Date:	Tue, 7 Jun 2011 15:47:59 +0530
From:	Viresh Kumar <viresh.kumar@...com>
To:	<linux-arm-kernel@...ts.infradead.org>, <arnd@...db.de>,
	<akpm@...ux-foundation.org>
Cc:	<armando.visconti@...com>, <shiraz.hashim@...com>,
	<vipin.kumar@...com>, <rajeev-dlh.kumar@...com>,
	<deepak.sikri@...com>, <vipulkumar.samar@...com>,
	<amit.virdi@...com>, <viresh.kumar@...com>,
	<pratyush.anand@...com>, <bhupesh.sharma@...com>,
	<viresh.linux@...il.com>, <linux-kernel@...r.kernel.org>
Subject: [PATCH V3 1/3] drivers/pwm st_pwm: Add support for ST's Pulse Width Modulator

This patch adds support for ST Microelectronics Pulse Width Modulator. This is
currently used by ST's SPEAr platform and tested on the same.

This patch also adds drivers/pwm directory as suggested by Arnd Bergmann in
following discussion:

http://comments.gmane.org/gmane.linux.ports.arm.kernel/118651

pwm framework is not separated in this patch as a separate file, as it has
already been submitted by multiple people. This driver will adopt the new pwm
framework requirements as soon as framework is pushed.

Reviewed-by: Stanley Miao <stanley.miao@...driver.com>
Signed-off-by: Viresh Kumar <viresh.kumar@...com>
---
 MAINTAINERS          |    5 +
 drivers/Kconfig      |    1 +
 drivers/Makefile     |    1 +
 drivers/pwm/Kconfig  |   22 +++
 drivers/pwm/Makefile |    5 +
 drivers/pwm/st_pwm.c |  496 ++++++++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 530 insertions(+), 0 deletions(-)
 create mode 100644 drivers/pwm/Kconfig
 create mode 100644 drivers/pwm/Makefile
 create mode 100644 drivers/pwm/st_pwm.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 48b0a4f..4e8ffa4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6031,6 +6031,11 @@ M:	Jan-Benedict Glaw <jbglaw@...-owl.de>
 S:	Maintained
 F:	arch/alpha/kernel/srm_env.c
 
+ST Microelectronics Pulse Width Modulator Support
+M:	Viresh Kumar <viresh.kumar@...com>
+S:	Maintained
+F:	drivers/pwm/st_pwm.c
+
 STABLE BRANCH
 M:	Greg Kroah-Hartman <greg@...ah.com>
 L:	stable@...nel.org
diff --git a/drivers/Kconfig b/drivers/Kconfig
index 3bb154d..4d3bb12 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -126,4 +126,5 @@ source "drivers/hwspinlock/Kconfig"
 
 source "drivers/clocksource/Kconfig"
 
+source "drivers/pwm/Kconfig"
 endmenu
diff --git a/drivers/Makefile b/drivers/Makefile
index 09f3232..c321763 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -6,6 +6,7 @@
 #
 
