Re: [PATCH] i2c: designware: Don't mask TX_EMPTY if write is in progress

From: Jarkko Nikula
Date: Fri Oct 30 2015 - 08:04:01 EST


On 10/30/2015 09:37 AM, Jisheng Zhang wrote:
Currently when i2c_msg index search is completed, TX_EMPTY interrupt
will be masked. But if the size of i2c_msg data is longer than the size
of the tx buffer, we still need TX_EMPTY interrupt, otherwise we will
get "controller timed out" error.

This patch fixes this issue by only masking TX_EMPTY if i2c_msg index
search is completed and write is not in progress.

Signed-off-by: Jisheng Zhang <jszhang@xxxxxxxxxxx>
drivers/i2c/busses/i2c-designware-core.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
index 7441cdc..a2eb212 100644
--- a/drivers/i2c/busses/i2c-designware-core.c
+++ b/drivers/i2c/busses/i2c-designware-core.c
@@ -542,10 +542,11 @@ i2c_dw_xfer_msg(struct dw_i2c_dev *dev)

- * If i2c_msg index search is completed, we don't need TX_EMPTY
- * interrupt any more.
+ * If i2c_msg index search is completed and writing is not in progress,
+ * we don't need TX_EMPTY interrupt any more.
- if (dev->msg_write_idx == dev->msgs_num)
+ if (dev->msg_write_idx == dev->msgs_num &&
+ !(dev->status & STATUS_WRITE_IN_PROGRESS))
intr_mask &= ~DW_IC_INTR_TX_EMPTY;

This looks a possible scenario here. What I'm wondering how is the transfer ending and what condition in i2c_dw_isr() causes the complete() call?

Assuming we break the for loop in i2c_dw_xfer_msg() with buf_len > 0 and dev->msg_write_idx == dev->msgs_num how we get back inside the for loop for writing the remaining bytes and stop command?

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