linux-kernel - Re: [PATCH] HID: intel_ish-hid: HBM: Use connected standby state bit during suspend/resume

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Message-ID: <69475ef69096587be23f632e79efce5711c82cf1.camel@linux.intel.com>
Date:   Tue, 09 Mar 2021 08:08:36 -0800
From:   Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To:     "Ye, Xiang" <xiang.ye@...el.com>, Jiri Kosina <jikos@...nel.org>
Cc:     jic23@...nel.org, linux-input@...r.kernel.org,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] HID: intel_ish-hid: HBM: Use connected standby state
 bit during suspend/resume

On Tue, 2021-03-09 at 11:47 +0800, Ye, Xiang wrote:
> Hi Srinivas, Jiri
> 
> On Mon, Mar 08, 2021 at 08:00:41AM -0800, Srinivas Pandruvada wrote:
> > On Mon, 2021-03-08 at 11:26 +0100, Jiri Kosina wrote:
> > > On Wed, 3 Mar 2021, Ye Xiang wrote:
> > > 
> > > > ISH firmware uses connected standby state bit
> > > > (CONNECTED_STANDBY_STATE_BIT bit 1)
> > > > to notify current power state to sensors instead of suspend
> > > > state
> > > > bit (bit 0).
> > > > So send both SUSPEND_STATE_BIT and CONNECTED_STANDBY_STATE_BIT
> > > > to
> > > > firmware
> > > > to be compatible with the previous version.
> > > 
> > > Could you please make the changelog more verbose -- namely what 
> > > user-visible issue this is fixing?
> > Xiang,
> > 
> > I think this change is for related to Elkhart Lake for support of
> > connected standby (keep listening for sensor events during Linux
> > suspend for some sensors). In this way some sensor can wake up the
> > system.
> This change is for all ISH platform. Currently, ISH firmware use
> both SUSPEND_STATE_BIT and CONNECTED_STANDBY_STATE_BIT to identify
> system state. It is related to system wake up by ISH and it enable
> each
> sensor in ISH to be notified the current system state, when system
> state
> change.
What will sensors do with this additional information?
I think the individual sensors in ISH can decide whether to power OFF
or ON based on this information to save power during system suspend to
idle.

Thanks,
Srinivas

> 
> Thanks
> Ye Xiang
> > 
> > 
> > 
> > 
> > 
> >