[PATCH v2 2/4] pwm: stm32: add driver to support pwm with timer
Cheick Traore
cheick.traore at foss.st.com
Tue Mar 11 15:30:35 CET 2025
Add driver to support pwm on STM32MP1X SoCs. The PWM signal is generated
using a multifuntion timer which provide a pwm feature. Clock rate and
addresses are retrieved from the multifunction timer driver.
Signed-off-by: Cheick Traore <cheick.traore at foss.st.com>
---
Changes in v2:
- add the check of duty_ns and period_ns parameters in pwm-stm32 driver
drivers/pwm/Kconfig | 8 ++
drivers/pwm/Makefile | 1 +
drivers/pwm/pwm-stm32.c | 205 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 214 insertions(+)
create mode 100644 drivers/pwm/pwm-stm32.c
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 6e79868d0ef..de312656746 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -105,6 +105,14 @@ config PWM_TEGRA
32KHz clock is supported by the driver but the duty cycle is
configurable.
+config PWM_STM32
+ bool "Enable support for STM32 PWM"
+ depends on DM_PWM && MFD_STM32_TIMERS
+ help
+ This enables PWM driver for STMicroelectronics STM32 pulse width
+ modulation. It uses STM32 timer devices that can have up to 4 output
+ channels, with complementary outputs and configurable polarity.
+
config PWM_SUNXI
bool "Enable support for the Allwinner Sunxi PWM"
depends on DM_PWM
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index e4d10c8dc3e..76305b93bc9 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -22,5 +22,6 @@ obj-$(CONFIG_PWM_ROCKCHIP) += rk_pwm.o
obj-$(CONFIG_PWM_SANDBOX) += sandbox_pwm.o
obj-$(CONFIG_PWM_SIFIVE) += pwm-sifive.o
obj-$(CONFIG_PWM_TEGRA) += tegra_pwm.o
+obj-$(CONFIG_PWM_STM32) += pwm-stm32.o
obj-$(CONFIG_PWM_SUNXI) += sunxi_pwm.o
obj-$(CONFIG_PWM_TI_EHRPWM) += pwm-ti-ehrpwm.o
diff --git a/drivers/pwm/pwm-stm32.c b/drivers/pwm/pwm-stm32.c
new file mode 100644
index 00000000000..5fa649b5903
--- /dev/null
+++ b/drivers/pwm/pwm-stm32.c
@@ -0,0 +1,205 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2025, STMicroelectronics - All Rights Reserved
+ * Author: Cheick Traore <cheick.traore at foss.st.com>
+ *
+ * Originally based on the Linux kernel v6.10 drivers/pwm/pwm-stm32.c.
+ */
+
+#include <div64.h>
+#include <dm.h>
+#include <pwm.h>
+#include <asm/io.h>
+#include <asm/arch/timers.h>
+#include <dm/device_compat.h>
+#include <linux/time.h>
+
+#define CCMR_CHANNEL_SHIFT 8
+#define CCMR_CHANNEL_MASK 0xFF
+
+struct stm32_pwm_priv {
+ bool have_complementary_output;
+ bool invert_polarity;
+};
+
+static u32 active_channels(struct stm32_timers_plat *plat)
+{
+ return readl(plat->base + TIM_CCER) & TIM_CCER_CCXE;
+}
+
+static int stm32_pwm_set_config(struct udevice *dev, uint channel,
+ uint period_ns, uint duty_ns)
+{
+ struct stm32_timers_plat *plat = dev_get_plat(dev_get_parent(dev));
+ struct stm32_timers_priv *priv = dev_get_priv(dev_get_parent(dev));
+ unsigned long long prd, div, dty;
+ unsigned int prescaler = 0;
+ u32 ccmr, mask, shift;
+
+ if (duty_ns > period_ns)
+ return -EINVAL;
+
+ /*
+ * Period and prescaler values depends on clock rate
+ * First we need to find the minimal value for prescaler such that
+ *
+ * period_ns * clkrate
+ * ------------------------------ < max_arr + 1
+ * NSEC_PER_SEC * (prescaler + 1)
+ *
+ * This equation is equivalent to
+ *
+ * period_ns * clkrate
+ * ---------------------------- < prescaler + 1
+ * NSEC_PER_SEC * (max_arr + 1)
+ *
+ * Using integer division and knowing that the right hand side is
+ * integer, this is further equivalent to
+ *
+ * (period_ns * clkrate) // (NSEC_PER_SEC * (max_arr + 1)) ≤ prescaler
+ */
+
+ div = (unsigned long long)priv->rate * period_ns;
+ do_div(div, NSEC_PER_SEC);
+ prd = div;
+
+ do_div(div, priv->max_arr + 1);
+ prescaler = div;
