lpc176x: Add support for SPI

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/lpc176x/Kconfig

@@ -7,6 +7,7 @@ config LPC_SELECT
     default y
     select HAVE_GPIO
     select HAVE_GPIO_ADC
+    select HAVE_GPIO_SPI
     select HAVE_USER_INTERFACE
 
 config BOARD_DIRECTORY

src/lpc176x/Makefile

@@ -14,6 +14,7 @@ CFLAGS_klipper.elf += --specs=nano.specs --specs=nosys.specs
 
 # Add source files
 src-y += lpc176x/main.c lpc176x/timer.c lpc176x/gpio.c lpc176x/i2c.c
+src-$(CONFIG_HAVE_GPIO_SPI) += lpc176x/spi.c
 src-y += generic/crc16_ccitt.c generic/alloc.c
 src-y += generic/armcm_irq.c generic/timer_irq.c
 src-y += ../lib/lpc176x/device/system_LPC17xx.c

src/lpc176x/gpio.h

@@ -27,4 +27,12 @@ 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 {
+    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/lpc176x/spi.c

@@ -0,0 +1,81 @@
+// SPI support on lpc176x
+//
+// Copyright (C) 2018  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include "LPC17xx.h" // LPC_SSP0
+#include "command.h" // shutdown
+#include "gpio.h" // spi_setup
+#include "internal.h" // gpio_peripheral
+#include "sched.h" // sched_shutdown
+
+static void
+spi_init(void)
+{
+    static int have_run_init;
+    if (have_run_init)
+        return;
+    have_run_init = 1;
+
+    // Configure SCK0, MISO0, MOSI0 pins
+    gpio_peripheral(0, 15, 2, 0);
+    gpio_peripheral(0, 17, 2, 0);
+    gpio_peripheral(0, 18, 2, 0);
+
+    // Set initial registers
+    LPC_SSP0->CR0 = 0x07;
+    LPC_SSP0->CPSR = 254;
+    LPC_SSP0->CR1 = 1<<1;
+}
+
+struct spi_config
+spi_setup(uint32_t bus, uint8_t mode, uint32_t rate)
+{
+    if (bus || mode > 3)
+        shutdown("Invalid spi_setup parameters");
+
+    // Make sure bus is enabled
+    spi_init();
+
+    // Setup clock rate and mode
+    struct spi_config res = {0, 0};
+    uint32_t pclk = SystemCoreClock / 4;
+    uint32_t div = DIV_ROUND_UP(pclk/2, rate) << 1;
+    res.cpsr = div < 2 ? 2 : (div > 254 ? 254 : div);
+    res.cr0 = 0x07 | (mode << 6);
+
+    return res;
+}
+
+void
+spi_prepare(struct spi_config config)
+{
+    LPC_SSP0->CR0 = config.cr0;
+    LPC_SSP0->CPSR = config.cpsr;
+}
+
+void
+spi_transfer(struct spi_config config, uint8_t receive_data
+             , uint8_t len, uint8_t *data)
+{
+    if (receive_data) {
+        while (len--) {
+            LPC_SSP0->DR = *data;
+            // wait for read data to be ready
+            while (!(LPC_SSP0->SR & (1<<2)))
+                ;
+            // get data
+            *data++ = LPC_SSP0->DR;
+        }
+    } else {
+        while (len--) {
+            LPC_SSP0->DR = *data++;
+            // wait for read data to be ready
+            while (!(LPC_SSP0->SR & (1<<2)))
+                ;
+            // read data (to clear receive fifo)
+            LPC_SSP0->DR;
+        }
+    }
+}