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

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Message-ID: <be9c99ac-ebdb-e0c1-669b-1257f630f267@linaro.org>
Date:   Thu, 24 Feb 2022 15:58:16 +0000
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        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



On 24/02/2022 15:41, Pierre-Louis Bossart wrote:
> 
>>   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.

controller register reads require clk to be ON, which might not be 
always ON. In suspended case we switch off the clocks.

Other places so far that I have seen is that controller is either 
already resumed or clk is on (interrupt case) and resume case.



>> struct qcom_swrm_ctrl *swrm
>> struct qcom_swrm_ctrl *ctrl
> 
> nit-pick: it helps reviewers when the same variable name is used
> consistently.

Yes, I did notice this, but for some reason I forgot to fix it.

> 
>> +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;
>> +}