[nrf fromtree] drivers: serial: nrfx_uarte: Add support for higher baudrates

nrf54x devices have UARTE instance capable of using baudrate higher
than 1M. Higher baudrates does not have predefined values for
BAUDRATE register. A formula can be used to calculate BAUDRATE
value that shall be used for desired baudrate. Add UARTE_ANY_HIGH_SPEED
macro which is set when high speed is enabled (uart00 in nrf54lx or
uart120 in nrf54h20). For high speed instance use formula for getting
value that shall be written to BAUDRATE register.

When runtime configuration is not used then same formula is used to
calculate fixed BAUDRATE value.

Signed-off-by: Krzysztof Chruściński <[email protected]>
(cherry picked from commit 972ec82)

Author: nordic-krch

drivers/serial/uart_nrfx_uarte.c

@@ -126,6 +126,16 @@ BUILD_ASSERT(IS_ENABLED(CONFIG_PM_DEVICE_RUNTIME));
 #endif
 #endif
 
+#define INSTANCE_IS_HIGH_SPEED(unused, prefix, idx, _) \
+	COND_CODE_1(DT_NODE_HAS_STATUS_OKAY(UARTE(prefix##idx)),				\
+	    ((NRF_PERIPH_GET_FREQUENCY(UARTE(prefix##idx)) > NRF_UARTE_BASE_FREQUENCY_16MHZ)),	\
+	    (0))
+
+/* Macro determines if there is any high speed instance (instance that is driven using
+ * clock that is faster than 16 MHz).
+ */
+#define UARTE_ANY_HIGH_SPEED (UARTE_FOR_EACH_INSTANCE(INSTANCE_IS_HIGH_SPEED, (||), (0)))
+
 #ifdef UARTE_ANY_CACHE
 /* uart120 instance does not retain BAUDRATE register when ENABLE=0. When this instance
  * is used then baudrate must be set after enabling the peripheral and not before.
@@ -256,6 +266,17 @@ struct uarte_nrfx_data {
 /* If enabled then UARTE peripheral is using memory which is cacheable. */
 #define UARTE_CFG_FLAG_CACHEABLE BIT(3)
 
+/* Formula for getting the baudrate settings is following:
+ * 2^12 * (2^20 / (f_PCLK / desired_baudrate)) where f_PCLK is a frequency that
+ * drives the UARTE.
+ *
+ * @param f_pclk Frequency of the clock that drives the peripheral.
+ * @param baudrate Desired baudrate.
+ *
+ * @return Baudrate setting to be written to the BAUDRATE register
+ */
+#define UARTE_GET_CUSTOM_BAUDRATE(f_pclk, baudrate) ((BIT(20) / (f_pclk / baudrate)) << 12)
+
 /* Macro for converting numerical baudrate to register value. It is convenient
  * to use this approach because for constant input it can calculate nrf setting
  * at compile time.
@@ -495,18 +516,19 @@ static void uarte_nrfx_isr_int(const void *arg)
 static int baudrate_set(const struct device *dev, uint32_t baudrate)
 {
 	const struct uarte_nrfx_config *config = dev->config;
+	nrf_uarte_baudrate_t nrf_baudrate;
+
 	/* calculated baudrate divisor */
-	nrf_uarte_baudrate_t nrf_baudrate = NRF_BAUDRATE(baudrate);
+	if (UARTE_ANY_HIGH_SPEED && (config->clock_freq > NRF_UARTE_BASE_FREQUENCY_16MHZ)) {
+		nrf_baudrate = UARTE_GET_CUSTOM_BAUDRATE(config->clock_freq, baudrate);
+	} else {
+		nrf_baudrate = NRF_BAUDRATE(baudrate);
+	}
 
 	if (nrf_baudrate == 0) {
 		return -EINVAL;
 	}
 
-	/* scale baudrate setting */
-	if (config->clock_freq > 0U) {
-		nrf_baudrate /= config->clock_freq / NRF_UARTE_BASE_FREQUENCY_16MHZ;
-	}
-
 #ifdef UARTE_BAUDRATE_RETENTION_WORKAROUND
 	struct uarte_nrfx_data *data = dev->data;
 
@@ -2413,17 +2435,21 @@ static int uarte_instance_init(const struct device *dev,
 #define UARTE_DISABLE_RX_INIT(node_id) \
 	.disable_rx = DT_PROP(node_id, disable_rx)
 
-/* Get frequency of the clock that driver the UARTE peripheral. Clock node can
- * have fixed or variable frequency. For fast UARTE use highest supported frequency.
- */
-#define UARTE_GET_BAUDRATE_DIV(idx) \
-	(NRF_PERIPH_GET_FREQUENCY(UARTE(idx)) / NRF_UARTE_BASE_FREQUENCY_16MHZ)
+/* Get frequency divider that is used to adjust the BAUDRATE value. */
+#define UARTE_GET_BAUDRATE_DIV(f_pclk) (f_pclk / NRF_UARTE_BASE_FREQUENCY_16MHZ)
 
 /* When calculating baudrate we need to take into account that high speed instances
  * must have baudrate adjust to the ratio between UARTE clocking frequency and 16 MHz.
+ * Additionally, >1Mbaud speeds are calculated using a formula.
  */
+#define UARTE_GET_BAUDRATE2(f_pclk, current_speed)					\
+	((f_pclk > NRF_UARTE_BASE_FREQUENCY_16MHZ) && (current_speed > 1000000)) ?	\
+		UARTE_GET_CUSTOM_BAUDRATE(f_pclk, current_speed) :			\
+		(NRF_BAUDRATE(current_speed) / UARTE_GET_BAUDRATE_DIV(f_pclk))
+
+/* Convert DT current-speed to a value that is written to the BAUDRATE register. */
 #define UARTE_GET_BAUDRATE(idx) \
-	(NRF_BAUDRATE(UARTE_PROP(idx, current_speed)) / UARTE_GET_BAUDRATE_DIV(idx))
+	UARTE_GET_BAUDRATE2(NRF_PERIPH_GET_FREQUENCY(UARTE(idx)), UARTE_PROP(idx, current_speed))
 
 /* Get initialization level of an instance. Instances that requires clock control
  * which is using nrfs (IPC) are initialized later.
@@ -2488,12 +2514,11 @@ static int uarte_instance_init(const struct device *dev,
 			    (.int_driven = &uarte##idx##_int_driven,))	       \
 	};								       \
 	COND_CODE_1(CONFIG_UART_USE_RUNTIME_CONFIGURE, (),		       \
-		(BUILD_ASSERT(NRF_BAUDRATE(UARTE_PROP(idx, current_speed)) > 0,\
-			  "Unsupported baudrate");))			       \
+		(BUILD_ASSERT(UARTE_GET_BAUDRATE(idx) > 0,		       \
+			      "Unsupported baudrate");))		       \
 	static const struct uarte_nrfx_config uarte_##idx##z_config = {	       \
 		COND_CODE_1(CONFIG_UART_USE_RUNTIME_CONFIGURE,		       \
-		    (IF_ENABLED(DT_CLOCKS_HAS_IDX(UARTE(idx), 0),	       \
-			   (.clock_freq = NRF_PERIPH_GET_FREQUENCY(UARTE(idx)),))), \
+			(.clock_freq = NRF_PERIPH_GET_FREQUENCY(UARTE(idx)),),  \
 		    (IF_ENABLED(UARTE_HAS_FRAME_TIMEOUT,		       \
 			(.baudrate = UARTE_PROP(idx, current_speed),))	       \
 		     .nrf_baudrate = UARTE_GET_BAUDRATE(idx),		       \