Message-id: <52D00C33.4060305@samsung.com>
Date: Fri, 10 Jan 2014 16:05:23 +0100
From: Tomasz Figa <t.figa@samsung.com>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101
 Thunderbird/24.1.1
MIME-version: 1.0
To: Yuvaraj Kumar C D <yuvaraj.cd@gmail.com>, kishon@ti.com,
        kgene.kim@samsung.com, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org,
        linux-doc@vger.kernel.org, Wolfram Sang <wsa@the-dreams.de>
Cc: mark.rutland@arm.com, jg1.han@samsung.com, b.zolnierkie@samsung.com,
        joshi@samsung.com, swarren@wwwdotorg.org, grant.likely@linaro.org,
        christoffer.dall@linaro.org, linux-ide@vger.kernel.org,
        Yuvaraj Kumar C D <yuvaraj.cd@samsung.com>,
        Girish K S <ks.giri@samsung.com>,
        Vasanth Ananthan <vasanth.a@samsung.com>
Subject: Re: [PATCH V6 1/2] PHY: Exynos: Add Exynos5250 SATA PHY driver
References: <1389337208-11325-1-git-send-email-yuvaraj.cd@samsung.com>
 <1389337208-11325-2-git-send-email-yuvaraj.cd@samsung.com>
In-reply-to: <1389337208-11325-2-git-send-email-yuvaraj.cd@samsung.com>
Content-type: text/plain; charset=ISO-8859-1; format=flowed
Content-transfer-encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org

Hi Yuvaraj,

In general this version looks pretty good, but I have some questions inline.

On 10.01.2014 08:00, Yuvaraj Kumar C D wrote:
[snip]
> diff --git a/drivers/phy/phy-exynos5250-sata-i2c.c b/drivers/phy/phy-exynos5250-sata-i2c.c
> new file mode 100644
> index 0000000..206e337
> --- /dev/null
> +++ b/drivers/phy/phy-exynos5250-sata-i2c.c
> @@ -0,0 +1,40 @@
> +/*
> + * Copyright (C) 2013 Samsung Electronics Co.Ltd
> + * Author:
> + *	Yuvaraj C D <yuvaraj.cd@samsung.com>
> + *
> + * This program is free software; you can redistribute  it and/or modify it
> + * under  the terms of  the GNU General  Public License as published by the
> + * Free Software Foundation;  either version 2 of the  License, or (at your
> + * option) any later version.
> + *
> + */
> +
> +#include <linux/i2c.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +
> +static int exynos_sata_i2c_probe(struct i2c_client *client,
> +		const struct i2c_device_id *i2c_id)
> +{
> +	return 0;
> +}
> +
> +static const struct i2c_device_id sataphy_i2c_device_match[] = {
> +	{ "exynos-sataphy-i2c", 0 },
> +};
> +
> +static struct i2c_driver sataphy_i2c_driver = {
> +	.probe		= exynos_sata_i2c_probe,
> +	.id_table	= sataphy_i2c_device_match,
> +	.driver   = {
> +		.name = "exynos-sataphy-i2c",
> +		.owner = THIS_MODULE,
> +	},
> +};
> +
> +static int __init exynos5250_phy_i2c_init(void)
> +{
> +	return i2c_add_driver(&sataphy_i2c_driver);
> +}
> +module_init(exynos5250_phy_i2c_init);

Hmm, is this driver even necessary now?

Wolfram, would it be possible to use an i2c_client without a driver 
bound to it?

> diff --git a/drivers/phy/phy-exynos5250-sata.c b/drivers/phy/phy-exynos5250-sata.c
> new file mode 100644
> index 0000000..6e5ff8d
> --- /dev/null
> +++ b/drivers/phy/phy-exynos5250-sata.c
> @@ -0,0 +1,238 @@
> +/*
> + * Samsung SATA SerDes(PHY) driver
> + *
> + * Copyright (C) 2013 Samsung Electronics Co., Ltd.
> + * Authors: Girish K S <ks.giri@samsung.com>
> + *         Yuvaraj Kumar C D <yuvaraj.cd@samsung.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/io.h>
> +#include <linux/i2c.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/phy/phy.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/spinlock.h>
> +#include <linux/mfd/syscon.h>
> +
> +#define EXYNOS5_SATA_RESET		0x4
> +#define RESET_CMN_RST_N			(1 << 1)
> +#define LINK_RESET			0xF0000

nit: Lowercase is preferred in hexadecimal notation.
+ all other occurrences in this file.

