Re: [RFC 00/12] RFC: Devicetree-ACPI hybrid mode

[Sudeep Holla <sudeep.holla@kernel.org>]

On Sun, Jun 28, 2026 at 10:23:15PM +0300, Dmitry Baryshkov wrote:
> On Sat, Jun 27, 2026 at 03:12:31PM +0100, Sudeep Holla wrote:
> > On Fri, Jun 26, 2026 at 11:57:47PM +0300, Dmitry Baryshkov wrote:
> > > On Fri, Jun 26, 2026 at 04:52:41PM +0100, Sudeep Holla wrote:
> > > > On Tue, Jun 23, 2026 at 04:52:13PM +0200, Hans de Goede wrote:
> > > > > Hi All,
> > > > > 
> > > > > Currently as soon as the kernel boots with a populated DT provided then
> > > > > the arch/arm64 code sets acpi_disabled=1 and the complete ACPI subsystem
> > > > > gets disabled. On WoA Snapdragon laptops where the factory Windows OS
> > > > > actually boots using these tables this is not necessarily desirable.
> > > > > 
> > > > 
> > > > I am bit lost reading the very first statement here.
> > > > 
> > > > Who is populating DT and why ? It seems that is the source of the problem.
> > > > 
> > > > If windows can boot with ACPI tables, why is it causing issues for the
> > > > Linux kernel, any specifics?
> > > 
> > > Windows uses a separate beast called PEP, which nobody wanted to
> > > implement for these platforms up to now. You can find a lot of ACPI
> > > dumps for these devices at [1].
> > > 
> > 
> > Agreed and I assume that is the reason why we want DT.
> 
> Not completely... Using DT forces us to reimplement bits and pieces for
> these laptops. E.g. drivers for EC, battery, etc.
> 

Not entirely clear still. I mean use ACPI for those as well.

> > 
> > > > IOW why is DT populated which creates the problem you are trying to address
> > > > here.
> > > 
> > > Most of the laptops resemble other Qualcomm platforms, which use DT for
> > > hardware description. In some cases, it is the same platform being used
> > > for both mobile, IoT and laptops. It was more or less natural to reuse
> > > existing support.
> > > 
> > 
> > Sure, just use DT then, why are we even talking about mixed/hybrid mode.
> > It gives no incentive to OEMs using PEP to get away from it and use
> > standard ACPI or improve if anything is missing.
> 
> Well. Here we are talking about the laptops which were being sold since
> 2018. I doubt there will be a UEFI update for all these models.
> 

This problem is discussed multiple times and yet OEMs are not interested in
fixing it 🙁.

> > 
> > So I don't like this idea of mixing at all. Use ACPI or DT, make up you
> > mind. You can't expect to get the best of both worlds if you are not improving
> > the missing parts in either of those. This is just a shortcut.
> 
> So, if we need to append the DSDT, what would be the best way to do it?
> Something like Surface platform drivers, providing extra device nodes?
> 

CONFIG_ACPI_TABLE_UPGRADE allows to override the ACPI tables via initrd IIRC.

-- 
Regards,
Sudeep