Re: [PATCH RFC] mfd: intel-lpss: Set d3hot_delay to 0

[Andy Shevchenko]

On Mon, Oct 19, 2026 at 06:34:37AM +0200, Mika Westerberg wrote:
> On Fri, Oct 16, 2026 at 04:16:20PM +0300, Andy Shevchenko wrote:
> > On Fri, Oct 16, 2026 at 05:13:47PM +0530, Navon John Lukose wrote:
> > > intel-lpss-pci already clears d3cold_delay, but every runtime resume of an
> > > LPSS controller still sleeps the default 10 ms d3hot_delay in
> > > pci_power_up().
> > > 
> > > On Arrow Lake-H (Lenovo Yoga Pro 7 14IAH10) the delay costs 8-16 ms per
> > > resume of the touchpad's I2C controller, which lands on the first
> > > touchpad report after each 1 s autosuspend. With d3hot_delay set to 0 the
> > > power-up takes 64-256 us and the I2C transfers that follow complete
> > > without errors.
> > 
> > So, do you state that this patch fixes some bad touchpad behaviour? If so,
> > please, provide some logs.
> > 
> > > Commit 815b4448198f ("i3c: mipi-i3c-hci-pci: Set d3hot_delay to 0 for Intel
> > > controllers") does the same for the Intel I3C controllers.
> > 
> > Okay, it means they were tested.

...

> > > Notes:
> > >     RFC because I could only test Arrow Lake-H, and this applies to every LPSS
> > >     generation the driver handles, back to Sunrise Point. Andy, do any of the
> > >     older ones need the D3hot->D0 delay? If so I can limit it to newer IDs
> > >     through the driver data.
> > 
> > AFAIK 10 ms for D3hot delay is in accordance with PCI specification.
> > Yes, we use quirk_remove_d3hot_delay() for very old Intel Atom SoCs,
> > but I have no idea about Skylake line of products.
> > 
> > Mika, Ilpo, do you have any ideas or comments on this?
> 
> Like you say it's requirement of the PCI spec. However, since these are
> really not PCI connected devices the delay likely is not needed as seen
> here. No objections from my side.

Okay, thanks.

Navon, please, issue a new version with the summary of this discussion being
embedded into the commit message.

-- 
With Best Regards,
Andy Shevchenko