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

Hi Tomasz,

On 06/16/2013 11:11 PM, Tomasz Figa wrote:

Hi Sylwester,

Looks good, but I added some nitpicks inline.

On Friday 14 of June 2013 19:45:47 Sylwester Nawrocki wrote:

quoted

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 <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
---
 .../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.

Hmm, OK, I'll simply put there the one compatible string supported now.

quoted

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

quoted

 	  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?

Yes, there seems currently to be no users of MIPI CSIS/DSIM in the mainline 
kernel among the non-dt platforms, so I initially focused on DT only. I will
rework this driver to make it usable on non-dt platforms, but I currently 
have not way to fully test it. I believe S5PV210 will get migrated to device
tree sooner than anyone needs the functionality this driver provides on 
non-dt, and S5PC100 seems to be forgotten anyway.

quoted

+	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 <s.nawrocki@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/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;

OK, thanks for the suggestion. I've addressed this in v2.

quoted

+	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)

Yeah, good point. Fixed.

quoted

+		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.

Indeed, I've added a comment.

quoted

+	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().

Fixed.

quoted

+
+	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,

quoted

+									

state);

quoted

+		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.

True, added after modifying the Kconfig entry to allow this driver 
to be built as a module.

Regards,
Sylwester