linux-kernel - [PATCH] RFC: arm64: arch_timer: Fix timer inconsistency test for A64

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Message-Id: <20200929111347.1967438-1-r.stratiienko@gmail.com>
Date:   Tue, 29 Sep 2020 14:13:47 +0300
From:   Roman Stratiienko <r.stratiienko@...il.com>
To:     linux-sunxi@...glegroups.com
Cc:     Roman Stratiienko <r.stratiienko@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        megous@...ous.com
Subject: [PATCH] RFC: arm64: arch_timer: Fix timer inconsistency test for A64

Fixes linux_kselftest:timers_inconsistency-check_arm_64

Test logs without the fix:
'''
binary returned non-zero. Exit code: 1, stderr: , stdout:
Consistent CLOCK_REALTIME
1601335525:467086804
1601335525:467087554
1601335525:467088345
1601335525:467089095
1601335525:467089887
1601335525:467090637
1601335525:467091429
1601335525:467092179
1601335525:467092929
1601335525:467093720
1601335525:467094470
1601335525:467095262
1601335525:467096012
1601335525:467096804
--------------------
1601335525:467097554
1601335525:467077012
--------------------
1601335525:467099095
1601335525:467099845
1601335525:467100637
1601335525:467101387
1601335525:467102179
1601335525:467102929
'''

Signed-off-by: Roman Stratiienko <r.stratiienko@...il.com>
CC: linux-arm-kernel@...ts.infradead.org
CC: linux-kernel@...r.kernel.org
CC: linux-sunxi@...glegroups.com
CC: megous@...ous.com
---
 drivers/clocksource/arm_arch_timer.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 6c3e841801461..d50aa43cb654b 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -346,16 +346,17 @@ static u64 notrace arm64_858921_read_cntvct_el0(void)
  * number of CPU cycles in 3 consecutive 24 MHz counter periods.
  */
 #define __sun50i_a64_read_reg(reg) ({					\
-	u64 _val;							\
+	u64 _val1, _val2;						\
 	int _retries = 150;						\
 									\
 	do {								\
-		_val = read_sysreg(reg);				\
+		_val1 = read_sysreg(reg);				\
+		_val2 = read_sysreg(reg);				\
 		_retries--;						\
-	} while (((_val + 1) & GENMASK(9, 0)) <= 1 && _retries);	\
+	} while (((_val2 - _val1) > 0x10) && _retries);			\
 									\
 	WARN_ON_ONCE(!_retries);					\
-	_val;								\
+	_val2;								\
 })
 
 static u64 notrace sun50i_a64_read_cntpct_el0(void)
-- 
2.25.1