/*
* Freescale MXS I2C bus driver
*
+ * Copyright (C) 2012-2013 Marek Vasut <marex@denx.de>
* Copyright (C) 2011-2012 Wolfram Sang, Pengutronix e.K.
*
* based on a (non-working) driver which was:
#define MXS_I2C_CTRL1_SLAVE_IRQ 0x01
#define MXS_I2C_STAT (0x50)
+#define MXS_I2C_STAT_GOT_A_NAK 0x10000000
#define MXS_I2C_STAT_BUS_BUSY 0x00000800
#define MXS_I2C_STAT_CLK_GEN_BUSY 0x00000400
return -EINVAL;
}
-static int mxs_i2c_pio_wait_dmareq(struct mxs_i2c_dev *i2c)
+static int mxs_i2c_pio_wait_xfer_end(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();
- }
-
- return 0;
-}
-
-static int mxs_i2c_pio_wait_cplt(struct mxs_i2c_dev *i2c, int last)
-{
- 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);
-
- /*
- * When ending a transfer with a stop, we have to wait for the bus to
- * go idle before we report the transfer as completed. Otherwise the
- * start of the next transfer may race with the end of the current one.
- */
- while (last && (readl(i2c->regs + MXS_I2C_STAT) &
- (MXS_I2C_STAT_BUS_BUSY | MXS_I2C_STAT_CLK_GEN_BUSY))) {
+ while (readl(i2c->regs + MXS_I2C_CTRL0) & MXS_I2C_CTRL0_RUN) {
if (time_after(jiffies, timeout))
return -ETIMEDOUT;
cond_resched();
writel(reg, i2c->regs + MXS_I2C_CTRL0);
}
+/*
+ * Start WRITE transaction on the I2C bus. By studying i.MX23 datasheet,
+ * CTRL0::PIO_MODE bit description clarifies the order in which the registers
+ * must be written during PIO mode operation. First, the CTRL0 register has
+ * to be programmed with all the necessary bits but the RUN bit. Then the
+ * payload has to be written into the DATA register. Finally, the transmission
+ * is executed by setting the RUN bit in CTRL0.
+ */
+static void mxs_i2c_pio_trigger_write_cmd(struct mxs_i2c_dev *i2c, u32 cmd,
+ u32 data)
+{
+ writel(cmd, i2c->regs + MXS_I2C_CTRL0);
+ writel(data, i2c->regs + MXS_I2C_DATA);
+ writel(MXS_I2C_CTRL0_RUN, i2c->regs + MXS_I2C_CTRL0_SET);
+}
+
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;
+ int i, ret, xlen = 0, xmit = 0;
+ uint32_t start;
/* Mute IRQs coming from this block. */
writel(MXS_I2C_IRQ_MASK << 8, i2c->regs + MXS_I2C_CTRL1_CLR);
+ /*
+ * MX23 idea:
+ * - Enable CTRL0::PIO_MODE (1 << 24)
+ * - Enable CTRL1::ACK_MODE (1 << 27)
+ *
+ * WARNING! The MX23 is broken in some way, even if it claims
+ * to support PIO, when we try to transfer any amount of data
+ * that is not aligned to 4 bytes, the DMA engine will have
+ * bits in DEBUG1::DMA_BYTES_ENABLES still set even after the
+ * transfer. This in turn will mess up the next transfer as
+ * the block it emit one byte write onto the bus terminated
+ * with a NAK+STOP. A possible workaround is to reset the IP
+ * block after every PIO transmission, which might just work.
+ *
+ * NOTE: The CTRL0::PIO_MODE description is important, since
+ * it outlines how the PIO mode is really supposed to work.
+ */
+
if (msg->flags & I2C_M_RD) {
+ /*
+ * PIO READ transfer:
+ *
+ * This transfer MUST be limited to 4 bytes maximum. It is not
+ * possible to transfer more than four bytes via PIO, since we
+ * can not in any way make sure we can read the data from the
+ * DATA register fast enough. Besides, the RX FIFO is only four
+ * bytes deep, thus we can only really read up to four bytes at
+ * time. Finally, there is no bit indicating us that new data
+ * arrived at the FIFO and can thus be fetched from the DATA
+ * register.
