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/* hw/rp2040_hwspi.c - `struct spi` implementation for the RP2040's
* ARM Primecell SSP (PL022) (implementation file)
*
* Copyright (C) 2024 Luke T. Shumaker <lukeshu@lukeshu.com>
* SPDX-Licence-Identifier: AGPL-3.0-or-later
*/
#include <assert.h>
#include <hardware/spi.h> /* pico-sdk:hardware_spi */
#include <hardware/gpio.h> /* pico-sdk:hardware_gpio5 */
#include <libmisc/vcall.h>
#include "hw/rp2040_hwspi.h"
static void rp2040_hwspi_readwritev(implements_spi *, const struct bidi_iovec *iov, int iovcnt);
struct spi_vtable rp2040_hwspi_vtable = {
.readwritev = rp2040_hwspi_readwritev,
};
void _rp2040_hwspi_init(struct rp2040_hwspi *self,
enum rp2040_hwspi_instance inst_num,
enum spi_mode mode,
uint baudrate_hz,
uint pin_miso,
uint pin_mosi,
uint pin_clk,
uint pin_cs) {
/* Be not weary: This is but 12 lines of actual code; and many
* lines of comments and assert()s. */
spi_inst_t *inst;
assert(self);
assert(baudrate_hz);
assert(pin_miso != pin_mosi);
assert(pin_miso != pin_clk);
assert(pin_miso != pin_cs);
assert(pin_mosi != pin_clk);
assert(pin_mosi != pin_cs);
assert(pin_clk != pin_cs);
/* I know we called this "hwspi", but we're actually going to
* disconnect the CS pin from the PL022 SSP and manually drive
* it from software. This is because the PL022 has a maximum
* of 16-bit frames, while we need to be able to do *at least*
* 32-bit frames (and ideally, much larger). By managing it
* ourselves, we can just keep CS pulled low extra-long,
* making the frame extra-long. */
/* Regarding the constraints on pin assignments: see the
* RP2040 datasheet, table 2, in §1.4.3 "GPIO Functions". */
switch (inst_num) {
case RP2040_HWSPI_0:
inst = spi0;
assert(pin_miso == 0 || pin_miso == 4 || pin_miso == 16 || pin_miso == 20);
/*assert(pin_cs == 1 || pin_cs == 5 || pin_cs == 17 || pin_cs == 21);*/
assert(pin_clk == 2 || pin_clk == 6 || pin_clk == 18 || pin_clk == 22);
assert(pin_mosi == 3 || pin_mosi == 7 || pin_mosi == 19 || pin_mosi == 23);
break;
case RP2040_HWSPI_1:
inst = spi1;
assert(pin_miso == 8 || pin_miso == 12 || pin_miso == 24 || pin_miso == 28);
/*assert(pin_cs == 9 || pin_cs == 13 || pin_cs == 25 || pin_cs == 29);*/
assert(pin_clk == 10 || pin_clk == 14 || pin_clk == 26);
assert(pin_mosi == 11 || pin_mosi == 15 || pin_mosi == 27);
break;
default:
assert(false);
}
spi_init(inst, baudrate_hz);
spi_set_format(inst, 8,
(mode & 0b10) ? SPI_CPOL_1 : SPI_CPOL_0,
(mode & 0b01) ? SPI_CPHA_1 : SPI_CPHA_0,
SPI_MSB_FIRST);
/* Connect the pins to the PL022; set them each to "function
* 1" (again, see the RP2040 datasheet, table 2, in §1.4.3
* "GPIO Functions").
*
* ("GPIO_FUNC_SPI" is how the pico-sdk spells "function 1",
* since on the RP2040 all of the "function 1" functions are
* some part of SPI.) */
gpio_set_function(pin_clk, GPIO_FUNC_SPI);
gpio_set_function(pin_mosi, GPIO_FUNC_SPI);
gpio_set_function(pin_miso, GPIO_FUNC_SPI);
/* Initialize the CS pin for software control. */
gpio_init(pin_cs);
gpio_set_dir(pin_cs, GPIO_OUT);
gpio_put(pin_cs, 1);
/* Return. */
self->vtable = &rp2040_hwspi_vtable;
self->inst = inst;
self->pin_cs = pin_cs;
}
static void rp2040_hwspi_readwritev(implements_spi *_self, const struct bidi_iovec *iov, int iovcnt) {
struct rp2040_hwspi *self = VCALL_SELF(struct rp2040_hwspi, implements_spi, _self);
assert(self);
spi_inst_t *inst = self->inst;
assert(inst);
assert(iov);
assert(iovcnt);
gpio_put(self->pin_cs, 0);
/* TODO: Replace blocking reads+writes with DMA. */
for (int i = 0; i < iovcnt; i++) {
if (iov[i].iov_write_src && iov[i].iov_read_dst)
spi_write_read_blocking(inst, iov[i].iov_write_src, iov[i].iov_read_dst, iov[i].iov_len);
else if (iov[i].iov_write_src)
spi_write_blocking(inst, iov[i].iov_write_src, iov[i].iov_len);
else if (iov[i].iov_read_dst)
spi_read_blocking(inst, 0, iov[i].iov_read_dst, iov[i].iov_len);
else
assert(false);
}
gpio_put(self->pin_cs, 1);
}
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