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save about 100 bytes of code (release) size for simple UART usage (#1431)

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Graham Sanderson 2024-01-12 09:41:37 -06:00 committed by GitHub
parent 3274cc8aec
commit 46bddd6b54
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1 changed files with 23 additions and 1 deletions
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24
src/rp2_common/hardware_uart/uart.c
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@ -52,10 +52,32 @@ uint uart_init(uart_inst_t *uart, uint baudrate) {
// Any LCR writes need to take place before enabling the UART
uint baud = uart_set_baudrate(uart, baudrate);
uart_set_format(uart, 8, 1, UART_PARITY_NONE);
// inline the uart_set_format() call, as we don't need the CR disable/re-enable
// protection, and also many people will never call it again, so having
// the generic function is not useful, and much bigger than this inlined
// code which is only a handful of instructions.
//
// The UART_UARTLCR_H_FEN_BITS setting is combined as well as it is the same register
#if 0
uart_set_format(uart, 8, 1, UART_PARITY_NONE);
// Enable FIFOs (must be before setting UARTEN, as this is an LCR access)
hw_set_bits(&uart_get_hw(uart)->lcr_h, UART_UARTLCR_H_FEN_BITS);
#else
uint data_bits = 8;
uint stop_bits = 1;
uint parity = UART_PARITY_NONE;
hw_write_masked(&uart_get_hw(uart)->lcr_h,
((data_bits - 5u) << UART_UARTLCR_H_WLEN_LSB) |
((stop_bits - 1u) << UART_UARTLCR_H_STP2_LSB) |
(bool_to_bit(parity != UART_PARITY_NONE) << UART_UARTLCR_H_PEN_LSB) |
(bool_to_bit(parity == UART_PARITY_EVEN) << UART_UARTLCR_H_EPS_LSB) |
UART_UARTLCR_H_FEN_BITS,
UART_UARTLCR_H_WLEN_BITS | UART_UARTLCR_H_STP2_BITS |
UART_UARTLCR_H_PEN_BITS | UART_UARTLCR_H_EPS_BITS |
UART_UARTLCR_H_FEN_BITS);
#endif
// Enable the UART, both TX and RX
uart_get_hw(uart)->cr = UART_UARTCR_UARTEN_BITS | UART_UARTCR_TXE_BITS | UART_UARTCR_RXE_BITS;
// Always enable DREQ signals -- no harm in this if DMA is not listening