linux-kernel - [PATCH V2] clocksource: riscv: Patch riscv_clock_next

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Message-Id: <CDDAB2D0-264E-42F3-8E31-BA210BEB8EC1@rivosinc.com>
Date:   Wed, 1 Feb 2023 19:49:42 +0000
From:   Matt Evans <mev@...osinc.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Atish Patra <atishp@...osinc.com>,
        Palmer Dabbelt <palmer@...belt.com>
Subject: [PATCH V2] clocksource: riscv: Patch riscv_clock_next_event() jump
 before first use

A static key is used to select between SBI and Sstc timer usage in
riscv_clock_next_event(), but currently the direction is resolved
after cpuhp_setup_state() is called (which sets the next event).  The
first event will therefore fall through the sbi_set_timer() path; this
breaks Sstc-only systems.  So, apply the jump patching before first
use.

Fixes: 9f7a8ff6391f ("RISC-V: Prefer sstc extension if available")
Signed-off-by: Matt Evans <mev@...osinc.com>
---

V1 -> V2: Commit msg tweak.

 drivers/clocksource/timer-riscv.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
index 969a552da8d2..a36d173fd6cd 100644
--- a/drivers/clocksource/timer-riscv.c
+++ b/drivers/clocksource/timer-riscv.c
@@ -177,6 +177,11 @@ static int __init riscv_timer_init_dt(struct device_node *n)
 		return error;
 	}
 
+	if (riscv_isa_extension_available(NULL, SSTC)) {
+		pr_info("Timer interrupt in S-mode is available via sstc extension\n");
+		static_branch_enable(&riscv_sstc_available);
+	}
+
 	error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING,
 			 "clockevents/riscv/timer:starting",
 			 riscv_timer_starting_cpu, riscv_timer_dying_cpu);
@@ -184,11 +189,6 @@ static int __init riscv_timer_init_dt(struct device_node *n)
 		pr_err("cpu hp setup state failed for RISCV timer [%d]\n",
 		       error);
 
-	if (riscv_isa_extension_available(NULL, SSTC)) {
-		pr_info("Timer interrupt in S-mode is available via sstc extension\n");
-		static_branch_enable(&riscv_sstc_available);
-	}
-
 	return error;
 }
 
-- 
2.30.2