cpu/stm32: implement periph_gpio_ll_switch_dir

maribu · maribu · commit 8839ccbe50af · 2024-08-08T22:17:35.000+02:00
This implements periph_gpio_ll_switch_dir for STM32 except for STM32F1,
which has a different register layout.
diff --git a/cpu/stm32/Makefile.features b/cpu/stm32/Makefile.features
@@ -25,6 +25,7 @@ FEATURES_PROVIDED += periph_uart_nonblocking
 
 ifneq (f1,$(CPU_FAM))
   FEATURES_PROVIDED += periph_gpio_ll_open_drain_pull_up
+  FEATURES_PROVIDED += periph_gpio_ll_switch_dir
 endif
 
 ifneq (,$(filter $(CPU_FAM),c0 f0 f1 f3 g0 g4 l0 l1 l4 l5 u5 wb wl))
diff --git a/cpu/stm32/include/gpio_ll_arch.h b/cpu/stm32/include/gpio_ll_arch.h
@@ -142,6 +142,31 @@ static inline void gpio_ll_write(gpio_port_t port, uword_t value)
     p->ODR = value;
 }
 
+#ifdef MODULE_PERIPH_GPIO_LL_SWITCH_DIR
+static inline uword_t gpio_ll_prepare_switch_dir(uword_t mask)
+{
+    /* implementation too large to always inline */
+    extern uword_t gpio_ll_prepare_switch_dir_impl(uword_t mask);
+    return gpio_ll_prepare_switch_dir_impl(mask);
+}
+
+static inline void gpio_ll_switch_dir_output(gpio_port_t port, uword_t pins)
+{
+    GPIO_TypeDef *p = (GPIO_TypeDef *)port;
+    unsigned irq_state = irq_disable();
+    p->MODER |= pins;
+    irq_restore(irq_state);
+}
+
+static inline void gpio_ll_switch_dir_input(gpio_port_t port, uword_t pins)
+{
+    GPIO_TypeDef *p = (GPIO_TypeDef *)port;
+    unsigned irq_state = irq_disable();
+    p->MODER &= ~pins;
+    irq_restore(irq_state);
+}
+#endif
+
 static inline gpio_port_t gpio_get_port(gpio_t pin)
 {
     return pin & 0xfffffff0LU;
diff --git a/cpu/stm32/include/periph/cpu_gpio_ll.h b/cpu/stm32/include/periph/cpu_gpio_ll.h
@@ -31,6 +31,11 @@ extern "C" {
  * public view on type */
 #ifndef DOXYGEN
 
+#if !defined(CPU_FAM_STM32F1)
+/* For the STM32F1 GPIO peripheral, the gpio_ll_switch_dir is not supported */
+#  define HAVE_GPIO_LL_PREPARE_SWITCH_DIR
+#endif
+
 #define HAVE_GPIO_PULL_STRENGTH_T
 typedef enum {
     GPIO_PULL_WEAKEST = 0,
diff --git a/cpu/stm32/periph/gpio_ll.c b/cpu/stm32/periph/gpio_ll.c
@@ -361,6 +361,50 @@ int gpio_ll_init(gpio_port_t port, uint8_t pin, gpio_conf_t conf)
     return 0;
 }
 
+uword_t gpio_ll_prepare_switch_dir_impl(uword_t mask)
+{
+    /* Mask contains a bitmask containing the pins needed to change
+     * the direction of. E.g. for pins 0 to 3 it looks like:
+     *
+     *   3    2    1    0
+     * +----+----+----+----+
+     * | P3 | P2 | P1 | P0 |
+     * +----+----+----+----+
+     *
+     * We need to update the GPIOX->MODER register, which for pins 0 to 3
+     * looks like this:
+     *
+     *   7    6    5    4    3    2    1    0
+     * +---------+---------+---------+---------+
+     * |  MODE3  |  MODE2  |  MODE1  |  MODE0  |
+     * +---------+---------+---------+---------+
+     *
+     * Where each mode field will have the value `0b00` for input or `0b01`
+     * for output (the others two values are for alternate function mode and
+     * analog mode, which are both not relevant here). So, we need a way to
+     * efficiently set and clear every second bit. Specifically, a bitmask
+     * that looks like this is our goal:
+     *
+     *   7    6    5    4    3    2    1    0
+     * +----+----+----+----+----+----+----+----+
+     * | 0  | P3 | 0  | P2 | 0  | P1 | 0  | P0 |
+     * +----+----+----+----+----+----+----+----+
+     *
+     * This is what below bit magic magic does (but for 16 pins instead of
+     * 4).
+     */
+    uword_t output = mask & 0xFFFF;
+    output |= output << 8;
+    output &= 0x00FF00FF;
+    output |= output << 4;
+    output &= 0x0F0F0F0F;
+    output |= output << 2;
+    output &= 0x33333333;
+    output |= output << 1;
+    output &= 0x55555555;
+    return output;
+}
+
 gpio_conf_t gpio_ll_query_conf(gpio_port_t port, uint8_t pin)
 {
     gpio_conf_t result = { 0 };