+ if (prescaler > MAX_TIM_PSC)
+ return -EINVAL;
+
+ do_div(prd, prescaler + 1);
+ if (!prd)
+ return -EINVAL;
+
+ /*
+ * All channels share the same prescaler and counter so when two
+ * channels are active at the same time we can't change them
+ */
+ if (active_channels(plat) & ~(1 << channel * 4)) {
+ u32 psc, arr;
+
+ psc = readl(plat->base + TIM_PSC);
+ arr = readl(plat->base + TIM_ARR);
+ if (psc != prescaler || arr != prd - 1)
+ return -EBUSY;
+ }
+
+ writel(prescaler, plat->base + TIM_PSC);
+ writel(prd - 1, plat->base + TIM_ARR);
+ setbits_le32(plat->base + TIM_CR1, TIM_CR1_ARPE);
+
+ /* Calculate the duty cycles */
+ dty = prd * duty_ns;
+ do_div(dty, period_ns);
+
+ writel(dty, plat->base + TIM_CCRx(channel + 1));
+
+ /* Configure output mode */
+ shift = (channel & 0x1) * CCMR_CHANNEL_SHIFT;
+ ccmr = (TIM_CCMR_PE | TIM_CCMR_M1) << shift;
+ mask = CCMR_CHANNEL_MASK << shift;
+ if (channel < 2)
+ clrsetbits_le32(plat->base + TIM_CCMR1, mask, ccmr);
+ else
+ clrsetbits_le32(plat->base + TIM_CCMR2, mask, ccmr);
+
+ setbits_le32(plat->base + TIM_BDTR, TIM_BDTR_MOE);
+
+ return 0;
+}
+
+static int stm32_pwm_set_enable(struct udevice *dev, uint channel,
+ bool enable)
+{
+ struct stm32_timers_plat *plat = dev_get_plat(dev_get_parent(dev));
+ struct stm32_pwm_priv *priv = dev_get_priv(dev);
+ u32 mask;
+
+ /* Enable channel */
+ mask = TIM_CCER_CC1E << (channel * 4);
+ if (priv->have_complementary_output)
+ mask |= TIM_CCER_CC1NE << (channel * 4);
+
+ if (enable) {
+ setbits_le32(plat->base + TIM_CCER, mask);
+ /* Make sure that registers are updated */
+ setbits_le32(plat->base + TIM_EGR, TIM_EGR_UG);
+ /* Enable controller */
+ setbits_le32(plat->base + TIM_CR1, TIM_CR1_CEN);
+ } else {
+ clrbits_le32(plat->base + TIM_CCER, mask);
+ /* When all channels are disabled, we can disable the controller */
+ if (!active_channels(plat))
+ clrbits_le32(plat->base + TIM_CR1, TIM_CR1_CEN);
+ }
+
+ return 0;
+}
+
+static int stm32_pwm_set_invert(struct udevice *dev, uint channel,
+ bool polarity)
+{
+ struct stm32_timers_plat *plat = dev_get_plat(dev_get_parent(dev));
+ struct stm32_pwm_priv *priv = dev_get_priv(dev);
+ u32 mask;
+
+ mask = TIM_CCER_CC1P << (channel * 4);
+ if (priv->have_complementary_output)
+ mask |= TIM_CCER_CC1NP << (channel * 4);
+
+ clrsetbits_le32(plat->base + TIM_CCER, mask, polarity ? mask : 0);
+
+ return 0;
+}
+
+static void stm32_pwm_detect_complementary(struct udevice *dev)
+{
+ struct stm32_timers_plat *plat = dev_get_plat(dev_get_parent(dev));
+ struct stm32_pwm_priv *priv = dev_get_priv(dev);
+ u32 ccer;
+
+ /*
+ * If complementary bit doesn't exist writing 1 will have no
+ * effect so we can detect it.
+ */
+ setbits_le32(plat->base + TIM_CCER, TIM_CCER_CC1NE);
+ ccer = readl(plat->base + TIM_CCER);
+ clrbits_le32(plat->base + TIM_CCER, TIM_CCER_CC1NE);
+
+ priv->have_complementary_output = (ccer != 0);
+}
+
+static int stm32_pwm_probe(struct udevice *dev)
+{
+ struct stm32_timers_priv *timer = dev_get_priv(dev_get_parent(dev));
+
+ if (timer->rate > 1000000000) {
+ dev_err(dev, "Clock freq too high (%lu)\n", timer->rate);
+ return -EINVAL;
+ }
+
+ stm32_pwm_detect_complementary(dev);
+
+ return 0;
+}
+
+static const struct pwm_ops stm32_pwm_ops = {
+ .set_config = stm32_pwm_set_config,
+ .set_enable = stm32_pwm_set_enable,
+ .set_invert = stm32_pwm_set_invert,
+};
+
+static const struct udevice_id stm32_pwm_ids[] = {
+ { .compatible = "st,stm32-pwm" },
+ { }
+};
+
+U_BOOT_DRIVER(stm32_pwm) = {
+ .name = "stm32_pwm",
+ .id = UCLASS_PWM,
+ .of_match = stm32_pwm_ids,
+ .ops = &stm32_pwm_ops,
+ .probe = stm32_pwm_probe,
+ .priv_auto = sizeof(struct stm32_pwm_priv),
+};
--
2.34.1
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