Re: [PATCH v3] i2c: designware: Do not complete i2c read without RX_FULL interrupt

[Jarkko Nikula <jarkko.nikula@linux.intel.com>]

On 12/14/21 16:24, tamal.saha@intel.com wrote:
> From: Tamal Saha <tamal.saha@intel.com>
> 
> 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@intel.com>
> ---
> 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@linux.intel.com>