Date:   Mon, 28 Nov 2016 15:14:24 -0800
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Vivek Gautam <vivek.gautam@...eaurora.org>
Cc:     kishon@...com, robh+dt@...nel.org, mark.rutland@....com,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        srinivas.kandagatla@...aro.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v2 2/4] phy: qcom-qusb2: New driver for QUSB2 PHY on Qcom
 chips

On 11/22, Vivek Gautam wrote:
> 
> diff --git a/drivers/phy/Kconfig b/drivers/phy/Kconfig
> index e8eb7f2..f1dcec1 100644
> --- a/drivers/phy/Kconfig
> +++ b/drivers/phy/Kconfig
> @@ -430,6 +430,17 @@ config PHY_STIH407_USB
>  	  Enable this support to enable the picoPHY device used by USB2
>  	  and USB3 controllers on STMicroelectronics STiH407 SoC families.
>  
> +config PHY_QCOM_QUSB2
> +	tristate "Qualcomm QUSB2 PHY Driver"
> +	depends on OF && (ARCH_QCOM || COMPILE_TEST)
> +	select GENERIC_PHY
> +	select RESET_CONTROLLER

This shouldn't be necessary. We only need to select it if we're
providing resets.

> +	help
> +	  Enable this to support the HighSpeed QUSB2 PHY transceiver for USB
> +	  controllers on Qualcomm chips. This driver supports the high-speed
> +	  PHY which is usually paired with either the ChipIdea or Synopsys DWC3
> +	  USB IPs on MSM SOCs.
> +
>  config PHY_QCOM_UFS
>  	tristate "Qualcomm UFS PHY driver"
>  	depends on OF && ARCH_QCOM
> diff --git a/drivers/phy/phy-qcom-qusb2.c b/drivers/phy/phy-qcom-qusb2.c
> new file mode 100644
> index 0000000..d3f9657
> --- /dev/null
> +++ b/drivers/phy/phy-qcom-qusb2.c
> @@ -0,0 +1,549 @@
> +/*
> + * Copyright (c) 2016, The Linux Foundation. All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 and
> + * only version 2 as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/mfd/syscon.h>
> +#include <linux/nvmem-consumer.h>
> +#include <linux/of.h>
> +#include <linux/phy/phy.h>
> +#include <linux/platform_device.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/regmap.h>
> +#include <linux/reset.h>
> +#include <linux/slab.h>
> +
> +#define QUSB2PHY_PLL_TEST		0x04
> +#define CLK_REF_SEL			BIT(7)
> +
> +#define QUSB2PHY_PLL_TUNE		0x08
> +#define QUSB2PHY_PLL_USER_CTL1		0x0c
> +#define QUSB2PHY_PLL_USER_CTL2		0x10
> +#define QUSB2PHY_PLL_AUTOPGM_CTL1	0x1c
> +#define QUSB2PHY_PLL_PWR_CTRL		0x18
> +
> +#define QUSB2PHY_PLL_STATUS		0x38
> +#define PLL_LOCKED			BIT(5)
> +
> +#define QUSB2PHY_PORT_TUNE1             0x80
> +#define QUSB2PHY_PORT_TUNE2             0x84
> +#define QUSB2PHY_PORT_TUNE3             0x88
> +#define QUSB2PHY_PORT_TUNE4             0x8C
> +#define QUSB2PHY_PORT_TUNE5		0x90
> +#define QUSB2PHY_PORT_TEST2		0x9c

Please use lowercase or uppercase consistently (I'd prefer
lowercase).

> +
> +#define QUSB2PHY_PORT_POWERDOWN		0xB4
> +#define CLAMP_N_EN			BIT(5)
> +#define FREEZIO_N			BIT(1)
> +#define POWER_DOWN			BIT(0)
> +
> +#define QUSB2PHY_REFCLK_ENABLE		BIT(0)
> +
> +#define PHY_CLK_SCHEME_SEL		BIT(0)
> +
> +struct qusb2_phy_init_tbl {
> +	unsigned int reg_offset;
> +	unsigned int cfg_val;
> +};
> +#define QCOM_QUSB2_PHY_INIT_CFG(reg, val) \
> +	{				\
> +		.reg_offset = reg,	\
> +		.cfg_val = val,		\
> +	}
> +
> +static struct qusb2_phy_init_tbl msm8996_phy_init_tbl[] = {

const?

