[PATCH 4.4 41/53] ARM: 8955/1: virt: Relax arch timer version check during early boot

Greg Kroah-Hartman
2020-02-03T16:21:54Z

From: Vladimir Murzin <vladimir.murzin@arm.com>

[ Upstream commit 6849b5eba1965ceb0cad3a75877ef4569dd3638e ]

Updates to the Generic Timer architecture allow ID_PFR1.GenTimer to
have values other than 0 or 1 while still preserving backward
compatibility. At the moment, Linux is quite strict in the way it
handles this field at early boot and will not configure arch timer if
it doesn't find the value 1.

Since here use ubfx for arch timer version extraction (hyb-stub build
with -march=armv7-a, so it is safe)

To help backports (even though the code was correct at the time of writing)

Fixes: 8ec58be9f3ff ("ARM: virt: arch_timers: enable access to physical timers")
Acked-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/arm/kernel/hyp-stub.S | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/arm/kernel/hyp-stub.S b/arch/arm/kernel/hyp-stub.S
index 2a55373f49bfb..f9948363111d1 100644
--- a/arch/arm/kernel/hyp-stub.S
+++ b/arch/arm/kernel/hyp-stub.S
@@ -144,10 +144,9 @@ ARM_BE8(orr r7, r7, #(1 << 25)) @ HSCTLR.EE
#if !defined(ZIMAGE) && defined(CONFIG_ARM_ARCH_TIMER)
@ make CNTP_* and CNTPCT accessible from PL1
mrc p15, 0, r7, c0, c1, 1 @ ID_PFR1
- lsr r7, #16
- and r7, #0xf
- cmp r7, #1
- bne 1f
+ ubfx r7, r7, #16, #4
+ teq r7, #0
+ beq 1f
mrc p15, 4, r7, c14, c1, 0 @ CNTHCTL
orr r7, r7, #3 @ PL1PCEN | PL1PCTEN
mcr p15, 4, r7, c14, c1, 0 @ CNTHCTL
--
2.20.1