+ */
+ BUG_ON(msg->len > 4);
+
addr_data |= I2C_SMBUS_READ;
/* SELECT command. */
- mxs_i2c_pio_trigger_cmd(i2c, MXS_CMD_I2C_SELECT);
-
- ret = mxs_i2c_pio_wait_dmareq(i2c);
- if (ret)
- return ret;
-
- writel(addr_data, i2c->regs + MXS_I2C_DATA);
- writel(MXS_I2C_DEBUG0_DMAREQ, i2c->regs + MXS_I2C_DEBUG0_CLR);
-
- ret = mxs_i2c_pio_wait_cplt(i2c, 0);
- if (ret)
- return ret;
+ mxs_i2c_pio_trigger_write_cmd(i2c, MXS_CMD_I2C_SELECT,
+ addr_data);
- if (mxs_i2c_pio_check_error_state(i2c))
+ ret = mxs_i2c_pio_wait_xfer_end(i2c);
+ if (ret) {
+ dev_err(i2c->dev,
+ "PIO: Failed to send SELECT command!\n");
goto cleanup;
+ }
/* READ command. */
mxs_i2c_pio_trigger_cmd(i2c,
MXS_CMD_I2C_READ | flags |
MXS_I2C_CTRL0_XFER_COUNT(msg->len));
+ ret = mxs_i2c_pio_wait_xfer_end(i2c);
+ if (ret) {
+ dev_err(i2c->dev,
+ "PIO: Failed to send SELECT command!\n");
+ goto cleanup;
+ }
+
+ data = readl(i2c->regs + MXS_I2C_DATA);
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);
- writel(MXS_I2C_DEBUG0_DMAREQ,
- i2c->regs + MXS_I2C_DEBUG0_CLR);
- }
msg->buf[i] = data & 0xff;
data >>= 8;
}
} else {
+ /*
+ * PIO WRITE transfer:
+ *
+ * The code below implements clock stretching to circumvent
+ * the possibility of kernel not being able to supply data
+ * fast enough. It is possible to transfer arbitrary amount
+ * of data using PIO write.
+ */
addr_data |= I2C_SMBUS_WRITE;
- /* WRITE command. */
- mxs_i2c_pio_trigger_cmd(i2c,
- MXS_CMD_I2C_WRITE | flags |
- MXS_I2C_CTRL0_XFER_COUNT(msg->len + 1));
-
/*
* 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;
+
+ /* Start the transfer with START condition. */
+ start = MXS_I2C_CTRL0_PRE_SEND_START;
+
+ /* If the transfer is long, use clock stretching. */
+ if (msg->len > 3)
+ start |= MXS_I2C_CTRL0_RETAIN_CLOCK;
+
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);
- writel(MXS_I2C_DEBUG0_DMAREQ,
- i2c->regs + MXS_I2C_DEBUG0_CLR);
+
+ xmit = 0;
+
+ /* This is the last transfer of the message. */
+ if (i + 1 == msg->len) {
+ /* Add optional STOP flag. */
+ start |= flags;
+ /* Remove RETAIN_CLOCK bit. */
+ start &= ~MXS_I2C_CTRL0_RETAIN_CLOCK;
+ xmit = 1;
}
- }
- 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);
+ /* Four bytes are ready in the "data" variable. */
+ if ((i & 3) == 2)
+ xmit = 1;
+
+ /* Nothing interesting happened, continue stuffing. */
+ if (!xmit)
+ continue;
+
+ /*
+ * Compute the size of the transfer and shift the
+ * data accordingly.
