linux-kernel - Re: [PATCH v3 4/4] phy: qcom-qmp: new qmp phy driver for qcom-chipsets

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Message-ID: <e83564d4-d731-44dd-40d1-e36fa56f4920@codeaurora.org>
Date:   Fri, 6 Jan 2017 15:17:01 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     robh+dt@...nel.org, kishon@...com, sboyd@...eaurora.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        mark.rutland@....com, srinivas.kandagatla@...aro.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v3 4/4] phy: qcom-qmp: new qmp phy driver for
 qcom-chipsets

Hi,


On 01/06/2017 12:48 PM, Bjorn Andersson wrote:
> On Tue 20 Dec 09:03 PST 2016, Vivek Gautam wrote:
>
>> diff --git a/drivers/phy/phy-qcom-qmp.c b/drivers/phy/phy-qcom-qmp.c
> [..]
>> +static int qcom_qmp_phy_poweron(struct phy *phy)
> [..]
>> +
>> +err3:
> Rather than naming your labels errX, it's idiomatic to give them
> descriptive names, e.g. "disable_ref_clk" here.
Sure will change these labels and any such occurrence further in the code.

>
>> +	clk_disable_unprepare(qphy->ref_clk);
>> +err2:
>> +	regulator_disable(qphy->vddp_ref_clk);
>> +err1:
>> +	regulator_disable(qphy->vdda_pll);
>> +err:
>> +	regulator_disable(qphy->vdda_phy);
>> +	return ret;
>> +}
> [..]
>> +static int qcom_qmp_phy_com_init(struct qcom_qmp_phy *qphy)
>> +{
>> +	const struct qmp_phy_cfg *cfg = qphy->cfg;
>> +	void __iomem *serdes = qphy->serdes;
>> +	int ret;
>> +
>> +	mutex_lock(&qphy->phy_mutex);
>> +	if (qphy->init_count++) {
>> +		mutex_unlock(&qphy->phy_mutex);
>> +		return 0;
>> +	}
> As far as I can see phy_init() and phy_exit() already keep reference
> count on the initialization and you only call this function from
> phy_ops->init, so you should be able to drop this.
This is an intermediary function that does the common block initialization.
PHYs like PCIe have a separate common block (apart from SerDes)
for all phy channels. We shouldn't program this common block
multiple times for each channel. That's why this init_count.

>
> [..]
>> +
>> +/* PHY Initialization */
>> +static int qcom_qmp_phy_init(struct phy *phy)
>> +{
> [..]
>> +	/* phy power down delay; given in PCIE phy programming guide only */
>> +	if (qphy->cfg->type == PHY_TYPE_PCIE)
> Rather than basing this off "is this pcie" it's preferred if you have a
> bool power_down_delay; (or optionally carrying the timeout value) to
> control this.
Sure, will modify this.

>
>> +		usleep_range(POWER_DOWN_DELAY_US_MIN, POWER_DOWN_DELAY_US_MAX);
>> +
>> +	/* start SerDes and Phy-Coding-Sublayer */
>> +	qphy_setbits(pcs + QPHY_START_CTRL, cfg->start_ctrl);
>> +
>> +	/* Pull PHY out of reset state */
>> +	qphy_clrbits(pcs + QPHY_SW_RESET, SW_RESET);
>> +
>> +	status = pcs + cfg->regs[QPHY_PCS_READY_STATUS];
>> +	mask = cfg->mask_pcs_ready;
>> +
>> +	ret = !mask ? 0 : readl_poll_timeout(status, val, !(val & mask), 1,
>> +						PHY_INIT_COMPLETE_TIMEOUT);
> I presume it's not okay to read the status register even once for pcie?
> If it is you can skip the conditional as !(val & 0) will break the poll
> after the first read.
Yea, it is okay to read the status register for pcie.

Will leave just readl_poll_timeout() that exits on !(val & mask).
We anyways don't set mask_pcs_ready for pcie.

> [..]
>> +static int qcom_qmp_phy_exit(struct phy *phy)
>> +{
> [..]
>> +}
>> +
>> +
> Extra blank line
Will remove it.
>
>> +static int qcom_qmp_phy_regulator_init(struct device *dev)
> [..]
>> +static
>> +struct qmp_phy_desc *qcom_qmp_phy_create(struct platform_device *pdev, int id)
>> +{
> [..]
>> +	phy_desc->pipe_clk = devm_clk_get(dev, prop_name);
>> +	if (IS_ERR(phy_desc->pipe_clk)) {
>> +		if (qphy->cfg->type == PHY_TYPE_PCIE ||
>> +		    qphy->cfg->type == PHY_TYPE_USB3) {
> Is this check adding any value?
The USB3 and PCIe phys are PIPE based phys, and hence the pipe
clock is mandatory for them. Other phys don't care about pipe clock.

>
>> +			ret = PTR_ERR(phy_desc->pipe_clk);
>> +			if (ret != -EPROBE_DEFER)
>> +				dev_err(dev,
>> +					"failed to get lane%d pipe_clk, %d\n",
>> +					id, ret);
>> +			return ERR_PTR(ret);
>> +		}
>> +		phy_desc->pipe_clk = NULL;
> Regards,
> Bjorn
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Regards
Vivek

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