linux-kernel - Re: `intel_lpss_pci_driver

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Date: Thu, 14 Mar 2024 15:30:37 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Paul Menzel <pmenzel@...gen.mpg.de>
Cc: Lee Jones <lee@...nel.org>,
	Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
	linux-i2c@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: `intel_lpss_pci_driver_init` takes 23.8 ms

On Sun, Feb 11, 2024 at 08:38:15PM +0100, Paul Menzel wrote:
> Am 08.02.24 um 18:33 schrieb Andy Shevchenko:
> > On Thu, Feb 08, 2024 at 08:59:28AM +0000, Lee Jones wrote:
> > > On Tue, 06 Feb 2024, Paul Menzel wrote:

..

> > > > On the Dell XPS 13 9360 and Linux 6.8-rc3+, `intel_lpss_pci_driver_init()`
> > > > takes 23.8 ms, making it one of Linux’ longer init functions on this device:
> > 
> > Does it mean on the previous releases it was different?
> > I mean is it a regression or always was like this?

Okay.

..

> but this seems to have a big affect on ACPI/ASL operations, and execution
> time increases to 125 ms. This breaks down to
> 
> 1.  `i2c_acpi_find_bus_speed()` (96.985 ms @ 3.008753), where
> `acpi_walk_namespace()` takes this time.
> 2.  `i2c_dw_probe_master()` (27.161 ms @ 3.105964) →
> i2c_add_numbered_adapter()` → `i2c_add_adapter()` → `i2c_register_adapter()`
> → `i2c_acpi_register_devices()` → `acpi_ns_walk_namespace()` (24.178 ms @
> 3.108927)
> 
> No idea if this is a red herring, and the long time is actually do to
> something else.

Might be related https://github.com/acpica/acpica/pull/897
Wonder if it helps you anyhow.

-- 
With Best Regards,
Andy Shevchenko