69 lines
2.5 KiB
C
69 lines
2.5 KiB
C
/**
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* Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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#include "pio_spi.h"
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// Just 8 bit functions provided here. The PIO program supports any frame size
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// 1...32, but the software to do the necessary FIFO shuffling is left as an
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// exercise for the reader :)
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//
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// Likewise we only provide MSB-first here. To do LSB-first, you need to
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// - Do shifts when reading from the FIFO, for general case n != 8, 16, 32
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// - Do a narrow read at a one halfword or 3 byte offset for n == 16, 8
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// in order to get the read data correctly justified.
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void __time_critical_func(pio_spi_write8_blocking)(const pio_spi_inst_t *spi, const uint8_t *src, size_t len) {
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size_t tx_remain = len, rx_remain = len;
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// Do 8 bit accesses on FIFO, so that write data is byte-replicated. This
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// gets us the left-justification for free (for MSB-first shift-out)
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io_rw_8 *txfifo = (io_rw_8 *) &spi->pio->txf[spi->sm];
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io_rw_8 *rxfifo = (io_rw_8 *) &spi->pio->rxf[spi->sm];
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while (tx_remain || rx_remain) {
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if (tx_remain && !pio_sm_is_tx_fifo_full(spi->pio, spi->sm)) {
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*txfifo = *src++;
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--tx_remain;
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}
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if (rx_remain && !pio_sm_is_rx_fifo_empty(spi->pio, spi->sm)) {
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(void) *rxfifo;
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--rx_remain;
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}
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}
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}
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void __time_critical_func(pio_spi_read8_blocking)(const pio_spi_inst_t *spi, uint8_t *dst, size_t len) {
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size_t tx_remain = len, rx_remain = len;
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io_rw_8 *txfifo = (io_rw_8 *) &spi->pio->txf[spi->sm];
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io_rw_8 *rxfifo = (io_rw_8 *) &spi->pio->rxf[spi->sm];
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while (tx_remain || rx_remain) {
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if (tx_remain && !pio_sm_is_tx_fifo_full(spi->pio, spi->sm)) {
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*txfifo = 0;
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--tx_remain;
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}
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if (rx_remain && !pio_sm_is_rx_fifo_empty(spi->pio, spi->sm)) {
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*dst++ = *rxfifo;
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--rx_remain;
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}
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}
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}
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void __time_critical_func(pio_spi_write8_read8_blocking)(const pio_spi_inst_t *spi, uint8_t *src, uint8_t *dst,
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size_t len) {
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size_t tx_remain = len, rx_remain = len;
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io_rw_8 *txfifo = (io_rw_8 *) &spi->pio->txf[spi->sm];
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io_rw_8 *rxfifo = (io_rw_8 *) &spi->pio->rxf[spi->sm];
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while (tx_remain || rx_remain) {
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if (tx_remain && !pio_sm_is_tx_fifo_full(spi->pio, spi->sm)) {
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*txfifo = *src++;
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--tx_remain;
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}
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if (rx_remain && !pio_sm_is_rx_fifo_empty(spi->pio, spi->sm)) {
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*dst++ = *rxfifo;
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--rx_remain;
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}
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}
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}
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