diff options
Diffstat (limited to 'arch/arm/plat-mxc/pwm.c')
| -rw-r--r-- | arch/arm/plat-mxc/pwm.c | 306 |
1 files changed, 306 insertions, 0 deletions
diff --git a/arch/arm/plat-mxc/pwm.c b/arch/arm/plat-mxc/pwm.c new file mode 100644 index 00000000..c0cab227 --- /dev/null +++ b/arch/arm/plat-mxc/pwm.c @@ -0,0 +1,306 @@ +/* + * simple driver for PWM (Pulse Width Modulator) controller + * + * 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. + * + * Derived from pxa PWM driver by eric miao <eric.miao@marvell.com> + */ + +#include <linux/module.h> +#include <linux/kernel.h> +#include <linux/platform_device.h> +#include <linux/slab.h> +#include <linux/err.h> +#include <linux/clk.h> +#include <linux/io.h> +#include <linux/pwm.h> +#include <mach/hardware.h> + + +/* i.MX1 and i.MX21 share the same PWM function block: */ + +#define MX1_PWMC 0x00 /* PWM Control Register */ +#define MX1_PWMS 0x04 /* PWM Sample Register */ +#define MX1_PWMP 0x08 /* PWM Period Register */ + + +/* i.MX27, i.MX31, i.MX35 share the same PWM function block: */ + +#define MX3_PWMCR 0x00 /* PWM Control Register */ +#define MX3_PWMSAR 0x0C /* PWM Sample Register */ +#define MX3_PWMPR 0x10 /* PWM Period Register */ +#define MX3_PWMCR_PRESCALER(x) (((x - 1) & 0xFFF) << 4) +#define MX3_PWMCR_DOZEEN (1 << 24) +#define MX3_PWMCR_WAITEN (1 << 23) +#define MX3_PWMCR_DBGEN (1 << 22) +#define MX3_PWMCR_CLKSRC_IPG_HIGH (2 << 16) +#define MX3_PWMCR_CLKSRC_IPG (1 << 16) +#define MX3_PWMCR_EN (1 << 0) + + + +struct pwm_device { + struct list_head node; + struct platform_device *pdev; + + const char *label; + struct clk *clk; + + int clk_enabled; + void __iomem *mmio_base; + + unsigned int use_count; + unsigned int pwm_id; +}; + +int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns) +{ + if (pwm == NULL || period_ns == 0 || duty_ns > period_ns) + return -EINVAL; + + if (!(cpu_is_mx1() || cpu_is_mx21())) { + unsigned long long c; + unsigned long period_cycles, duty_cycles, prescale; + u32 cr; + + c = clk_get_rate(pwm->clk); + c = c * period_ns; + do_div(c, 1000000000); + period_cycles = c; + + prescale = period_cycles / 0x10000 + 1; + + period_cycles /= prescale; + c = (unsigned long long)period_cycles * duty_ns; + do_div(c, period_ns); + duty_cycles = c; + + /* + * according to imx pwm RM, the real period value should be + * PERIOD value in PWMPR plus 2. + */ + if (period_cycles > 2) + period_cycles -= 2; + else + period_cycles = 0; + + writel(duty_cycles, pwm->mmio_base + MX3_PWMSAR); + writel(period_cycles, pwm->mmio_base + MX3_PWMPR); + + cr = MX3_PWMCR_PRESCALER(prescale) | + MX3_PWMCR_DOZEEN | MX3_PWMCR_WAITEN | + MX3_PWMCR_DBGEN | MX3_PWMCR_EN; + + if (cpu_is_mx25()) + cr |= MX3_PWMCR_CLKSRC_IPG; + else + cr |= MX3_PWMCR_CLKSRC_IPG_HIGH; + + writel(cr, pwm->mmio_base + MX3_PWMCR); + } else if (cpu_is_mx1() || cpu_is_mx21()) { + /* The PWM subsystem allows for exact frequencies. However, + * I cannot connect a scope on my device to the PWM line and + * thus cannot provide the program the PWM controller + * exactly. Instead, I'm relying on the fact that the + * Bootloader (u-boot or WinCE+haret) has programmed the PWM + * function group already. So I'll just modify the PWM sample + * register to follow the ratio of duty_ns vs. period_ns + * accordingly. + * + * This is good enough for programming the brightness of + * the LCD backlight. + * + * The real implementation would divide PERCLK[0] first by + * both the prescaler (/1 .. /128) and then by CLKSEL + * (/2 .. /16). + */ + u32 max = readl(pwm->mmio_base + MX1_PWMP); + u32 p = max * duty_ns / period_ns; + writel(max - p, pwm->mmio_base + MX1_PWMS); + } else { + BUG(); + } + + return 0; +} +EXPORT_SYMBOL(pwm_config); + +int pwm_enable(struct pwm_device *pwm) +{ + int rc = 0; + + if (!pwm->clk_enabled) { + rc = clk_prepare_enable(pwm->clk); + if (!rc) + pwm->clk_enabled = 1; + } + return rc; +} +EXPORT_SYMBOL(pwm_enable); + +void pwm_disable(struct pwm_device *pwm) +{ + writel(0, pwm->mmio_base + MX3_PWMCR); + + if (pwm->clk_enabled) { + clk_disable_unprepare(pwm->clk); + pwm->clk_enabled = 0; + } +} +EXPORT_SYMBOL(pwm_disable); + +static DEFINE_MUTEX(pwm_lock); +static LIST_HEAD(pwm_list); + +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 int __devinit mxc_pwm_probe(struct platform_device *pdev) +{ + struct pwm_device *pwm; + struct resource *r; + int ret = 0; + + pwm = kzalloc(sizeof(struct pwm_device), GFP_KERNEL); + if (pwm == NULL) { + dev_err(&pdev->dev, "failed to allocate memory\n"); + return -ENOMEM; + } + + pwm->clk = clk_get(&pdev->dev, "pwm"); + + if (IS_ERR(pwm->clk)) { + ret = PTR_ERR(pwm->clk); + goto err_free; + } + + pwm->clk_enabled = 0; + + pwm->use_count = 0; + pwm->pwm_id = pdev->id; + pwm->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_clk; + } + + 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_clk; + } + + pwm->mmio_base = ioremap(r->start, resource_size(r)); + if (pwm->mmio_base == NULL) { + dev_err(&pdev->dev, "failed to ioremap() registers\n"); + ret = -ENODEV; + goto err_free_mem; + } + + mutex_lock(&pwm_lock); + list_add_tail(&pwm->node, &pwm_list); + mutex_unlock(&pwm_lock); + + platform_set_drvdata(pdev, pwm); + return 0; + +err_free_mem: + release_mem_region(r->start, resource_size(r)); +err_free_clk: + clk_put(pwm->clk); +err_free: + kfree(pwm); + return ret; +} + +static int __devexit mxc_pwm_remove(struct platform_device *pdev) +{ + struct pwm_device *pwm; + struct resource *r; + + pwm = platform_get_drvdata(pdev); + if (pwm == NULL) + return -ENODEV; + + mutex_lock(&pwm_lock); + list_del(&pwm->node); + mutex_unlock(&pwm_lock); + + iounmap(pwm->mmio_base); + + r = platform_get_resource(pdev, IORESOURCE_MEM, 0); + release_mem_region(r->start, resource_size(r)); + + clk_put(pwm->clk); + + kfree(pwm); + return 0; +} + +static struct platform_driver mxc_pwm_driver = { + .driver = { + .name = "mxc_pwm", + }, + .probe = mxc_pwm_probe, + .remove = __devexit_p(mxc_pwm_remove), +}; + +static int __init mxc_pwm_init(void) +{ + return platform_driver_register(&mxc_pwm_driver); +} +arch_initcall(mxc_pwm_init); + +static void __exit mxc_pwm_exit(void) +{ + platform_driver_unregister(&mxc_pwm_driver); +} +module_exit(mxc_pwm_exit); + +MODULE_LICENSE("GPL v2"); +MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>"); |