Re: [PATCH v6 3/4] pwm: add microchip soft ip corePWM driver

From: Conor.Dooley
Date: Wed Jul 13 2022 - 04:54:58 EST

On 12/07/2022 15:25, Conor Dooley wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>
> Add a driver that supports the Microchip FPGA "soft" PWM IP core.

Looks like there's a couple W=1 warnings about the mutex use, I'll not respin
until you've had a chance to have a look at this version.
Thanks,
Conor.

>
> Signed-off-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
> ---
> drivers/pwm/Kconfig | 10 +
> drivers/pwm/Makefile | 1 +
> drivers/pwm/pwm-microchip-core.c | 370 +++++++++++++++++++++++++++++++
> 3 files changed, 381 insertions(+)
> create mode 100644 drivers/pwm/pwm-microchip-core.c
>
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index 904de8d61828..007ea5750e73 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -383,6 +383,16 @@ config PWM_MEDIATEK
> To compile this driver as a module, choose M here: the module
> will be called pwm-mediatek.
>
> +config PWM_MICROCHIP_CORE
> + tristate "Microchip corePWM PWM support"
> + depends on SOC_MICROCHIP_POLARFIRE || COMPILE_TEST
> + depends on HAS_IOMEM && OF
> + help
> + PWM driver for Microchip FPGA soft IP core.
> +
> + To compile this driver as a module, choose M here: the module
> + will be called pwm-microchip-core.
> +
> config PWM_MXS
> tristate "Freescale MXS PWM support"
> depends on ARCH_MXS || COMPILE_TEST
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> index 5c08bdb817b4..43feb7cfc66a 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -33,6 +33,7 @@ obj-$(CONFIG_PWM_LPSS_PCI) += pwm-lpss-pci.o
> obj-$(CONFIG_PWM_LPSS_PLATFORM) += pwm-lpss-platform.o
> obj-$(CONFIG_PWM_MESON) += pwm-meson.o
> obj-$(CONFIG_PWM_MEDIATEK) += pwm-mediatek.o
> +obj-$(CONFIG_PWM_MICROCHIP_CORE) += pwm-microchip-core.o
> obj-$(CONFIG_PWM_MTK_DISP) += pwm-mtk-disp.o
> obj-$(CONFIG_PWM_MXS) += pwm-mxs.o
> obj-$(CONFIG_PWM_NTXEC) += pwm-ntxec.o
> diff --git a/drivers/pwm/pwm-microchip-core.c b/drivers/pwm/pwm-microchip-core.c
> new file mode 100644
> index 000000000000..3e28868ee499
> --- /dev/null
> +++ b/drivers/pwm/pwm-microchip-core.c
> @@ -0,0 +1,370 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * corePWM driver for Microchip "soft" FPGA IP cores.
> + *
> + * Copyright (c) 2021-2022 Microchip Corporation. All rights reserved.
> + * Author: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
> + * Documentation:
> + * https://www.microsemi.com/document-portal/doc_download/1245275-corepwm-hb
> + *
> + * Limitations:
> + * - If the IP block is configured without "shadow registers", all register
> + * writes will take effect immediately, causing glitches on the output.
> + * If shadow registers *are* enabled, a write to the "SYNC_UPDATE" register
> + * notifies the core that it needs to update the registers defining the
> + * waveform from the contents of the "shadow registers".
> + * - The IP block has no concept of a duty cycle, only rising/falling edges of
> + * the waveform. Unfortunately, if the rising & falling edges registers have
> + * the same value written to them the IP block will do whichever of a rising
> + * or a falling edge is possible. I.E. a 50% waveform at twice the requested
> + * period. Therefore to get a 0% waveform, the output is set the max high/low
> + * time depending on polarity.
