linux-kernel - Re: [PATCH v3] efi: arm: defer probe of PCIe backed efifb on DT systems

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Date:   Fri, 10 Jan 2020 09:06:05 -0800
From:   Saravana Kannan <saravanak@...gle.com>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     Ard Biesheuvel <ardb@...nel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Will Deacon <will@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        linux-efi <linux-efi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] efi: arm: defer probe of PCIe backed efifb on DT systems

On Thu, Jan 9, 2020 at 10:41 PM Ard Biesheuvel
<ard.biesheuvel@...aro.org> wrote:
>
> On Fri, 10 Jan 2020 at 04:01, Saravana Kannan <saravanak@...gle.com> wrote:
> >
> > From: Ard Biesheuvel <ardb@...nel.org>
> >
> > The new of_devlink support breaks PCIe probing on ARM platforms booting
> > via UEFI if the firmware exposes a EFI framebuffer that is backed by a
> > PCI device. The reason is that the probing order gets reversed,
> > resulting in a resource conflict on the framebuffer memory window when
> > the PCIe probes last, causing it to give up entirely.
> >
> > Given that we rely on PCI quirks to deal with EFI framebuffers that get
> > moved around in memory, we cannot simply drop the memory reservation, so
> > instead, let's use the device link infrastructure to register this
> > dependency, and force the probing to occur in the expected order.
> >
> > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
> > Co-developed-by: Saravana Kannan <saravanak@...gle.com>
> > Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> > Reviewed-by: Ard Biesheuvel <ardb@...nel.org>
> > ---
> >
> > v1 -> v2:
> > - Rewrote the device linking part to not depend on initcall ordering
> > v2 -> v3:
> > - Added const and check for CONFIG_PCI
> >
>
> Thanks. I've queued this version in efi/next for v5.6

Awesome, thanks!

-Saravana