 obj-y				+= gpio/
+obj-y				+= pwm/
 obj-$(CONFIG_PCI)		+= pci/
 obj-$(CONFIG_PARISC)		+= parisc/
 obj-$(CONFIG_RAPIDIO)		+= rapidio/
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
new file mode 100644
index 0000000..85fd25c
--- /dev/null
+++ b/drivers/pwm/Kconfig
@@ -0,0 +1,22 @@
+#
+# Pulse Width Modulator (PWM) devices
+#
+
+menuconfig PWMLIB
+	bool "PWM Support"
+	help
+	  This enables PWM support for kernel. You only need to enable this, if
+	  you also want to enable one or more of the PWM drivers below.
+
+	  If unsure, say N.
+
+if PWMLIB
+
+config ST_PWM
+	tristate "ST Microelectronics Pulse Width Modulator"
+	default n
+	help
+	  Support for ST Microelectronics Pulse Width Modulator. Currently it is
+	  present and tested on SPEAr Platform only.
+
+endif # PWMLIB
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
new file mode 100644
index 0000000..7c3b338
--- /dev/null
+++ b/drivers/pwm/Makefile
@@ -0,0 +1,5 @@
+#
+# Makefile for PWM devices
+#
+
+obj-$(CONFIG_ST_PWM)		+= st_pwm.o
diff --git a/drivers/pwm/st_pwm.c b/drivers/pwm/st_pwm.c
new file mode 100644
index 0000000..97317fb
--- /dev/null
+++ b/drivers/pwm/st_pwm.c
@@ -0,0 +1,496 @@
+/*
+ * drivers/pwm/st_pwm.c
+ *
+ * ST Microelectronics Pulse Width Modulator driver
+ *
+ * Copyright (C) 2010-2011 ST Microelectronics
+ * Viresh Kumar<viresh.kumar@...com>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+/* Tested on ST's SPEAr Platform */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+#include <linux/kernel.h>
+#include <linux/math64.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+
+/* PWM registers and bits definitions */
+#define PWMCR			0x00
+#define PWMDCR			0x04
+#define PWMPCR			0x08
+
+#define PWM_EN_MASK		0x1
+#define MIN_PRESCALE		0x00
+#define MAX_PRESCALE		0x3FFF
+#define PRESCALE_SHIFT		2
+#define MIN_DUTY		0x0001
+#define MAX_DUTY		0xFFFF
+#define MAX_PERIOD		0xFFFF
+#define MIN_PERIOD		0x0001
+
+#define PWM_DEVICE_PER_IP	4
+#define PWM_DEVICE_OFFSET	0x10
+
+/* lock for accessing list of all pwm ips */
+static DEFINE_SPINLOCK(list_lock);
+/* list of all pwm ips available in system */
+static LIST_HEAD(pwm_list);
+
+/**
+ * struct pwm_device: struct representing pwm device/channel
+ *
+ * pwmd_id: id of pwm device
+ * pwm: pointer to parent pwm ip
+ * label: used for storing label passed in pwm_request
+ * offset: base address offset from parent pwm mmio_base
+ * busy: represents usage status of a pwm device
+ * lock: lock specific to a pwm device. User for accessing struct pwm_device
+ * fields and programming pwmd registers.
+ * node: node for adding device to parent pwm's devices list
+ *
+ * Each pwm IP contains four independent pwm device/channels. Some or all of
+ * which may be present in our configuration.
+ */
+struct pwm_device {
+	unsigned pwmd_id;
+	struct pwm *pwm;
+	const char *label;
+	unsigned offset;
+	unsigned busy;
+	spinlock_t lock;
+	struct list_head node;
+};
+
+/**
+ * struct pwm: struct representing pwm ip
+ *
+ * id: id of pwm ip
+ * mmio_base: base address of pwm
+ * clk: pointer to clk structure of pwm ip
+ * clk_enabled: clock enable status
+ * pdev: pointer to pdev structure of pwm
