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")
Signed-off-by: Vladimir Murzin <vladimir.murzin@xxxxxxx>
---
Changelog:
v1 -> v2
- Clarify that backward compatibility is preserved (per Marc)
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 ae50203..6607fa8 100644
--- a/arch/arm/kernel/hyp-stub.S
+++ b/arch/arm/kernel/hyp-stub.S
@@ -146,10 +146,9 @@ 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
--
2.7.4
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