> +	QCOM_QUSB2_PHY_INIT_CFG(QUSB2PHY_PORT_TUNE1, 0xF8),
> +	QCOM_QUSB2_PHY_INIT_CFG(QUSB2PHY_PORT_TUNE2, 0xB3),
> +	QCOM_QUSB2_PHY_INIT_CFG(QUSB2PHY_PORT_TUNE3, 0x83),
> +	QCOM_QUSB2_PHY_INIT_CFG(QUSB2PHY_PORT_TUNE4, 0xC0),
> +	QCOM_QUSB2_PHY_INIT_CFG(QUSB2PHY_PLL_TUNE, 0x30),
> +	QCOM_QUSB2_PHY_INIT_CFG(QUSB2PHY_PLL_USER_CTL1, 0x79),
> +	QCOM_QUSB2_PHY_INIT_CFG(QUSB2PHY_PLL_USER_CTL2, 0x21),
> +	QCOM_QUSB2_PHY_INIT_CFG(QUSB2PHY_PORT_TEST2, 0x14),
> +	QCOM_QUSB2_PHY_INIT_CFG(QUSB2PHY_PLL_AUTOPGM_CTL1, 0x9F),
> +	QCOM_QUSB2_PHY_INIT_CFG(QUSB2PHY_PLL_PWR_CTRL, 0x00),
> +};
> +
> +struct qusb2_phy_init_cfg {
> +	struct qusb2_phy_init_tbl *phy_init_tbl;
> +	int phy_init_tbl_sz;
> +	/* offset to PHY_CLK_SCHEME register in TCSR map. */
> +	unsigned int clk_scheme_offset;
> +};
> +
> +const struct qusb2_phy_init_cfg msm8996_phy_init_cfg = {

static?

> +	.phy_init_tbl = msm8996_phy_init_tbl,
> +	.phy_init_tbl_sz = ARRAY_SIZE(msm8996_phy_init_tbl),
> +};
> +
> +/**
> + * struct qusb2_phy: Structure holding qusb2 phy attributes.
> + *
> + * @phy: pointer to generic phy.
> + * @base: pointer to iomapped memory space for qubs2 phy.
> + *
> + * @cfg_ahb_clk: pointer to AHB2PHY interface clock.
> + * @ref_clk: pointer to reference clock.
> + * @ref_clk_src: pointer to source to reference clock.
> + * @iface_src: pointer to phy interface clock.
> + *
> + * @phy_reset: Pointer to phy reset control
> + *
> + * @vdda_phy: vdd supply to the phy core block.
> + * @vdda_pll: 1.8V vdd supply to ref_clk block.
> + * @vdda_phy_dpdm: 3.1V vdd supply to Dp/Dm port signals.
> + * @tcsr: pointer to TCSR syscon register map.

Drop all the full stops on these comments please.

> + *
> + * @cfg: phy initialization config data
> + * @has_se_clk_scheme: indicate if PHY has Single-ended ref clock scheme

Why is single capitalized?

