diff options
Diffstat (limited to 'drivers/pwm/pwm-bcm-kona.c')
| -rw-r--r-- | drivers/pwm/pwm-bcm-kona.c | 344 |
1 files changed, 344 insertions, 0 deletions
diff --git a/drivers/pwm/pwm-bcm-kona.c b/drivers/pwm/pwm-bcm-kona.c new file mode 100644 index 000000000..16c5898b9 --- /dev/null +++ b/drivers/pwm/pwm-bcm-kona.c @@ -0,0 +1,344 @@ +/* + * Copyright (C) 2014 Broadcom Corporation + * + * 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 version 2. + * + * This program is distributed "as is" WITHOUT ANY WARRANTY of any + * kind, whether express or implied; without even the implied warranty + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + */ + +#include <linux/clk.h> +#include <linux/delay.h> +#include <linux/err.h> +#include <linux/io.h> +#include <linux/ioport.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> + +/* + * The Kona PWM has some unusual characteristics. Here are the main points. + * + * 1) There is no disable bit and the hardware docs advise programming a zero + * duty to achieve output equivalent to that of a normal disable operation. + * + * 2) Changes to prescale, duty, period, and polarity do not take effect until + * a subsequent rising edge of the trigger bit. + * + * 3) If the smooth bit and trigger bit are both low, the output is a constant + * high signal. Otherwise, the earlier waveform continues to be output. + * + * 4) If the smooth bit is set on the rising edge of the trigger bit, output + * will transition to the new settings on a period boundary (which could be + * seconds away). If the smooth bit is clear, new settings will be applied + * as soon as possible (the hardware always has a 400ns delay). + * + * 5) When the external clock that feeds the PWM is disabled, output is pegged + * high or low depending on its state at that exact instant. + */ + +#define PWM_CONTROL_OFFSET 0x00000000 +#define PWM_CONTROL_SMOOTH_SHIFT(chan) (24 + (chan)) +#define PWM_CONTROL_TYPE_SHIFT(chan) (16 + (chan)) +#define PWM_CONTROL_POLARITY_SHIFT(chan) (8 + (chan)) +#define PWM_CONTROL_TRIGGER_SHIFT(chan) (chan) + +#define PRESCALE_OFFSET 0x00000004 +#define PRESCALE_SHIFT(chan) ((chan) << 2) +#define PRESCALE_MASK(chan) (0x7 << PRESCALE_SHIFT(chan)) +#define PRESCALE_MIN 0x00000000 +#define PRESCALE_MAX 0x00000007 + +#define PERIOD_COUNT_OFFSET(chan) (0x00000008 + ((chan) << 3)) +#define PERIOD_COUNT_MIN 0x00000002 +#define PERIOD_COUNT_MAX 0x00ffffff + +#define DUTY_CYCLE_HIGH_OFFSET(chan) (0x0000000c + ((chan) << 3)) +#define DUTY_CYCLE_HIGH_MIN 0x00000000 +#define DUTY_CYCLE_HIGH_MAX 0x00ffffff + +struct kona_pwmc { + struct pwm_chip chip; + void __iomem *base; + struct clk *clk; +}; + +static inline struct kona_pwmc *to_kona_pwmc(struct pwm_chip *_chip) +{ + return container_of(_chip, struct kona_pwmc, chip); +} + +/* + * Clear trigger bit but set smooth bit to maintain old output. + */ +static void kona_pwmc_prepare_for_settings(struct kona_pwmc *kp, + unsigned int chan) +{ + unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET); + + value |= 1 << PWM_CONTROL_SMOOTH_SHIFT(chan); + value &= ~(1 << PWM_CONTROL_TRIGGER_SHIFT(chan)); + writel(value, kp->base + PWM_CONTROL_OFFSET); + + /* + * There must be a min 400ns delay between clearing trigger and setting + * it. Failing to do this may result in no PWM signal. + */ + ndelay(400); +} + +static void kona_pwmc_apply_settings(struct kona_pwmc *kp, unsigned int chan) +{ + unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET); + + /* Set trigger bit and clear smooth bit to apply new settings */ + value &= ~(1 << PWM_CONTROL_SMOOTH_SHIFT(chan)); + value |= 1 << PWM_CONTROL_TRIGGER_SHIFT(chan); + writel(value, kp->base + PWM_CONTROL_OFFSET); + + /* Trigger bit must be held high for at least 400 ns. */ + ndelay(400); +} + +static int kona_pwmc_config(struct pwm_chip *chip, struct pwm_device *pwm, + int duty_ns, int period_ns) +{ + struct kona_pwmc *kp = to_kona_pwmc(chip); + u64 val, div, rate; + unsigned long prescale = PRESCALE_MIN, pc, dc; + unsigned int value, chan = pwm->hwpwm; + + /* + * Find period count, duty count and prescale to suit duty_ns and + * period_ns. This is done according to formulas described below: + * + * period_ns = 10^9 * (PRESCALE + 1) * PC / PWM_CLK_RATE + * duty_ns = 10^9 * (PRESCALE + 1) * DC / PWM_CLK_RATE + * + * PC = (PWM_CLK_RATE * period_ns) / (10^9 * (PRESCALE + 1)) + * DC = (PWM_CLK_RATE * duty_ns) / (10^9 * (PRESCALE + 1)) + */ + + rate = clk_get_rate(kp->clk); + + while (1) { + div = 1000000000; + div *= 1 + prescale; + val = rate * period_ns; + pc = div64_u64(val, div); + val = rate * duty_ns; + dc = div64_u64(val, div); + + /* If duty_ns or period_ns are not achievable then return */ + if (pc < PERIOD_COUNT_MIN) + return -EINVAL; + + /* If pc and dc are in bounds, the calculation is done */ + if (pc <= PERIOD_COUNT_MAX && dc <= DUTY_CYCLE_HIGH_MAX) + break; + + /* Otherwise, increase prescale and recalculate pc and dc */ + if (++prescale > PRESCALE_MAX) + return -EINVAL; + } + + /* + * Don't apply settings if disabled. The period and duty cycle are + * always calculated above to ensure the new values are + * validated immediately instead of on enable. + */ + if (pwm_is_enabled(pwm)) { + kona_pwmc_prepare_for_settings(kp, chan); + + value = readl(kp->base + PRESCALE_OFFSET); + value &= ~PRESCALE_MASK(chan); + value |= prescale << PRESCALE_SHIFT(chan); + writel(value, kp->base + PRESCALE_OFFSET); + + writel(pc, kp->base + PERIOD_COUNT_OFFSET(chan)); + + writel(dc, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan)); + + kona_pwmc_apply_settings(kp, chan); + } + + return 0; +} + +static int kona_pwmc_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm, + enum pwm_polarity polarity) +{ + struct kona_pwmc *kp = to_kona_pwmc(chip); + unsigned int chan = pwm->hwpwm; + unsigned int value; + int ret; + + ret = clk_prepare_enable(kp->clk); + if (ret < 0) { + dev_err(chip->dev, "failed to enable clock: %d\n", ret); + return ret; + } + + kona_pwmc_prepare_for_settings(kp, chan); + + value = readl(kp->base + PWM_CONTROL_OFFSET); + + if (polarity == PWM_POLARITY_NORMAL) + value |= 1 << PWM_CONTROL_POLARITY_SHIFT(chan); + else + value &= ~(1 << PWM_CONTROL_POLARITY_SHIFT(chan)); + + writel(value, kp->base + PWM_CONTROL_OFFSET); + + kona_pwmc_apply_settings(kp, chan); + + clk_disable_unprepare(kp->clk); + + return 0; +} + +static int kona_pwmc_enable(struct pwm_chip *chip, struct pwm_device *pwm) +{ + struct kona_pwmc *kp = to_kona_pwmc(chip); + int ret; + + ret = clk_prepare_enable(kp->clk); + if (ret < 0) { + dev_err(chip->dev, "failed to enable clock: %d\n", ret); + return