Implement I2C support in the SAM4E8E port

Signed-off-by: Florian Heilmann <Florian.Heilmann@gmx.net>

src/sam4e8e/Kconfig

@@ -6,7 +6,7 @@ config SAM_SELECT
     bool
     default y
     select HAVE_GPIO
-#    select HAVE_GPIO_I2C
+    select HAVE_GPIO_I2C
     select HAVE_GPIO_ADC
     select HAVE_GPIO_SPI
     select HAVE_GPIO_BITBANGING

src/sam4e8e/Makefile

@@ -19,6 +19,7 @@ src-y +=  ../lib/cmsis-sam4e/gcc/system_sam4e.c \
 		  ../lib/cmsis-sam4e/gcc/gcc/startup_sam4e.c
 
 src-$(CONFIG_HAVE_GPIO_SPI) += sam4e8e/spi.c
+src-$(CONFIG_HAVE_GPIO_I2C) += sam4e8e/i2c.c
 src-$(CONFIG_SERIAL) += sam4e8e/serial.c generic/serial_irq.c
 src-$(CONFIG_HAVE_GPIO) += sam4e8e/gpio.c
 src-y += generic/crc16_ccitt.c generic/alloc.c

src/sam4e8e/gpio.h

@@ -46,4 +46,16 @@ struct spi_config spi_setup(uint32_t bus, uint8_t mode, uint32_t rate);
 void spi_transfer(struct spi_config config, uint8_t receive_data
                   , uint8_t len, uint8_t *data);
 void spi_prepare(struct spi_config config);
+
+struct i2c_config {
+    void *twi;
+    uint8_t addr;
+};
+
+struct i2c_config i2c_setup(uint32_t bus, uint32_t rate, uint8_t addr);
+void i2c_write(struct i2c_config config,
+                uint8_t write_len, uint8_t *write);
+void i2c_read(struct i2c_config config,
+              uint8_t reg_len, uint8_t *reg,
+              uint8_t read_len, uint8_t *read);
 #endif // gpio.h

