samd21: Add support for hardware pwm

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

4 files changed, 110 insertions, 0 deletions

diff --git a/src/samd21/Kconfig b/src/samd21/Kconfig
index 858fcca5..225eae17 100644
--- a/src/samd21/Kconfig
+++ b/src/samd21/Kconfig
@@ -8,6 +8,7 @@ config SAMD_SELECT
     select HAVE_GPIO
     select HAVE_GPIO_I2C
     select HAVE_GPIO_SPI
+    select HAVE_GPIO_HARD_PWM
     select HAVE_GPIO_BITBANGING
 
 config BOARD_DIRECTORY
diff --git a/src/samd21/Makefile b/src/samd21/Makefile
index a5135d24..34de8e48 100644
--- a/src/samd21/Makefile
+++ b/src/samd21/Makefile
@@ -22,6 +22,7 @@ src-$(CONFIG_USBSERIAL) += samd21/usbserial.c generic/usb_cdc.c
 src-$(CONFIG_SERIAL) += samd21/serial.c generic/serial_irq.c
 src-$(CONFIG_HAVE_GPIO_I2C) += samd21/i2c.c
 src-$(CONFIG_HAVE_GPIO_SPI) += samd21/spi.c
+src-$(CONFIG_HAVE_GPIO_HARD_PWM) += samd21/hard_pwm.c
 
 # Support bootloader offset address
 target-y := $(OUT)samd21.ld $(target-y)
diff --git a/src/samd21/gpio.h b/src/samd21/gpio.h
index 41787b85..6c910da8 100644
--- a/src/samd21/gpio.h
+++ b/src/samd21/gpio.h
@@ -21,6 +21,12 @@ struct gpio_in gpio_in_setup(uint8_t pin, int8_t pull_up);
 void gpio_in_reset(struct gpio_in g, int8_t pull_up);
 uint8_t gpio_in_read(struct gpio_in g);
 
