lkml.org 
[lkml]   [2018]   [Jan]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRE: [PATCH] PCI/ACPI: Disable AER when _OSC control bit is clear.
Date
> -----Original Message-----
> From: rjwysocki@gmail.com [mailto:rjwysocki@gmail.com] On Behalf Of
> Rafael J. Wysocki
> Sent: Thursday, January 11, 2018 12:39 PM
> To: Ghannam, Yazen <Yazen.Ghannam@amd.com>
> Cc: ACPI Devel Maling List <linux-acpi@vger.kernel.org>; Linux Kernel Mailing
> List <linux-kernel@vger.kernel.org>; Linux PCI <linux-pci@vger.kernel.org>;
> Rafael J. Wysocki <rjw@rjwysocki.net>; Len Brown <lenb@kernel.org>; Bjorn
> Helgaas <bhelgaas@google.com>; Borislav Petkov <bp@suse.de>
> Subject: Re: [PATCH] PCI/ACPI: Disable AER when _OSC control bit is clear.
>
> On Thu, Jan 11, 2018 at 4:03 PM, Yazen Ghannam
> <Yazen.Ghannam@amd.com> wrote:
> > From: Yazen Ghannam <yazen.ghannam@amd.com>
> >
> > Currently, aer_service_init() checks if AER is available and that
> > Firmware First handling is not enabled. The _OSC request for AER is
> > not taken into account when deciding to enable AER in Linux.
> >
> > We should check that the _OSC control for AER is set. If it's not
> > then AER should be disabled.
> >
> > The _OSC control for AER is not requested when APEI Firmware First is
> > used, so the same condition applies.
> >
> > Mark AER as disabled if the _OSC request was not made or accepted.
> >
> > Remove redunant check for aer_acpi_firmware_first() when calling
> > aer_service_init(), since this is check is already included when
> > checking the _OSC control.
> >
> > Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
> > ---
> > drivers/acpi/pci_root.c | 3 +++
> > drivers/pci/pcie/aer/aerdrv.c | 2 +-
> > 2 files changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> > index 6fc204a52493..19a625ed8de9 100644
> > --- a/drivers/acpi/pci_root.c
> > +++ b/drivers/acpi/pci_root.c
> > @@ -512,6 +512,9 @@ static void negotiate_os_control(struct
> acpi_pci_root *root, int *no_aspm)
> > */
> > *no_aspm = 1;
> > }
> > +
> > + if (!(requested & control & OSC_PCI_EXPRESS_AER_CONTROL))
>
> One of the operators above needs to be a && I suppose?
>

It's a 3-way bitwise AND to check that OSC_PCI_EXPRESS_AER_CONTROL is
set in both "requested" and "control".

IOW, we check if AER was requested by the OS and that the platform
granted the request.

Thanks,
Yazen
\
 
 \ /
  Last update: 2018-01-14 23:24    [W:0.050 / U:1.660 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site