From: Jason A. Donenfeld <Jason@xxxxxxxxx>
[ 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@xxxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Jonas Bonn <jonas@xxxxxxxxxxxx>
Cc: Stefan Kristiansson <stefan.kristiansson@xxxxxxxxxxxxx>
Acked-by: Stafford Horne <shorne@xxxxxxxxx>
Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
arch/openrisc/include/asm/timex.h | 1 +
arch/openrisc/kernel/head.S | 9 +++++++++
2 files changed, 10 insertions(+)
diff --git a/arch/openrisc/include/asm/timex.h b/arch/openrisc/include/asm/timex.h
index 9935cad1b9b9..34d015bf0462 100644
--- a/arch/openrisc/include/asm/timex.h
+++ b/arch/openrisc/include/asm/timex.h
@@ -27,6 +27,7 @@ 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
diff --git a/arch/openrisc/kernel/head.S b/arch/openrisc/kernel/head.S
index 31ed257ff061..d7e49b947164 100644
--- a/arch/openrisc/kernel/head.S
+++ b/arch/openrisc/kernel/head.S
@@ -525,6 +525,15 @@ _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)
--
2.35.1