> + * - The PWM period is set for the whole IP block not per channel. The driver
> + * will only change the period if no other PWM output is enabled.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/math.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +
> +#define PREG_TO_VAL(PREG) ((PREG) + 1)
> +
> +#define MCHPCOREPWM_PRESCALE_MAX 0x100
> +#define MCHPCOREPWM_PERIOD_STEPS_MAX 0xff
> +#define MCHPCOREPWM_PERIOD_MAX 0xff00
> +
> +#define MCHPCOREPWM_PRESCALE 0x00
> +#define MCHPCOREPWM_PERIOD 0x04
> +#define MCHPCOREPWM_EN(i) (0x08 + 0x04 * (i)) /* 0x08, 0x0c */
> +#define MCHPCOREPWM_POSEDGE(i) (0x10 + 0x08 * (i)) /* 0x10, 0x18, ..., 0x88 */
> +#define MCHPCOREPWM_NEGEDGE(i) (0x14 + 0x08 * (i)) /* 0x14, 0x1c, ..., 0x8c */
> +#define MCHPCOREPWM_SYNC_UPD 0xe4
> +
> +struct mchp_core_pwm_chip {
> + struct pwm_chip chip;
> + struct clk *clk;
> + struct mutex lock; /* protect the shared period */
> + void __iomem *base;
> + u32 sync_update_mask;
> + u16 channel_enabled;
> +};
> +
> +static inline struct mchp_core_pwm_chip *to_mchp_core_pwm(struct pwm_chip *chip)
> +{
> + return container_of(chip, struct mchp_core_pwm_chip, chip);
> +}
> +
> +static void mchp_core_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm,
> + bool enable, u64 period)
> +{
> + struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
> + u8 channel_enable, reg_offset, shift;
> +
> + /*
> + * There are two adjacent 8 bit control regs, the lower reg controls
> + * 0-7 and the upper reg 8-15. Check if the pwm is in the upper reg
> + * and if so, offset by the bus width.
> + */
> + reg_offset = MCHPCOREPWM_EN(pwm->hwpwm >> 3);
> + shift = pwm->hwpwm & 7;
> +
> + channel_enable = readb_relaxed(mchp_core_pwm->base + reg_offset);
> + channel_enable &= ~(1 << shift);
> + channel_enable |= (enable << shift);
> +
> + writel_relaxed(channel_enable, mchp_core_pwm->base + reg_offset);
> + mchp_core_pwm->channel_enabled &= ~BIT(pwm->hwpwm);
> + mchp_core_pwm->channel_enabled |= enable << pwm->hwpwm;
> +
> + /*
> + * Notify the block to update the waveform from the shadow registers.
> + * The updated values will not appear on the bus until they have been
> + * applied to the waveform at the beginning of the next period. We must
> + * write these registers and wait for them to be applied before calling
> + * enable().
> + */
> + if (mchp_core_pwm->sync_update_mask & (1 << pwm->hwpwm)) {
> + writel_relaxed(1U, mchp_core_pwm->base + MCHPCOREPWM_SYNC_UPD);
> + usleep_range(period, period * 2);
> + }
> +}
> +
> +static u64 mchp_core_pwm_calc_duty(struct pwm_chip *chip, struct pwm_device *pwm,
> + const struct pwm_state *state, u8 prescale, u8 period_steps)
> +{
> + struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
> + u64 duty_steps, period, tmp;
> + u16 prescale_val = PREG_TO_VAL(prescale);
> + u8 period_steps_val = PREG_TO_VAL(period_steps);
> +
> + period = period_steps_val * prescale_val * NSEC_PER_SEC;
> + period = DIV64_U64_ROUND_UP(period, clk_get_rate(mchp_core_pwm->clk));
> +
> + /*
> + * Calculate the duty cycle in multiples of the prescaled period:
> + * duty_steps = duty_in_ns / step_in_ns
> + * step_in_ns = (prescale * NSEC_PER_SEC) / clk_rate
> + * The code below is rearranged slightly to only divide once.
> + */
> + duty_steps = state->duty_cycle * clk_get_rate(mchp_core_pwm->clk);
> + tmp = prescale_val * NSEC_PER_SEC;
> + return div64_u64(duty_steps, tmp);
> +}
> +
> +static void mchp_core_pwm_apply_duty(struct pwm_chip *chip, struct pwm_device *pwm,
> + const struct pwm_state *state, u64 duty_steps, u8 period_steps)
> +{
> + struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
> + u8 posedge, negedge;
> + u8 period_steps_val = PREG_TO_VAL(period_steps);
> +
> + /*
> + * Turn the output on unless posedge == negedge, in which case the
> + * duty is intended to be 0, but limitations of the IP block don't
> + * allow a zero length duty cycle - so just set the max high/low time
> + * respectively.
> + */
> + if (state->polarity == PWM_POLARITY_INVERSED) {
> + negedge = !duty_steps ? period_steps_val : 0u;
> + posedge = duty_steps;
> + } else {
> + posedge = !duty_steps ? period_steps_val : 0u;
> + negedge = duty_steps;
> + }
> +
> + writel_relaxed(posedge, mchp_core_pwm->base + MCHPCOREPWM_POSEDGE(pwm->hwpwm));
> + writel_relaxed(negedge, mchp_core_pwm->base + MCHPCOREPWM_NEGEDGE(pwm->hwpwm));
> +}
> +
> +static int mchp_core_pwm_calc_period(struct pwm_chip *chip, const struct pwm_state *state,
> + u8 *prescale, u8 *period_steps)
> +{
> + struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
> + u64 tmp, clk_rate;
> +
> + /*
> + * Calculate the period cycles and prescale values.
