Message-id: <534506B1.4040908@samsung.com>
Date: Wed, 09 Apr 2014 10:37:05 +0200
From: Andrzej Hajda <a.hajda@samsung.com>
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To: Tomasz Stanislawski <t.stanislaws@samsung.com>,
        linux-kernel@vger.kernel.org, linux-samsung-soc@vger.kernel.org,
        devicetree@vger.kernel.org, linux-media@vger.kernel.org,
        dri-devel@lists.freedesktop.org
Cc: kgene.kim@samsung.com, kishon@ti.com, kyungmin.park@samsung.com,
        robh+dt@kernel.org, grant.likely@linaro.org,
        sylvester.nawrocki@gmail.com, rahul.sharma@samsung.com
Subject: Re: [PATCHv2 1/3] phy: Add exynos-simple-phy driver
References: <1396967856-27470-1-git-send-email-t.stanislaws@samsung.com>
 <1396967856-27470-2-git-send-email-t.stanislaws@samsung.com>
In-reply-to: <1396967856-27470-2-git-send-email-t.stanislaws@samsung.com>
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Sender: linux-kernel-owner@vger.kernel.org

Hi Tomasz,

On 04/08/2014 04:37 PM, Tomasz Stanislawski wrote:
> Add exynos-simple-phy driver to support a single register
> PHY interfaces present on Exynos4 SoC.
> 
> Signed-off-by: Tomasz Stanislawski <t.stanislaws@samsung.com>
> ---
>  .../devicetree/bindings/phy/samsung-phy.txt        |   24 +++
>  drivers/phy/Kconfig                                |    5 +
>  drivers/phy/Makefile                               |    1 +
>  drivers/phy/exynos-simple-phy.c                    |  154 ++++++++++++++++++++
>  4 files changed, 184 insertions(+)
>  create mode 100644 drivers/phy/exynos-simple-phy.c
> 
> diff --git a/Documentation/devicetree/bindings/phy/samsung-phy.txt b/Documentation/devicetree/bindings/phy/samsung-phy.txt
> index b422e38..f97c4c3 100644
> --- a/Documentation/devicetree/bindings/phy/samsung-phy.txt
> +++ b/Documentation/devicetree/bindings/phy/samsung-phy.txt
> @@ -114,3 +114,27 @@ Example:
>  		compatible = "samsung,exynos-sataphy-i2c";
>  		reg = <0x38>;
>  	};
> +
> +Samsung S5P/EXYNOS SoC series SIMPLE PHY
> +-------------------------------------------------
> +
> +Required properties:
> +- compatible : should be one of the listed compatibles:
> +	- "samsung,exynos4210-simple-phy"
> +	- "samsung,exynos4412-simple-phy"
> +- reg : offset and length of the register set;
> +- #phy-cells : from the generic phy bindings, must be 1;
> +
> +For "samsung,exynos4210-simple-phy" compatible PHYs the second cell in
> +the PHY specifier identifies the PHY and its meaning is as follows:
> +  0 - HDMI PHY,
> +  1 - DAC PHY,
> +  2 - ADC PHY,
> +  3 - PCIE PHY.
> +  4 - SATA PHY.
> +
> +For "samsung,exynos4412-simple-phy" compatible PHYs the second cell in
> +the PHY specifier identifies the PHY and its meaning is as follows:
> +  0 - HDMI PHY,
> +  1 - ADC PHY,

What about using preprocessor macros?

> +
> diff --git a/drivers/phy/Kconfig b/drivers/phy/Kconfig
> index 3bb05f1..65ab783 100644
> --- a/drivers/phy/Kconfig
> +++ b/drivers/phy/Kconfig
> @@ -166,4 +166,9 @@ config PHY_XGENE
>  	help
>  	  This option enables support for APM X-Gene SoC multi-purpose PHY.
>  
> +config EXYNOS_SIMPLE_PHY
> +	tristate "Exynos Simple PHY driver"
> +	help
> +	  Support for 1-bit PHY controllers on SoCs from Exynos family.
> +
>  endmenu
> diff --git a/drivers/phy/Makefile b/drivers/phy/Makefile
> index 2faf78e..88c5b60 100644
> --- a/drivers/phy/Makefile
> +++ b/drivers/phy/Makefile
> @@ -18,3 +18,4 @@ obj-$(CONFIG_PHY_EXYNOS4210_USB2)	+= phy-exynos4210-usb2.o
>  obj-$(CONFIG_PHY_EXYNOS4X12_USB2)	+= phy-exynos4x12-usb2.o
>  obj-$(CONFIG_PHY_EXYNOS5250_USB2)	+= phy-exynos5250-usb2.o
>  obj-$(CONFIG_PHY_XGENE)			+= phy-xgene.o
> +obj-$(CONFIG_EXYNOS_SIMPLE_PHY)		+= exynos-simple-phy.o
> diff --git a/drivers/phy/exynos-simple-phy.c b/drivers/phy/exynos-simple-phy.c
> new file mode 100644
> index 0000000..57ad338
> --- /dev/null
> +++ b/drivers/phy/exynos-simple-phy.c
> @@ -0,0 +1,154 @@
> +/*
> + * Exynos Simple PHY driver
> + *
> + * Copyright (C) 2013 Samsung Electronics Co., Ltd.
> + * Author: Tomasz Stanislawski <t.stanislaws@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/io.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/of_device.h>
> +#include <linux/phy/phy.h>
> +
> +#define EXYNOS_PHY_ENABLE	(1 << 0)
> +
> +static int exynos_phy_power_on(struct phy *phy)
> +{
> +	void __iomem *reg = phy_get_drvdata(phy);
> +	u32 val;
> +
> +	val = readl(reg);
> +	val |= EXYNOS_PHY_ENABLE;
> +	writel(val, reg);
> +
> +	return 0;
> +}
> +
> +static int exynos_phy_power_off(struct phy *phy)
> +{
> +	void __iomem *reg = phy_get_drvdata(phy);
> +	u32 val;
> +
> +	val = readl(reg);
> +	val &= ~EXYNOS_PHY_ENABLE;
> +	writel(val, reg);
> +
> +	return 0;
> +}
> +
> +static struct phy_ops exynos_phy_ops = {
> +	.power_on	= exynos_phy_power_on,
> +	.power_off	= exynos_phy_power_off,
> +	.owner		= THIS_MODULE,
> +};
> +
> +static const u32 exynos4210_offsets[] = {
> +	0x0700, /* HDMI_PHY */
> +	0x070C, /* DAC_PHY */
> +	0x0718, /* ADC_PHY */
> +	0x071C, /* PCIE_PHY */
> +	0x0720, /* SATA_PHY */
> +	~0, /* end mark */
> +};
> +
> +static const u32 exynos4412_offsets[] = {
> +	0x0700, /* HDMI_PHY */
> +	0x0718, /* ADC_PHY */
> +	~0, /* end mark */
> +};