+ * lock: lock specific to current pwm ip. Used for accessing strut pwm fields
+ * and enabling/disabling clk.
+ * devices: list of devices/childrens of pwm ip
+ * node: node for adding pwm to global list of all pwm ips
+ */
+struct pwm {
+	unsigned id;
+	void __iomem *mmio_base;
+	struct clk *clk;
+	int clk_enabled;
+	struct platform_device *pdev;
+	spinlock_t lock;
+	struct list_head devices;
+	struct list_head node;
+};
+
+/*
+ * NOTE: If both pwm & pwmd locks are required, then they should be taken in
+ * following order: pwm->lock & then pwmd->lock and they should be released in
+ * reverse order.
+ */
+
+/*
+ * period_ns = 10^9 * (PRESCALE + 1) * PV / PWM_CLK_RATE
+ * duty_ns = 10^9 * (PRESCALE + 1) * DC / PWM_CLK_RATE
+ *
+ * PV = (PWM_CLK_RATE * period_ns)/ (10^9 * (PRESCALE + 1))
+ * DC = (PWM_CLK_RATE * duty_ns)/ (10^9 * (PRESCALE + 1))
+ */
+int pwm_config(struct pwm_device *pwmd, int duty_ns, int period_ns)
+{
+	u64 val, div, clk_rate;
+	unsigned long prescale = MIN_PRESCALE, pv, dc;
+	int ret = -EINVAL;
+
+	if (!pwmd) {
+		pr_err("config - NULL pwm device pointer\n");
+		return -EFAULT;
+	}
+
+	if (period_ns == 0 || duty_ns > period_ns)
+		goto err;
+
+	/* TODO: Need to optimize this loop */
+	/*
+	 * Find pv, dc and prescale to suit duty_ns and period_ns. This is done
+	 * according to formulas provided above this routine.
+	 */
+	while (1) {
+		div = 1000000000;
+		div *= 1 + prescale;
+		clk_rate = clk_get_rate(pwmd->pwm->clk);
+		val = clk_rate * period_ns;
+		pv = div64_u64(val, div);
+		val = clk_rate * duty_ns;
+		dc = div64_u64(val, div);
+
+		/* if duty_ns and period_ns are not acheivable then return */
+		if (!pv || !dc || pv < MIN_PERIOD || dc < MIN_DUTY)
+			goto err;
+
+		/*
+		 * if pv and dc have crossed their upper limit, then increase
+		 * prescale and recalculate pv and dc.
+		 */
+		if ((pv > MAX_PERIOD) || (dc > MAX_DUTY)) {
+			prescale++;
+			if (prescale > MAX_PRESCALE)
+				goto err;
+			continue;
+		}
+		break;
+	}
+
+	/*
+	 * NOTE: the clock to PWM has to be enabled first before writing to the
+	 * registers.
+	 */
+	spin_lock(&pwmd->pwm->lock);
+	ret = clk_enable(pwmd->pwm->clk);
+	if (ret) {
+		spin_unlock(&pwmd->pwm->lock);
+		goto err;
+	}
+
+	spin_lock(&pwmd->lock);
+	writel(prescale << PRESCALE_SHIFT, pwmd->pwm->mmio_base +
+			pwmd->offset + PWMCR);
+	writel(dc, pwmd->pwm->mmio_base + pwmd->offset + PWMDCR);
+	writel(pv, pwmd->pwm->mmio_base + pwmd->offset + PWMPCR);
+	spin_unlock(&pwmd->lock);
+	clk_disable(pwmd->pwm->clk);
+	spin_unlock(&pwmd->pwm->lock);
+
+	return 0;
+err:
+	dev_err(&pwmd->pwm->pdev->dev, "pwm config fail\n");
+	return ret;
+}
+EXPORT_SYMBOL(pwm_config);
+
+int pwm_enable(struct pwm_device *pwmd)
+{
+	int ret = 0;
+	u32 val = 0;
+
+	if (!pwmd) {
+		pr_err("enable - NULL pwm device pointer\n");
+		return -EFAULT;
+	}
+
+	spin_lock(&pwmd->pwm->lock);
+	ret = clk_enable(pwmd->pwm->clk);
+	if (!ret)
+		pwmd->pwm->clk_enabled++;
+	else {
+		spin_unlock(&pwmd->pwm->lock);
+		goto err;
+	}
+
+	spin_lock(&pwmd->lock);
+	val = readl(pwmd->pwm->mmio_base + pwmd->offset + PWMCR);
+	writel(val | PWM_EN_MASK, pwmd->pwm->mmio_base + pwmd->offset + PWMCR);
