[PATCH i2c-next v6] i2c: aspeed: Handle master/slave combined irq events properly

Jae Hyun Yoo jae.hyun.yoo at linux.intel.com
Wed Sep 12 08:18:27 AEST 2018

On 9/11/2018 1:41 PM, Guenter Roeck wrote:
> On Tue, Sep 11, 2018 at 01:30:41PM -0700, Jae Hyun Yoo wrote:
>> On 9/11/2018 11:37 AM, Guenter Roeck wrote:
>>> Hi,
>>> On Thu, Aug 23, 2018 at 03:57:31PM -0700, Jae Hyun Yoo wrote:
>>>> In most of cases, interrupt bits are set one by one but there are
>>>> also a lot of other cases that Aspeed I2C IP sends multiple
>>>> interrupt bits with combining master and slave events using a
>>>> single interrupt call. It happens much more in multi-master
>>>> environment than single-master. For an example, when master is
>>>> waiting for a NORMAL_STOP interrupt in its MASTER_STOP state,
>>>> SLAVE_MATCH and RX_DONE interrupts could come along with the
>>>> NORMAL_STOP in case of an another master immediately sends data
>>>> just after acquiring the bus. In this case, the NORMAL_STOP
>>>> interrupt should be handled by master_irq and the SLAVE_MATCH and
>>>> RX_DONE interrupts should be handled by slave_irq. This commit
>>>> modifies irq hadling logic to handle the master/slave combined
>>>> events properly.
>>>> Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo at linux.intel.com>
>>>> Reviewed-by: Brendan Higgins <brendanhiggins at google.com>
>>> This patch causes a boot stall when booting witherspoon-bmc with
>>> qemu v3.0, and all i2c device probes fail with error -110 (timeout).
>>> Bisect log is attached for reference.
>>> With the same kernel configuration (aspeed_g5_defconfig),
>>> ast2500-evb and romulus-bmc are still able to boot.
>>> palmetto-bmc with aspeed_g4_defconfig also appears to work.
>>> Is this a problem with qemu ? Should I drop the qemu test
>>> for witherspoon-bmc starting with the next kernel release ?
>>> Thanks,
>>> Guenter
>> Hi Guenter,
>> Thanks for your report.
>> I checked this patch again but it doesn't have any change that could
>> affect to the probing flow. I'll debug the issue on qemu 3.0 environment
>> and will share if I find something.
> The problem may be that qemu and the new code disagree how interrupts
> should be generated and handled, and the new code does not handle the
> interrupts it receives from the simulated hardware. This will result
> in i2c device probe failure, which in turn can cause all kinds of
> problems.

Yes, that makes sense. Looks like it should be reverted until the issue
is fixed. Will submit a patch to revert it.


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