> + * The registers are each 8 bits wide & multiplied to compute the period
> + * using the formula:
> + * (clock_period) * (prescale + 1) * (period_steps + 1)
> + * so the maximum period that can be generated is 0x10000 times the
> + * period of the input clock.
> + * However, due to the design of the "hardware", it is not possible to
> + * attain a 100% duty cycle if the full range of period_steps is used.
> + * Therefore period_steps is restricted to 0xFE and the maximum multiple
> + * of the clock period attainable is 0xFF00.
> + */
> + clk_rate = clk_get_rate(mchp_core_pwm->clk);
> +
> + /*
> + * If clk_rate is too big, the following multiplication might overflow.
> + * However this is implausible, as the fabric of current FPGAs cannot
> + * provide clocks at a rate high enough.
> + */
> + if (clk_rate >= NSEC_PER_SEC)
> + return -EINVAL;
> +
> + tmp = mul_u64_u64_div_u64(state->period, clk_rate, NSEC_PER_SEC);
> +
> + if (tmp >= MCHPCOREPWM_PERIOD_MAX) {
> + *prescale = MCHPCOREPWM_PRESCALE_MAX - 1;
> + *period_steps = MCHPCOREPWM_PERIOD_STEPS_MAX - 1;
> + return 0;
> + }
> +
> + *prescale = div_u64(tmp, MCHPCOREPWM_PERIOD_STEPS_MAX);
> + /* PREG_TO_VAL() can produce a value larger than UINT8_MAX */
> + *period_steps = div_u64(tmp, PREG_TO_VAL((u32)*prescale)) - 1;
> +
> + return 0;
> +}
> +
> +static inline void mchp_core_pwm_apply_period(struct mchp_core_pwm_chip *mchp_core_pwm,
> + u8 prescale, u8 period_steps)
> +{
> + writel_relaxed(prescale, mchp_core_pwm->base + MCHPCOREPWM_PRESCALE);
> + writel_relaxed(period_steps, mchp_core_pwm->base + MCHPCOREPWM_PERIOD);
> +}
> +
> +static int mchp_core_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> + const struct pwm_state *state)
> +{
> + struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
> + struct pwm_state current_state = pwm->state;
> + bool period_locked;
> + u64 duty_steps;
> + u16 channel_enabled;
> + u8 prescale, period_steps, hw_prescale, hw_period_steps;
> + int ret;
> +
> + mutex_lock_interruptible(&mchp_core_pwm->lock);
> +
> + if (!state->enabled) {
> + mchp_core_pwm_enable(chip, pwm, false, current_state.period);
> + mutex_unlock(&mchp_core_pwm->lock);
> + return 0;
> + }
> +
> + /*
> + * If the only thing that has changed is the duty cycle or the polarity,
> + * we can shortcut the calculations and just compute/apply the new duty
> + * cycle pos & neg edges
> + * As all the channels share the same period, do not allow it to be
> + * changed if any other channels are enabled.
> + * If the period is locked, it may not be possible to use a period
> + * less than that requested. In that case, we just abort.
> + */
> + period_locked = mchp_core_pwm->channel_enabled & ~(1 << pwm->hwpwm);
> +
> + if (period_locked) {
> + mchp_core_pwm_calc_period(chip, state, &prescale, &period_steps);
> + hw_prescale = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PRESCALE);
> + hw_period_steps = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PERIOD);
> +
> + if ((period_steps * prescale) < (hw_period_steps * hw_prescale)) {
> + mutex_unlock(&mchp_core_pwm->lock);
> + return -EINVAL;
> + }
> +
> + prescale = hw_prescale;
> + period_steps = hw_period_steps;
> + } else if (!current_state.enabled || current_state.period != state->period) {
> + ret = mchp_core_pwm_calc_period(chip, state, &prescale, &period_steps);
> + if (ret) {
> + mutex_unlock(&mchp_core_pwm->lock);
> + return ret;
> + }
> + mchp_core_pwm_apply_period(mchp_core_pwm, prescale, period_steps);
> + } else {
> + prescale = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PRESCALE);
> + period_steps = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PERIOD);
> + }
> +
> + duty_steps = mchp_core_pwm_calc_duty(chip, pwm, state, prescale, period_steps);
> +
> + /*
> + * Because the period is per channel, it is possible that the requested
> + * duty cycle is longer than the period, in which case cap it to the
> + * period, IOW a 100% duty cycle.
