Hi Torsten,
> Hi Marek,
>
> > Thinking about this, did you correctly configure the EEPROM write sector
> > size? I think it's 32 bytes for this device.
>
> The EEPROM is correctly configured, i.e. page size is set to 32.
>
> I made a test by writing one byte (0x01) to the address 0x0100 of the
> EEPROM. The EEPROM's I2C bus address is 0x54.
> The test has only one transfer with a message length of 3 bytes.
>
> I figured out that the value written to the MXS_I2C_DATA register should be
> 0x010001a8. But instead of that a value of 0x00000000 is written to the
> register.
>
> I think that the reason for that can be found in the following code
> section:
>
> if (i + 1 == msg->len) {
> /* This is the last transfer. */
> start |= flags;
> start &= ~MXS_I2C_CTRL0_RETAIN_CLOCK;
> xlen = (i + 2) % 4;
> data >>= (4 - xlen) * 8;
> } else if ((i & 3) == 2) {
> /* Regular transfer. */
> xlen = 4;
> } else {
> /* Just stuff data. */
> continue;
> }
>
> After the last byte is stuffed into the variable data (i = 2) xlen is
> calculated (with xlen = (i + 2) % 4) to zero. Thus the following shift
> operation (data >>= (4 - xlen) * 8) shifts all the bits out of data that
> already contains 0x010001a8.
You're right, thanks for finding this! Does the following fix look OK ? I added
some more comments and "decompressed" the code some more.
diff --git a/drivers/i2c/busses/i2c-mxs.c b/drivers/i2c/busses/i2c-mxs.c
index fb6f110..ee17b6a 100644
--- a/drivers/i2c/busses/i2c-mxs.c
+++ b/drivers/i2c/busses/i2c-mxs.c
@@ -366,7 +366,7 @@ static int mxs_i2c_pio_setup_xfer(struct i2c_adapter *adap,
struct mxs_i2c_dev *i2c = i2c_get_adapdata(adap);
uint32_t addr_data = msg->addr << 1;
uint32_t data = 0;
- int i, ret, xlen = 0;
+ int i, ret, xlen = 0, xmit = 0;
uint32_t start;
/* Mute IRQs coming from this block. */
@@ -463,20 +463,42 @@ static int mxs_i2c_pio_setup_xfer(struct i2c_adapter
*adap,
data >>= 8;
data |= (msg->buf[i] << 24);
+ xmit = 0;
+
+ /* This is the last transfer of the message. */
if (i + 1 == msg->len) {
- /* This is the last transfer. */
+ /* Add optional STOP flag. */
start |= flags;
+ /* Remove RETAIN_CLOCK bit. */
start &= ~MXS_I2C_CTRL0_RETAIN_CLOCK;
- xlen = (i + 2) % 4;
- data >>= (4 - xlen) * 8;
- } else if ((i & 3) == 2) {
- /* Regular transfer. */
- xlen = 4;
- } else {
- /* Just stuff data. */
- continue;
+ xmit = 1;
}
+ /* 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,
Best regards,
Marek Vasut
--
To unsubscribe from this list: send the line "unsubscribe linux-i2c" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
