Subject: [RFC PATCH 1/5] phy: Add driver for Exynos MIPI CSIS/DSIM DPHYs

From: [email-masked] (Tomasz Figa)
Date: Sun, 16 Jun 2013 23:11:48 +0200

Hi Sylwester,

Looks good, but I added some nitpicks inline.

On Friday 14 of June 2013 19:45:47 Sylwester Nawrocki wrote:
> Add a PHY provider driver for the Samsung S5P/Exynos SoC MIPI CSI-2
> receiver and MIPI DSI transmitter DPHYs.
> 
> Signed-off-by: Sylwester Nawrocki <[email-masked]>
> Signed-off-by: Kyungmin Park <[email-masked]>
> ---
>  .../bindings/phy/exynos-video-mipi-phy.txt         |   16 ++
>  drivers/phy/Kconfig                                |   10 ++
>  drivers/phy/Makefile                               |    3 +-
>  drivers/phy/exynos_video_mipi_phy.c                |  166
> ++++++++++++++++++++ 4 files changed, 194 insertions(+), 1 deletion(-)
>  create mode 100644
> Documentation/devicetree/bindings/phy/exynos-video-mipi-phy.txt create
> mode 100644 drivers/phy/exynos_video_mipi_phy.c
> 
> diff --git
> a/Documentation/devicetree/bindings/phy/exynos-video-mipi-phy.txt
> b/Documentation/devicetree/bindings/phy/exynos-video-mipi-phy.txt new
> file mode 100644
> index 0000000..32311c89
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/phy/exynos-video-mipi-phy.txt
> @@ -0,0 +1,16 @@
> +Samsung S5P/EXYNOS SoC series MIPI CSIS/DSIM DPHY
> +-------------------------------------------------
> +
> +Required properties:
> +- compatible : "samsung,<soc_name>-video-phy", currently most SoCs can

I don't like this <soc_name> here. It sounds like any SoC name can be put 
here. IMHO just listing all supported compatible values should be enough.

> claim +  compatibility with the S5PV210 MIPI CSIS/DSIM PHY and thus
> should use +  "samsung,s5pv210-video-phy";
> +- reg : offset and length of the MIPI DPHY register set;
> +- #phy-cells : from the generic phy bindings, must be 1;
> +
> +For "samsung,s5pv210-video-phy" compatible DPHYs the second cell in the
> PHY +specifier identifies the DPHY and its meaning is as follows:
> +  0 - MIPI CSIS 0,
> +  1 - MIPI DSIM 0,
> +  2 - MIPI CSIS 1,
> +  3 - MIPI DSIM 1.
> diff --git a/drivers/phy/Kconfig b/drivers/phy/Kconfig
> index 0764a54..d234e99 100644
> --- a/drivers/phy/Kconfig
> +++ b/drivers/phy/Kconfig
> @@ -11,3 +11,13 @@ menuconfig GENERIC_PHY
>  	  devices present in the kernel. This layer will have the generic
>  	  API by which phy drivers can create PHY using the phy framework 
and
>  	  phy users can obtain reference to the PHY.
> +
> +if GENERIC_PHY
> +
> +config EXYNOS_VIDEO_MIPI_PHY
> +	bool "S5P/EXYNOS MIPI CSI-2/DSI PHY driver"
> +	depends on OF

Hmm. Is this driver designed only for OF-enabled boards?

> +	help
> +	  Support for MIPI CSI-2 and MIPI DSI DPHY found on Samsung
> +	  S5P and EXYNOS SoCs.
> +endif
> diff --git a/drivers/phy/Makefile b/drivers/phy/Makefile
> index 9e9560f..b16f2c1 100644
> --- a/drivers/phy/Makefile
> +++ b/drivers/phy/Makefile
> @@ -2,4 +2,5 @@
>  # Makefile for the phy drivers.
>  #
> 
> -obj-$(CONFIG_GENERIC_PHY)	+= phy-core.o
> +obj-$(CONFIG_GENERIC_PHY)		+= phy-core.o
> +obj-$(CONFIG_EXYNOS_VIDEO_MIPI_PHY)	+= exynos_video_mipi_phy.o
> diff --git a/drivers/phy/exynos_video_mipi_phy.c
> b/drivers/phy/exynos_video_mipi_phy.c new file mode 100644
> index 0000000..8d4976f
> --- /dev/null
> +++ b/drivers/phy/exynos_video_mipi_phy.c
> @@ -0,0 +1,166 @@
> +/*
> + * Samsung S5P/EXYNOS SoC series MIPI CSIS/DSIM DPHY driver
> + *
> + * Copyright (C) 2013 Samsung Electronics Co., Ltd.
> + * Author: Sylwester Nawrocki <[email-masked]>
> + *
> + * 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/delay.h>
> +#include <linux/io.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/spinlock.h>
> +
> +/* MIPI_PHYn_CONTROL register bit definitions */
> +#define EXYNOS_MIPI_PHY_ENABLE		(1 << 0)
> +#define EXYNOS_MIPI_PHY_SRESETN		(1 << 1)
> +#define EXYNOS_MIPI_PHY_MRESETN		(1 << 2)
> +#define EXYNOS_MIPI_PHY_RESET_MASK	(3 << 1)
> +
> +#define EXYNOS_MAX_VIDEO_PHYS		4
> +
> +struct exynos_video_phy {
> +	spinlock_t slock;
> +	struct phy *phys[EXYNOS_MAX_VIDEO_PHYS];
> +	void __iomem *regs;
> +};
> +
> +/*
> + * The @id argument specifies MIPI CSIS or DSIM PHY as follows:
> + *  0 - MIPI CSIS 0
> + *  1 - MIPI DSIM 0
> + *  2 - MIPI CSIS 1
> + *  3 - MIPI DSIM 1
> + */
> +static int set_phy_state(struct exynos_video_phy *state,
> +					unsigned int id, int on)
> +{
> +	void __iomem *addr = id < 2 ? state->regs : state->regs + 4;

