diff options
Diffstat (limited to 'drivers/pwm/pwm-spear.c')
| -rw-r--r-- | drivers/pwm/pwm-spear.c | 262 |
1 files changed, 262 insertions, 0 deletions
diff --git a/drivers/pwm/pwm-spear.c b/drivers/pwm/pwm-spear.c new file mode 100644 index 000000000..2d11ac277 --- /dev/null +++ b/drivers/pwm/pwm-spear.c @@ -0,0 +1,262 @@ +/* + * ST Microelectronics SPEAr Pulse Width Modulator driver + * + * Copyright (C) 2012 ST Microelectronics + * Shiraz Hashim <shiraz.linux.kernel@gmail.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. + */ + +#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/of.h> +#include <linux/platform_device.h> +#include <linux/pwm.h> +#include <linux/slab.h> +#include <linux/types.h> + +#define NUM_PWM 4 + +/* PWM registers and bits definitions */ +#define PWMCR 0x00 /* Control Register */ +#define PWMCR_PWM_ENABLE 0x1 +#define PWMCR_PRESCALE_SHIFT 2 +#define PWMCR_MIN_PRESCALE 0x00 +#define PWMCR_MAX_PRESCALE 0x3FFF + +#define PWMDCR 0x04 /* Duty Cycle Register */ +#define PWMDCR_MIN_DUTY 0x0001 +#define PWMDCR_MAX_DUTY 0xFFFF + +#define PWMPCR 0x08 /* Period Register */ +#define PWMPCR_MIN_PERIOD 0x0001 +#define PWMPCR_MAX_PERIOD 0xFFFF + +/* Following only available on 13xx SoCs */ +#define PWMMCR 0x3C /* Master Control Register */ +#define PWMMCR_PWM_ENABLE 0x1 + +/** + * struct spear_pwm_chip - struct representing pwm chip + * + * @mmio_base: base address of pwm chip + * @clk: pointer to clk structure of pwm chip + * @chip: linux pwm chip representation + */ +struct spear_pwm_chip { + void __iomem *mmio_base; + struct clk *clk; + struct pwm_chip chip; +}; + +static inline struct spear_pwm_chip *to_spear_pwm_chip(struct pwm_chip *chip) +{ + return container_of(chip, struct spear_pwm_chip, chip); +} + +static inline u32 spear_pwm_readl(struct spear_pwm_chip *chip, unsigned int num, + unsigned long offset) +{ + return readl_relaxed(chip->mmio_base + (num << 4) + offset); +} + +static inline void spear_pwm_writel(struct spear_pwm_chip *chip, + unsigned int num, unsigned long offset, + unsigned long val) +{ + writel_relaxed(val, chip->mmio_base + (num << 4) + offset); +} + +static int spear_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, + int duty_ns, int period_ns) +{ + struct spear_pwm_chip *pc = to_spear_pwm_chip(chip); + u64 val, div, clk_rate; + unsigned long prescale = PWMCR_MIN_PRESCALE, pv, dc; + int ret; + + /* + * Find pv, dc and prescale to suit duty_ns and period_ns. This is done + * according to formulas described below: + * + * 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)) + */ + clk_rate = clk_get_rate(pc->clk); + while (1) { + div = 1000000000; + div *= 1 + prescale; + 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 achievable then return */ + if (pv < PWMPCR_MIN_PERIOD || dc < PWMDCR_MIN_DUTY) + return -EINVAL; + + /* + * if pv and dc have crossed their upper limit, then increase + * prescale and recalculate pv and dc. + */ + if (pv > PWMPCR_MAX_PERIOD || dc > PWMDCR_MAX_DUTY) { + if (++prescale > PWMCR_MAX_PRESCALE) + return -EINVAL; + continue; + } + break; + } + + /* + * NOTE: the clock to PWM has to be enabled first before writing to the + * registers. + */ + ret = clk_enable(pc->clk); + if (ret) + return