linux-kernel - [PATCH 6/7] clocksource: mips-gic-timer: Refine rating computation

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Date: Sat, 11 May 2024 17:00:13 +0100
From: Jiaxun Yang <jiaxun.yang@...goat.com>
To: Thomas Bogendoerfer <tsbogend@...ha.franken.de>, 
 Serge Semin <fancer.lancer@...il.com>, 
 Daniel Lezcano <daniel.lezcano@...aro.org>, 
 Thomas Gleixner <tglx@...utronix.de>
Cc: linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Jiaxun Yang <jiaxun.yang@...goat.com>
Subject: [PATCH 6/7] clocksource: mips-gic-timer: Refine rating computation

It is a good clocksource which usually go as fast as CPU core
and have a low access latency, so raise the base of rating
from Good to desired when we know that it has a stable frequency.

Increase frequency addend dividend to 100000000 (10MHz) to
reasonably accommodate multi GHz level clock, also cap rating
within current level.

Signed-off-by: Jiaxun Yang <jiaxun.yang@...goat.com>
---
 drivers/clocksource/mips-gic-timer.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/clocksource/mips-gic-timer.c b/drivers/clocksource/mips-gic-timer.c
index b3ae38f36720..67498dc9c5a5 100644
--- a/drivers/clocksource/mips-gic-timer.c
+++ b/drivers/clocksource/mips-gic-timer.c
@@ -197,7 +197,11 @@ static int __init __gic_clocksource_init(void)
 	gic_clocksource.mask = CLOCKSOURCE_MASK(count_width);
 
 	/* Calculate a somewhat reasonable rating value. */
-	gic_clocksource.rating = 200 + gic_frequency / 10000000;
+	if (mips_cm_revision() >= CM_REV_CM3 || !IS_ENABLED(CONFIG_CPU_FREQ))
+		gic_clocksource.rating = 300; /* Good when frequecy is stable */
+	else
+		gic_clocksource.rating = 200;
+	gic_clocksource.rating += clamp(gic_frequency / 100000000, 0, 99);
 
 	ret = clocksource_register_hz(&gic_clocksource, gic_frequency);
 	if (ret < 0)

-- 
2.34.1