parent;
> +	}
> +
> +	return 0;
> +
> +err_restore_parent:
> +	clk_set_parent(qphy->pipemux_clk, qphy->piperef_clk);
> +
> +	return ret;
> +}
> +
> +static void qcom_qmp_phy_pipe_clk_disable(struct qmp_phy *qphy)
> +{
> +	struct qcom_qmp *qmp = qphy->qmp;
> +	int ret;
> +
> +	clk_disable_unprepare(qphy->pipe_clk);
> +
> +	ret = clk_set_parent(qphy->pipemux_clk, qphy->piperef_clk);
> +	if (ret)
> +		dev_err(qmp->dev, "failed to reparent pipe clock: %d\n", ret);
> +}
> +
>   static int qcom_qmp_phy_power_on(struct phy *phy)
>   {
>   	struct qmp_phy *qphy = phy_get_drvdata(phy);
> @@ -5379,11 +5420,9 @@ static int qcom_qmp_phy_power_on(struct phy *phy)
>   		}
>   	}
>   
> -	ret = clk_prepare_enable(qphy->pipe_clk);
> -	if (ret) {
> -		dev_err(qmp->dev, "pipe_clk enable failed err=%d\n", ret);
> +	ret = qcom_qmp_phy_pipe_clk_enable(qphy);
> +	if (ret)
>   		goto err_reset_lane;
> -	}
>   
>   	/* Tx, Rx, and PCS configurations */
>   	qcom_qmp_phy_configure_lane(tx, cfg->regs,
> @@ -5478,7 +5517,7 @@ static int qcom_qmp_phy_power_on(struct phy *phy)
>   	return 0;
>   
>   err_disable_pipe_clk:
> -	clk_disable_unprepare(qphy->pipe_clk);
> +	qcom_qmp_phy_pipe_clk_disable(qphy);
>   err_reset_lane:
>   	if (cfg->has_lane_rst)
>   		reset_control_assert(qphy->lane_rst);
> @@ -5491,7 +5530,7 @@ static int qcom_qmp_phy_power_off(struct phy *phy)
>   	struct qmp_phy *qphy = phy_get_drvdata(phy);
>   	const struct qmp_phy_cfg *cfg = qphy->cfg;
>   
> -	clk_disable_unprepare(qphy->pipe_clk);
> +	qcom_qmp_phy_pipe_clk_disable(qphy);
>   
>   	if (cfg->type == PHY_TYPE_DP) {
>   		/* Assert DP PHY power down */
> @@ -5777,6 +5816,8 @@ static int phy_pipe_clk_register(struct qcom_qmp *qmp, struct device_node *np)
>   	if (ret)
>   		return ret;
>   
> +	qmp->pipe_clksrc = fixed->hw.clk;
> +
>   	ret = of_clk_add_hw_provider(np, of_clk_hw_simple_get, &fixed->hw);
>   	if (ret)
>   		return ret;
> @@ -6091,6 +6132,24 @@ int qcom_qmp_phy_create(struct device *dev, struct device_node *np, int id,
>   		qphy->pipe_clk = NULL;
>   	}
>   
> +	/* Get optional pipe clock mux and default reference source clock. */
> +	qphy->pipemux_clk = of_clk_get_by_name(np, "mux");
> +	if (IS_ERR(qphy->pipemux_clk)) {
> +		ret = PTR_ERR(qphy->pipemux_clk);
> +		if (ret == -EPROBE_DEFER)
> +			return ret;
> +
> +		qphy->pipemux_clk = NULL;

This makes the driver ignore every possible erorr except -EPROBE_DEFER. 
However the driver should behave in quite the oppposite way. Please use 
devm_clk_get_optional() instead. It would do that in better way.

Not to mention that this code leaks a refcount on the clock.

> +	} else {
> +		qphy->piperef_clk = of_clk_get_by_name(np, "ref");
> +		if (IS_ERR(qphy->piperef_clk)) {
> +			ret = PTR_ERR(qphy->piperef_clk);
> +			return dev_err_probe(dev, ret,
> +					     "failed to get lane%d piperef_clk\n",
> +					     id);
> +		}
> +	}
> +

As a second thought.
This needs to be more explicit. If the chipset requires the pipe clock 
remuxing, we must fail if the clocks were not provided. So depending on 
the qmp instance/property the driver should either use devm_clk_get() 
(instead of _optional) or skip this block completely.

But this will not work with earlier DTS files.

>   	/* Get lane reset, if any */
>   	if (cfg->has_lane_rst) {
>   		snprintf(prop_name, sizeof(prop_name), "lane%d", id);


-- 
With best wishes
Dmitry