[tip: timers/urgent] clocksource/drivers/arm_arch_timer: Force inlining of erratum_set_next_event_generic()

[tip-bot2 for Marc Zyngier]

The following commit has been merged into the timers/urgent branch of tip:

Commit-ID:     1edb7e74a7d3d64dc4e69e7059b4eea526d19a10
Gitweb:        https://git.kernel.org/tip/1edb7e74a7d3d64dc4e69e7059b4eea526d19a10
Author:        Marc Zyngier <maz@xxxxxxxxxx>
AuthorDate:    Wed, 17 Nov 2021 11:35:32 
Committer:     Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
CommitterDate: Fri, 10 Dec 2021 17:47:00 +01:00

clocksource/drivers/arm_arch_timer: Force inlining of erratum_set_next_event_generic()

With some specific kernel configuration and Clang, the kernel fails
to like with something like:

ld.lld: error: undefined symbol: __compiletime_assert_200
>>> referenced by arch_timer.h:156 (./arch/arm64/include/asm/arch_timer.h:156)
>>>               clocksource/arm_arch_timer.o:(erratum_set_next_event_generic) in archive drivers/built-in.a

ld.lld: error: undefined symbol: __compiletime_assert_197
>>> referenced by arch_timer.h:133 (./arch/arm64/include/asm/arch_timer.h:133)
>>>               clocksource/arm_arch_timer.o:(erratum_set_next_event_generic) in archive drivers/built-in.a
make: *** [Makefile:1161: vmlinux] Error 1

These are due to the BUILD_BUG() macros contained in the low-level
accessors (arch_timer_reg_{write,read}_cp15) being emitted, as the
access type wasn't known at compile time.

Fix this by making erratum_set_next_event_generic() __force_inline,
resulting in the 'access' parameter to be resolved at compile time,
similarly to what is already done for set_next_event().

Fixes: 4775bc63f880 ("Add build-time guards for unhandled register accesses")
Reported-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
Cc: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Tested-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Tested-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20211117113532.3895208-1-maz@xxxxxxxxxx
Signed-off-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
---
 drivers/clocksource/arm_arch_timer.c |  9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 9a04eac..1ecd52f 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -394,8 +394,13 @@ EXPORT_SYMBOL_GPL(timer_unstable_counter_workaround);
 
 static atomic_t timer_unstable_counter_workaround_in_use = ATOMIC_INIT(0);
 
-static void erratum_set_next_event_generic(const int access, unsigned long evt,
-						struct clock_event_device *clk)
+/*
+ * Force the inlining of this function so that the register accesses
+ * can be themselves correctly inlined.
+ */
+static __always_inline
+void erratum_set_next_event_generic(const int access, unsigned long evt,
+				    struct clock_event_device *clk)
 {
 	unsigned long ctrl;
 	u64 cval;