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openrisc: start CPU timer early in boot

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[ Upstream commit 516dd4aacd67a0f27da94f3fe63fe0f4dbab6e2b ]

In order to measure the boot process, the timer should be switched on as
early in boot as possible. As well, the commit defines the get_cycles
macro, like the previous patches in this series, so that generic code is
aware that it's implemented by the platform, as is done on other archs.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Acked-by: Stafford Horne <shorne@gmail.com>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Jason A. Donenfeld 2022-04-23 21:11:41 +02:00 committed by Greg Kroah-Hartman
parent 22cdbb1354
commit 8671aeeef2
2 changed files with 10 additions and 0 deletions
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1
arch/openrisc/include/asm/timex.h
View File

@ -23,6 +23,7 @@ static inline cycles_t get_cycles(void)
{
return mfspr(SPR_TTCR);
}
#define get_cycles get_cycles
/* This isn't really used any more */
#define CLOCK_TICK_RATE 1000

9
arch/openrisc/kernel/head.S
View File

@ -521,6 +521,15 @@ _start:
l.ori r3,r0,0x1
l.mtspr r0,r3,SPR_SR
/*
* Start the TTCR as early as possible, so that the RNG can make use of
* measurements of boot time from the earliest opportunity. Especially
* important is that the TTCR does not return zero by the time we reach
* rand_initialize().
*/
l.movhi r3,hi(SPR_TTMR_CR)
l.mtspr r0,r3,SPR_TTMR
CLEAR_GPR(r1)
CLEAR_GPR(r2)
CLEAR_GPR(r3)