> + */
> + if (duty_steps > period_steps)
> + duty_steps = period_steps + 1;
> +
> + mchp_core_pwm_apply_duty(chip, pwm, state, duty_steps, period_steps);
> +
> + mchp_core_pwm_enable(chip, pwm, true, state->period);
> +
> + mutex_unlock(&mchp_core_pwm->lock);
> +
> + return 0;
> +}
> +
> +static void mchp_core_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
> + struct pwm_state *state)
> +{
> + struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
> + u16 prescale;
> + u8 period_steps, duty_steps, posedge, negedge;
> + u16 channel_enabled;
> +
> + mutex_lock_interruptible(&mchp_core_pwm->lock);
> +
> + channel_enabled = mchp_core_pwm->channel_enabled;
> +
> + if (channel_enabled & (1 << pwm->hwpwm))
> + state->enabled = true;
> + else
> + state->enabled = false;
> +
> + prescale = PREG_TO_VAL(readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PRESCALE));
> +
> + period_steps = PREG_TO_VAL(readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PERIOD));
> + state->period = period_steps * prescale * NSEC_PER_SEC;
> + state->period = DIV64_U64_ROUND_UP(state->period, clk_get_rate(mchp_core_pwm->clk));
> +
> + posedge = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_POSEDGE(pwm->hwpwm));
> + negedge = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_NEGEDGE(pwm->hwpwm));
> +
> + if (negedge == posedge) {
> + state->duty_cycle = state->period / 2;
> + } else {
> + duty_steps = abs((s16)posedge - (s16)negedge);
> + state->duty_cycle = duty_steps * prescale * NSEC_PER_SEC;
> + state->duty_cycle = DIV64_U64_ROUND_UP(state->duty_cycle,
> + clk_get_rate(mchp_core_pwm->clk));
> + }
> +
> + state->polarity = negedge < posedge ? PWM_POLARITY_INVERSED : PWM_POLARITY_NORMAL;
> +
> + mutex_unlock(&mchp_core_pwm->lock);
> +}
> +
> +static const struct pwm_ops mchp_core_pwm_ops = {
> + .apply = mchp_core_pwm_apply,
> + .get_state = mchp_core_pwm_get_state,
> + .owner = THIS_MODULE,
> +};
> +
> +static const struct of_device_id mchp_core_of_match[] = {
> + {
> + .compatible = "microchip,corepwm-rtl-v4",
> + },
> + { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, mchp_core_of_match);
> +
> +static int mchp_core_pwm_probe(struct platform_device *pdev)
> +{
> + struct mchp_core_pwm_chip *mchp_pwm;
> + struct resource *regs;
> + int ret;
> +
> + mchp_pwm = devm_kzalloc(&pdev->dev, sizeof(*mchp_pwm), GFP_KERNEL);
> + if (!mchp_pwm)
> + return -ENOMEM;
> +
> + mchp_pwm->base = devm_platform_get_and_ioremap_resource(pdev, 0, &regs);
> + if (IS_ERR(mchp_pwm->base))
> + return PTR_ERR(mchp_pwm->base);
> +
> + mchp_pwm->clk = devm_clk_get_enabled(&pdev->dev, NULL);
> + if (IS_ERR(mchp_pwm->clk))
> + return dev_err_probe(&pdev->dev, PTR_ERR(mchp_pwm->clk),
> + "failed to get PWM clock\n");
> +
> + if (of_property_read_u32(pdev->dev.of_node, "microchip,sync-update-mask",
> + &mchp_pwm->sync_update_mask))
> + mchp_pwm->sync_update_mask = 0u;
> +
> + mutex_init(&mchp_pwm->lock);
> +
> + mchp_pwm->chip.dev = &pdev->dev;
> + mchp_pwm->chip.ops = &mchp_core_pwm_ops;
> + mchp_pwm->chip.npwm = 16;
> +
> + ret = devm_pwmchip_add(&pdev->dev, &mchp_pwm->chip);
> + if (ret < 0)
> + return dev_err_probe(&pdev->dev, ret, "failed to add PWM chip\n");
> +
> + return 0;
> +}
> +
> +static struct platform_driver mchp_core_pwm_driver = {
> + .driver = {
> + .name = "mchp-core-pwm",
> + .of_match_table = mchp_core_of_match,
> + },
> + .probe = mchp_core_pwm_probe,
> +};
> +module_platform_driver(mchp_core_pwm_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Conor Dooley <conor.dooley@xxxxxxxxxxxxx>");
> +MODULE_DESCRIPTION("corePWM driver for Microchip FPGAs");
> --
> 2.36.1
>
>
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