diff options
| -rw-r--r-- | drivers/i2c/busses/i2c-mxs.c | 176 |
1 files changed, 163 insertions, 13 deletions
diff --git a/drivers/i2c/busses/i2c-mxs.c b/drivers/i2c/busses/i2c-mxs.c index d6abaf2cf2e3..e55736077d23 100644 --- a/drivers/i2c/busses/i2c-mxs.c +++ b/drivers/i2c/busses/i2c-mxs.c @@ -39,6 +39,7 @@ #define MXS_I2C_CTRL0_SET (0x04) #define MXS_I2C_CTRL0_SFTRST 0x80000000 +#define MXS_I2C_CTRL0_RUN 0x20000000 #define MXS_I2C_CTRL0_SEND_NAK_ON_LAST 0x02000000 #define MXS_I2C_CTRL0_RETAIN_CLOCK 0x00200000 #define MXS_I2C_CTRL0_POST_SEND_STOP 0x00100000 @@ -64,6 +65,13 @@ #define MXS_I2C_CTRL1_SLAVE_STOP_IRQ 0x02 #define MXS_I2C_CTRL1_SLAVE_IRQ 0x01 +#define MXS_I2C_DATA (0xa0) + +#define MXS_I2C_DEBUG0 (0xb0) +#define MXS_I2C_DEBUG0_CLR (0xb8) + +#define MXS_I2C_DEBUG0_DMAREQ 0x80000000 + #define MXS_I2C_IRQ_MASK (MXS_I2C_CTRL1_DATA_ENGINE_CMPLT_IRQ | \ MXS_I2C_CTRL1_NO_SLAVE_ACK_IRQ | \ MXS_I2C_CTRL1_EARLY_TERM_IRQ | \ @@ -298,6 +306,135 @@ write_init_pio_fail: return -EINVAL; } +static int mxs_i2c_pio_wait_dmareq(struct mxs_i2c_dev *i2c) +{ + unsigned long timeout = jiffies + msecs_to_jiffies(1000); + + while (!(readl(i2c->regs + MXS_I2C_DEBUG0) & + MXS_I2C_DEBUG0_DMAREQ)) { + if (time_after(jiffies, timeout)) + return -ETIMEDOUT; + cond_resched(); + } + + writel(MXS_I2C_DEBUG0_DMAREQ, i2c->regs + MXS_I2C_DEBUG0_CLR); + + return 0; +} + +static int mxs_i2c_pio_wait_cplt(struct mxs_i2c_dev *i2c) +{ + unsigned long timeout = jiffies + msecs_to_jiffies(1000); + + /* + * We do not use interrupts in the PIO mode. Due to the + * maximum transfer length being 8 bytes in PIO mode, the + * overhead of interrupt would be too large and this would + * neglect the gain from using the PIO mode. + */ + + while (!(readl(i2c->regs + MXS_I2C_CTRL1) & + MXS_I2C_CTRL1_DATA_ENGINE_CMPLT_IRQ)) { + if (time_after(jiffies, timeout)) + return -ETIMEDOUT; + cond_resched(); + } + + writel(MXS_I2C_CTRL1_DATA_ENGINE_CMPLT_IRQ, + i2c->regs + MXS_I2C_CTRL1_CLR); + + return 0; +} + +static int mxs_i2c_pio_setup_xfer(struct i2c_adapter *adap, + struct i2c_msg *msg, uint32_t flags) +{ + struct mxs_i2c_dev *i2c = i2c_get_adapdata(adap); + uint32_t addr_data = msg->addr << 1; + uint32_t data = 0; + int i, shifts_left, ret; + + /* Mute IRQs coming from this block. */ + writel(MXS_I2C_IRQ_MASK << 8, i2c->regs + MXS_I2C_CTRL1_CLR); + + if (msg->flags & I2C_M_RD) { + addr_data |= I2C_SMBUS_READ; + + /* SELECT command. */ + writel(MXS_I2C_CTRL0_RUN | MXS_CMD_I2C_SELECT, + i2c->regs + MXS_I2C_CTRL0); + + ret = mxs_i2c_pio_wait_dmareq(i2c); + if (ret) + return ret; + + writel(addr_data, i2c->regs + MXS_I2C_DATA); + + ret = mxs_i2c_pio_wait_cplt(i2c); + if (ret) + return ret; + + /* READ command. */ + writel(MXS_I2C_CTRL0_RUN | MXS_CMD_I2C_READ | flags | + MXS_I2C_CTRL0_XFER_COUNT(msg->len), + i2c->regs + MXS_I2C_CTRL0); + + for (i = 0; i < msg->len; i++) { + if ((i & 3) == 0) { + ret = mxs_i2c_pio_wait_dmareq(i2c); + if (ret) + return ret; + data = readl(i2c->regs + MXS_I2C_DATA); + } + msg->buf[i] = data & 0xff; + data >>= 8; + } + } else { + addr_data |= I2C_SMBUS_WRITE; + + /* WRITE command. */ + writel(MXS_I2C_CTRL0_RUN | MXS_CMD_I2C_WRITE | flags | + MXS_I2C_CTRL0_XFER_COUNT(msg->len + 1), + i2c->regs + MXS_I2C_CTRL0); + + /* + * The LSB of data buffer is the first byte blasted across + * the bus. Higher order bytes follow. Thus the following + * filling schematic. + */ + data = addr_data << 24; + for (i = 0; i < msg->len; i++) { + data >>= 8; + data |= (msg->buf[i] << 24); + if ((i & 3) == 2) { + ret = mxs_i2c_pio_wait_dmareq(i2c); + if (ret) + return ret; + writel(data, i2c->regs + MXS_I2C_DATA); + } + } + + shifts_left = 24 - (i & 3) * 8; + if (shifts_left) { + data >>= shifts_left; + ret = mxs_i2c_pio_wait_dmareq(i2c); + if (ret) + return ret; + writel(data, i2c->regs + MXS_I2C_DATA); + } + } + + ret = mxs_i2c_pio_wait_cplt(i2c); + if (ret) + return ret; + + /* Clear any dangling IRQs and re-enable interrupts. */ + writel(MXS_I2C_IRQ_MASK, i2c->regs + MXS_I2C_CTRL1_CLR); + writel(MXS_I2C_IRQ_MASK << 8, i2c->regs + MXS_I2C_CTRL1_SET); + + return 0; +} + /* * Low level master read/write transaction. */ @@ -316,24 +453,37 @@ static int mxs_i2c_xfer_msg(struct i2c_adapter *adap, struct i2c_msg *msg, if (msg->len == 0) return -EINVAL; - INIT_COMPLETION(i2c->cmd_complete); - i2c->cmd_err = 0; - - ret = mxs_i2c_dma_setup_xfer(adap, msg, flags); - if (ret) - return ret; + /* + * The current boundary to select between PIO/DMA transfer method + * is set to 8 bytes, transfers shorter than 8 bytes are transfered + * using PIO mode while longer transfers use DMA. The 8 byte border is + * based on this empirical measurement and a lot of previous frobbing. + */ + if (msg->len < 8) { + ret = mxs_i2c_pio_setup_xfer(adap, msg, flags); + if (ret) + mxs_i2c_reset(i2c); + } else { + i2c->cmd_err = 0; + INIT_COMPLETION(i2c->cmd_complete); + ret = mxs_i2c_dma_setup_xfer(adap, msg, flags); + if (ret) + return ret; - ret = wait_for_completion_timeout(&i2c->cmd_complete, + ret = wait_for_completion_timeout(&i2c->cmd_complete, msecs_to_jiffies(1000)); - if (ret == 0) - goto timeout; + if (ret == 0) + goto timeout; + + if (i2c->cmd_err == -ENXIO) + mxs_i2c_reset(i2c); - if (i2c->cmd_err == -ENXIO) - mxs_i2c_reset(i2c); + ret = i2c->cmd_err; + } - dev_dbg(i2c->dev, "Done with err=%d\n", i2c->cmd_err); + dev_dbg(i2c->dev, "Done with err=%d\n", ret); - return i2c->cmd_err; + return ret; timeout: dev_dbg(i2c->dev, "Timeout!\n"); |