+	spin_unlock(&pwmd->lock);
+	spin_unlock(&pwmd->pwm->lock);
+	return 0;
+err:
+	dev_err(&pwmd->pwm->pdev->dev, "pwm enable fail\n");
+	return ret;
+}
+EXPORT_SYMBOL(pwm_enable);
+
+void pwm_disable(struct pwm_device *pwmd)
+{
+	if (!pwmd) {
+		pr_err("disable - NULL pwm device pointer\n");
+		return;
+	}
+
+	spin_lock(&pwmd->pwm->lock);
+	spin_lock(&pwmd->lock);
+	writel(0, pwmd->pwm->mmio_base + pwmd->offset + PWMCR);
+	if (pwmd->pwm->clk_enabled) {
+		clk_disable(pwmd->pwm->clk);
+		pwmd->pwm->clk_enabled--;
+	}
+	spin_unlock(&pwmd->lock);
+	spin_unlock(&pwmd->pwm->lock);
+}
+EXPORT_SYMBOL(pwm_disable);
+
+struct pwm_device *pwm_request(int pwmd_id, const char *label)
+{
+	int found = 0;
+	struct pwm *pwm;
+	struct pwm_device *pwmd = NULL;
+
+	spin_lock(&list_lock);
+	list_for_each_entry(pwm, &pwm_list, node) {
+		spin_lock(&pwm->lock);
+		list_for_each_entry(pwmd, &pwm->devices, node) {
+			if (pwmd->pwmd_id == pwmd_id) {
+				found = 1;
+				break;
+			}
+		}
+		spin_unlock(&pwm->lock);
+		if (found)
+			break;
+	}
+	spin_unlock(&list_lock);
+
+	if (found) {
+		spin_lock(&pwmd->lock);
+		if (pwmd->busy == 0) {
+			pwmd->busy++;
+			pwmd->label = label;
+		} else
+			pwmd = ERR_PTR(-EBUSY);
+		spin_unlock(&pwmd->lock);
+	} else
+		pwmd = ERR_PTR(-ENOENT);
+
+	if (IS_ERR(pwmd))
+		pr_err("request fail\n");
+
+	return pwmd;
+}
+EXPORT_SYMBOL(pwm_request);
+
+void pwm_free(struct pwm_device *pwmd)
+{
+	if (!pwmd) {
+		pr_err("disable - NULL pwm device pointer\n");
+		return;
+	}
+
+	spin_lock(&pwmd->lock);
+	if (pwmd->busy) {
+		pwmd->busy--;
+		pwmd->label = NULL;
+	} else {
+		spin_unlock(&pwmd->lock);
+		dev_warn(&pwmd->pwm->pdev->dev, "pwm device already freed\n");
+		return;
+	}
+
+	spin_unlock(&pwmd->lock);
+}
+EXPORT_SYMBOL(pwm_free);
+
+/* creates and add pwmd device to parent pwm's devices list */
+static int add_pwm_device(unsigned int pwmd_id, struct pwm *pwm)
+{
+	struct pwm_device *pwmd;
+
+	pwmd = kzalloc(sizeof(*pwmd), GFP_KERNEL);
+	if (!pwmd)
+		return -ENOMEM;
+
+	pwmd->pwm = pwm;
+	pwmd->busy = 0;
+	pwmd->pwmd_id = pwmd_id + pwm->id * PWM_DEVICE_PER_IP;
+	pwmd->offset = pwmd_id * PWM_DEVICE_OFFSET;
+	spin_lock_init(&pwmd->lock);
+
+	spin_lock(&pwm->lock);
+	list_add_tail(&pwmd->node, &pwm->devices);
+	spin_unlock(&pwm->lock);
+
+	return 0;
+}
+
+/* removes all pwmd devices from parent pwm's devices list */
+static void remove_pwm_devices(struct pwm *pwm)
+{
+	struct pwm_device *pwmd;
+
+	spin_lock(&pwm->lock);
+	list_for_each_entry(pwmd, &pwm->devices, node) {
+		list_del(&pwmd->node);
+		kfree(pwmd);
+	}
+	spin_unlock(&pwm->lock);
+}
+
+static int __devinit st_pwm_probe(struct platform_device *pdev)
+{
+	struct pwm *pwm = NULL;
+	struct resource *res;
+	int ret = 0, pwmd_id = 0;
+
+	pwm = kzalloc(sizeof(*pwm), GFP_KERNEL);
+	if (!pwm) {
+		ret = -ENOMEM;
+		dev_dbg(&pdev->dev, "failed to allocate memory\n");
+		goto err;
+	}
+
+	pwm->clk = clk_get(&pdev->dev, NULL);
+	if (IS_ERR(pwm->clk)) {
+		ret = PTR_ERR(pwm->clk);
+		dev_dbg(&pdev->dev, "Error getting clock\n");
+		goto err_free;
+	}
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		ret = -ENODEV;
+		dev_dbg(&pdev->dev, "no memory resource defined\n");
