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

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Date:   Wed, 10 Mar 2021 11:56:04 +0800
From:   "Ye, Xiang" <xiang.ye@...el.com>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc:     Jiri Kosina <jikos@...nel.org>, jic23@...nel.org,
        linux-input@...r.kernel.org, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, Xu@...t, Even <even.xu@...el.com>,
        "Ye, Xiang" <xiang.ye@...el.com>
Subject: Re: [PATCH] HID: intel_ish-hid: HBM: Use connected standby state bit
 during suspend/resume

Hi Srinivas

Thanks for the review.

On Tue, Mar 09, 2021 at 08:08:36AM -0800, Srinivas Pandruvada wrote:
> 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.
Currently, In ISH firmware, we are using CONNECTED_STANDBY_STATE_BIT
(To be compatible with Windows os which are using CONNECTED_STANDBY_STATE_BIT) to
notify sensor system power state. Then some sensor(such as hinge sensor)
can power On/Off itself according to current system power state.

Thanks
Ye Xiang