ARM: i.MX7: Make sure CNTFRQ is initialized early enough

We need to make sure that CNTFRQ is initialized before corresponding
clocksource driver tries to use it, otherwise we'll end up crashing
due to division by zero.

We can't convert imx7_timer_init() to be an initcall since it is an
i.MX7 specific task, but CPU type information won't be availible until
after imx_init() gets executed at postcore_initcall() level. To solve
this move all of the necessary code to be a part of
imx7_cpu_lowlevel_init().

Note, that original code both hardcoded frequency value to 8MHz as
well as tried to write it to the first element of the frequency mode
table which appears to be read-only on i.MX7. So while we are at it,
simplify the code by adding set_cntfrq() implementation for ARMv7 and
copy the code we already using for i.MX8MQ.

Fixes: dece70752 ("clocksource: Enable architected timer support for CPU_V7")
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 5 insertions, 0 deletions

diff --git a/arch/arm/include/asm/system.h b/arch/arm/include/asm/system.h
index e55b19a13c..ef9cb98bf0 100644
--- a/arch/arm/include/asm/system.h
+++ b/arch/arm/include/asm/system.h
@@ -127,6 +127,11 @@ static inline unsigned long get_cntpct(void)
 	return cntpct;
 }
 #else
+static inline void set_cntfrq(unsigned long cntfrq)
+{
+	asm("mcr p15, 0, %0, c14, c0, 0" : : "r" (cntfrq));
+}
+
 static inline unsigned int get_cntfrq(void)
 {
 	unsigned int val;