> + */
> +struct qusb2_phy {
> +	struct phy *phy;
> +	void __iomem *base;
> +
> +	struct clk *cfg_ahb_clk;
> +	struct clk *ref_clk;
> +	struct clk *ref_clk_src;
> +	struct clk *iface_clk;
> +
> +	struct reset_control *phy_reset;
> +
> +	struct regulator *vdd_phy;
> +	struct regulator *vdda_pll;
> +	struct regulator *vdda_phy_dpdm;
> +
> +	struct regmap *tcsr;
> +
> +	const struct qusb2_phy_init_cfg *cfg;
> +	bool has_se_clk_scheme;
> +};
> +
> +static inline void qusb2_setbits(void __iomem *reg, u32 val)
> +{
> +	u32 reg_val;
> +
> +	reg_val = readl_relaxed(reg);
> +	reg_val |= val;
> +	writel_relaxed(reg_val, reg);
> +
> +	/* Ensure above write is completed */
> +	mb();
> +}
> +
> +static inline void qusb2_clrbits(void __iomem *reg, u32 val)
> +{
> +	u32 reg_val;
> +
> +	reg_val = readl_relaxed(reg);
> +	reg_val &= ~val;
> +	writel_relaxed(reg_val, reg);
> +
> +	/* Ensure above write is completed */
> +	mb();
> +}
> +
> +static void qcom_qusb2_phy_configure(void __iomem *base,
> +				struct qusb2_phy_init_tbl init_tbl[],
> +				int init_tbl_sz)
> +{
> +	int i;
> +
> +	for (i = 0; i < init_tbl_sz; i++) {
> +		writel_relaxed(init_tbl[i].cfg_val,
> +				base + init_tbl[i].reg_offset);
> +	}
> +
> +	/* flush buffered writes */
> +	mb();
> +}
> +
> +static void qusb2_phy_enable_clocks(struct qusb2_phy *qphy, bool on)

Maybe s/enable/toggle/ because we're not always enabling.

> +{
> +	if (on) {
> +		clk_prepare_enable(qphy->iface_clk);
> +		clk_prepare_enable(qphy->ref_clk_src);
> +	} else {
> +		clk_disable_unprepare(qphy->ref_clk_src);
> +		clk_disable_unprepare(qphy->iface_clk);
> +	}
> +
> +	dev_vdbg(&qphy->phy->dev, "%s(): clocks enabled\n", __func__);

Heh or disabled!

> +}
> +
> +static int qusb2_phy_enable_power(struct qusb2_phy *qphy, bool on)

Maybe s/enable/toggle/ because we're not always enabling.

> +{
> +	int ret;
> +	struct device *dev = &qphy->phy->dev;
> +
> +	if (!on)
> +		goto disable_vdda_phy_dpdm;
> +
> +	ret = regulator_enable(qphy->vdd_phy);
> +	if (ret) {
> +		dev_err(dev, "Unable to enable vdd-phy:%d\n", ret);
> +		goto err_vdd_phy;
> +	}
> +
> +	ret = regulator_enable(qphy->vdda_pll);
> +	if (ret) {
> +		dev_err(dev, "Unable to enable vdda-pll:%d\n", ret);
> +		goto disable_vdd_phy;
> +	}
> +
> +	ret = regulator_enable(qphy->vdda_phy_dpdm);
> +	if (ret) {
> +		dev_err(dev, "Unable to enable vdda-phy-dpdm:%d\n", ret);
> +		goto disable_vdda_pll;
> +	}
> +
> +	dev_vdbg(dev, "%s() regulators are turned on.\n", __func__);

Drop the full stop please.

> +
> +	return ret;
> +
> +disable_vdda_phy_dpdm:
> +	regulator_disable(qphy->vdda_phy_dpdm);
> +disable_vdda_pll:
> +	regulator_disable(qphy->vdda_pll);
> +disable_vdd_phy:
> +	regulator_disable(qphy->vdd_phy);
> +err_vdd_phy:
> +	dev_vdbg(dev, "%s() regulators are turned off.\n", __func__);
> +	return ret;
> +}
> +
> +/*
> + * Fetches HS Tx tuning value from e-fuse and sets QUSB2PHY_PORT_TUNE2
> + * register.
> + * For any error case, skip setting the value and use the default value.
> + */
> +static int qusb2_phy_set_tune2_param(struct qusb2_phy *qphy)
> +{
> +	struct device *dev = &qphy->phy->dev;
> +	struct nvmem_cell *cell;
> +	ssize_t len;
> +	u8 *val;
> +
> +	/*
> +	 * Read EFUSE register having TUNE2 parameter's high nibble.
> +	 * If efuse register shows value as 0x0, or if we fail to find
> +	 * a valid efuse register settings, then use default value
> +	 * as 0xB for high nibble that we have already set while
> +	 * configuring phy.
> +	 */
> +	cell = devm_nvmem_cell_get(dev, "tune2_hstx_trim_efuse");
> +	if (IS_ERR(cell)) {
> +		if (PTR_ERR(cell) == -EPROBE_DEFER)
> +			return PTR_ERR(cell);
> +		goto skip;

Why do we get the nvmem cell here? Wouldn't we want to get it
during probe? Returning probe defer here during init would be
odd.

