pwm: Add TI PWM subsystem driver

In some platforms (like am33xx), PWM sub modules (ECAP, EHRPWM, EQEP)
are integrated to PWM subsystem. These PWM submodules has resources
shared and only one register bit-field is provided to control
module/clock enable/disable, makes it difficult to handle common
resources from independent PWMSS submodule drivers.

So the solution here implemented in this patch is, to create driver for
PWMSS and take the role of parent driver for PWM submodules. PWMSS
parent driver enumerates all the child nodes under PWMSS module. Also
symbol "pwmss_submodule_state_change" exported to enable clock gating
for individual PWMSS submodules, and submodule drivers has to enable
clock gating from their drivers.

As this is only supported during DT boot, the parent/child relationship
is created and populated in DT execution flow. The only required change
is inside DTS file, making EHRPWM & ECAP as a child to PWMSS node.

Signed-off-by: Philip, Avinash <avinashphilip@ti.com>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>

1 files changed, 139 insertions, 0 deletions

diff --git a/drivers/pwm/pwm-tipwmss.c b/drivers/pwm/pwm-tipwmss.c
new file mode 100644
index 00000000000..3448a1c8859
--- /dev/null
+++ b/drivers/pwm/pwm-tipwmss.c
@@ -0,0 +1,139 @@
+/*
+ * TI PWM Subsystem driver
+ *
+ * Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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/module.h>
+#include <linux/platform_device.h>
+#include <linux/io.h>
+#include <linux/err.h>
+#include <linux/pm_runtime.h>
+#include <linux/of_device.h>
+
+#include "pwm-tipwmss.h"
+
+#define PWMSS_CLKCONFIG		0x8	/* Clock gating reg */
+#define PWMSS_CLKSTATUS		0xc	/* Clock gating status reg */
+
+struct pwmss_info {
+	void __iomem	*mmio_base;
+	struct mutex	pwmss_lock;
+	u16		pwmss_clkconfig;
+};
+
+u16 pwmss_submodule_state_change(struct device *dev, int set)
+{
+	struct pwmss_info *info = dev_get_drvdata(dev);
+	u16 val;
+
+	mutex_lock(&info->pwmss_lock);
+	val = readw(info->mmio_base + PWMSS_CLKCONFIG);
+	val |= set;
+	writew(val , info->mmio_base + PWMSS_CLKCONFIG);
+	mutex_unlock(&info->pwmss_lock);
+
+	return readw(info->mmio_base + PWMSS_CLKSTATUS);
+}
+EXPORT_SYMBOL(pwmss_submodule_state_change);
+
+static const struct of_device_id pwmss_of_match[] = {
+	{ .compatible	= "ti,am33xx-pwmss" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, pwmss_of_match);
+
+static int pwmss_probe(struct platform_device *pdev)
+{
+	int ret;
+	struct resource *r;
+	struct pwmss_info *info;
+	struct device_node *node = pdev->dev.of_node;
+
+	info = devm_kzalloc(&pdev->dev, sizeof(*info), GFP_KERNEL);
+	if (!info) {
+		dev_err(&pdev->dev, "failed to allocate memory\n");
+		return -ENOMEM;
+	}
+
+	mutex_init(&info->pwmss_lock);
+
+	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!r) {
+		dev_err(&pdev->dev, "no memory resource defined\n");
+		return -ENODEV;
+	}
+
+	info->mmio_base = devm_request_and_ioremap(&pdev->dev, r);
+	if (!info->mmio_base)
+		return -EADDRNOTAVAIL;
+
+	pm_runtime_enable(&pdev->dev);
+	pm_runtime_get_sync(&pdev->dev);
+	platform_set_drvdata(pdev, info);
+
+	/* Populate all the child nodes here... */
+	ret = of_platform_populate(node, NULL, NULL, &pdev->dev);
+	if (ret)
+		dev_err(&pdev->dev, "no child node found\n");
+
+	return ret;
+}
+
+static int pwmss_remove(struct platform_device *pdev)
+{
+	struct pwmss_info *info = platform_get_drvdata(pdev);
+
+	pm_runtime_put_sync(&pdev->dev);
+	pm_runtime_disable(&pdev->dev);
+	mutex_destroy(&info->pwmss_lock);
+	return 0;
+}
+
+static int pwmss_suspend(struct device *dev)
+{
+	struct pwmss_info *info = dev_get_drvdata(dev);
+
+	info->pwmss_clkconfig = readw(info->mmio_base + PWMSS_CLKCONFIG);
+	pm_runtime_put_sync(dev);
+	return 0;
+}
+
+static int pwmss_resume(struct device *dev)
+{
+	struct pwmss_info *info = dev_get_drvdata(dev);
+
+	pm_runtime_get_sync(dev);
+	writew(info->pwmss_clkconfig, info->mmio_base + PWMSS_CLKCONFIG);
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(pwmss_pm_ops, pwmss_suspend, pwmss_resume);
+
+static struct platform_driver pwmss_driver = {
+	.driver	= {
+		.name	= "pwmss",
+		.owner	= THIS_MODULE,
+		.pm	= &pwmss_pm_ops,
+		.of_match_table	= pwmss_of_match,
+	},
+	.probe	= pwmss_probe,
+	.remove	= pwmss_remove,
+};
+
+module_platform_driver(pwmss_driver);
+
+MODULE_DESCRIPTION("PWM Subsystem driver");
+MODULE_AUTHOR("Texas Instruments");
+MODULE_LICENSE("GPL");