Bug 1123882 - Please enable CONFIG_RTC_DRV_PL031 on aarch64 [NEEDINFO]
Summary: Please enable CONFIG_RTC_DRV_PL031 on aarch64
Alias: None
Product: Fedora
Classification: Fedora
Component: kernel
Version: rawhide
Hardware: Unspecified
OS: Unspecified
Target Milestone: ---
Assignee: Kernel Maintainer List
QA Contact: Fedora Extras Quality Assurance
Depends On:
Blocks: TRACKER-bugs-affecting-libguestfs
TreeView+ depends on / blocked
Reported: 2014-07-28 14:25 UTC by Richard W.M. Jones
Modified: 2014-10-21 18:58 UTC (History)
8 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Last Closed: 2014-10-21 18:58:55 UTC
Type: Bug
rjones: needinfo? (kernel-maint)

Attachments (Terms of Use)

Description Richard W.M. Jones 2014-07-28 14:25:07 UTC
Description of problem:

PL031 is a real time clock.

Although it is not found on real hardware AFAICT, it is emulated by
qemu-system-aarch64 and therefore it's a useful way to get wallclock
time in VMs.

There is no kvmclock on !x86, and without PL031 the VM's time will
be set to 1/1/1970 for a long time (until you start ntpd which is quite
a long time into the boot process, and never happens in libguestfs VMs).

I have enabled this option in my kernel and tested it booting on
both the real hardware and inside a VM.  It has no effect on the
real hardware.

In the VM it ensures that the wallclock is set correctly close to boot.
You will see this message during VM boot:

[    0.742380] rtc-pl031 90010000.pl031: rtc core: registered pl031 as rtc0
[    0.789316] rtc-pl031 90010000.pl031: setting system clock to 2014-07-28 14:21:39 UTC (1406557299)

Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
1. Start a KVM VM.
2. Observe the clock in the VM.  It is set to 1/1/1970.

Comment 1 Don Dutile (Red Hat) 2014-07-28 17:11:38 UTC
CONFIG =y or =m ?

Comment 2 Richard W.M. Jones 2014-07-28 17:37:39 UTC
(In reply to Don Dutile from comment #1)
> CONFIG =y or =m ?

I'm testing it compiled in (=y).  It doesn't affect boot on the
aarch64 real hardware.  I believe it'd be better for the clock to
be compiled in so that it can be initialized as soon as possible.

Comment 3 Richard W.M. Jones 2014-10-21 10:13:21 UTC
I've been testing this patch for months.  What can I do to
get this actioned?  I will push it myself if permitted.

diff --git a/config-arm64 b/config-arm64
index bdcc9b9..eac2b9a 100644
--- a/config-arm64
+++ b/config-arm64
@@ -52,7 +52,7 @@ CONFIG_NFS_USE_KERNEL_DNS=y
 # CONFIG_PL330_DMA is not set
 # CONFIG_RTC_DRV_PL030 is not set
-# CONFIG_RTC_DRV_PL031 is not set
 # CONFIG_SERIAL_AMBA_PL010 is not set

Comment 4 Josh Boyer 2014-10-21 12:26:40 UTC
I'll change it in today's rawhide build.

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