> +	}
> +
> +	/*
> +	 * we need to read only one byte here, since the required
> +	 * parameter value fits in one nibble
> +	 */
> +	val = (u8 *)nvmem_cell_read(cell, &len);

Shouldn't need the cast here. Also it would be nice if
nvmem_cell_read() didn't require a second argument if we don't
care for it. We should update the API to allow NULL there.

> +	if (!IS_ERR(val)) {
> +		/* Fused TUNE2 value is the higher nibble only */
> +		qusb2_setbits(qphy->base + QUSB2PHY_PORT_TUNE2,
> +							val[0] << 0x4);
> +	} else {
> +		dev_dbg(dev, "failed reading hs-tx trim value: %ld\n",
> +							PTR_ERR(val));
> +	}
> +
> +skip:
> +	return 0;
> +}
> +
[...]
> +
> +static int qusb2_phy_init(struct phy *phy)
> +{
> +	struct qusb2_phy *qphy = phy_get_drvdata(phy);
> +	unsigned int reset_val;
> +	unsigned int clk_scheme;
> +	int ret;
> +
> +	dev_vdbg(&phy->dev, "Initializing QUSB2 phy\n");
> +
> +	/* enable ahb interface clock to program phy */
> +	clk_prepare_enable(qphy->cfg_ahb_clk);

What if that fails?

> +
> +	/* Perform phy reset */
> +	ret = reset_control_assert(qphy->phy_reset);
> +	if (ret) {
> +		dev_err(&phy->dev, "Failed to assert phy_reset\n");
> +		return ret;
> +	}
> +	/* 100 us delay to keep PHY in reset mode */
> +	usleep_range(100, 150);
> +	ret = reset_control_deassert(qphy->phy_reset);
> +	if (ret) {
> +		dev_err(&phy->dev, "Failed to de-assert phy_reset\n");
> +		return ret;
> +	}
> +
> +	/* Disable the PHY */
> +	qusb2_setbits(qphy->base + QUSB2PHY_PORT_POWERDOWN,
> +			CLAMP_N_EN | FREEZIO_N | POWER_DOWN);
> +
> +	/* save reset value to override based on clk scheme */
> +	reset_val = readl_relaxed(qphy->base + QUSB2PHY_PLL_TEST);
> +
> +	qcom_qusb2_phy_configure(qphy->base, qphy->cfg->phy_init_tbl,
> +				qphy->cfg->phy_init_tbl_sz);
> +
> +	/* Check for efuse value for tuning the PHY */
> +	ret = qusb2_phy_set_tune2_param(qphy);
> +	if (ret)
> +		return ret;
> +
> +	/* Enable the PHY */
> +	qusb2_clrbits(qphy->base + QUSB2PHY_PORT_POWERDOWN, POWER_DOWN);
> +
> +	/* Require to get phy pll lock successfully */
> +	usleep_range(150, 160);
> +
> +	/* Default is Single-ended clock on msm8996 */
> +	qphy->has_se_clk_scheme = true;
> +	/*
> +	 * read TCSR_PHY_CLK_SCHEME register to check if Single-ended

Capital Single again?