+ *
+ * i = (4k + 0) .... xlen = 2
+ * i = (4k + 1) .... xlen = 3
+ * i = (4k + 2) .... xlen = 4
+ * i = (4k + 3) .... xlen = 1
+ */
+
+ if ((i % 4) == 3)
+ xlen = 1;
+ else
+ xlen = (i % 4) + 2;
+
+ data >>= (4 - xlen) * 8;
+
+ dev_dbg(i2c->dev,
+ "PIO: len=%i pos=%i total=%i [W%s%s%s]\n",
+ xlen, i, msg->len,
+ start & MXS_I2C_CTRL0_PRE_SEND_START ? "S" : "",
+ start & MXS_I2C_CTRL0_POST_SEND_STOP ? "E" : "",
+ start & MXS_I2C_CTRL0_RETAIN_CLOCK ? "C" : "");
+
writel(MXS_I2C_DEBUG0_DMAREQ,
i2c->regs + MXS_I2C_DEBUG0_CLR);
+
+ mxs_i2c_pio_trigger_write_cmd(i2c,
+ start | MXS_I2C_CTRL0_MASTER_MODE |
+ MXS_I2C_CTRL0_DIRECTION |
+ MXS_I2C_CTRL0_XFER_COUNT(xlen), data);
+
+ /* The START condition is sent only once. */
+ start &= ~MXS_I2C_CTRL0_PRE_SEND_START;
+
+ /* Wait for the end of the transfer. */
+ ret = mxs_i2c_pio_wait_xfer_end(i2c);
+ if (ret) {
+ dev_err(i2c->dev,
+ "PIO: Failed to finish WRITE cmd!\n");
+ break;
+ }
+
+ /* Check NAK here. */
+ ret = readl(i2c->regs + MXS_I2C_STAT) &
+ MXS_I2C_STAT_GOT_A_NAK;
+ if (ret) {
+ ret = -ENXIO;
+ goto cleanup;
+ }
}
}
- ret = mxs_i2c_pio_wait_cplt(i2c, flags & MXS_I2C_CTRL0_POST_SEND_STOP);
- if (ret)
- return ret;
-
/* make sure we capture any occurred error into cmd_err */
- mxs_i2c_pio_check_error_state(i2c);
+ ret = mxs_i2c_pio_check_error_state(i2c);
cleanup:
/* 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;
+ return ret;
}
/*
int stop)
{
struct mxs_i2c_dev *i2c = i2c_get_adapdata(adap);
- int ret, err;
+ int ret;
int flags;
+ int use_pio = 0;
flags = stop ? MXS_I2C_CTRL0_POST_SEND_STOP : 0;
return -EINVAL;
/*
- * 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.
- * Note: this special feature only works on i.MX28 SoC
+ * The MX28 I2C IP block can only do PIO READ for transfer of to up
+ * 4 bytes of length. The write transfer is not limited as it can use
+ * clock stretching to avoid FIFO underruns.
*/
+ if ((msg->flags & I2C_M_RD) && (msg->len <= 4))
+ use_pio = 1;
+ if (!(msg->flags & I2C_M_RD) && (msg->len < 7))
+ use_pio = 1;
+
+ /* Disable PIO on MX23. */
+ if (i2c->dev_type == MXS_I2C_V1)
+ use_pio = 0;
+
i2c->cmd_err = 0;
- if (0) { /* disable PIO mode until a proper fix is made */
+ if (use_pio) {
ret = mxs_i2c_pio_setup_xfer(adap, msg, flags);
- if (ret) {
- err = mxs_i2c_reset(i2c);
- if (err)
- return err;
- }
+ /* No need to reset the block if NAK was received. */
+ if (ret && (ret != -ENXIO))
+ mxs_i2c_reset(i2c);
} else {
INIT_COMPLETION(i2c->cmd_complete);
ret = mxs_i2c_dma_setup_xfer(adap, msg, flags);
msecs_to_jiffies(1000));
if (ret == 0)
goto timeout;
+
+ ret = i2c->cmd_err;
}
- if (i2c->cmd_err == -ENXIO) {
+ if (ret == -ENXIO) {
/*
* If the transfer fails with a NAK from the slave the
* controller halts until it gets told to return to idle state.
i2c->regs + MXS_I2C_CTRL1_SET);
}
- ret = i2c->cmd_err;
-
dev_dbg(i2c->dev, "Done with err=%d\n", ret);
return ret;
}
module_exit(mxs_i2c_exit);
+MODULE_AUTHOR("Marek Vasut <marex@denx.de>");
MODULE_AUTHOR("Wolfram Sang <w.sang@pengutronix.de>");
MODULE_DESCRIPTION("MXS I2C Bus Driver");
MODULE_LICENSE("GPL");
projects / profile / common / kernel-common.git / commitdiff