linux-kernel - Re: [PATCH] soundwire: qcom: add debugfs entry for soundwire register dump

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Date:   Fri, 1 Oct 2021 06:45:43 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Vinod Koul <vkoul@...nel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     sanyog.r.kale@...el.com, yung-chuan.liao@...ux.intel.com,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] soundwire: qcom: add debugfs entry for soundwire register
 dump



On 9/30/21 11:20 PM, Vinod Koul wrote:
> HI Srini,
> 
> On 07-09-21, 11:56, Srinivas Kandagatla wrote:
>> +#ifdef CONFIG_DEBUG_FS
>> +static int swrm_reg_show(struct seq_file *s_file, void *data)
>> +{
>> +	struct qcom_swrm_ctrl *swrm = s_file->private;
>> +	int reg, reg_val;
>> +
>> +	for (reg = 0; reg <= SWR_MSTR_MAX_REG_ADDR; reg += 4) {
>> +		swrm->reg_read(swrm, reg, &reg_val);
> 
> Why not use regmap_read here, that would avoid reading from the bus when
> we already have the values...

It's an indirect read based on regmap.

	ctrl->reg_read = qcom_swrm_ahb_reg_read;
	ctrl->reg_write = qcom_swrm_ahb_reg_write;

static int qcom_swrm_ahb_reg_read(struct qcom_swrm_ctrl *ctrl, int reg,
				  u32 *val)
{
	struct regmap *wcd_regmap = ctrl->regmap;
	int ret;

	/* pg register + offset */
	ret = regmap_bulk_write(wcd_regmap, SWRM_AHB_BRIDGE_RD_ADDR_0,
			  (u8 *)&reg, 4);
	if (ret < 0)
		return SDW_CMD_FAIL;

	ret = regmap_bulk_read(wcd_regmap, SWRM_AHB_BRIDGE_RD_DATA_0,
			       val, 4);
	if (ret < 0)
		return SDW_CMD_FAIL;

	return SDW_CMD_OK;
}

> Second make sure later when pm_runtime support is added, this take a
> reference ..

Yes indeed, the SoundWire regmap doesn't change the pm_runtime status.