From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mika Westerberg <mika.westerberg@linux.intel.com>
Subject: Re: [PATCH] ACPI / LPSS: Ignore 10ms delay for Braswell and Baytrail
Date: Fri, 21 Aug 2015 16:20:15 +0300
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To: "Kasagar, Srinidhi" <srinidhi.kasagar@intel.com>
Cc: linux-acpi@vger.kernel.org, rafael.j.wysocki@intel.com, Kumar P Mahesh <mahesh.kumar.p@intel.com>, Heikki Krogerus <heikki.krogerus@intel.com>

On Fri, Aug 21, 2015 at 09:36:41AM +0300, Mika Westerberg wrote:
> On Fri, Aug 21, 2015 at 05:41:52PM +0530, Kasagar, Srinidhi wrote:
> > On Thu, Aug 20, 2015 at 03:38:05PM +0300, Mika Westerberg wrote:
> > > +Heikki
> > > 
> > > On Thu, Aug 20, 2015 at 10:46:07PM +0530, Srinidhi Kasagar wrote:
> > > > LPSS devices in Braswell and Baytrail does not need the default
> > > > 10ms d3_delay imposed by PCI specification. Removing this
> > > > unnecessary delay significantly reduces the resume time
> > > > (~200ms on Braswell/Cherrytrail) on these platforms.
> > > > 
> > > > Signed-off-by: Srinidhi Kasagar <srinidhi.kasagar@intel.com>
> > > > Signed-off-by: Kumar P Mahesh <mahesh.kumar.p@intel.com>
> > > 
> > > Have you tested this on Asus T100? The delay was actually needed in
> > > order to restore the context IIRC.
> > 
> > Sorry, I do not have T100 h/w :(
> 
> OK. We have one and I'm going to test this patch on it. In particular
> the T100 needed to have these delays otherwise writes failed.

The patch does not apply on top of v4.2-rc7 or linux-pm/bleeding-edge.
So I just unconditionally set the delay to 0 for all LPSS devices on
T100.

Having msleep(0) seems to be enough and the touch panel including I2C
host controller runtime resumes just fine :-)

If I remove msleep() completely then things break apart and runtime
resuming the touch panel triggers this:

[   46.143111] i2c_hid i2c-ATML1000:00: i2c_hid_set_power
[   46.145758] i2c_hid i2c-ATML1000:00: __i2c_hid_command: cmd=fb 00 00 08
[   46.148483] i2c_designware 80860F41:05: Unknown Synopsys component type: 0x00000000
[   46.252125] i2c_designware 80860F41:05: timeout in enabling adapter
[   47.254426] i2c_designware 80860F41:05: controller timed out

So clearly it needs some delay but it does not have to be 10ms.