diff options
Diffstat (limited to 'drivers/i2c/busses/i2c-mxs.c')
| -rw-r--r-- | drivers/i2c/busses/i2c-mxs.c | 272 |
1 files changed, 218 insertions, 54 deletions
diff --git a/drivers/i2c/busses/i2c-mxs.c b/drivers/i2c/busses/i2c-mxs.c index d6abaf2cf2e..120f2464669 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 | \ @@ -85,35 +93,6 @@ #define MXS_CMD_I2C_READ (MXS_I2C_CTRL0_SEND_NAK_ON_LAST | \ MXS_I2C_CTRL0_MASTER_MODE) -struct mxs_i2c_speed_config { - uint32_t timing0; - uint32_t timing1; - uint32_t timing2; -}; - -/* - * Timing values for the default 24MHz clock supplied into the i2c block. - * - * The bus can operate at 95kHz or at 400kHz with the following timing - * register configurations. The 100kHz mode isn't present because it's - * values are not stated in the i.MX233/i.MX28 datasheet. The 95kHz mode - * shall be close enough replacement. Therefore when the bus is configured - * for 100kHz operation, 95kHz timing settings are actually loaded. - * - * For details, see i.MX233 [25.4.2 - 25.4.4] and i.MX28 [27.5.2 - 27.5.4]. - */ -static const struct mxs_i2c_speed_config mxs_i2c_95kHz_config = { - .timing0 = 0x00780030, - .timing1 = 0x00800030, - .timing2 = 0x00300030, -}; - -static const struct mxs_i2c_speed_config mxs_i2c_400kHz_config = { - .timing0 = 0x000f0007, - .timing1 = 0x001f000f, - .timing2 = 0x00300030, -}; - /** * struct mxs_i2c_dev - per device, private MXS-I2C data * @@ -129,7 +108,9 @@ struct mxs_i2c_dev { struct completion cmd_complete; int cmd_err; struct i2c_adapter adapter; - const struct mxs_i2c_speed_config *speed; + + uint32_t timing0; + uint32_t timing1; /* DMA support components */ int dma_channel; @@ -145,9 +126,16 @@ static void mxs_i2c_reset(struct mxs_i2c_dev *i2c) { stmp_reset_block(i2c->regs); - writel(i2c->speed->timing0, i2c->regs + MXS_I2C_TIMING0); - writel(i2c->speed->timing1, i2c->regs + MXS_I2C_TIMING1); - writel(i2c->speed->timing2, i2c->regs + MXS_I2C_TIMING2); + /* + * Configure timing for the I2C block. The I2C TIMING2 register has to + * be programmed with this particular magic number. The rest is derived + * from the XTAL speed and requested I2C speed. + * + * For details, see i.MX233 [25.4.2 - 25.4.4] and i.MX28 [27.5.2 - 27.5.4]. + */ + writel(i2c->timing0, i2c->regs + MXS_I2C_TIMING0); + writel(i2c->timing1, i2c->regs + MXS_I2C_TIMING1); + writel(0x00300030, i2c->regs + MXS_I2C_TIMING2); writel(MXS_I2C_IRQ_MASK << 8, i2c->regs + MXS_I2C_CTRL1_SET); } @@ -298,6 +286,135 @@ 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 +433,37 @@ 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"); @@ -403,6 +533,43 @@ static bool mxs_i2c_dma_filter(struct dma_chan *chan, void *param) return true; } +static void mxs_i2c_derive_timing(struct mxs_i2c_dev *i2c, int speed) +{ + /* The I2C block clock run at 24MHz */ + const uint32_t clk = 24000000; + uint32_t base; + uint16_t high_count, low_count, rcv_count, xmit_count; + struct device *dev = i2c->dev; + + if (speed > 540000) { + dev_warn(dev, "Speed too high (%d Hz), using 540 kHz\n", speed); + speed = 540000; + } else if (speed < 12000) { + dev_warn(dev, "Speed too low (%d Hz), using 12 kHz\n", speed); + speed = 12000; + } + + /* + * The timing derivation algorithm. There is no documentation for this + * algorithm available, it was derived by using the scope and fiddling + * with constants until the result observed on the scope was good enough + * for 20kHz, 50kHz, 100kHz, 200kHz, 300kHz and 400kHz. It should be + * possible to assume the algorithm works for other frequencies as well. + * + * Note it was necessary to cap the frequency on both ends as it's not + * possible to configure completely arbitrary frequency for the I2C bus + * clock. + */ + base = ((clk / speed) - 38) / 2; + high_count = base + 3; + low_count = base - 3; + rcv_count = (high_count * 3) / 4; + xmit_count = low_count / 4; + + i2c->timing0 = (high_count << 16) | rcv_count; + i2c->timing1 = (low_count << 16) | xmit_count; +} + static int mxs_i2c_get_ofdata(struct mxs_i2c_dev *i2c) { uint32_t speed; @@ -422,12 +589,12 @@ static int mxs_i2c_get_ofdata(struct mxs_i2c_dev *i2c) } ret = of_property_read_u32(node, "clock-frequency", &speed); - if (ret) + if (ret) { dev_warn(dev, "No I2C speed selected, using 100kHz\n"); - else if (speed == 400000) - i2c->speed = &mxs_i2c_400kHz_config; - else if (speed != 100000) - dev_warn(dev, "Unsupported I2C speed selected, using 100kHz\n"); + speed = 100000; + } + + mxs_i2c_derive_timing(i2c, speed); return 0; } @@ -471,7 +638,6 @@ static int mxs_i2c_probe(struct platform_device *pdev) return err; i2c->dev = dev; - i2c->speed = &mxs_i2c_95kHz_config; init_completion(&i2c->cmd_complete); @@ -531,8 +697,6 @@ static int mxs_i2c_remove(struct platform_device *pdev) writel(MXS_I2C_CTRL0_SFTRST, i2c->regs + MXS_I2C_CTRL0_SET); - platform_set_drvdata(pdev, NULL); - return 0; } |