diff options
Diffstat (limited to 'drivers/pwm/pwm-xilinx.c')
| -rw-r--r-- | drivers/pwm/pwm-xilinx.c | 321 |
1 files changed, 321 insertions, 0 deletions
diff --git a/drivers/pwm/pwm-xilinx.c b/drivers/pwm/pwm-xilinx.c new file mode 100644 index 000000000000..4dab2b86c427 --- /dev/null +++ b/drivers/pwm/pwm-xilinx.c @@ -0,0 +1,321 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Copyright (C) 2021 Sean Anderson <sean.anderson@seco.com> + * + * Limitations: + * - When changing both duty cycle and period, we may end up with one cycle + * with the old duty cycle and the new period. This is because the counters + * may only be reloaded by first stopping them, or by letting them be + * automatically reloaded at the end of a cycle. If this automatic reload + * happens after we set TLR0 but before we set TLR1 then we will have a + * bad cycle. This could probably be fixed by reading TCR0 just before + * reprogramming, but I think it would add complexity for little gain. + * - Cannot produce 100% duty cycle by configuring the TLRs. This might be + * possible by stopping the counters at an appropriate point in the cycle, + * but this is not (yet) implemented. + * - Only produces "normal" output. + * - Always produces low output if disabled. + */ + +#include <clocksource/timer-xilinx.h> +#include <linux/clk.h> +#include <linux/clk-provider.h> +#include <linux/device.h> +#include <linux/module.h> +#include <linux/of.h> +#include <linux/platform_device.h> +#include <linux/pwm.h> +#include <linux/regmap.h> + +/* + * The following functions are "common" to drivers for this device, and may be + * exported at a future date. + */ +u32 xilinx_timer_tlr_cycles(struct xilinx_timer_priv *priv, u32 tcsr, + u64 cycles) +{ + WARN_ON(cycles < 2 || cycles - 2 > priv->max); + + if (tcsr & TCSR_UDT) + return cycles - 2; + return priv->max - cycles + 2; +} + +unsigned int xilinx_timer_get_period(struct xilinx_timer_priv *priv, + u32 tlr, u32 tcsr) +{ + u64 cycles; + + if (tcsr & TCSR_UDT) + cycles = tlr + 2; + else + cycles = (u64)priv->max - tlr + 2; + + /* cycles has a max of 2^32 + 2, so we can't overflow */ + return DIV64_U64_ROUND_UP(cycles * NSEC_PER_SEC, + clk_get_rate(priv->clk)); +} + +/* + * The idea here is to capture whether the PWM is actually running (e.g. + * because we or the bootloader set it up) and we need to be careful to ensure + * we don't cause a glitch. According to the data sheet, to enable the PWM we + * need to + * + * - Set both timers to generate mode (MDT=1) + * - Set both timers to PWM mode (PWMA=1) + * - Enable the generate out signals (GENT=1) + * + * In addition, + * + * - The timer must be running (ENT=1) + * - The timer must auto-reload TLR into TCR (ARHT=1) + * - We must not be in the process of loading TLR into TCR (LOAD=0) + * - Cascade mode must be disabled (CASC=0) + * + * If any of these differ from usual, then the PWM is either disabled, or is + * running in a mode that this driver does not support. + */ +#define TCSR_PWM_SET (TCSR_GENT | TCSR_ARHT | TCSR_ENT | TCSR_PWMA) +#define TCSR_PWM_CLEAR (TCSR_MDT | TCSR_LOAD) +#define TCSR_PWM_MASK (TCSR_PWM_SET | TCSR_PWM_CLEAR) + +struct xilinx_pwm_device { + struct pwm_chip chip; + struct xilinx_timer_priv priv; +}; + +static inline struct xilinx_timer_priv +*xilinx_pwm_chip_to_priv(struct pwm_chip *chip) +{ + return &container_of(chip, struct xilinx_pwm_device, chip)->priv; +} + +static bool xilinx_timer_pwm_enabled(u32 tcsr0, u32 tcsr1) +{ + return ((TCSR_PWM_MASK | TCSR_CASC) & tcsr0) == TCSR_PWM_SET && + (TCSR_PWM_MASK & tcsr1) == TCSR_PWM_SET; +} + +static int xilinx_pwm_apply(struct pwm_chip *chip, struct pwm_device *unused, + const struct pwm_state *state) +{ + struct xilinx_timer_priv *priv = xilinx_pwm_chip_to_priv(chip); + u32 tlr0, tlr1, tcsr0, tcsr1; + u64 period_cycles, duty_cycles; + unsigned long rate; + + if (state->polarity != PWM_POLARITY_NORMAL) + return -EINVAL; + + /* + * To be representable by TLR, cycles must be between 2 and + * priv->max + 2. To enforce this we can reduce the cycles, but we may + * not increase them. Caveat emptor: while this does result in more + * predictable rounding, it may also result in a completely different + * duty cycle (% high time) than what was requested. + */ + rate = clk_get_rate(priv->clk); + /* Avoid overflow */ + period_cycles = min_t(u64, state->period, U32_MAX * NSEC_PER_SEC); + period_cycles = mul_u64_u32_div(period_cycles, rate, NSEC_PER_SEC); + period_cycles = min_t(u64, period_cycles, priv->max + 2); + if (period_cycles < 2) + return -ERANGE; + + /* Same thing for duty cycles */ + duty_cycles = min_t(u64, state->duty_cycle, U32_MAX * NSEC_PER_SEC); + duty_cycles = mul_u64_u32_div(duty_cycles, rate, NSEC_PER_SEC); + duty_cycles = min_t(u64, duty_cycles, priv->max + 2); + + /* + * If we specify 100% duty cycle, we will get 0% instead, so decrease + * the duty cycle count by one. + */ + if (duty_cycles >= period_cycles) + duty_cycles = period_cycles - 1; + + /* Round down to 0% duty cycle for unrepresentable duty cycles */ + if (duty_cycles < 2) + duty_cycles = period_cycles; + + regmap_read(priv->map, TCSR0, &tcsr0); + regmap_read(priv->map, TCSR1, &tcsr1); + tlr0 = xilinx_timer_tlr_cycles(priv, tcsr0, period_cycles); + tlr1 = xilinx_timer_tlr_cycles(priv, tcsr1, duty_cycles); + regmap_write(priv->map, TLR0, tlr0); + regmap_write(priv->map, TLR1, tlr1); + + if (state->enabled) { + /* + * If the PWM is already running, then the counters will be + * reloaded at the end of the current cycle. + */ + if (!xilinx_timer_pwm_enabled(tcsr0, tcsr1)) { + /* Load TLR into TCR */ + regmap_write(priv->map, TCSR0, tcsr0 | TCSR_LOAD); + regmap_write(priv->map, TCSR1, tcsr1 | TCSR_LOAD); + /* Enable timers all at once with ENALL */ + tcsr0 = (TCSR_PWM_SET & ~TCSR_ENT) | (tcsr0 & TCSR_UDT); + tcsr1 = TCSR_PWM_SET | TCSR_ENALL | (tcsr1 & TCSR_UDT); + regmap_write(priv->map, TCSR0, tcsr0); + regmap_write(priv->map, TCSR1, tcsr1); + } + } else { + regmap_write(priv->map, TCSR0, 0); + regmap_write(priv->map, TCSR1, 0); + } + + return 0; +} + +static void xilinx_pwm_get_state(struct pwm_chip *chip, + struct pwm_device *unused, + struct pwm_state *state) +{ + struct xilinx_timer_priv *priv = xilinx_pwm_chip_to_priv(chip); + u32 tlr0, tlr1, tcsr0, tcsr1; + + regmap_read(priv->map, TLR0, &tlr0); + regmap_read(priv->map, TLR1, &tlr1); + regmap_read(priv->map, TCSR0, &tcsr0); + regmap_read(priv->map, TCSR1, &tcsr1); + state->period = xilinx_timer_get_period(priv, tlr0, tcsr0); + state->duty_cycle = xilinx_timer_get_period(priv, tlr1, tcsr1); + state->enabled = xilinx_timer_pwm_enabled(tcsr0, tcsr1); + state->polarity = PWM_POLARITY_NORMAL; + + /* + * 100% duty cycle results in constant low output. This may be (very) + * wrong if rate > 1 GHz, so fix this if you have such hardware :) + */ + if (state->period == state->duty_cycle) + state->duty_cycle = 0; +} + +static const struct pwm_ops xilinx_pwm_ops = { + .apply = xilinx_pwm_apply, + .get_state = xilinx_pwm_get_state, + .owner = THIS_MODULE, +}; + +static const struct regmap_config xilinx_pwm_regmap_config = { + .reg_bits = 32, + .reg_stride = 4, + .val_bits = 32, + .val_format_endian = REGMAP_ENDIAN_LITTLE, + .max_register = TCR1, +}; + +static int xilinx_pwm_probe(struct platform_device *pdev) +{ + int ret; + struct device *dev = &pdev->dev; + struct device_node *np = dev->of_node; + struct xilinx_timer_priv *priv; + struct xilinx_pwm_device *xilinx_pwm; + u32 pwm_cells, one_timer, width; + void __iomem *regs; + + /* If there are no PWM cells, this binding is for a timer */ + ret = of_property_read_u32(np, "#pwm-cells", &pwm_cells); + if (ret == -EINVAL) + return -ENODEV; + if (ret) + return dev_err_probe(dev, ret, "could not read #pwm-cells\n"); + + xilinx_pwm = devm_kzalloc(dev, sizeof(*xilinx_pwm), GFP_KERNEL); + if (!xilinx_pwm) + return -ENOMEM; + platform_set_drvdata(pdev, xilinx_pwm); + priv = &xilinx_pwm->priv; + + regs = devm_platform_ioremap_resource(pdev, 0); + if (IS_ERR(regs)) + return PTR_ERR(regs); + + priv->map = devm_regmap_init_mmio(dev, regs, + &xilinx_pwm_regmap_config); + if (IS_ERR(priv->map)) + return dev_err_probe(dev, PTR_ERR(priv->map), + "Could not create regmap\n"); + + ret = of_property_read_u32(np, "xlnx,one-timer-only", &one_timer); + if (ret) + return dev_err_probe(dev, ret, + "Could not read xlnx,one-timer-only\n"); + + if (one_timer) + return dev_err_probe(dev, -EINVAL, + "Two timers required for PWM mode\n"); + + ret = of_property_read_u32(np, "xlnx,count-width", &width); + if (ret == -EINVAL) + width = 32; + else if (ret) + return dev_err_probe(dev, ret, + "Could not read xlnx,count-width\n"); + + if (width != 8 && width != 16 && width != 32) + return dev_err_probe(dev, -EINVAL, + "Invalid counter width %d\n", width); + priv->max = BIT_ULL(width) - 1; + + /* + * The polarity of the Generate Out signals must be active high for PWM + * mode to work. We could determine this from the device tree, but + * alas, such properties are not allowed to be used. + */ + + priv->clk = devm_clk_get(dev, "s_axi_aclk"); + if (IS_ERR(priv->clk)) + return dev_err_probe(dev, PTR_ERR(priv->clk), + "Could not get clock\n"); + + ret = clk_prepare_enable(priv->clk); + if (ret) + return dev_err_probe(dev, ret, "Clock enable failed\n"); + clk_rate_exclusive_get(priv->clk); + + xilinx_pwm->chip.dev = dev; + xilinx_pwm->chip.ops = &xilinx_pwm_ops; + xilinx_pwm->chip.npwm = 1; + ret = pwmchip_add(&xilinx_pwm->chip); + if (ret) { + clk_rate_exclusive_put(priv->clk); + clk_disable_unprepare(priv->clk); + return dev_err_probe(dev, ret, "Could not register PWM chip\n"); + } + + return 0; +} + +static int xilinx_pwm_remove(struct platform_device *pdev) +{ + struct xilinx_pwm_device *xilinx_pwm = platform_get_drvdata(pdev); + + pwmchip_remove(&xilinx_pwm->chip); + clk_rate_exclusive_put(xilinx_pwm->priv.clk); + clk_disable_unprepare(xilinx_pwm->priv.clk); + return 0; +} + +static const struct of_device_id xilinx_pwm_of_match[] = { + { .compatible = "xlnx,xps-timer-1.00.a", }, + {}, +}; +MODULE_DEVICE_TABLE(of, xilinx_pwm_of_match); + +static struct platform_driver xilinx_pwm_driver = { + .probe = xilinx_pwm_probe, + .remove = xilinx_pwm_remove, + .driver = { + .name = "xilinx-pwm", + .of_match_table = of_match_ptr(xilinx_pwm_of_match), + }, +}; +module_platform_driver(xilinx_pwm_driver); + +MODULE_ALIAS("platform:xilinx-pwm"); +MODULE_DESCRIPTION("PWM driver for Xilinx LogiCORE IP AXI Timer"); +MODULE_LICENSE("GPL"); |