diff options
Diffstat (limited to 'libhw/rp2040_hwspi.c')
| -rw-r--r-- | libhw/rp2040_hwspi.c | 123 |
1 files changed, 123 insertions, 0 deletions
diff --git a/libhw/rp2040_hwspi.c b/libhw/rp2040_hwspi.c new file mode 100644 index 0000000..b041bc9 --- /dev/null +++ b/libhw/rp2040_hwspi.c @@ -0,0 +1,123 @@ +/* libhw/rp2040_hwspi.c - `implements_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_gpio */ + +#include <libmisc/vcall.h> + +#include <libhw/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); +} |