On 12/14/21 16:24, tamal.saha@xxxxxxxxx wrote:
From: Tamal Saha <tamal.saha@xxxxxxxxx>
Intel Keem Bay platform supports multi-master operations over same i2c
bus using Synopsys i2c DesignWare IP. When multi-masters initiate i2c
operation simultaneously in a loop, SCL line is stucked low forever
after few i2c operations. Following interrupt sequences are observed
in:
working case: TX_EMPTY, RX_FULL and STOP_DET
non working case: TX_EMPTY, STOP_DET, RX_FULL.
DW_apb_i2c stretches the SCL line when the TX FIFO is empty or when
RX FIFO is full. The DW_apb_i2c master will continue to hold the SCL
line LOW until RX FIFO is read.
Linux kernel i2c DesignWare driver does not handle above non working
sequence. TX_EMPTY, RX_FULL and STOP_DET routine execution are required
in sequence although RX_FULL interrupt is raised after STOP_DET by
hardware. Clear STOP_DET for the following conditions:
(STOP_DET ,RX_FULL, rx_outstanding)
Write Operation: (1, 0, 0)
Read Operation:
RX_FULL followed by STOP_DET: (0, 1, 1) -> (1, 0, 0)
STOP_DET followed by RX_FULL: (1, 0, 1) -> (1, 1, 0)
RX_FULL and STOP_DET together: (1, 1, 1)
Signed-off-by: Tamal Saha <tamal.saha@xxxxxxxxx>
---
Changes in v3:
- "multi-master" is used in commit message
Changes in v2:
- Commit message updated as suggested by Andy Shevchenko
- Replaced Synopsis by Synopsys, designware by DesignWare, software by driver
---
drivers/i2c/busses/i2c-designware-master.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
Acked-by: Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx>