+struct gpio_pwm {
+    void *reg;
+};
+struct gpio_pwm gpio_pwm_setup(uint8_t pin, uint32_t cycle_time, uint8_t val);
+void gpio_pwm_write(struct gpio_pwm g, uint8_t val);
+
 struct spi_config {
     uint32_t ctrla, baud;
 };
diff --git a/src/samd21/hard_pwm.c b/src/samd21/hard_pwm.c
new file mode 100644
index 00000000..7deecfb9
--- /dev/null
+++ b/src/samd21/hard_pwm.c
@@ -0,0 +1,102 @@
+// Hardware PWM support on samd21
+//
+// Copyright (C) 2018  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include "command.h" // shutdown
+#include "gpio.h" // gpio_pwm_write
+#include "internal.h" // GPIO
+#include "samd21.h" // TCC0
+#include "sched.h" // sched_shutdown
+
+struct gpio_pwm_info {
+    uint32_t gpio;
+    Tcc *tcc;
+    uint32_t clock_id, power_id, channel;
+    char ptype;
+};
+
+static const struct gpio_pwm_info pwm_regs[] = {
+    { GPIO('A', 4), TCC0, TCC0_GCLK_ID, PM_APBCMASK_TCC0, 0, 'E' },
+    { GPIO('A', 5), TCC0, TCC0_GCLK_ID, PM_APBCMASK_TCC0, 1, 'E' },
+    { GPIO('A', 6), TCC1, TCC1_GCLK_ID, PM_APBCMASK_TCC1, 0, 'E' },
+    { GPIO('A', 7), TCC1, TCC1_GCLK_ID, PM_APBCMASK_TCC1, 1, 'E' },
+    { GPIO('A', 8), TCC0, TCC0_GCLK_ID, PM_APBCMASK_TCC0, 0, 'E' },
+    { GPIO('A', 9), TCC0, TCC0_GCLK_ID, PM_APBCMASK_TCC0, 1, 'E' },
+    { GPIO('A', 10), TCC1, TCC1_GCLK_ID, PM_APBCMASK_TCC1, 0, 'E' },
+    { GPIO('A', 11), TCC1, TCC1_GCLK_ID, PM_APBCMASK_TCC1, 1, 'E' },
+    { GPIO('A', 12), TCC2, TCC2_GCLK_ID, PM_APBCMASK_TCC2, 0, 'E' },
+    { GPIO('A', 13), TCC2, TCC2_GCLK_ID, PM_APBCMASK_TCC2, 1, 'E' },
+    { GPIO('A', 16), TCC2, TCC2_GCLK_ID, PM_APBCMASK_TCC2, 0, 'E' },
+    { GPIO('A', 17), TCC2, TCC2_GCLK_ID, PM_APBCMASK_TCC2, 1, 'E' },
+    { GPIO('A', 18), TCC0, TCC0_GCLK_ID, PM_APBCMASK_TCC0, 2, 'F' },
+    { GPIO('A', 19), TCC0, TCC0_GCLK_ID, PM_APBCMASK_TCC0, 3, 'F' },
+    { GPIO('A', 24), TCC1, TCC1_GCLK_ID, PM_APBCMASK_TCC1, 2, 'F' },
+    { GPIO('A', 25), TCC1, TCC1_GCLK_ID, PM_APBCMASK_TCC1, 3, 'F' },
+    { GPIO('A', 30), TCC1, TCC1_GCLK_ID, PM_APBCMASK_TCC1, 0, 'E' },
+    { GPIO('A', 31), TCC1, TCC1_GCLK_ID, PM_APBCMASK_TCC1, 1, 'E' },
+    { GPIO('B', 30), TCC0, TCC0_GCLK_ID, PM_APBCMASK_TCC0, 0, 'E' },
+    { GPIO('B', 31), TCC0, TCC0_GCLK_ID, PM_APBCMASK_TCC0, 1, 'E' },
+};
+
+#define MAX_PWM 255
+
+DECL_CONSTANT(PWM_MAX, MAX_PWM);
+
+struct gpio_pwm
+gpio_pwm_setup(uint8_t pin, uint32_t cycle_time, uint8_t val)
+{
+    // Find pin in pwm_regs table
+    const struct gpio_pwm_info *p = pwm_regs;
+    for (; ; p++) {
+        if (p >= &pwm_regs[ARRAY_SIZE(pwm_regs)])
+            shutdown("Not a valid PWM pin");
+        if (p->gpio == pin)
+            break;
+    }
+
+    // Enable timer clock
+    enable_pclock(p->clock_id, p->power_id);
+
+    // Map cycle_time to pwm clock divisor
+    uint32_t cs;
+    switch (cycle_time) {
+    case                      0 ...      (1+2) * MAX_PWM / 2 - 1: cs = 0; break;
+    case    (1+2) * MAX_PWM / 2 ...      (2+4) * MAX_PWM / 2 - 1: cs = 1; break;
+    case    (2+4) * MAX_PWM / 2 ...      (4+8) * MAX_PWM / 2 - 1: cs = 2; break;
+    case    (4+8) * MAX_PWM / 2 ...     (8+16) * MAX_PWM / 2 - 1: cs = 3; break;
+    case   (8+16) * MAX_PWM / 2 ...    (16+64) * MAX_PWM / 2 - 1: cs = 4; break;
+    case  (16+64) * MAX_PWM / 2 ...   (64+256) * MAX_PWM / 2 - 1: cs = 5; break;
+    case (64+256) * MAX_PWM / 2 ... (256+1024) * MAX_PWM / 2 - 1: cs = 6; break;
+    default:                                                      cs = 7; break;
+    }
+    uint32_t ctrla = TCC_CTRLA_ENABLE | TCC_CTRLA_PRESCALER(cs);
+
+    // Enable timer
+    Tcc *tcc = p->tcc;
+    uint32_t old_ctrla = tcc->CTRLA.reg;
+    if (old_ctrla != ctrla) {
+        if (old_ctrla & TCC_CTRLA_ENABLE)
+            shutdown("PWM already programmed at different speed");
+        tcc->CTRLA.reg = ctrla & ~TCC_CTRLA_ENABLE;
+        tcc->WAVE.reg = TCC_WAVE_WAVEGEN_NPWM;
+        tcc->PER.reg = MAX_PWM;
+        tcc->CTRLA.reg = ctrla;
+    }
+
+    // Set initial value
+    struct gpio_pwm g = (struct gpio_pwm) { (void*)&tcc->CCB[p->channel].reg };
+    gpio_pwm_write(g, val);
+
+    // Route output to pin
+    gpio_peripheral(pin, p->ptype, 0);
+
+    return g;
+}
+
+void
+gpio_pwm_write(struct gpio_pwm g, uint8_t val)
+{
+    *(volatile uint32_t*)g.reg = val;
+}