rp2040: implement SPI

This implements SPI for the rp2040 target. All output groupings of both
SPI blocks are available for use.

Signed-off-by: Lasse Dalegaard <dalegaard@gmail.com>

src/rp2040/Kconfig

@@ -7,6 +7,7 @@ config RP2040_SELECT
     default y
     select HAVE_GPIO
     select HAVE_GPIO_ADC
+    select HAVE_GPIO_SPI
     select HAVE_GPIO_BITBANGING
     select HAVE_STRICT_TIMING
     select HAVE_CHIPID

src/rp2040/Makefile

@@ -20,6 +20,7 @@ src-$(CONFIG_USBSERIAL) += rp2040/usbserial.c generic/usb_cdc.c
 src-$(CONFIG_USBSERIAL) += rp2040/chipid.c
 src-$(CONFIG_SERIAL) += rp2040/serial.c generic/serial_irq.c
 src-$(CONFIG_HAVE_GPIO_HARD_PWM) += rp2040/hard_pwm.c
+src-$(CONFIG_HAVE_GPIO_SPI) += rp2040/spi.c
 
 # rp2040 stage2 building
 $(OUT)stage2.o: lib/rp2040/boot_stage2/boot2_w25q080.S

src/rp2040/gpio.h

@@ -35,4 +35,13 @@ uint32_t gpio_adc_sample(struct gpio_adc g);
 uint16_t gpio_adc_read(struct gpio_adc g);
 void gpio_adc_cancel_sample(struct gpio_adc g);
 
+struct spi_config {
+    void *spi;
+    uint32_t cr0, cpsr;
+};
+struct spi_config spi_setup(uint32_t bus, uint8_t mode, uint32_t rate);
+void spi_prepare(struct spi_config config);
+void spi_transfer(struct spi_config config, uint8_t receive_data
+                  , uint8_t len, uint8_t *data);
+
 #endif // gpio.h

src/rp2040/spi.c

@@ -0,0 +1,110 @@
+// SPI functions on rp2040
+//
+// Copyright (C) 2021  Lasse Dalegaard <dalegaard@gmail.com>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include "gpio.h" // spi_setup, spi_prepare, spi_transfer
+#include "command.h" // shutdown"
+#include "sched.h" // sched_shutdown"
+#include "internal.h" // pclock, gpio_peripheral
+#include "hardware/structs/spi.h" // spi_hw_t
+#include "hardware/regs/resets.h" // RESETS_RESET_SPI*_BITS
+
+DECL_ENUMERATION("spi_bus", "spi0a", 0);
+DECL_CONSTANT_STR("BUS_PINS_spi0a", "gpio0,gpio3,gpio2");
+DECL_ENUMERATION("spi_bus", "spi0b", 1);
+DECL_CONSTANT_STR("BUS_PINS_spi0b", "gpio4,gpio7,gpio6");
+DECL_ENUMERATION("spi_bus", "spi0c", 2);
+DECL_CONSTANT_STR("BUS_PINS_spi0c", "gpio16,gpio19,gpio18");
+DECL_ENUMERATION("spi_bus", "spi0d", 3);
+DECL_CONSTANT_STR("BUS_PINS_spi0d", "gpio20,gpio23,gpio22");
+
+DECL_ENUMERATION("spi_bus", "spi1a", 4);
+DECL_CONSTANT_STR("BUS_PINS_spi1a", "gpio8,gpio11,gpio10");
+DECL_ENUMERATION("spi_bus", "spi1b", 5);
+DECL_CONSTANT_STR("BUS_PINS_spi1b", "gpio12,gpio15,gpio14");
+DECL_ENUMERATION("spi_bus", "spi1c", 6);
+DECL_CONSTANT_STR("BUS_PINS_spi1c", "gpio24,gpio27,gpio26");
+
+struct spi_info {
+    spi_hw_t *spi;
+    uint8_t miso_pin, mosi_pin, sck_pin;
+    uint32_t pclk;
+};
+
+static const struct spi_info spi_bus[] = {
+    {spi0_hw, 0,  3,  2,  RESETS_RESET_SPI0_BITS},
+    {spi0_hw, 4,  7,  6,  RESETS_RESET_SPI0_BITS},
+    {spi0_hw, 16, 19, 18, RESETS_RESET_SPI0_BITS},
+    {spi0_hw, 20, 23, 22, RESETS_RESET_SPI0_BITS},
+
+    {spi1_hw, 8,  11, 10, RESETS_RESET_SPI1_BITS},
+    {spi1_hw, 12, 15, 14, RESETS_RESET_SPI1_BITS},
+    {spi1_hw, 24, 27, 26, RESETS_RESET_SPI1_BITS},
+};
+
+struct spi_config
+spi_setup(uint32_t bus, uint8_t mode, uint32_t rate)
+{
+    if (bus >= ARRAY_SIZE(spi_bus))
+        shutdown("Invalid spi bus");
+
+    if (!is_enabled_pclock(spi_bus[bus].pclk))
+            enable_pclock(spi_bus[bus].pclk);
+
+    gpio_peripheral(spi_bus[bus].miso_pin, 1, 1);
+    gpio_peripheral(spi_bus[bus].mosi_pin, 1, 0);
+    gpio_peripheral(spi_bus[bus].sck_pin, 1, 0);
+
+    uint32_t pclk = get_pclock_frequency(spi_bus[bus].pclk);
+
+    struct spi_config res = {spi_bus[bus].spi, 0, 0};
+
+    uint8_t prescale;
+    for (prescale = 2; prescale <= 254; prescale += 2) {
+        if (pclk < (prescale + 2) * 256 * rate)
+            break;
+    }
+
+    uint8_t postdiv;
+    for (postdiv = 255; postdiv > 0; --postdiv) {
+        if ((pclk / (prescale * postdiv)) > rate)
+            break;
+    }
+
+    res.cr0 |= postdiv << SPI_SSPCR0_SCR_LSB;
+    res.cr0 |= ((mode & 2) != 0) << SPI_SSPCR0_SPO_LSB;
+    res.cr0 |= ((mode & 1) != 0) << SPI_SSPCR0_SPH_LSB;
+    res.cr0 |= 7 << SPI_SSPCR0_DSS_LSB; // 8bit mode
+    res.cpsr = prescale;
+
+    // Enable the peripheral
+    spi_bus[bus].spi->cr1 = SPI_SSPCR1_SSE_BITS;
+
+    return res;
+}
+
+void
+spi_prepare(struct spi_config config)
+{
+    spi_hw_t *spi = config.spi;
+    spi->cr0 = config.cr0;
+    spi->cpsr = config.cpsr;
+}
+
+void
+spi_transfer(struct spi_config config, uint8_t receive_data,
+             uint8_t len, uint8_t *data)
+{
+    spi_hw_t *spi = config.spi;
+    while (len--) {
+        spi->dr = *data;
+        while (!(spi->sr & SPI_SSPSR_RNE_BITS))
+            ;
+        uint8_t rdata = spi->dr;
+        if(receive_data)
+            *data = rdata;
+        data++;
+    }
+}