> +	 * clock scheme is selected. If yes, then disable differential
> +	 * ref_clk and use single-ended clock, otherwise use differential
> +	 * ref_clk only.
> +	 */
> +	if (qphy->tcsr) {
> +		ret = regmap_read(qphy->tcsr, qphy->cfg->clk_scheme_offset,
> +							&clk_scheme);
> +		/* is it a differential clock scheme ? */
> +		if (!(clk_scheme & PHY_CLK_SCHEME_SEL)) {
> +			dev_vdbg(&phy->dev, "%s: select differential clk src\n",
> +								__func__);
> +			qphy->has_se_clk_scheme = false;
> +		} else {
> +			dev_vdbg(&phy->dev, "%s: select single-ended clk src\n",
> +								__func__);
> +		}
> +	}
> +
> +	if (!qphy->has_se_clk_scheme) {
> +		reset_val &= ~CLK_REF_SEL;
> +		clk_prepare_enable(qphy->ref_clk);

And if that fails?

> +	} else {
> +		reset_val |= CLK_REF_SEL;
> +	}
> +
> +	writel_relaxed(reset_val, qphy->base + QUSB2PHY_PLL_TEST);
> +
> +	/* Make sure that above write is completed to get PLL source clock */
> +	wmb();
> +
> +	/* Required to get PHY PLL lock successfully */
> +	usleep_range(100, 110);
> +
> +	if (!(readb_relaxed(qphy->base + QUSB2PHY_PLL_STATUS) &
> +					PLL_LOCKED)) {
> +		dev_err(&phy->dev, "QUSB PHY PLL LOCK fails:%x\n",
> +			readb_relaxed(qphy->base + QUSB2PHY_PLL_STATUS));

Would be pretty funny if this was locked now when the error
printk runs. Are there other bits in there that are helpful?

> +		return -EBUSY;
> +	}
> +
> +	return 0;
> +}
> +
> +static int qusb2_phy_exit(struct phy *phy)
> +{
> +	struct qusb2_phy *qphy = phy_get_drvdata(phy);
> +
> +	/* Disable the PHY */
> +	qusb2_setbits(qphy->base + QUSB2PHY_PORT_POWERDOWN,
> +			CLAMP_N_EN | FREEZIO_N | POWER_DOWN);
> +
> +	if (!qphy->has_se_clk_scheme)
> +		clk_disable_unprepare(qphy->ref_clk);
> +
> +	clk_disable_unprepare(qphy->cfg_ahb_clk);
> +
> +	return 0;
> +}
> +
> +static const struct phy_ops qusb2_phy_gen_ops = {
> +	.init		= qusb2_phy_init,
> +	.exit		= qusb2_phy_exit,
> +	.power_on	= qusb2_phy_poweron,
> +	.power_off	= qusb2_phy_poweroff,
> +	.owner		= THIS_MODULE,
> +};
> +
> +static const struct of_device_id qusb2_phy_of_match_table[] = {
> +	{
> +		.compatible	= "qcom,msm8996-qusb2-phy",
> +		.data		= &msm8996_phy_init_cfg,
> +	},
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, qusb2_phy_of_match_table);
> +
> +static int qusb2_phy_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct qusb2_phy *qphy;
> +	struct phy_provider *phy_provider;
> +	struct phy *generic_phy;
> +	const struct of_device_id *match;
> +	struct resource *res;
> +	int ret;
> +
> +	qphy = devm_kzalloc(dev, sizeof(*qphy), GFP_KERNEL);
> +	if (!qphy)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	qphy->base = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(qphy->base))
> +		return PTR_ERR(qphy->base);
> +
> +	qphy->cfg_ahb_clk = devm_clk_get(dev, "cfg_ahb_clk");
> +	if (IS_ERR(qphy->cfg_ahb_clk)) {
> +		ret = PTR_ERR(qphy->cfg_ahb_clk);
> +		if (ret != -EPROBE_DEFER)
> +			dev_err(dev, "failed to get cfg_ahb_clk\n");
> +		return ret;
> +	}
> +
> +	qphy->ref_clk_src = devm_clk_get(dev, "ref_clk_src");
> +	if (IS_ERR(qphy->ref_clk_src)) {
> +		ret = PTR_ERR(qphy->ref_clk_src);
> +		if (ret != -EPROBE_DEFER)
> +			dev_err(dev, "clk get failed for ref_clk_src\n");
> +		return ret;
> +	}
> +
> +	qphy->ref_clk = devm_clk_get(dev, "ref_clk");
> +	if (IS_ERR(qphy->ref_clk)) {
> +		ret = PTR_ERR(qphy->ref_clk);
> +		if (ret != -EPROBE_DEFER)
> +			dev_err(dev, "clk get failed for ref_clk\n");
> +		return ret;
> +	} else {
> +		clk_set_rate(qphy->ref_clk, 19200000);

Drop the else. Also what if clk_set_rate() fails?