ret; + } + + ret = kona_pwmc_config(chip, pwm, pwm_get_duty_cycle(pwm), + pwm_get_period(pwm)); + if (ret < 0) { + clk_disable_unprepare(kp->clk); + return ret; + } + + return 0; +} + +static void kona_pwmc_disable(struct pwm_chip *chip, struct pwm_device *pwm) +{ + struct kona_pwmc *kp = to_kona_pwmc(chip); + unsigned int chan = pwm->hwpwm; + unsigned int value; + + kona_pwmc_prepare_for_settings(kp, chan); + + /* Simulate a disable by configuring for zero duty */ + writel(0, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan)); + writel(0, kp->base + PERIOD_COUNT_OFFSET(chan)); + + /* Set prescale to 0 for this channel */ + value = readl(kp->base + PRESCALE_OFFSET); + value &= ~PRESCALE_MASK(chan); + writel(value, kp->base + PRESCALE_OFFSET); + + kona_pwmc_apply_settings(kp, chan); + + clk_disable_unprepare(kp->clk); +} + +static const struct pwm_ops kona_pwm_ops = { + .config = kona_pwmc_config, + .set_polarity = kona_pwmc_set_polarity, + .enable = kona_pwmc_enable, + .disable = kona_pwmc_disable, + .owner = THIS_MODULE, +}; + +static int kona_pwmc_probe(struct platform_device *pdev) +{ + struct kona_pwmc *kp; + struct resource *res; + unsigned int chan; + unsigned int value = 0; + int ret = 0; + + kp = devm_kzalloc(&pdev->dev, sizeof(*kp), GFP_KERNEL); + if (kp == NULL) + return -ENOMEM; + + platform_set_drvdata(pdev, kp); + + kp->chip.dev = &pdev->dev; + kp->chip.ops = &kona_pwm_ops; + kp->chip.base = -1; + kp->chip.npwm = 6; + kp->chip.of_xlate = of_pwm_xlate_with_flags; + kp->chip.of_pwm_n_cells = 3; + + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); + kp->base = devm_ioremap_resource(&pdev->dev, res); + if (IS_ERR(kp->base)) + return PTR_ERR(kp->base); + + kp->clk = devm_clk_get(&pdev->dev, NULL); + if (IS_ERR(kp->clk)) { + dev_err(&pdev->dev, "failed to get clock: %ld\n", + PTR_ERR(kp->clk)); + return PTR_ERR(kp->clk); + } + + ret = clk_prepare_enable(kp->clk); + if (ret < 0) { + dev_err(&pdev->dev, "failed to enable clock: %d\n", ret); + return ret; + } + + /* Set push/pull for all channels */ + for (chan = 0; chan < kp->chip.npwm; chan++) + value |= (1 << PWM_CONTROL_TYPE_SHIFT(chan)); + + writel(value, kp->base + PWM_CONTROL_OFFSET); + + clk_disable_unprepare(kp->clk); + + ret = pwmchip_add_with_polarity(&kp->chip, PWM_POLARITY_INVERSED); + if (ret < 0) + dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret); + + return ret; +} + +static int kona_pwmc_remove(struct platform_device *pdev) +{ + struct kona_pwmc *kp = platform_get_drvdata(pdev); + unsigned int chan; + + for (chan = 0; chan < kp->chip.npwm; chan++) + if (pwm_is_enabled(&kp->chip.pwms[chan])) + clk_disable_unprepare(kp->clk); + + return pwmchip_remove(&kp->chip); +} + +static const struct of_device_id bcm_kona_pwmc_dt[] = { + { .compatible = "brcm,kona-pwm" }, + { }, +}; +MODULE_DEVICE_TABLE(of, bcm_kona_pwmc_dt); + +static struct platform_driver kona_pwmc_driver = { + .driver = { + .name = "bcm-kona-pwm", + .of_match_table = bcm_kona_pwmc_dt, + }, + .probe = kona_pwmc_probe, + .remove = kona_pwmc_remove, +}; +module_platform_driver(kona_pwmc_driver); + +MODULE_AUTHOR("Broadcom Corporation <bcm-kernel-feedback-list@broadcom.com>"); +MODULE_AUTHOR("Tim Kryger <tkryger@broadcom.com>"); +MODULE_DESCRIPTION("Broadcom Kona PWM driver"); +MODULE_LICENSE("GPL v2"); |