diff options
Diffstat (limited to 'drivers/pwm/pwm-imx27.c')
| -rw-r--r-- | drivers/pwm/pwm-imx27.c | 432 |
1 files changed, 432 insertions, 0 deletions
diff --git a/drivers/pwm/pwm-imx27.c b/drivers/pwm/pwm-imx27.c new file mode 100644 index 000000000000..3d34cdc4a3a5 --- /dev/null +++ b/drivers/pwm/pwm-imx27.c @@ -0,0 +1,432 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * simple driver for PWM (Pulse Width Modulator) controller + * + * Derived from pxa PWM driver by eric miao <eric.miao@marvell.com> + * + * Limitations: + * - When disabled the output is driven to 0 independent of the configured + * polarity. + */ + +#include <linux/bitfield.h> +#include <linux/bitops.h> +#include <linux/clk.h> +#include <linux/delay.h> +#include <linux/err.h> +#include <linux/io.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/of.h> +#include <linux/platform_device.h> +#include <linux/pwm.h> +#include <linux/slab.h> + +#define MX3_PWMCR 0x00 /* PWM Control Register */ +#define MX3_PWMSR 0x04 /* PWM Status Register */ +#define MX3_PWMSAR 0x0C /* PWM Sample Register */ +#define MX3_PWMPR 0x10 /* PWM Period Register */ +#define MX3_PWMCNR 0x14 /* PWM Counter Register */ + +#define MX3_PWMCR_FWM GENMASK(27, 26) +#define MX3_PWMCR_STOPEN BIT(25) +#define MX3_PWMCR_DOZEN BIT(24) +#define MX3_PWMCR_WAITEN BIT(23) +#define MX3_PWMCR_DBGEN BIT(22) +#define MX3_PWMCR_BCTR BIT(21) +#define MX3_PWMCR_HCTR BIT(20) + +#define MX3_PWMCR_POUTC GENMASK(19, 18) +#define MX3_PWMCR_POUTC_NORMAL 0 +#define MX3_PWMCR_POUTC_INVERTED 1 +#define MX3_PWMCR_POUTC_OFF 2 + +#define MX3_PWMCR_CLKSRC GENMASK(17, 16) +#define MX3_PWMCR_CLKSRC_OFF 0 +#define MX3_PWMCR_CLKSRC_IPG 1 +#define MX3_PWMCR_CLKSRC_IPG_HIGH 2 +#define MX3_PWMCR_CLKSRC_IPG_32K 3 + +#define MX3_PWMCR_PRESCALER GENMASK(15, 4) + +#define MX3_PWMCR_SWR BIT(3) + +#define MX3_PWMCR_REPEAT GENMASK(2, 1) +#define MX3_PWMCR_REPEAT_1X 0 +#define MX3_PWMCR_REPEAT_2X 1 +#define MX3_PWMCR_REPEAT_4X 2 +#define MX3_PWMCR_REPEAT_8X 3 + +#define MX3_PWMCR_EN BIT(0) + +#define MX3_PWMSR_FWE BIT(6) +#define MX3_PWMSR_CMP BIT(5) +#define MX3_PWMSR_ROV BIT(4) +#define MX3_PWMSR_FE BIT(3) + +#define MX3_PWMSR_FIFOAV GENMASK(2, 0) +#define MX3_PWMSR_FIFOAV_EMPTY 0 +#define MX3_PWMSR_FIFOAV_1WORD 1 +#define MX3_PWMSR_FIFOAV_2WORDS 2 +#define MX3_PWMSR_FIFOAV_3WORDS 3 +#define MX3_PWMSR_FIFOAV_4WORDS 4 + +#define MX3_PWMCR_PRESCALER_SET(x) FIELD_PREP(MX3_PWMCR_PRESCALER, (x) - 1) +#define MX3_PWMCR_PRESCALER_GET(x) (FIELD_GET(MX3_PWMCR_PRESCALER, \ + (x)) + 1) + +#define MX3_PWM_SWR_LOOP 5 + +/* PWMPR register value of 0xffff has the same effect as 0xfffe */ +#define MX3_PWMPR_MAX 0xfffe + +static const char * const pwm_imx27_clks[] = {"ipg", "per"}; +#define PWM_IMX27_PER 1 + +struct pwm_imx27_chip { + struct clk_bulk_data clks[ARRAY_SIZE(pwm_imx27_clks)]; + int clks_cnt; + void __iomem *mmio_base; + + /* + * The driver cannot read the current duty cycle from the hardware if + * the hardware is disabled. Cache the last programmed duty cycle + * value to return in that case. + */ + unsigned int duty_cycle; +}; + +static inline struct pwm_imx27_chip *to_pwm_imx27_chip(struct pwm_chip *chip) +{ + return pwmchip_get_drvdata(chip); +} + +static int pwm_imx27_get_state(struct pwm_chip *chip, + struct pwm_device *pwm, struct pwm_state *state) +{ + struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip); + u32 period, prescaler, pwm_clk, val; + u64 tmp; + int ret; + + ret = clk_bulk_prepare_enable(imx->clks_cnt, imx->clks); + if (ret < 0) + return ret; + + val = readl(imx->mmio_base + MX3_PWMCR); + + if (val & MX3_PWMCR_EN) + state->enabled = true; + else + state->enabled = false; + + switch (FIELD_GET(MX3_PWMCR_POUTC, val)) { + case MX3_PWMCR_POUTC_NORMAL: + state->polarity = PWM_POLARITY_NORMAL; + break; + case MX3_PWMCR_POUTC_INVERTED: + state->polarity = PWM_POLARITY_INVERSED; + break; + default: + dev_warn(pwmchip_parent(chip), "can't set polarity, output disconnected"); + } + + prescaler = MX3_PWMCR_PRESCALER_GET(val); + pwm_clk = clk_get_rate(imx->clks[PWM_IMX27_PER].clk); + val = readl(imx->mmio_base + MX3_PWMPR); + period = val >= MX3_PWMPR_MAX ? MX3_PWMPR_MAX : val; + + /* PWMOUT (Hz) = PWMCLK / (PWMPR + 2) */ + tmp = NSEC_PER_SEC * (u64)(period + 2) * prescaler; + state->period = DIV_ROUND_UP_ULL(tmp, pwm_clk); + + /* + * PWMSAR can be read only if PWM is enabled. If the PWM is disabled, + * use the cached value. + */ + if (state->enabled) + val = readl(imx->mmio_base + MX3_PWMSAR); + else + val = imx->duty_cycle; + + tmp = NSEC_PER_SEC * (u64)(val) * prescaler; + state->duty_cycle = DIV_ROUND_UP_ULL(tmp, pwm_clk); + + clk_bulk_disable_unprepare(imx->clks_cnt, imx->clks); + + return 0; +} + +static void pwm_imx27_sw_reset(struct pwm_chip *chip) +{ + struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip); + struct device *dev = pwmchip_parent(chip); + int wait_count = 0; + u32 cr; + + writel(MX3_PWMCR_SWR, imx->mmio_base + MX3_PWMCR); + do { + usleep_range(200, 1000); + cr = readl(imx->mmio_base + MX3_PWMCR); + } while ((cr & MX3_PWMCR_SWR) && + (wait_count++ < MX3_PWM_SWR_LOOP)); + + if (cr & MX3_PWMCR_SWR) + dev_warn(dev, "software reset timeout\n"); +} + +static void pwm_imx27_wait_fifo_slot(struct pwm_chip *chip, + struct pwm_device *pwm) +{ + struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip); + struct device *dev = pwmchip_parent(chip); + unsigned int period_ms; + int fifoav; + u32 sr; + + sr = readl(imx->mmio_base + MX3_PWMSR); + fifoav = FIELD_GET(MX3_PWMSR_FIFOAV, sr); + if (fifoav == MX3_PWMSR_FIFOAV_4WORDS) { + period_ms = DIV_ROUND_UP_ULL(pwm->state.period, + NSEC_PER_MSEC); + msleep(period_ms); + + sr = readl(imx->mmio_base + MX3_PWMSR); + if (fifoav == FIELD_GET(MX3_PWMSR_FIFOAV, sr)) + dev_warn(dev, "there is no free FIFO slot\n"); + } +} + +static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm, + const struct pwm_state *state) +{ + unsigned long period_cycles, duty_cycles, prescale, period_us, tmp; + struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip); + unsigned long long c; + unsigned long long clkrate; + unsigned long flags; + int val; + int ret; + u32 cr; + + clkrate = clk_get_rate(imx->clks[PWM_IMX27_PER].clk); + c = clkrate * state->period; + + do_div(c, NSEC_PER_SEC); + period_cycles = c; + + prescale = period_cycles / 0x10000 + 1; + + period_cycles /= prescale; + c = clkrate * state->duty_cycle; + do_div(c, NSEC_PER_SEC); + duty_cycles = c; + duty_cycles /= prescale; + + /* + * 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; + + /* + * Wait for a free FIFO slot if the PWM is already enabled, and flush + * the FIFO if the PWM was disabled and is about to be enabled. + */ + if (pwm->state.enabled) { + pwm_imx27_wait_fifo_slot(chip, pwm); + } else { + ret = clk_bulk_prepare_enable(imx->clks_cnt, imx->clks); + if (ret) + return ret; + + pwm_imx27_sw_reset(chip); + } + + val = readl(imx->mmio_base + MX3_PWMPR); + val = val >= MX3_PWMPR_MAX ? MX3_PWMPR_MAX : val; + cr = readl(imx->mmio_base + MX3_PWMCR); + tmp = NSEC_PER_SEC * (u64)(val + 2) * MX3_PWMCR_PRESCALER_GET(cr); + tmp = DIV_ROUND_UP_ULL(tmp, clkrate); + period_us = DIV_ROUND_UP_ULL(tmp, 1000); + + /* + * ERR051198: + * PWM: PWM output may not function correctly if the FIFO is empty when + * a new SAR value is programmed + * + * Description: + * When the PWM FIFO is empty, a new value programmed to the PWM Sample + * register (PWM_PWMSAR) will be directly applied even if the current + * timer period has not expired. + * + * If the new SAMPLE value programmed in the PWM_PWMSAR register is + * less than the previous value, and the PWM counter register + * (PWM_PWMCNR) that contains the current COUNT value is greater than + * the new programmed SAMPLE value, the current period will not flip + * the level. This may result in an output pulse with a duty cycle of + * 100%. + * + * Consider a change from + * ________ + * / \______/ + * ^ * ^ + * to + * ____ + * / \__________/ + * ^ ^ + * At the time marked by *, the new write value will be directly applied + * to SAR even the current period is not over if FIFO is empty. + * + * ________ ____________________ + * / \______/ \__________/ + * ^ ^ * ^ ^ + * |<-- old SAR -->| |<-- new SAR -->| + * + * That is the output is active for a whole period. + * + * Workaround: + * Check new SAR less than old SAR and current counter is in errata + * windows, write extra old SAR into FIFO and new SAR will effect at + * next period. + * + * Sometime period is quite long, such as over 1 second. If add old SAR + * into FIFO unconditional, new SAR have to wait for next period. It + * may be too long. + * + * Turn off the interrupt to ensure that not IRQ and schedule happen + * during above operations. If any irq and schedule happen, counter + * in PWM will be out of data and take wrong action. + * + * Add a safety margin 1.5us because it needs some time to complete + * IO write. + * + * Use writel_relaxed() to minimize the interval between two writes to + * the SAR register to increase the fastest PWM frequency supported. + * + * When the PWM period is longer than 2us(or <500kHz), this workaround + * can solve this problem. No software workaround is available if PWM + * period is shorter than IO write. Just try best to fill old data + * into FIFO. + */ + c = clkrate * 1500; + do_div(c, NSEC_PER_SEC); + + local_irq_save(flags); + val = FIELD_GET(MX3_PWMSR_FIFOAV, readl_relaxed(imx->mmio_base + MX3_PWMSR)); + + if (duty_cycles < imx->duty_cycle && (cr & MX3_PWMCR_EN)) { + if (period_us < 2) { /* 2us = 500 kHz */ + /* Best effort attempt to fix up >500 kHz case */ + udelay(3 * period_us); + writel_relaxed(imx->duty_cycle, imx->mmio_base + MX3_PWMSAR); + writel_relaxed(imx->duty_cycle, imx->mmio_base + MX3_PWMSAR); + } else if (val < MX3_PWMSR_FIFOAV_2WORDS) { + val = readl_relaxed(imx->mmio_base + MX3_PWMCNR); + /* + * If counter is close to period, controller may roll over when + * next IO write. + */ + if ((val + c >= duty_cycles && val < imx->duty_cycle) || + val + c >= period_cycles) + writel_relaxed(imx->duty_cycle, imx->mmio_base + MX3_PWMSAR); + } + } + writel_relaxed(duty_cycles, imx->mmio_base + MX3_PWMSAR); + local_irq_restore(flags); + + writel(period_cycles, imx->mmio_base + MX3_PWMPR); + + /* + * Store the duty cycle for future reference in cases where the + * MX3_PWMSAR register can't be read (i.e. when the PWM is disabled). + */ + imx->duty_cycle = duty_cycles; + + cr = MX3_PWMCR_PRESCALER_SET(prescale) | + MX3_PWMCR_STOPEN | MX3_PWMCR_DOZEN | MX3_PWMCR_WAITEN | + FIELD_PREP(MX3_PWMCR_CLKSRC, MX3_PWMCR_CLKSRC_IPG_HIGH) | + MX3_PWMCR_DBGEN; + + if (state->polarity == PWM_POLARITY_INVERSED) + cr |= FIELD_PREP(MX3_PWMCR_POUTC, + MX3_PWMCR_POUTC_INVERTED); + + if (state->enabled) + cr |= MX3_PWMCR_EN; + + writel(cr, imx->mmio_base + MX3_PWMCR); + + if (!state->enabled) + clk_bulk_disable_unprepare(imx->clks_cnt, imx->clks); + + return 0; +} + +static const struct pwm_ops pwm_imx27_ops = { + .apply = pwm_imx27_apply, + .get_state = pwm_imx27_get_state, +}; + +static const struct of_device_id pwm_imx27_dt_ids[] = { + { .compatible = "fsl,imx27-pwm", }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(of, pwm_imx27_dt_ids); + +static int pwm_imx27_probe(struct platform_device *pdev) +{ + struct pwm_chip *chip; + struct pwm_imx27_chip *imx; + int ret; + u32 pwmcr; + int i; + + chip = devm_pwmchip_alloc(&pdev->dev, 1, sizeof(*imx)); + if (IS_ERR(chip)) + return PTR_ERR(chip); + imx = to_pwm_imx27_chip(chip); + + imx->clks_cnt = ARRAY_SIZE(pwm_imx27_clks); + for (i = 0; i < imx->clks_cnt; ++i) + imx->clks[i].id = pwm_imx27_clks[i]; + + ret = devm_clk_bulk_get(&pdev->dev, imx->clks_cnt, imx->clks); + + if (ret) + return dev_err_probe(&pdev->dev, ret, + "getting clocks failed\n"); + + chip->ops = &pwm_imx27_ops; + + imx->mmio_base = devm_platform_ioremap_resource(pdev, 0); + if (IS_ERR(imx->mmio_base)) + return PTR_ERR(imx->mmio_base); + + ret = clk_bulk_prepare_enable(imx->clks_cnt, imx->clks); + if (ret) + return ret; + + /* keep clks on if pwm is running */ + pwmcr = readl(imx->mmio_base + MX3_PWMCR); + if (!(pwmcr & MX3_PWMCR_EN)) + clk_bulk_disable_unprepare(imx->clks_cnt, imx->clks); + + return devm_pwmchip_add(&pdev->dev, chip); +} + +static struct platform_driver imx_pwm_driver = { + .driver = { + .name = "pwm-imx27", + .of_match_table = pwm_imx27_dt_ids, + }, + .probe = pwm_imx27_probe, +}; +module_platform_driver(imx_pwm_driver); + +MODULE_DESCRIPTION("i.MX27 and later i.MX SoCs Pulse Width Modulator driver"); +MODULE_LICENSE("GPL v2"); +MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>"); |