> +	}
> +
> +	qphy->iface_clk = devm_clk_get(dev, "iface_clk");
> +	if (IS_ERR(qphy->iface_clk)) {
> +		ret = PTR_ERR(qphy->iface_clk);
> +		if (ret != -EPROBE_DEFER) {
> +			qphy->iface_clk = NULL;
> +			dev_dbg(dev, "clk get failed for iface_clk\n");
> +		} else {
> +			return ret;
> +		}

		if (PTR_ERR(qphy->iface_clk) == -EPROBE_DEFER)
			return -EPROBE_DEFER;
		qphy->iface_clk = NULL;
		dev_dbg(dev, "clk get failed for iface_clk\n");

Is shorter.
		
> +	}
> +
> +	qphy->phy_reset = devm_reset_control_get(&pdev->dev, "phy");
> +	if (IS_ERR(qphy->phy_reset)) {
> +		dev_err(dev, "failed to get phy core reset\n");
> +		return PTR_ERR(qphy->phy_reset);
> +	}
> +
> +	qphy->vdd_phy = devm_regulator_get(dev, "vdd-phy");
> +	if (IS_ERR(qphy->vdd_phy)) {
> +		dev_err(dev, "unable to get vdd-phy supply\n");
> +		return PTR_ERR(qphy->vdd_phy);
> +	}
> +
> +	qphy->vdda_pll = devm_regulator_get(dev, "vdda-pll");
> +	if (IS_ERR(qphy->vdda_pll)) {
> +		dev_err(dev, "unable to get vdda-pll supply\n");
> +		return PTR_ERR(qphy->vdda_pll);
> +	}
> +
> +	qphy->vdda_phy_dpdm = devm_regulator_get(dev, "vdda-phy-dpdm");
> +	if (IS_ERR(qphy->vdda_phy_dpdm)) {
> +		dev_err(dev, "unable to get vdda-phy-dpdm supply\n");
> +		return PTR_ERR(qphy->vdda_phy_dpdm);
> +	}
> +
> +	/* Get the specific init parameters of QMP phy */
> +	match = of_match_node(qusb2_phy_of_match_table, dev->of_node);
> +	qphy->cfg = match->data;

Use of_device_get_match_data() instead.

> +
> +	qphy->tcsr = syscon_regmap_lookup_by_phandle(dev->of_node,
> +							"qcom,tcsr-syscon");
> +	if (IS_ERR(qphy->tcsr)) {
> +		dev_dbg(dev, "Failed to lookup TCSR regmap\n");
> +		qphy->tcsr = NULL;
> +	}
> +
> +	generic_phy = devm_phy_create(dev, NULL, &qusb2_phy_gen_ops);
> +	if (IS_ERR(generic_phy)) {
> +		ret = PTR_ERR(generic_phy);
> +		dev_err(dev, "%s: failed to create phy %d\n", __func__, ret);
> +		return ret;
> +	}
> +	qphy->phy = generic_phy;
> +
> +	dev_set_drvdata(dev, qphy);
> +	phy_set_drvdata(generic_phy, qphy);
> +
> +	phy_provider = devm_of_phy_provider_register(dev, of_phy_simple_xlate);
> +	if (IS_ERR(phy_provider)) {
> +		ret = PTR_ERR(phy_provider);
> +		dev_err(dev, "%s: failed to register phy %d\n", __func__, ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> 

-- 
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a Linux Foundation Collaborative Project

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