I don't find this statement too readable. What about:

	void __iomem *addr = state->regs;

and below:

	/* CSIS 1 and DSIM 1 PHYs have separate register */
	if (id >= 2)
		addr += 4;

> +	unsigned long flags;
> +	u32 reg, reset;
> +
> +	pr_debug("%s(): id: %d, on: %d, addr: %#x, base: %#x\n",
> +		 __func__, id, on, (u32)addr, (u32)state->regs);
> +
> +	if (WARN_ON(id > EXYNOS_MAX_VIDEO_PHYS))
> +		return -EINVAL;
> +
> +	if (id & 1)

Nice trick ;), but not very readable. What about creating an enum of PHYs 
and using those defined values here:

	if (id == PHY_DSI0 || id == PHY_DSI1)

> +		reset = EXYNOS_MIPI_PHY_MRESETN;
> +	else
> +		reset = EXYNOS_MIPI_PHY_SRESETN;
> +
> +	spin_lock_irqsave(&state->slock, flags);
> +
> +	reg = readl(addr);
> +	if (on)
> +		reg |= reset;
> +	else
> +		reg &= ~reset;
> +	writel(reg, addr);
> +
> +	if (on)
> +		reg |= EXYNOS_MIPI_PHY_ENABLE;

I believe this is a kind of reference counting, but a comment here would 
be nice.

> +	else if (!(reg & EXYNOS_MIPI_PHY_RESET_MASK))
> +		reg &= ~EXYNOS_MIPI_PHY_ENABLE;
> +
> +	writel(reg, addr);
> +
> +	spin_unlock_irqrestore(&state->slock, flags);
> +	return 0;
> +}
> +
> +static int exynos_video_phy_power_on(struct phy *phy)
> +{
> +	struct exynos_video_phy *state = dev_get_drvdata(&phy->dev);
> +	return set_phy_state(state, phy->id, 1);
> +}
> +
> +static int exynos_video_phy_power_off(struct phy *phy)
> +{
> +	struct exynos_video_phy *state = dev_get_drvdata(&phy->dev);
> +	return set_phy_state(state, phy->id, 0);
> +}
> +
> +static struct phy *exynos_video_phy_xlate(struct device *dev,
> +					struct of_phandle_args *args)
> +{
> +	struct exynos_video_phy *state = dev_get_drvdata(dev);
> +
> +	if (WARN_ON(args->args[0] > EXYNOS_MAX_VIDEO_PHYS))
> +		return NULL;
> +
> +	return state->phys[args->args[0]];
> +}
> +
> +static struct phy_ops exynos_video_phy_ops = {
> +	.power_on	= exynos_video_phy_power_on,
> +	.power_off	= exynos_video_phy_power_off,
> +	.owner		= THIS_MODULE,
> +};
> +
> +static int exynos_video_phy_probe(struct platform_device *pdev)
> +{
> +	struct exynos_video_phy *state;
> +	struct device *dev = &pdev->dev;
> +	struct resource res;
> +	struct phy_provider *phy_provider;
> +	int ret, i;
> +
> +	state = devm_kzalloc(dev, sizeof(*state), GFP_KERNEL);
> +	if (!state)
> +		return -ENOMEM;
> +
> +	ret = of_address_to_resource(dev->of_node, 0, &res);
> +	if (ret < 0)
> +		return ret;

You can use platform_get_resource() here to get a resource generated for 
you by of_platform_populate().

In addition you don't need to check the pointer returned by 
platform_get_resource() because it is checked in devm_ioremap_resource().

> +
> +	state->regs = devm_ioremap_resource(dev, &res);
> +	if (IS_ERR(state->regs))
> +		return PTR_ERR(state->regs);
> +
> +	dev_set_drvdata(dev, state);
> +
> +	phy_provider = devm_of_phy_provider_register(dev, THIS_MODULE,
> +					    exynos_video_phy_xlate);
> +	if (IS_ERR(phy_provider))
> +		return PTR_ERR(phy_provider);
> +
> +	for (i = 0; i < EXYNOS_MAX_VIDEO_PHYS; i++) {
> +		state->phys[i] = devm_phy_create(dev, i, 
&exynos_video_phy_ops,
> +									
state);
> +		if (IS_ERR(state->phys[i])) {
> +			dev_err(dev, "failed to create PHY %d\n", i);
> +			return PTR_ERR(state->phys[i]);
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id exynos_video_phy_of_match[] = {
> +	{ .compatible = "samsung,s5pv210-video-phy" },
> +	{ },
> +};

IMHO a MODULE_DEVICE_TABLE should be added here.

Best regards,
Tomasz

> +
> +static struct platform_driver exynos_video_phy_driver = {
> +	.probe	= exynos_video_phy_probe,
> +	.driver = {
> +		.of_match_table	= exynos_video_phy_of_match,
> +		.name  = "exynos-video-phy",
> +		.owner = THIS_MODULE,
> +	}
> +};
> +module_platform_driver(exynos_video_phy_driver);
> +
> +MODULE_DESCRIPTION("Samsung S5P/EXYNOS SoC MIPI CSI-2/DSI DPHY
> driver"); +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Sylwester Nawrocki <[email-masked]>");