linux-kernel - Re: [PATCH v2 1/3] soundwire: qcom: add runtime pm support

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Date:   Thu, 24 Feb 2022 09:41:35 -0600
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        robh+dt@...nel.org, vkoul@...nel.org,
        yung-chuan.liao@...ux.intel.com
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        alsa-devel@...a-project.org, quic_srivasam@...cinc.com
Subject: Re: [PATCH v2 1/3] soundwire: qcom: add runtime pm support


>  static const struct snd_soc_dai_ops qcom_swrm_pdm_dai_ops = {
> @@ -1197,12 +1224,23 @@ static int qcom_swrm_get_port_config(struct qcom_swrm_ctrl *ctrl)
>  static int swrm_reg_show(struct seq_file *s_file, void *data)
>  {
>  	struct qcom_swrm_ctrl *swrm = s_file->private;
> -	int reg, reg_val;
> +	int reg, reg_val, ret;
> +
> +	ret = pm_runtime_get_sync(swrm->dev);
> +	if (ret < 0 && ret != -EACCES) {
> +		dev_err_ratelimited(swrm->dev,
> +				    "pm_runtime_get_sync failed in %s, ret %d\n",
> +				    __func__, ret);
> +		pm_runtime_put_noidle(swrm->dev);
> +	}
>  
>  	for (reg = 0; reg <= SWR_MSTR_MAX_REG_ADDR; reg += 4) {
>  		swrm->reg_read(swrm, reg, &reg_val);
>  		seq_printf(s_file, "0x%.3x: 0x%.2x\n", reg, reg_val);
>  	}
> +	pm_runtime_mark_last_busy(swrm->dev);
> +	pm_runtime_put_autosuspend(swrm->dev);
> +

question: is there a reason why this specific set of reg_read() is
surrounded pm_runtime stuff? Is this saying that in all other case where
the callback is used, the controller is already resumed and fully
operational? That's be worthy of a comment.

> struct qcom_swrm_ctrl *swrm
> struct qcom_swrm_ctrl *ctrl

nit-pick: it helps reviewers when the same variable name is used
consistently.

> +static int __maybe_unused swrm_runtime_suspend(struct device *dev)
> +{
> +	struct qcom_swrm_ctrl *ctrl = dev_get_drvdata(dev);
> +	int ret;
> +
> +	if (!ctrl->clock_stop_not_supported) {
> +		/* Mask bus clash interrupt */
> +		ctrl->intr_mask &= ~SWRM_INTERRUPT_STATUS_MASTER_CLASH_DET;
> +		ctrl->reg_write(ctrl, SWRM_INTERRUPT_MASK_ADDR, ctrl->intr_mask);
> +		ctrl->reg_write(ctrl, SWRM_INTERRUPT_CPU_EN, ctrl->intr_mask);
> +	}
> +	/* Prepare slaves for clock stop */
> +	ret = sdw_bus_prep_clk_stop(&ctrl->bus);
> +	if (ret < 0) {

if (ret < 0 && ret != -ENODATA) {

?

> +		dev_err(dev, "prepare clock stop failed %d", ret);
> +		return ret;
> +	}
> +
> +	ret = sdw_bus_clk_stop(&ctrl->bus);
> +	if (ret < 0 && ret != -ENODATA) {
> +		dev_err(dev, "bus clock stop failed %d", ret);
> +		return ret;
> +	}
> +
> +	clk_disable_unprepare(ctrl->hclk);
> +
> +	usleep_range(300, 305);
> +
> +	return 0;
> +}