ret; + + spear_pwm_writel(pc, pwm->hwpwm, PWMCR, + prescale << PWMCR_PRESCALE_SHIFT); + spear_pwm_writel(pc, pwm->hwpwm, PWMDCR, dc); + spear_pwm_writel(pc, pwm->hwpwm, PWMPCR, pv); + clk_disable(pc->clk); + + return 0; +} + +static int spear_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm) +{ + struct spear_pwm_chip *pc = to_spear_pwm_chip(chip); + int rc = 0; + u32 val; + + rc = clk_enable(pc->clk); + if (rc) + return rc; + + val = spear_pwm_readl(pc, pwm->hwpwm, PWMCR); + val |= PWMCR_PWM_ENABLE; + spear_pwm_writel(pc, pwm->hwpwm, PWMCR, val); + + return 0; +} + +static void spear_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm) +{ + struct spear_pwm_chip *pc = to_spear_pwm_chip(chip); + u32 val; + + val = spear_pwm_readl(pc, pwm->hwpwm, PWMCR); + val &= ~PWMCR_PWM_ENABLE; + spear_pwm_writel(pc, pwm->hwpwm, PWMCR, val); + + clk_disable(pc->clk); +} + +static const struct pwm_ops spear_pwm_ops = { + .config = spear_pwm_config, + .enable = spear_pwm_enable, + .disable = spear_pwm_disable, + .owner = THIS_MODULE, +}; + +static int spear_pwm_probe(struct platform_device *pdev) +{ + struct device_node *np = pdev->dev.of_node; + struct spear_pwm_chip *pc; + struct resource *r; + int ret; + u32 val; + + pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL); + if (!pc) + return -ENOMEM; + + r = platform_get_resource(pdev, IORESOURCE_MEM, 0); + pc->mmio_base = devm_ioremap_resource(&pdev->dev, r); + if (IS_ERR(pc->mmio_base)) + return PTR_ERR(pc->mmio_base); + + pc->clk = devm_clk_get(&pdev->dev, NULL); + if (IS_ERR(pc->clk)) + return PTR_ERR(pc->clk); + + platform_set_drvdata(pdev, pc); + + pc->chip.dev = &pdev->dev; + pc->chip.ops = &spear_pwm_ops; + pc->chip.base = -1; + pc->chip.npwm = NUM_PWM; + + ret = clk_prepare(pc->clk); + if (ret) + return ret; + + if (of_device_is_compatible(np, "st,spear1340-pwm")) { + ret = clk_enable(pc->clk); + if (ret) { + clk_unprepare(pc->clk); + return ret; + } + /* + * Following enables PWM chip, channels would still be + * enabled individually through their control register + */ + val = readl_relaxed(pc->mmio_base + PWMMCR); + val |= PWMMCR_PWM_ENABLE; + writel_relaxed(val, pc->mmio_base + PWMMCR); + + clk_disable(pc->clk); + } + + ret = pwmchip_add(&pc->chip); + if (ret < 0) { + clk_unprepare(pc->clk); + dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret); + } + + return ret; +} + +static int spear_pwm_remove(struct platform_device *pdev) +{ + struct spear_pwm_chip *pc = platform_get_drvdata(pdev); + + /* clk was prepared in probe, hence unprepare it here */ + clk_unprepare(pc->clk); + return pwmchip_remove(&pc->chip); +} + +static const struct of_device_id spear_pwm_of_match[] = { + { .compatible = "st,spear320-pwm" }, + { .compatible = "st,spear1340-pwm" }, + { } +}; + +MODULE_DEVICE_TABLE(of, spear_pwm_of_match); + +static struct platform_driver spear_pwm_driver = { + .driver = { + .name = "spear-pwm", + .of_match_table = spear_pwm_of_match, + }, + .probe = spear_pwm_probe, + .remove = spear_pwm_remove, +}; + +module_platform_driver(spear_pwm_driver); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Shiraz Hashim <shiraz.linux.kernel@gmail.com>"); +MODULE_AUTHOR("Viresh Kumar <viresh.kumar@linaro.com>"); +MODULE_ALIAS("platform:spear-pwm"); |