linux-kernel - Re: [PATCH V6 4/4] firmware: ti_sci: Introduce system suspend resume support

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Message-ID: <20230803160815.yfpkdfssv75d4inf@dhruva>
Date:   Thu, 3 Aug 2023 21:38:15 +0530
From:   Dhruva Gole <d-gole@...com>
To:     Andrew Davis <afd@...com>
CC:     Nishanth Menon <nm@...com>, Tero Kristo <kristo@...nel.org>,
        "Santosh Shilimkar" <ssantosh@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-pm@...r.kernel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Praneeth Bajjuri <praneeth@...com>,
        Tony Lindgren <tony@...mide.com>,
        Dave Gerlach <d-gerlach@...com>,
        Vibhore Vardhan <vibhore@...com>, Georgi Vlaev <g-vlaev@...com>
Subject: Re: [PATCH V6 4/4] firmware: ti_sci: Introduce system suspend resume
 support

On Aug 03, 2023 at 11:00:11 -0500, Andrew Davis wrote:
> On 8/3/23 10:55 AM, Dhruva Gole wrote:
> > On Aug 03, 2023 at 10:26:32 -0500, Andrew Davis wrote:
> > > On 8/3/23 1:42 AM, Dhruva Gole wrote:
> > > > Introduce system suspend resume calls that will allow the ti_sci
> > > > driver to support deep sleep low power mode when the user space issues a
> > > > suspend to mem.
> > > > 
> > > > Also, write a ti_sci_prepare_system_suspend call to be used in the driver
> > > > suspend handler to allow the system to identify the low power mode being
> > > > entered and if necessary, send TISCI_MSG_PREPARE_SLEEP with information
> > > > about the mode is being entered and the address for allocated memory for
> > > > storing the context during Deep Sleep.
> > > > 
> > > > We're using "pm_suspend_target_state" to map the kernel's target suspend
> > > > state to SysFW low power mode. Make sure this is available only when
> > > > CONFIG_SUSPEND is enabled.
> > > > 
> > > > Co-developed-by: Dave Gerlach <d-gerlach@...com>
> > > > Signed-off-by: Dave Gerlach <d-gerlach@...com>
> > > > Signed-off-by: Vibhore Vardhan <vibhore@...com>
> > > > Signed-off-by: Georgi Vlaev <g-vlaev@...com>
> > > > Signed-off-by: Dhruva Gole <d-gole@...com>
> > > > ---
> > > >    drivers/firmware/ti_sci.c | 63 +++++++++++++++++++++++++++++++++++++++
> > > >    1 file changed, 63 insertions(+)
> > > > 
> > [..snip..]
> > > > +static int ti_sci_suspend(struct device *dev)
> > > > +{
> > > > +	struct ti_sci_info *info = dev_get_drvdata(dev);
> > > > +	int ret;
> > > > +
> > > > +	ret = ti_sci_cmd_set_io_isolation(&info->handle, TISCI_MSG_VALUE_IO_ENABLE);
> > > 
> > > After this the will the IOs be in isolation? Or does the firmware wait
> > > until power down begins later?
> > 
> >  From what I understand,
> > IOs will be in isolation immediately
> > 
> 
> That is what I understand too, so then any device that may need to do some
> external communication for its suspend will not function, this must be the
> last driver _suspend() the system calls, how do you enforce that?

I will make use of .suspend_noirq callbacks in that case. Does that
sound better, or is there anything else I may not be aware of?

> 
> Andrew
> 
> > > 
> > > Andrew
> > > 
[..snip..]
> > 

-- 
Best regards,
Dhruva Gole <d-gole@...com>