linux-kernel - Re: `pci_apply_final_quirks()` taking half a second

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Message-ID: <CAHp75VcZs++L0svPq5W7gz0sH3RZvF=wMoFcjEUn8puF+mvQ-Q@mail.gmail.com>
Date:   Wed, 3 May 2017 21:42:06 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        Paul Menzel <pmenzel@...gen.mpg.de>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: `pci_apply_final_quirks()` taking half a second

On Sat, Apr 8, 2017 at 10:06 PM, Bjorn Helgaas <helgaas@...nel.org> wrote:
> On Sat, Apr 08, 2017 at 07:00:19PM +0200, David Woodhouse wrote:
>> ...
>> I note it's also reading PCI_CACHE_LINE_SIZE From config space for each
>> device in pci_apply_final_quirks(). How long does that take?
>
> I don't know, but it's pointless on modern PCIe systems where the
> Cache Line Size has no effect.  It'd be really nice if somebody
> cleaned that up and got rid of the read itself and the useless
> messages.

What I can think of is 10ms delay for PM. The laptop might be one of
Intel BayTrails where we have it.
But it's just a guess.

-- 
With Best Regards,
Andy Shevchenko