Re: [PATCH] i2c: designware: separate ops for system_sleep_pm and runtime_pm

Dear Mika,

On Wed, 20 May 2015 19:34:22 +0800
Jisheng Zhang [off-list ref] wrote:

Dear Mika,

On Tue, 19 May 2015 16:15:16 +0300
Mika Westerberg [off-list ref] wrote:

quoted

On Tue, May 19, 2015 at 08:32:42PM +0800, Jisheng Zhang wrote:

quoted

quoted

I can see that this fixes the issue with the platform driver (as the
platform bus core doesn't power on the device automatically as opposed
to other buses, like PCI). However, I'm thinking that can we do better
here.

Instead of powering the device on again, can't we leave it in low power
state? Recently added 'dev->power.direct_complete' may be used to
achieve that, I think.

how to handle runtime suspended via just being clock gated?

As far as I can tell driver's suspend hook does the clock gating so why
would you need to handle it differently? Once the device is runtime
suspended, it is both clock and power gated depending on the platform.

Sorry for confusion. Considering one platform which doesn't support power off
the i2c host but it can disable the host's clock. So in such platform, when
the host is runtime suspended, its clock is disabled, then i2c_dw_disable() will
hang when s2ram. Except using the runtime pm API to ensure the host is in
a correct state, is there any other solution? AFAIK, 'dev->power.direct_complete'
doesn't help such case.

I misunderstood the direct_complete flag usage. I think it can help such case
will investigate and provide new patch if necessary.

Thanks a lot