Message-ID: <57F4EE05.8000407@ti.com>
Date:   Wed, 5 Oct 2016 17:41:49 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Vivek Gautam <vivek.gautam@...eaurora.org>
CC:     <robh+dt@...nel.org>, <mark.rutland@....com>,
        <linux-usb@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Felipe Balbi <balbi@...nel.org>
Subject: Re: [PATCH] phy: nop: Add a new phy driver for No-Op transceiver

Hi,

On Tuesday 04 October 2016 04:13 PM, Vivek Gautam wrote:
> No-Op phy transceiver can be used on platforms that have
> controllers which themselves provide PHY functionality and
> there's no separate PHY controller available.
> 
> This driver provides a basic skeleton for a nop-phy driver.
> This can be further extended to add required features.
> 
> Inspired by phy-generic driver in drivers/usb/phy.
> 
> Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
> Cc: Kishon Vijay Abraham I <kishon@...com>
> Cc: Felipe Balbi <balbi@...nel.org>
> ---
> 
> Hi Kishon, Felipe,
> 
> This patch has been lying in my tree for sometime.
> This introduces a skeletal nop-phy driver based on generic
> phy framework.
> I mainly use this driver when I have only one phy driver available
> for testing for a controller that uses more than one phy.
> 
> But this can be further extended to add any feature support for
> controllers that don't have a separate PHY controller and that
> themselves provide the PHY functionality, a purpose similar
> to what drivers/usb/phy/phy-generic.c driver serves.
> 
> Do you think we have a requirement for such a driver in the generic
> phy layer? I hope this driver can do some good.
> Let me know your comments on this.
> 
> Thanks
> Vivek
> 
>  Documentation/devicetree/bindings/phy/phy-nop.txt |  22 +++
>  drivers/phy/Kconfig                               |  10 ++
>  drivers/phy/Makefile                              |   1 +
>  drivers/phy/phy-nop.c                             | 193 ++++++++++++++++++++++
>  4 files changed, 226 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/phy/phy-nop.txt
>  create mode 100644 drivers/phy/phy-nop.c
> 
> diff --git a/Documentation/devicetree/bindings/phy/phy-nop.txt b/Documentation/devicetree/bindings/phy/phy-nop.txt
> new file mode 100644
> index 0000000..6cb6779
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/phy/phy-nop.txt
> @@ -0,0 +1,22 @@
> +Generic No-Op PHY
> +-----------------
> +
> +Required properties:
> + - compatible: compatible list, contains "phy-nop".
> + - #phy-cells: must be 0.
> +
> +Optional properties:
> + - clocks: a list of phandles and clock-specifier pairs,
> +	   one for each entry in clock-names.
> + - clock-names: must be "main_clk" for phy core clock,
> +			"ref_clk" for phy reference clk.
> + - resets: a list of phandles and reset controller specifier pairs,
> +	   one for each entry in reset-names.
> + - reset-names: must be	"phy" for reset of phy block.
> + - vdd-supply: Phandle to a regulator supply to PHY core block.
> +
> +Example:
> +	phy_nop: phy_nop {
> +		compatible = "phy-nop";
> +		#phy-cells = <0>;
> +	};

I don't think this qualifies to be modeled as dt. device tree should try to
represent HW and not workaround SW issues by creating dummy nodes. For such
cases phy_optional_get should suffice?

I'm more towards having a simple-phy, along the lines of [1]

