[PATCH v3 1/2] pwm: add microchip soft ip corePWM driver

From: Conor Dooley
Date: Fri Jun 17 2022 - 07:46:38 EST


Add a driver that supports the Microchip FPGA "soft" PWM IP core.

Signed-off-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
---
drivers/pwm/Kconfig | 10 +
drivers/pwm/Makefile | 1 +
drivers/pwm/pwm-microchip-core.c | 325 +++++++++++++++++++++++++++++++
3 files changed, 336 insertions(+)
create mode 100644 drivers/pwm/pwm-microchip-core.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 21e3b05a5153..a651848e444b 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 708840b7fba8..d29754c20f91 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..abbfc1cd23c4
--- /dev/null
+++ b/drivers/pwm/pwm-microchip-core.c
@@ -0,0 +1,325 @@
+// 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/module.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/math.h>
+
+#define PREG_TO_VAL(PREG) ((PREG) + 1)
+
+#define COREPWM_PRESCALE_REG 0x00u
+#define COREPWM_PERIOD_REG 0x04u
+#define COREPWM_EN_LOW_REG 0x08u
+#define COREPWM_EN_HIGH_REG 0x0Cu
+#define COREPWM_SYNC_UPD_REG 0xE4u
+#define COREPWM_POSEDGE_OFFSET 0x10u
+#define COREPWM_NEGEDGE_OFFSET 0x14u
+#define COREPWM_CHANNEL_OFFSET 0x08u
+
+struct mchp_core_pwm_chip {
+ struct pwm_chip chip;
+ struct clk *clk;
+ void __iomem *base;
+ u32 sync_update_mask;
+};
+
+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)
+{
+ 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 = COREPWM_EN_LOW_REG + (pwm->hwpwm >> 3) * sizeof(u32);
+ shift = pwm->hwpwm > 7 ? pwm->hwpwm - 8 : pwm->hwpwm;
+
+ 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);
+
+ /*
+ * Write to the sync update registers so that channels with shadow
+ * registers will also get their enable update. This operation is a NOP
+ * for channels without shadow registers.
+ */
+ writel_relaxed(1U, mchp_core_pwm->base + COREPWM_SYNC_UPD_REG);
+}
+
+static void mchp_core_pwm_apply_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);
+ void __iomem *channel_base = mchp_core_pwm->base + pwm->hwpwm * COREPWM_CHANNEL_OFFSET;
+ u64 duty_steps, period, tmp;
+ u8 posedge, negedge;
+ u8 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(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.
+ *
+ * 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.
+ */
+ if (state->duty_cycle > period) {
+ duty_steps = period_steps;
+ } else {
+ duty_steps = state->duty_cycle * clk_get_rate(mchp_core_pwm->clk);
+ tmp = prescale_val * NSEC_PER_SEC;
+ duty_steps = div64_u64(duty_steps, tmp);
+ }
+
+ /*
+ * 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 : 0u;
+ posedge = duty_steps;
+ } else {
+ posedge = !duty_steps ? period_steps : 0u;
+ negedge = duty_steps;
+ }
+
+ writel_relaxed(posedge, channel_base + COREPWM_POSEDGE_OFFSET);
+ writel_relaxed(negedge, channel_base + COREPWM_NEGEDGE_OFFSET);
+}
+
+static void mchp_core_pwm_apply_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 = state->period;
+
+ /*
+ * Calculate the period cycles and prescale values.
+ * The registers are each 8 bits wide & multiplied to compute the period
+ * so the maximum period that can be generated is 0xFFFF times the period
+ * of the input clock.
+ */
+ tmp *= clk_get_rate(mchp_core_pwm->clk);
+ do_div(tmp, NSEC_PER_SEC);
+
+ if (tmp > 0xFFFFu) {
+ *prescale = 0xFFu;
+ *period_steps = 0xFFu;
+ } else {
+ *prescale = tmp >> 8;
+ do_div(tmp, PREG_TO_VAL(*prescale));
+ *period_steps = tmp - 1;
+ }
+
+ writel_relaxed(*prescale, mchp_core_pwm->base + COREPWM_PRESCALE_REG);
+ writel_relaxed(*period_steps, mchp_core_pwm->base + COREPWM_PERIOD_REG);
