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