[1] -> https://patchwork.kernel.org/patch/8153691/

Thanks
Kishon
> diff --git a/drivers/phy/Kconfig b/drivers/phy/Kconfig
> index fe00f91..1923c4f 100644
> --- a/drivers/phy/Kconfig
> +++ b/drivers/phy/Kconfig
> @@ -489,4 +489,14 @@ config PHY_NS2_PCIE
>  	help
>  	  Enable this to support the Broadcom Northstar2 PCIe PHY.
>  	  If unsure, say N.
> +
> +config PHY_NOP
> +	tristate "No-Operation PHY transceiver driver"
> +	depends on OF || COMPILE_TEST
> +	select GENERIC_PHY
> +	help
> +	  Enable this to support the generic no-operation PHY
> +	  transeiver. This driver can be used with consumers
> +	  requiring a no-op phy for few of the handlers.
> +
>  endmenu
> diff --git a/drivers/phy/Makefile b/drivers/phy/Makefile
> index a534cf5..d6e0e60 100644
> --- a/drivers/phy/Makefile
> +++ b/drivers/phy/Makefile
> @@ -60,3 +60,4 @@ obj-$(CONFIG_PHY_PISTACHIO_USB)		+= phy-pistachio-usb.o
>  obj-$(CONFIG_PHY_CYGNUS_PCIE)		+= phy-bcm-cygnus-pcie.o
>  obj-$(CONFIG_ARCH_TEGRA) += tegra/
>  obj-$(CONFIG_PHY_NS2_PCIE)		+= phy-bcm-ns2-pcie.o
> +obj-$(CONFIG_PHY_NOP)			+= phy-nop.o
> diff --git a/drivers/phy/phy-nop.c b/drivers/phy/phy-nop.c
> new file mode 100644
> index 0000000..cab01a1
> --- /dev/null
> +++ b/drivers/phy/phy-nop.c
> @@ -0,0 +1,193 @@
> +/*
> + * 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/module.h>
> +#include <linux/of.h>
> +#include <linux/phy/phy.h>
> +#include <linux/platform_device.h>
> +#include <linux/reset.h>
> +
> +/**
> + * struct phy_nop:- structure holding NOP PHY attributes.
> + *
> + * @dev: pointer to device.
> + * @phy: pointer to generic phy.
> + * @clk: pointer to phy clock.
> + * @refclk: pointer to phy reference clock.
> + * @vdd: vdd supply to the phy core block.
> + * @rst: pointer to reset controller for the phy block.
> + */
> +struct phy_nop {
> +	struct device *dev;
> +	struct phy *phy;
> +	struct clk *clk;
> +	struct clk *refclk;
> +	struct regulator *vdd;
> +	struct reset_control *rst;
> +};
> +
> +static int phy_nop_poweron(struct phy *generic_phy)
> +{
> +	struct phy_nop *phy = phy_get_drvdata(generic_phy);
> +	int ret = 0;
> +
> +	if (phy->vdd) {
> +		ret = regulator_enable(phy->vdd);
> +		if (ret) {
> +			dev_err(phy->dev, "vdd enable failed: %d\n", ret);
> +			return ret;
> +		}
> +	}
> +
> +	if (phy->clk) {
> +		ret = clk_prepare_enable(phy->clk);
> +		if (ret) {
> +			dev_err(phy->dev, "main clk enable failed: %d\n", ret);
> +			goto err_clk;
> +		}
> +	}
> +
> +	if (phy->refclk) {
> +		ret = clk_prepare_enable(phy->refclk);
> +		if (ret) {
> +			dev_err(phy->dev, "ref clk enable failed: %d\n", ret);
> +			goto err_refclk;
> +		}
> +	}
> +
> +	if (phy->rst) {
> +		ret = reset_control_deassert(phy->rst);
> +		if (ret) {
> +			dev_err(phy->dev, "phy reset deassert failed\n");
> +			goto err_rst;
> +		}
> +	}
> +
> +	return 0;
> +
> +err_rst:
> +	clk_disable_unprepare(phy->refclk);
> +err_refclk:
> +	clk_disable_unprepare(phy->clk);
> +err_clk:
> +	regulator_disable(phy->vdd);
> +	return ret;
> +}
> +
> +static int phy_nop_poweroff(struct phy *generic_phy)
> +{
> +	struct phy_nop *phy = phy_get_drvdata(generic_phy);
> +
> +	if (phy->rst)
> +		reset_control_assert(phy->rst);
> +
> +	if (phy->clk)
> +		clk_disable_unprepare(phy->clk);
> +	if (phy->refclk)
> +		clk_disable_unprepare(phy->refclk);
> +
> +	if (phy->vdd)
> +		regulator_disable(phy->vdd);
> +
> +	return 0;
> +}
> +
> +static const struct phy_ops phy_nop_gen_ops = {
> +	.power_on	= phy_nop_poweron,
> +	.power_off	= phy_nop_poweroff,
> +	.owner		= THIS_MODULE,
> +};
> +
> +static int phy_nop_probe(struct platform_device *pdev)
> +{
> +	struct phy_nop *phy;
> +	struct phy *generic_phy;
> +	struct device *dev = &pdev->dev;
> +	struct phy_provider *phy_provider;
> +	int ret = 0;
> +
> +	phy = devm_kzalloc(dev, sizeof(*phy), GFP_KERNEL);
> +	if (!phy)
> +		return -ENOMEM;
> +	phy->dev = dev;
> +
> +	/* XXX: Do we need to request any clocks ? */
> +	phy->clk = devm_clk_get(dev, "main_clk");
> +	if (IS_ERR(phy->clk)) {
> +		dev_dbg(dev, "failed to get main_clk: %ld\n",
> +						PTR_ERR(phy->clk));
> +		phy->clk = NULL;
> +	}
> +	phy->refclk = devm_clk_get(dev, "ref_clk");
> +	if (IS_ERR(phy->refclk)) {
> +		dev_dbg(dev, "failed to get ref_clk: %ld\n",
> +						PTR_ERR(phy->refclk));
> +		phy->refclk = NULL;
> +	}
> +
> +	/* XXX: Do we need to request any regulators ? */
> +	phy->vdd = devm_regulator_get(dev, "vdd");
> +	if (IS_ERR(phy->vdd)) {
> +		dev_dbg(dev, "failed to get vdd for phy: %ld\n",
> +						PTR_ERR(phy->vdd));
> +		phy->vdd = NULL;
> +	}
> +
> +	/* XXX: Do we need to request any phy-reset ? */
> +	phy->rst = devm_reset_control_get(dev, "phy");
> +	if (IS_ERR(phy->rst)) {
> +		dev_dbg(dev, "failed to get phy core reset: %ld\n",
> +						PTR_ERR(phy->rst));
> +		phy->rst = NULL;
> +	}
> +
> +	generic_phy = devm_phy_create(dev, NULL, &phy_nop_gen_ops);
> +	if (IS_ERR(generic_phy)) {
> +		ret = PTR_ERR(generic_phy);
> +		dev_err(dev, "failed to create generic phy %d\n", ret);
> +		return ret;
> +	}
> +	phy->phy = generic_phy;
> +	phy_set_drvdata(generic_phy, phy);
> +
> +	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, "failed to register phy %d\n", ret);
> +	}
> +
> +	return ret;
> +}
> +
> +static const struct of_device_id phy_nop_id_table[] = {
> +	{
> +		.compatible = "phy-nop",
> +	},
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, phy_nop_id_table);
> +
> +static struct platform_driver phy_nop_driver = {
> +	.probe		= phy_nop_probe,
> +	.driver = {
> +		.name	= "phy_nop",
> +		.of_match_table = of_match_ptr(phy_nop_id_table),
> +	},
> +};
> +
> +module_platform_driver(phy_nop_driver);
> +
> +MODULE_DESCRIPTION("Generic No-op PHY driver");
> +MODULE_LICENSE("GPL v2");
> 

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