Why have you selected only these registers?
According to specs Exynos 4210 has 9 and 4412 has 7 control registers
with 'phy-enable' functionality.
I guess MIPI would require little more work as it has also reset bits,
but it will be still better than separate driver.

> +
> +static const struct of_device_id exynos_phy_of_match[] = {
> +	{ .compatible = "samsung,exynos4210-simple-phy",
> +	  .data = exynos4210_offsets},
> +	{ .compatible = "samsung,exynos4412-simple-phy",
> +	  .data = exynos4412_offsets},
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, exynos_phy_of_match);
> +
> +static struct phy *exynos_phy_xlate(struct device *dev,
> +					struct of_phandle_args *args)
> +{
> +	struct phy **phys = dev_get_drvdata(dev);
> +	int index = args->args[0];
> +	int i;
> +
> +	/* verify if index is valid */
> +	for (i = 0; i <= index; ++i)
> +		if (!phys[i])
> +			return ERR_PTR(-ENODEV);
> +
> +	return phys[index];
> +}
> +
> +static int exynos_phy_probe(struct platform_device *pdev)
> +{
> +	const struct of_device_id *of_id = of_match_device(
> +		of_match_ptr(exynos_phy_of_match), &pdev->dev);
> +	const u32 *offsets = of_id->data;
> +	int count;
> +	struct device *dev = &pdev->dev;
> +	struct phy **phys;
> +	struct resource *res;
> +	void __iomem *regs;
> +	int i;
> +	struct phy_provider *phy_provider;
> +
> +	/* count number of phys to create */
> +	for (count = 0; offsets[count] != ~0; ++count)
> +		;

count = ARRAY_SIZE(offsets) - 1;

> +
> +	phys = devm_kzalloc(dev, (count + 1) * sizeof(phys[0]), GFP_KERNEL);
> +	if (!phys)
> +		return -ENOMEM;
> +
> +	dev_set_drvdata(dev, phys);
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +
> +	regs = devm_ioremap(dev, res->start, res->end - res->start);
> +	if (!regs) {
> +		dev_err(dev, "failed to ioremap registers\n");
> +		return -EFAULT;
> +	}

Why not devm_ioremap_resource? If not, resource_size function calculates
length of resource correctly.

Anyway I like the idea of implementing multiple phys in one driver.
The only drawback I see is that some phys will be created even there are
no consumers for them. To avoid such situation you can try to use
lazy approach - create phy only if there is request for it,
exynos_phy_xlate callback should allow this.

Regards
Andrzej

> +
> +	/* NOTE: last entry in phys[] is NULL */
> +	for (i = 0; i < count; ++i) {
> +		phys[i] = devm_phy_create(dev, &exynos_phy_ops, NULL);
> +		if (IS_ERR(phys[i])) {
> +			dev_err(dev, "failed to create PHY %d\n", i);
> +			return PTR_ERR(phys[i]);
> +		}
> +		phy_set_drvdata(phys[i], regs + offsets[i]);
> +	}
> +
> +	phy_provider = devm_of_phy_provider_register(dev, exynos_phy_xlate);
> +	if (IS_ERR(phy_provider)) {
> +		dev_err(dev, "failed to register PHY provider\n");
> +		return PTR_ERR(phy_provider);
> +	}
> +
> +	dev_info(dev, "added %d phys\n", count);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver exynos_phy_driver = {
> +	.probe	= exynos_phy_probe,
> +	.driver = {
> +		.of_match_table	= exynos_phy_of_match,
> +		.name  = "exynos-simple-phy",
> +		.owner = THIS_MODULE,
> +	}
> +};
> +module_platform_driver(exynos_phy_driver);
> +
> +MODULE_DESCRIPTION("Exynos Simple PHY driver");
> +MODULE_AUTHOR("Tomasz Stanislawski <t.stanislaws@samsung.com>");
> +MODULE_LICENSE("GPL v2");
> 

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