From 5c4bde70ae92626fc92ee51249912961a668bba1 Mon Sep 17 00:00:00 2001 From: Alexandru Gagniuc Date: Sat, 28 Dec 2013 21:50:54 -0500 Subject: cpu/allwinner/a10: Add basic TWI (I²C) driver MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Change-Id: I11b10301199e5ff1a45d9b7d2958cc7b6667a29c Signed-off-by: Alexandru Gagniuc Reviewed-on: http://review.coreboot.org/4588 Tested-by: build bot (Jenkins) Reviewed-by: Paul Menzel Reviewed-by: Stefan Reinauer --- src/cpu/allwinner/a10/twi.c | 206 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 206 insertions(+) create mode 100644 src/cpu/allwinner/a10/twi.c (limited to 'src/cpu/allwinner/a10/twi.c') diff --git a/src/cpu/allwinner/a10/twi.c b/src/cpu/allwinner/a10/twi.c new file mode 100644 index 0000000000..692a498a36 --- /dev/null +++ b/src/cpu/allwinner/a10/twi.c @@ -0,0 +1,206 @@ +/* + * Setup helpers for Two Wire Interface (TWI) (I²C) Allwinner CPUs + * + * Only functionality for I²C master is provided. + * Largely based on the uboot-sunxi code. + * + * Copyright (C) 2012 Henrik Nordstrom + * Copyright (C) 2013 Alexandru Gagniuc + * Subject to the GNU GPL v2, or (at your option) any later version. + */ + +#include "memmap.h" +#include "twi.h" + +#include +#include +#include + +#define TWI_BASE(n) (A1X_TWI0_BASE + 0x400 * (n)) + +#define TWI_TIMEOUT (50 * 1000) + +static u8 is_busy(struct a1x_twi *twi) +{ + return (read32(&twi->stat) != TWI_STAT_IDLE); +} + +static enum cb_err wait_until_idle(struct a1x_twi *twi) +{ + u32 i = TWI_TIMEOUT; + while (i-- && is_busy((twi))) + udelay(1); + return i ? CB_SUCCESS : CB_ERR; +} + +/* FIXME: This function is basic, and unintelligent */ +static void configure_clock(struct a1x_twi *twi, u32 speed_hz) +{ + /* FIXME: We assume clock is 24MHz, which may not be the case */ + u32 apb_clk = 24000000, m, n; + + /* Pre-divide the clock by 8 */ + n = 3; + m = (apb_clk >> n) / speed_hz; + write32(TWI_CLK_M(m) | TWI_CLK_N(n), &twi->clk); +} + +void a1x_twi_init(u8 bus, u32 speed_hz) +{ + u32 i = TWI_TIMEOUT; + struct a1x_twi *twi = (void *)TWI_BASE(bus); + + configure_clock(twi, speed_hz); + + /* Enable the I²C bus */ + write32(TWI_CTL_BUS_EN, &twi->ctl); + /* Issue soft reset */ + write32(1, &twi->reset); + + while (i-- && read32(&twi->reset)) + udelay(1); +} + +static void clear_interrupt_flag(struct a1x_twi *twi) +{ + write32(read32(&twi->ctl) & ~TWI_CTL_INT_FLAG, &twi->ctl); +} + +static void i2c_send_data(struct a1x_twi *twi, u8 data) +{ + write32(data, &twi->data); + clear_interrupt_flag(twi); +} + +static enum twi_status wait_for_status(struct a1x_twi *twi) +{ + u32 i = TWI_TIMEOUT; + /* Wait until interrupt is asserted again */ + while (i-- && !(read32(&twi->ctl) & TWI_CTL_INT_FLAG)) + udelay(1); + /* A timeout here most likely indicates a bus error */ + return i ? read32(&twi->stat) : TWI_STAT_BUS_ERROR; +} + +static void i2c_send_start(struct a1x_twi *twi) +{ + u32 reg32, i; + + /* Send START condition */ + reg32 = read32(&twi->ctl); + reg32 &= ~TWI_CTL_INT_FLAG; + reg32 |= TWI_CTL_M_START; + write32(reg32, &twi->ctl); + + /* M_START is automatically cleared after condition is transmitted */ + i = TWI_TIMEOUT; + while (i-- && (read32(&twi->ctl) & TWI_CTL_M_START)) + udelay(1); +} + +static void i2c_send_stop(struct a1x_twi *twi) +{ + u32 reg32; + + /* Send STOP condition */ + reg32 = read32(&twi->ctl); + reg32 &= ~TWI_CTL_INT_FLAG; + reg32 |= TWI_CTL_M_STOP; + write32(reg32, &twi->ctl); +} + +int i2c_read(unsigned bus, unsigned chip, unsigned addr, + unsigned alen, uint8_t *buf, unsigned len) +{ + unsigned count = len; + enum twi_status expected_status; + struct a1x_twi *twi = (void *)TWI_BASE(bus); + + if (wait_until_idle(twi) != CB_SUCCESS) + return CB_ERR; + + i2c_send_start(twi); + if (wait_for_status(twi) != TWI_STAT_TX_START) + return CB_ERR; + + /* Send chip address */ + i2c_send_data(twi, chip << 1); + if (wait_for_status(twi) != TWI_STAT_TX_AW_ACK) + return CB_ERR; + + /* Send data address */ + i2c_send_data(twi, addr); + if (wait_for_status(twi) != TWI_STAT_TXD_ACK) + return CB_ERR; + + /* Send restart for read */ + i2c_send_start(twi); + if (wait_for_status(twi) != TWI_STAT_TX_RSTART) + return CB_ERR; + + /* Send chip address */ + i2c_send_data(twi, chip << 1 | 1); + if (wait_for_status(twi) != TWI_STAT_TX_AR_ACK) + return CB_ERR; + + /* Start ACK-ing received data */ + setbits_le32(&twi->ctl, TWI_CTL_A_ACK); + expected_status = TWI_STAT_RXD_ACK; + + /* Read data */ + while (count > 0) { + if (count == 1) { + /* Do not ACK the last byte */ + clrbits_le32(&twi->ctl, TWI_CTL_A_ACK); + expected_status = TWI_STAT_RXD_NAK; + } + + clear_interrupt_flag(twi); + + if (wait_for_status(twi) != expected_status) + return CB_ERR; + + *buf++ = read32(&twi->data); + count--; + } + + i2c_send_stop(twi); + + return len; +} + +int i2c_write(unsigned bus, unsigned chip, unsigned addr, + unsigned alen, const uint8_t *buf, unsigned len) +{ + unsigned count = len; + struct a1x_twi *twi = (void *)TWI_BASE(bus); + + if (wait_until_idle(twi) != CB_SUCCESS) + return CB_ERR; + + i2c_send_start(twi); + if (wait_for_status(twi) != TWI_STAT_TX_START) + return CB_ERR; + + /* Send chip address */ + i2c_send_data(twi, chip << 1); + if (wait_for_status(twi) != TWI_STAT_TX_AW_ACK) + return CB_ERR; + + /* Send data address */ + i2c_send_data(twi, addr); + if (wait_for_status(twi) != TWI_STAT_TXD_ACK) + return CB_ERR; + + /* Send data */ + while (count > 0) { + i2c_send_data(twi, *buf++); + if (wait_for_status(twi) != TWI_STAT_TXD_ACK) + return CB_ERR; + count--; + } + + i2c_send_stop(twi); + + return len; +} -- cgit v1.2.3