sam3x8e: Add SPI support

Signed-off-by: Petri Honkala <cruwaller@gmail.com>
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

1 files changed, 123 insertions, 0 deletions

diff --git a/src/sam3x8e/spi.c b/src/sam3x8e/spi.c
new file mode 100644
index 00000000..791d71b3
--- /dev/null
+++ b/src/sam3x8e/spi.c
@@ -0,0 +1,123 @@
+// SPI transmissions on sam3x8e
+//
+// Copyright (C) 2018  Petri Honkala <cruwaller@gmail.com>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include <stddef.h>   // NULL
+#include "autoconf.h"
+#include "command.h" // shutdown
+#include "gpio.h"
+#include "sched.h"
+#include <sam3x8e.h>
+#include <string.h>
+
+#define REGPTR     SPI0
+#define PERIPH_ID  ID_SPI0
+
+#define CHANNEL    0 // Use same channel for all
+
+static void
+spi_init(void)
+{
+    /* Configure SCK, MISO and MOSI */
+    gpio_peripheral('A', PIO_PA25A_SPI0_MISO, 'A', 0); // Arduino 74
+    gpio_peripheral('A', PIO_PA26A_SPI0_MOSI, 'A', 0); // Arduino 75
+    gpio_peripheral('A', PIO_PA27A_SPI0_SPCK, 'A', 0); // Arduino 76
+
+    // Enable SPI clocks
+    if (!(PMC->PMC_PCSR0 & (1u << PERIPH_ID))) {
+        PMC->PMC_PCER0 = (1 << PERIPH_ID);
+    }
+
+    /* Disable SPI */
+    REGPTR->SPI_CR  = SPI_CR_SPIDIS;
+    /* Execute a software reset of the SPI twice */
+    REGPTR->SPI_CR  = SPI_CR_SWRST;
+    REGPTR->SPI_CR  = SPI_CR_SWRST;
+
+    REGPTR->SPI_MR = ( SPI_MR_MSTR |       // Set master mode
+                       SPI_MR_MODFDIS |    // Disable fault detection
+                       SPI_MR_PCS(CHANNEL) // Fixes peripheral select
+                     );
+    REGPTR->SPI_IDR = 0xffffffff; // Disable ISRs
+
+    /* Clear Chip Select Registers */
+    REGPTR->SPI_CSR[0] = 0;
+    REGPTR->SPI_CSR[1] = 0;
+    REGPTR->SPI_CSR[2] = 0;
+    REGPTR->SPI_CSR[3] = 0;
+
+    /* Set basic channel config */
+    REGPTR->SPI_CSR[CHANNEL] = 0;
+    /* Enable SPI */
+    REGPTR->SPI_CR = SPI_CR_SPIEN;
+}
+
+struct spi_config
+spi_setup(uint32_t bus, uint8_t mode, uint32_t rate)
+{
+    if (bus != CHANNEL || mode > 3)
+        shutdown("Invalid spi_setup parameters");
+
+    // Make sure bus is enabled
+    spi_init();
+
+    uint32_t config = 0;
+    uint32_t clockDiv;
+    if (rate < (CHIP_FREQ_CPU_MAX / 255)) {
+        clockDiv = 255;
+    } else if (rate >= (CHIP_FREQ_CPU_MAX / 2)) {
+        clockDiv = 2;
+    } else {
+        clockDiv = (CHIP_FREQ_CPU_MAX / (rate + 1)) + 1;
+    }
+
+    /****** Will be written to SPI_CSRx register ******/
+    // CSAAT  : Chip Select Active After Transfer
+    config  = SPI_CSR_CSAAT;
+    config |= SPI_CSR_BITS_8_BIT; // TODO: support for SPI_CSR_BITS_16_BIT
+    // NOTE: NCPHA is inverted, CPHA normal!!
+    switch(mode) {
+        case 0:
+            config |= SPI_CSR_NCPHA;
+            break;
+        case 1:
+            config |= 0;
+            break;
+        case 2:
+            config |= SPI_CSR_NCPHA;
+            config |= SPI_CSR_CPOL;
+            break;
+        case 3:
+            config |= SPI_CSR_CPOL;
+            break;
+    };
+
+    config |= ((clockDiv & 0xffu) << SPI_CSR_SCBR_Pos);
+    return (struct spi_config){.cfg = config};
+}
+
+void
+spi_transfer(struct spi_config config, uint8_t receive_data
+             , uint8_t len, uint8_t *data)
+{
+    REGPTR->SPI_CSR[CHANNEL] = config.cfg;
+
+    Spi* const pSpi = REGPTR;
+    if (receive_data) {
+        while (len--) {
+            pSpi->SPI_TDR = *data;
+            // wait for receive register
+            while (!(pSpi->SPI_SR & SPI_SR_RDRF)) { asm volatile("nop"); };
+            // get data
+            *data++ = pSpi->SPI_RDR;
+        }
+    } else {
+        while (len--) {
+            pSpi->SPI_TDR = *data++;
+            // wait for receive register
+            while (!(pSpi->SPI_SR & SPI_SR_RDRF)) { asm volatile("nop"); };
+        }
+    }
+}