[tip: timers/core] clocksource/drivers/riscv: Increase the clock source rating

[tip-bot2 for Samuel Holland]

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

Commit-ID:     674402b0098b66b8ba91fe93c0d27af703256098
Gitweb:        https://git.kernel.org/tip/674402b0098b66b8ba91fe93c0d27af703256098
Author:        Samuel Holland <samuel@xxxxxxxxxxxx>
AuthorDate:    Tue, 27 Dec 2022 18:44:44 -06:00
Committer:     Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
CommitterDate: Mon, 13 Feb 2023 13:10:16 +01:00

clocksource/drivers/riscv: Increase the clock source rating

RISC-V provides an architectural clock source via the time CSR. This
clock source exposes a 64-bit counter synchronized across all CPUs.
Because it is accessed using a CSR, it is much more efficient to read
than MMIO clock sources. For example, on the Allwinner D1, reading the
sun4i timer in a loop takes 131 cycles/iteration, while reading the
RISC-V time CSR takes only 5 cycles/iteration.

Adjust the RISC-V clock source rating so it is preferred over the
various platform-specific MMIO clock sources.

Signed-off-by: Samuel Holland <samuel@xxxxxxxxxxxx>
Acked-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
Reviewed-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
Reviewed-by: Anup Patel <anup@xxxxxxxxxxxxxx>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20221228004444.61568-1-samuel@xxxxxxxxxxxx
Signed-off-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
---
 drivers/clocksource/timer-riscv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
index 1b4b36d..adf7f98 100644
--- a/drivers/clocksource/timer-riscv.c
+++ b/drivers/clocksource/timer-riscv.c
@@ -74,7 +74,7 @@ static u64 notrace riscv_sched_clock(void)
 
 static struct clocksource riscv_clocksource = {
 	.name		= "riscv_clocksource",
-	.rating		= 300,
+	.rating		= 400,
 	.mask		= CLOCKSOURCE_MASK(64),
 	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
 	.read		= riscv_clocksource_rdtime,