linux/arch/arm/mach-vt8500/pwm.c
Alexey Charkov 21f47fbc5b ARM: 6597/1: Add basic architecture support for VIA/WonderMedia 85xx SoC's
This adds support for the family of Systems-on-Chip produced initially
by VIA and now its subsidiary WonderMedia that have recently become
widespread in lower-end Chinese ARM-based tablets and netbooks.

Support is included for both VT8500 and WM8505, selectable by a
configuration switch at kernel build time.

Included are basic machine initialization files, register and
interrupt definitions, support for the on-chip interrupt controller,
high-precision OS timer, GPIO lines, necessary macros for early debug,
pulse-width-modulated outputs control, as well as platform device
configurations for the specific drivers implemented elsewhere.

Signed-off-by: Alexey Charkov <alchark@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2011-01-25 15:07:01 +00:00

266 lines
5.6 KiB
C

/*
* arch/arm/mach-vt8500/pwm.c
*
* Copyright (C) 2010 Alexey Charkov <alchark@gmail.com>
*
* This software is licensed under the terms of the GNU General Public
* License version 2, as published by the Free Software Foundation, and
* may be copied, distributed, and modified under those terms.
*
* 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/kernel.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/pwm.h>
#include <linux/delay.h>
#include <asm/div64.h>
#define VT8500_NR_PWMS 4
static DEFINE_MUTEX(pwm_lock);
static LIST_HEAD(pwm_list);
struct pwm_device {
struct list_head node;
struct platform_device *pdev;
const char *label;
void __iomem *regbase;
unsigned int use_count;
unsigned int pwm_id;
};
#define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t)
static inline void pwm_busy_wait(void __iomem *reg, u8 bitmask)
{
int loops = msecs_to_loops(10);
while ((readb(reg) & bitmask) && --loops)
cpu_relax();
if (unlikely(!loops))
pr_warning("Waiting for status bits 0x%x to clear timed out\n",
bitmask);
}
int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
{
unsigned long long c;
unsigned long period_cycles, prescale, pv, dc;
if (pwm == NULL || period_ns == 0 || duty_ns > period_ns)
return -EINVAL;
c = 25000000/2; /* wild guess --- need to implement clocks */
c = c * period_ns;
do_div(c, 1000000000);
period_cycles = c;
if (period_cycles < 1)
period_cycles = 1;
prescale = (period_cycles - 1) / 4096;
pv = period_cycles / (prescale + 1) - 1;
if (pv > 4095)
pv = 4095;
if (prescale > 1023)
return -EINVAL;
c = (unsigned long long)pv * duty_ns;
do_div(c, period_ns);
dc = c;
pwm_busy_wait(pwm->regbase + 0x40 + pwm->pwm_id, (1 << 1));
writel(prescale, pwm->regbase + 0x4 + (pwm->pwm_id << 4));
pwm_busy_wait(pwm->regbase + 0x40 + pwm->pwm_id, (1 << 2));
writel(pv, pwm->regbase + 0x8 + (pwm->pwm_id << 4));
pwm_busy_wait(pwm->regbase + 0x40 + pwm->pwm_id, (1 << 3));
writel(dc, pwm->regbase + 0xc + (pwm->pwm_id << 4));
return 0;
}
EXPORT_SYMBOL(pwm_config);
int pwm_enable(struct pwm_device *pwm)
{
pwm_busy_wait(pwm->regbase + 0x40 + pwm->pwm_id, (1 << 0));
writel(5, pwm->regbase + (pwm->pwm_id << 4));
return 0;
}
EXPORT_SYMBOL(pwm_enable);
void pwm_disable(struct pwm_device *pwm)
{
pwm_busy_wait(pwm->regbase + 0x40 + pwm->pwm_id, (1 << 0));
writel(0, pwm->regbase + (pwm->pwm_id << 4));
}
EXPORT_SYMBOL(pwm_disable);
struct pwm_device *pwm_request(int pwm_id, const char *label)
{
struct pwm_device *pwm;
int found = 0;
mutex_lock(&pwm_lock);
list_for_each_entry(pwm, &pwm_list, node) {
if (pwm->pwm_id == pwm_id) {
found = 1;
break;
}
}
if (found) {
if (pwm->use_count == 0) {
pwm->use_count++;
pwm->label = label;
} else {
pwm = ERR_PTR(-EBUSY);
}
} else {
pwm = ERR_PTR(-ENOENT);
}
mutex_unlock(&pwm_lock);
return pwm;
}
EXPORT_SYMBOL(pwm_request);
void pwm_free(struct pwm_device *pwm)
{
mutex_lock(&pwm_lock);
if (pwm->use_count) {
pwm->use_count--;
pwm->label = NULL;
} else {
pr_warning("PWM device already freed\n");
}
mutex_unlock(&pwm_lock);
}
EXPORT_SYMBOL(pwm_free);
static inline void __add_pwm(struct pwm_device *pwm)
{
mutex_lock(&pwm_lock);
list_add_tail(&pwm->node, &pwm_list);
mutex_unlock(&pwm_lock);
}
static int __devinit pwm_probe(struct platform_device *pdev)
{
struct pwm_device *pwms;
struct resource *r;
int ret = 0;
int i;
pwms = kzalloc(sizeof(struct pwm_device) * VT8500_NR_PWMS, GFP_KERNEL);
if (pwms == NULL) {
dev_err(&pdev->dev, "failed to allocate memory\n");
return -ENOMEM;
}
for (i = 0; i < VT8500_NR_PWMS; i++) {
pwms[i].use_count = 0;
pwms[i].pwm_id = i;
pwms[i].pdev = pdev;
}
r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (r == NULL) {
dev_err(&pdev->dev, "no memory resource defined\n");
ret = -ENODEV;
goto err_free;
}
r = request_mem_region(r->start, resource_size(r), pdev->name);
if (r == NULL) {
dev_err(&pdev->dev, "failed to request memory resource\n");
ret = -EBUSY;
goto err_free;
}
pwms[0].regbase = ioremap(r->start, resource_size(r));
if (pwms[0].regbase == NULL) {
dev_err(&pdev->dev, "failed to ioremap() registers\n");
ret = -ENODEV;
goto err_free_mem;
}
for (i = 1; i < VT8500_NR_PWMS; i++)
pwms[i].regbase = pwms[0].regbase;
for (i = 0; i < VT8500_NR_PWMS; i++)
__add_pwm(&pwms[i]);
platform_set_drvdata(pdev, pwms);
return 0;
err_free_mem:
release_mem_region(r->start, resource_size(r));
err_free:
kfree(pwms);
return ret;
}
static int __devexit pwm_remove(struct platform_device *pdev)
{
struct pwm_device *pwms;
struct resource *r;
int i;
pwms = platform_get_drvdata(pdev);
if (pwms == NULL)
return -ENODEV;
mutex_lock(&pwm_lock);
for (i = 0; i < VT8500_NR_PWMS; i++)
list_del(&pwms[i].node);
mutex_unlock(&pwm_lock);
iounmap(pwms[0].regbase);
r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
release_mem_region(r->start, resource_size(r));
kfree(pwms);
return 0;
}
static struct platform_driver pwm_driver = {
.driver = {
.name = "vt8500-pwm",
.owner = THIS_MODULE,
},
.probe = pwm_probe,
.remove = __devexit_p(pwm_remove),
};
static int __init pwm_init(void)
{
return platform_driver_register(&pwm_driver);
}
arch_initcall(pwm_init);
static void __exit pwm_exit(void)
{
platform_driver_unregister(&pwm_driver);
}
module_exit(pwm_exit);
MODULE_LICENSE("GPL");