src/sam4e8e/i2c.c

@@ -0,0 +1,166 @@
+// SAM4 I2C Port
+//
+// Copyright (C) 2018  Florian Heilmann <Florian.Heilmann@gmx.net>
+// Copyright (C) 2018  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include "gpio.h"
+#include "internal.h"
+#include "command.h" // shutdown
+#include "sched.h" // sched_shutdown
+#include "autoconf.h" // CONFIG_CLOCK_FREQ
+#include "board/misc.h" //timer_from_us
+
+void
+i2c_init(Twi *p_twi, uint32_t rate)
+{
+    uint32_t twi_id = (p_twi == TWI0) ? ID_TWI0 : ID_TWI1;
+    if ((PMC->PMC_PCSR0 & (1u << twi_id)) == 0) {
+        PMC->PMC_PCER0 = 1 << twi_id;
+    }
+    if (p_twi == TWI0) {
+        gpio_set_peripheral(TWI0_SCL_BANK, TWI0_SCL_PIN, TWI0_SCL_PERIPH, 0);
+        gpio_set_peripheral(TWI0_SDA_BANK, TWI0_SDA_PIN, TWI0_SDA_PERIPH, 0);
+    } else {
+        gpio_set_peripheral(TWI1_SCL_BANK, TWI1_SCL_PIN, TWI1_SCL_PERIPH, 0);
+        gpio_set_peripheral(TWI1_SDA_BANK, TWI1_SDA_PIN, TWI1_SDA_PERIPH, 0);
+    }
+    p_twi->TWI_IDR = 0xFFFFFFFF;
+    (void)p_twi->TWI_SR;
+    p_twi->TWI_CR = TWI_CR_SWRST;
+    (void)p_twi->TWI_RHR;
+    p_twi->TWI_CR = TWI_CR_MSDIS;
+    p_twi->TWI_CR = TWI_CR_SVDIS;
+    p_twi->TWI_CR = TWI_CR_MSEN;
+
+    uint32_t cldiv = 0;
+    uint32_t chdiv = 0;
+    uint32_t ckdiv = 0;
+
+    cldiv = CONFIG_CLOCK_FREQ / ((rate > 384000 ? 384000 : rate) * 2) - 4;
+
+    while((cldiv > 255) && (ckdiv < 7)) {
+        ckdiv++;
+        cldiv /= 2;
+    }
+
+    if (rate > 348000) {
+        chdiv = CONFIG_CLOCK_FREQ / ((2 * rate - 384000) * 2) - 4;
+        while((chdiv > 255) && (ckdiv < 7)) {
+            ckdiv++;
+            chdiv /= 2;
+        }
+    } else {
+        chdiv = cldiv;
+    }
+    p_twi->TWI_CWGR = TWI_CWGR_CLDIV(cldiv) | \
+                      TWI_CWGR_CHDIV(chdiv) | \
+                      TWI_CWGR_CKDIV(ckdiv);
+}
+
+uint32_t
+addr_to_u32(uint8_t addr_len, uint8_t *addr)
+{
+    uint32_t address = addr[0];
+    if (addr_len > 1) {
+        address <<= 8;
+        address |= addr[1];
+    }
+    if (addr_len > 2) {
+        address <<= 8;
+        address |= addr[2];
+    }
+    if (addr_len > 3) {
+        shutdown("Addresses larger than 3 bytes are not supported");
+    }
+    return address;
+}
+
+struct i2c_config
+i2c_setup(uint32_t bus, uint32_t rate, uint8_t addr)
+{
+    if ((bus > 1) | (rate > 400000))
+        shutdown("Invalid i2c_setup parameters!");
+    Twi *p_twi = (bus == 0) ? TWI0 : TWI1;
+    i2c_init(p_twi, rate);
+    return (struct i2c_config){ .twi=p_twi, .addr=addr};
+}
+
+void
+i2c_write(struct i2c_config config,
+                uint8_t write_len, uint8_t *write)
+{
+    Twi *p_twi = config.twi;
+    uint32_t status;
+    uint32_t bytes_to_send = write_len;
+    p_twi->TWI_MMR = TWI_MMR_DADR(config.addr);
+    for(;;) {
+        status = p_twi->TWI_SR;
+        if (status & TWI_SR_NACK)
+            shutdown("I2C NACK error encountered!");
+        if (!(status & TWI_SR_TXRDY))
+            continue;
+        if (!bytes_to_send)
+            break;
+        p_twi->TWI_THR = *write++;
+        bytes_to_send--;
+    }
+    p_twi->TWI_CR = TWI_CR_STOP;
+    while(!(p_twi->TWI_SR& TWI_SR_TXCOMP)) {
+    }
+}
+
+static void
+i2c_wait(Twi* p_twi, uint32_t bit, uint32_t timeout)
+{
+    for (;;) {
+        uint32_t flags = p_twi->TWI_SR;
+        if (flags & bit)
+            break;
+        if (!timer_is_before(timer_read_time(), timeout))
+            shutdown("I2C timeout occured");
+    }
+}
+
+void
+i2c_read(struct i2c_config config,
+              uint8_t reg_len, uint8_t *reg,
+              uint8_t read_len, uint8_t *read)
+{
+    Twi *p_twi = config.twi;
+    uint32_t status;
+    uint32_t bytes_to_send=read_len;
+    uint8_t stop = 0;
+    p_twi->TWI_MMR = 0;
+    p_twi->TWI_MMR = TWI_MMR_MREAD | TWI_MMR_DADR(config.addr) |
+                     ((reg_len << TWI_MMR_IADRSZ_Pos) &
+                     TWI_MMR_IADRSZ_Msk);
+    p_twi->TWI_IADR = 0;
+    p_twi->TWI_IADR = addr_to_u32(reg_len, reg);
+    if (bytes_to_send == 1) {
+        p_twi->TWI_CR = TWI_CR_START | TWI_CR_STOP;
+        stop = 1;
+    } else {
+        p_twi->TWI_CR = TWI_CR_START;
+        stop = 0;
+    }
+    while (bytes_to_send > 0) {
+        status = p_twi->TWI_SR;
+        if (status & TWI_SR_NACK) {
+            shutdown("I2C NACK error encountered!");
+        }
+        if (bytes_to_send == 1 && !stop) {
+            p_twi->TWI_CR = TWI_CR_STOP;
+            stop = 1;
+        }
+        i2c_wait(p_twi, TWI_SR_RXRDY, timer_read_time() + timer_from_us(5000));
+        if (!(status & TWI_SR_RXRDY)) {
+            continue;
+        }
+        *read++ = p_twi->TWI_RHR;
+        bytes_to_send--;
+    }
+    while (!(p_twi->TWI_SR & TWI_SR_TXCOMP)) {}
+    (void)p_twi->TWI_SR;
+}

src/sam4e8e/internal.h

@@ -0,0 +1,18 @@
+#include "sam4e.h"
+
+// I2C pin definitions
+#define TWI0_SCL_BANK 'A'
+#define TWI0_SCL_PIN PIO_PA4A_TWCK0
+#define TWI0_SCL_PERIPH 'A'
+
+#define TWI0_SDA_BANK 'A'
+#define TWI0_SDA_PIN PIO_PA3A_TWD0
+#define TWI0_SDA_PERIPH 'A'
+
+#define TWI1_SCL_BANK 'B'
+#define TWI1_SCL_PIN PIO_PB5A_TWCK1
+#define TWI1_SCL_PERIPH 'A'
+
+#define TWI1_SDA_BANK 'B'
+#define TWI1_SDA_PIN PIO_PB4A_TWD1
+#define TWI1_SDA_PERIPH 'A'