drivers: serial: nrfx_uarte: Add mode with TIMER byte counting

Add mode to be used on UARTE with frame timeout which is using a bounce
buffers and TIMER to count bytes. This mode shall be used to reliably
receive data without HWFC as frame timeout approach is not 100% reliable
because it can loose or corrupt a byte when new byte arrives after
frame timeout is detected but before it is fully handled. This mode is
similar to the one enabled with CONFIG_UART_x_NRF_HW_ASYNC but
additional bounce buffers are used and UARTE is receiving data to
internal buffers and copies data to the user buffer. Legacy apporach
cannot be used because in new SoC DMA attempts to copy data in words
so when byte is received it stays in the DMA internal buffer until
4 bytes are received or end of transfer happens then internal DMA
buffer is flushed.

Signed-off-by: Krzysztof Chruściński <[email protected]>

Author: nordic-krch

drivers/serial/Kconfig.nrfx

@@ -79,6 +79,32 @@ config UART_ASYNC_TX_CACHE_SIZE
 	  in RAM, because EasyDMA in UARTE peripherals can only transfer data
 	  from RAM.
 
+config UARTE_NRFX_UARTE_COUNT_BYTES_WITH_TIMER
+	bool "Use TIMER to count RX bytes"
+	depends on UART_ASYNC_API
+	depends on UART_NRFX_UARTE_LEGACY_SHIM
+	depends on !ARCH_POSIX # Mode not supported on BSIM target
+	select NRFX_GPPI
+
+config UART_NRFX_UARTE_BOUNCE_BUF_LEN
+	int "RX bounce buffer size"
+	depends on UARTE_NRFX_UARTE_COUNT_BYTES_WITH_TIMER
+	default 256
+	range 64 1024
+	help
+	  Buffer is used when workaround with bounce buffers is applied
+
+config UART_NRFX_UARTE_BOUNCE_BUF_SWAP_LATENCY
+	int "RX bounce buffer swap latency (in microseconds)"
+	depends on UARTE_NRFX_UARTE_COUNT_BYTES_WITH_TIMER
+	default 300
+	help
+	  Option decides how long before current bounce buffer is filled driver
+	  attempts to swap the buffer. It must be long enough to ensure that
+	  space following the buffer is not overwritten. Too high value results
+	  in more frequent buffer swaps so it impacts performance. Setting should
+	  take into account potential interrupt handling latency.
+
 config UART_NRFX_UARTE_DIRECT_ISR
 	bool "Use direct ISR"
 

drivers/serial/Kconfig.nrfx_uart_instance

@@ -18,6 +18,13 @@ config UART_$(nrfx_uart_num)_ASYNC
 	help
 	  This option enables UART Asynchronous API support on port $(nrfx_uart_num).
 
+config UART_$(nrfx_uart_num)_COUNT_BYTES_WITH_TIMER
+	bool
+	depends on $(dt_nodelabel_has_prop,uart$(nrfx_uart_num),timer)
+	depends on HAS_HW_NRF_UARTE$(nrfx_uart_num)
+	default y
+	imply UARTE_NRFX_UARTE_COUNT_BYTES_WITH_TIMER
+
 config UART_$(nrfx_uart_num)_ENHANCED_POLL_OUT
 	bool "Efficient poll out on port $(nrfx_uart_num)"
 	depends on !$(dt_nodelabel_bool_prop,uart$(nrfx_uart_num),endtx-stoptx-supported)