> +#define EXYNOS5_SATA_MODE0		0x10
> +#define EXYNOS5_SATAPHY_PMU_ENABLE	(1 << 0)
> +#define SATA_SPD_GEN3			(2 << 0)
> +#define EXYNOS5_SATA_CTRL0		0x14
> +#define CTRL0_P0_PHY_CALIBRATED_SEL	(1 << 9)
> +#define CTRL0_P0_PHY_CALIBRATED		(1 << 8)
> +#define EXYNOS5_SATA_PHSATA_CTRLM	0xE0
> +#define PHCTRLM_REF_RATE		(1 << 1)
> +#define PHCTRLM_HIGH_SPEED		(1 << 0)
> +#define EXYNOS5_SATA_PHSATA_STATM	0xF0
> +#define PHSTATM_PLL_LOCKED		(1 << 0)
> +#define EXYNOS_SATA_PHY_EN		(1 << 0)
> +#define SATAPHY_CONTROL_OFFSET		0x0724
> +
> +struct exynos_sata_phy {
> +	struct phy *phy;
> +	struct clk *phyclk;
> +	void __iomem *regs;
> +	void __iomem *pmureg;
> +	struct i2c_client *client;
> +};
> +
> +static bool wait_for_reg_status(void __iomem *base, u32 reg, u32 checkbit,
> +				u32 status)
> +{
> +	unsigned long timeout = jiffies + usecs_to_jiffies(1000);

nit: It would be better to define the timeout using a macro to not use 
magic numbers.

> +
> +	while (time_before(jiffies, timeout)) {
> +		if ((readl(base + reg) & checkbit) == status)
> +			return true;
> +	}
> +
> +	return false;
> +}
> +
> +static int exynos_sata_phy_power_on(struct phy *phy)
> +{
> +	struct exynos_sata_phy *sata_phy = phy_get_drvdata(phy);
> +
> +	regmap_update_bits(sata_phy->pmureg, SATAPHY_CONTROL_OFFSET,
> +			EXYNOS5_SATAPHY_PMU_ENABLE, EXYNOS_SATA_PHY_EN);

regmap_update_bits can return an error. Wouldn't it be better to return 
it as return value of this function instead of returning 0 all the time? 
As a side effect, this would make the function smaller by two lines.

> +
> +	return 0;
> +}
> +
> +static int exynos_sata_phy_power_off(struct phy *phy)
> +{
> +	struct exynos_sata_phy *sata_phy = phy_get_drvdata(phy);
> +
> +	regmap_update_bits(sata_phy->pmureg, SATAPHY_CONTROL_OFFSET,
> +			EXYNOS5_SATAPHY_PMU_ENABLE, ~EXYNOS_SATA_PHY_EN);

Same here.

> +
> +	return 0;
> +}
> +
> +static int exynos_sata_phy_init(struct phy *phy)
> +{
> +	u32 val = 0;
> +	int ret = 0;
> +	u8 buf[] = { 0x3A, 0x0B };
> +	struct exynos_sata_phy *sata_phy = phy_get_drvdata(phy);
> +
> +	regmap_update_bits(sata_phy->pmureg, SATAPHY_CONTROL_OFFSET,
> +			EXYNOS5_SATAPHY_PMU_ENABLE, EXYNOS_SATA_PHY_EN);

regmap_update_bits returns an error code.

> +
> +	writel(val, sata_phy->regs + EXYNOS5_SATA_RESET);
> +
> +	val = readl(sata_phy->regs + EXYNOS5_SATA_RESET);
> +	val |= 0xFF;
> +	writel(val, sata_phy->regs + EXYNOS5_SATA_RESET);
> +
> +	val = readl(sata_phy->regs + EXYNOS5_SATA_RESET);
> +	val |= LINK_RESET;
> +	writel(val, sata_phy->regs + EXYNOS5_SATA_RESET);
> +
> +	val = readl(sata_phy->regs + EXYNOS5_SATA_RESET);
> +	val |= RESET_CMN_RST_N;
> +	writel(val, sata_phy->regs + EXYNOS5_SATA_RESET);
> +
> +	val = readl(sata_phy->regs + EXYNOS5_SATA_PHSATA_CTRLM);
> +	val &= ~PHCTRLM_REF_RATE;
> +	writel(val, sata_phy->regs + EXYNOS5_SATA_PHSATA_CTRLM);
> +
> +	/* High speed enable for Gen3 */
> +	val = readl(sata_phy->regs + EXYNOS5_SATA_PHSATA_CTRLM);
> +	val |= PHCTRLM_HIGH_SPEED;
> +	writel(val, sata_phy->regs + EXYNOS5_SATA_PHSATA_CTRLM);
> +
> +	val = readl(sata_phy->regs + EXYNOS5_SATA_CTRL0);
> +	val |= CTRL0_P0_PHY_CALIBRATED_SEL | CTRL0_P0_PHY_CALIBRATED;
> +	writel(val, sata_phy->regs + EXYNOS5_SATA_CTRL0);
> +
> +	val = readl(sata_phy->regs + EXYNOS5_SATA_MODE0);
> +	val |= SATA_SPD_GEN3;
> +	writel(val, sata_phy->regs + EXYNOS5_SATA_MODE0);
> +
> +	ret = i2c_master_send(sata_phy->client, buf, sizeof(buf));
> +	if (ret < 0)
> +		return -ENXIO;

Wouldn't it be better to return the same error code as i2c_master_send 
returned?