+		goto err_free_clk;
+	}
+
+	if (!request_mem_region(res->start, resource_size(res), pdev->name)) {
+		ret = -EBUSY;
+		dev_dbg(&pdev->dev, "failed to request memory resource\n");
+		goto err_free_clk;
+	}
+
+	pwm->mmio_base = ioremap(res->start, resource_size(res));
+	if (!pwm->mmio_base) {
+		ret = -ENOMEM;
+		dev_dbg(&pdev->dev, "failed to ioremap\n");
+		goto err_free_mem;
+	}
+
+	/* initialize pwm structure */
+	pwm->clk_enabled = 0;
+	pwm->pdev = pdev;
+	/* if pdev->id is -1, only one pwm ip is present */
+	if (pdev->id == -1)
+		pwm->id = 0;
+	else
+		pwm->id = pdev->id;
+
+	spin_lock_init(&pwm->lock);
+	INIT_LIST_HEAD(&pwm->devices);
+	platform_set_drvdata(pdev, pwm);
+
+	/* add pwm to pwm list */
+	spin_lock(&list_lock);
+	list_add_tail(&pwm->node, &pwm_list);
+	spin_unlock(&list_lock);
+
+	/* add pwm devices */
+	for (pwmd_id = 0; pwmd_id < PWM_DEVICE_PER_IP; pwmd_id++) {
+		ret = add_pwm_device(pwmd_id, pwm);
+		if (!ret)
+			continue;
+		dev_err(&pdev->dev, "Add device fail for pwm device id: %d\n",
+				pwmd_id);
+	}
+
+	if (list_empty(&pwm->node))
+		goto err_remove_pwm;
+
+	dev_info(&pdev->dev, "Initialization successful\n");
+	return 0;
+
+err_remove_pwm:
+	spin_lock(&list_lock);
+	list_del(&pwm->node);
+	spin_unlock(&list_lock);
+
+	platform_set_drvdata(pdev, NULL);
+	iounmap(pwm->mmio_base);
+err_free_mem:
+	release_mem_region(res->start, resource_size(res));
+err_free_clk:
+	clk_put(pwm->clk);
+err_free:
+	kfree(pwm);
+err:
+	dev_err(&pdev->dev, "Initialization Fail. Error: %d\n", ret);
+
+	return ret;
+}
+
+static int __devexit st_pwm_remove(struct platform_device *pdev)
+{
+	struct pwm *pwm;
+	struct resource *res;
+	int ret = 0;
+
+	pwm = platform_get_drvdata(pdev);
+	if (pwm == NULL) {
+		ret = -ENODEV;
+		dev_dbg(&pdev->dev, "Remove: get_drvdata fail\n");
+		goto err;
+	}
+	platform_set_drvdata(pdev, NULL);
+
+	/* remove pwm devices */
+	remove_pwm_devices(pwm);
+
+	/* remove pwm from pwm_list */
+	spin_lock(&list_lock);
+	list_del(&pwm->node);
+	spin_unlock(&list_lock);
+
+	iounmap(pwm->mmio_base);
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		ret = -ENODEV;
+		dev_dbg(&pdev->dev, "Remove: get_resource fail\n");
+		goto err;
+	}
+	release_mem_region(res->start, resource_size(res));
+
+	if (pwm->clk_enabled)
+		clk_disable(pwm->clk);
+	clk_put(pwm->clk);
+
+	kfree(pwm);
+	return 0;
+
+err:
+	dev_err(&pdev->dev, "Remove: Fail - %d\n", ret);
+	return ret;
+}
+
+static struct platform_driver st_pwm_driver = {
+	.driver = {
+		.name = "st_pwm",
+		.bus = &platform_bus_type,
+		.owner = THIS_MODULE,
+	},
+	.probe = st_pwm_probe,
+	.remove = __devexit_p(st_pwm_remove)
+};
+
+static int __init st_pwm_init(void)
+{
+	int ret = 0;
+
+	ret = platform_driver_register(&st_pwm_driver);
+	if (ret)
+		pr_err("failed to register st_pwm_driver\n");
+
+	return ret;
+}
+module_init(st_pwm_init);
+
+static void __exit st_pwm_exit(void)
+{
+	platform_driver_unregister(&st_pwm_driver);
+}
+module_exit(st_pwm_exit);
+
+MODULE_AUTHOR("Viresh Kumar <viresh.kumar@...com>");
+MODULE_DESCRIPTION("ST PWM Driver");
+MODULE_LICENSE("GPL");
-- 
1.7.2.2

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