+}
+
+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;
+ u16 channel_enabled;
+ u8 prescale, period_steps;
+
+ if (!state->enabled) {
+ mchp_core_pwm_enable(chip, pwm, false);
+ 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.
+ */
+ channel_enabled = (((u16)readb_relaxed(mchp_core_pwm->base + COREPWM_EN_HIGH_REG) << 8) |
+ readb_relaxed(mchp_core_pwm->base + COREPWM_EN_LOW_REG));
+ period_locked = channel_enabled & ~(1 << pwm->hwpwm);
+
+ if ((!current_state.enabled || current_state.period != state->period) && !period_locked) {
+ mchp_core_pwm_apply_period(chip, state, &prescale, &period_steps);
+ } else {
+ prescale = readb_relaxed(mchp_core_pwm->base + COREPWM_PRESCALE_REG);
+ period_steps = readb_relaxed(mchp_core_pwm->base + COREPWM_PERIOD_REG);
+ }
+
+ mchp_core_pwm_apply_duty(chip, pwm, state, prescale, period_steps);
+
+ /*
+ * 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.
+ */
+ if (mchp_core_pwm->sync_update_mask & (1 << pwm->hwpwm)) {
+ writel_relaxed(1U, mchp_core_pwm->base + COREPWM_SYNC_UPD_REG);
+ usleep_range(state->period, state->period * 2);
+ }
+
+ mchp_core_pwm_enable(chip, pwm, true);
+
+ 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);
+ void __iomem *channel_base = mchp_core_pwm->base + pwm->hwpwm * COREPWM_CHANNEL_OFFSET;
+ u8 prescale, period_steps, duty_steps;
+ u8 posedge, negedge;
+ u16 channel_enabled;
+
+ channel_enabled = (((u16)readb_relaxed(mchp_core_pwm->base + COREPWM_EN_HIGH_REG) << 8) |
+ readb_relaxed(mchp_core_pwm->base + COREPWM_EN_LOW_REG));
+
+ if (channel_enabled & 1 << pwm->hwpwm)
+ state->enabled = true;
+ else
+ state->enabled = false;
+
+ prescale = PREG_TO_VAL(readb_relaxed(mchp_core_pwm->base + COREPWM_PRESCALE_REG));
+
+ posedge = readb_relaxed(channel_base + COREPWM_POSEDGE_OFFSET);
+ negedge = readb_relaxed(channel_base + COREPWM_NEGEDGE_OFFSET);
+
+ duty_steps = abs((s16)posedge - (s16)negedge);
+ state->duty_cycle = duty_steps * prescale * NSEC_PER_SEC;
+ do_div(state->duty_cycle, clk_get_rate(mchp_core_pwm->clk));
+
+ state->polarity = negedge < posedge ? PWM_POLARITY_INVERSED : PWM_POLARITY_NORMAL;
+
+ period_steps = PREG_TO_VAL(readb_relaxed(mchp_core_pwm->base + COREPWM_PERIOD_REG));
+ state->period = period_steps * prescale * NSEC_PER_SEC;
+ do_div(state->period, clk_get_rate(mchp_core_pwm->clk));
+}
+
+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(&pdev->dev, NULL);
+ if (IS_ERR(mchp_pwm->clk))
+ return PTR_ERR(mchp_pwm->clk);
+
+ if (of_property_read_u32(pdev->dev.of_node, "microchip,sync-update-mask",
+ &mchp_pwm->sync_update_mask))
+ mchp_pwm->sync_update_mask = 0u;
+
+ ret = clk_prepare_enable(mchp_pwm->clk);
+ if (ret)
+ return dev_err_probe(&pdev->dev, ret, "failed to prepare PWM clock\n");
+
+ mchp_pwm->chip.dev = &pdev->dev;
+ mchp_pwm->chip.ops = &mchp_core_pwm_ops;
+ mchp_pwm->chip.of_xlate = of_pwm_xlate_with_flags;
+ mchp_pwm->chip.of_pwm_n_cells = 3;
+ mchp_pwm->chip.npwm = 16;
+
+ ret = pwmchip_add(&mchp_pwm->chip);
+ if (ret < 0) {
+ clk_disable_unprepare(mchp_pwm->clk);
+ return dev_err_probe(&pdev->dev, ret, "failed to add PWM chip\n");
+ }
+
+ platform_set_drvdata(pdev, mchp_pwm);
+ dev_info(&pdev->dev, "Successfully registered Microchip corePWM\n");
+
+ return 0;
+}
+
+static int mchp_core_pwm_remove(struct platform_device *pdev)
+{
+ struct mchp_core_pwm_chip *mchp_pwm = platform_get_drvdata(pdev);
+
+ pwmchip_remove(&mchp_pwm->chip);
+ clk_disable_unprepare(mchp_pwm->clk);
+
+ 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,
+ .remove = mchp_core_pwm_remove,
+};
+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