> +
> +	/* release cmu reset */
> +	val = readl(sata_phy->regs + EXYNOS5_SATA_RESET);
> +	val &= ~RESET_CMN_RST_N;
> +	writel(val, sata_phy->regs + EXYNOS5_SATA_RESET);
> +
> +	val = readl(sata_phy->regs + EXYNOS5_SATA_RESET);
> +	val |= RESET_CMN_RST_N;
> +	writel(val, sata_phy->regs + EXYNOS5_SATA_RESET);
> +
> +	return (wait_for_reg_status(sata_phy->regs, EXYNOS5_SATA_PHSATA_STATM,
> +		PHSTATM_PLL_LOCKED, 1)) ? 0 : -EINVAL;
> +

nit: Stray blank line.

Also it might be more readable after making wait_for_reg_status() return 
an integer error code (0 and e.g. -EFAULT) and rewriting the last line to:

	ret = wait_for_reg_status(sata_phy->regs, 		
					EXYNOS5_SATA_PHSATA_STATM,
					PHSTATM_PLL_LOCKED, 1);
	if (ret < 0)
		dev_err(&sata_phy->client->dev,
			"PHY PLL locking failed\n");

	return ret;

By the way, isn't this initialization really needed whenever the PHY is 
powered on?

> +}
> +
> +static struct phy_ops exynos_sata_phy_ops = {
> +	.init		= exynos_sata_phy_init,
> +	.power_on	= exynos_sata_phy_power_on,
> +	.power_off	= exynos_sata_phy_power_off,
> +	.owner		= THIS_MODULE,
> +};
> +
> +static int exynos_sata_phy_probe(struct platform_device *pdev)
> +{
> +	struct exynos_sata_phy *sata_phy;
> +	struct device *dev = &pdev->dev;
> +	struct resource *res;
> +	struct phy_provider *phy_provider;
> +	struct device_node *node;
> +	int ret = 0;
> +
> +	sata_phy = devm_kzalloc(dev, sizeof(*sata_phy), GFP_KERNEL);
> +	if (!sata_phy)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +
> +	sata_phy->regs = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(sata_phy->regs))
> +		return PTR_ERR(sata_phy->regs);
> +
> +	sata_phy->pmureg = syscon_regmap_lookup_by_phandle(dev->of_node,
> +					"samsung,syscon-phandle");

pmureg is defined as (void __iomem *) in struct exynos_sata_phy, but 
syscon_regmap_lookup_by_phandle() returns (struct regmap *). Moreover it 
does not return NULL on error, but rather ERR_PTR(). Please correct this.

> +	if (!sata_phy->pmureg) {
> +		dev_err(dev, "syscon regmap lookup failed.\n");
> +		return PTR_ERR(sata_phy->pmureg);
> +	}
> +
> +	node = of_parse_phandle(dev->of_node,
> +			"samsung,exynos-sataphy-i2c-phandle", 0);
> +	if (!node)
> +		return -ENODEV;

An error here means that a required DT property was not specified or was 
specified incorrectly. IMHO -EINVAL would be better here.

> +
> +	sata_phy->client = of_find_i2c_device_by_node(node);
> +	if (!sata_phy->client)
> +		return -EPROBE_DEFER;
> +
> +	dev_set_drvdata(dev, sata_phy);
> +
> +	sata_phy->phyclk = devm_clk_get(dev, "sata_phyctrl");
> +	if (IS_ERR(sata_phy->phyclk)) {
> +		dev_err(dev, "failed to get clk for PHY\n");
> +		return PTR_ERR(sata_phy->phyclk);
> +	}
> +
> +	ret = clk_prepare_enable(sata_phy->phyclk);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to enable source clk\n");
> +		return ret;
> +	}
> +
> +	sata_phy->phy = devm_phy_create(dev, &exynos_sata_phy_ops, NULL);
> +	if (IS_ERR(sata_phy->phy)) {
> +		clk_disable_unprepare(sata_phy->phyclk);
> +		dev_err(dev, "failed to create PHY\n");
> +		return PTR_ERR(sata_phy->phy);
> +	}
> +
> +	phy_set_drvdata(sata_phy->phy, sata_phy);
> +
> +	phy_provider = devm_of_phy_provider_register(dev,
> +					of_phy_simple_xlate);
> +	if (IS_ERR(phy_provider)) {
> +		clk_disable_unprepare(sata_phy->phyclk);
> +		return PTR_ERR(phy_provider);
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id exynos_sata_phy_of_match[] = {
> +	{ .compatible = "samsung,exynos5250-sata-phy" },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, exynos_sata_phy_of_match);
> +
> +static struct platform_driver exynos_sata_phy_driver = {
> +	.probe	= exynos_sata_phy_probe,

If this driver can be compiled as module, don't you also need remove?

Best regards,
Tomasz
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/