linux-kernel - [PATCH] MIPS: Loongson64: Set timer mode in cpu-probe

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Message-Id: <20240723-loongson-exttimer-v1-1-974bef8c2f88@flygoat.com>
Date: Tue, 23 Jul 2024 17:15:44 +0800
From: Jiaxun Yang <jiaxun.yang@...goat.com>
To: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc: linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org, 
 stable@...r.kernel.org, Jiaxun Yang <jiaxun.yang@...goat.com>
Subject: [PATCH] MIPS: Loongson64: Set timer mode in cpu-probe

Loongson64 C and G processors have EXTIMER feature which
is conflicting with CP0 counter.

Although the processor resets in EXTIMER disabled & INTIMER
enabled mode, which is compatible with MIPS CP0 compare, firmware
may attempt to enable EXTIMER and interfere CP0 compare.

Set timer mode back to MIPS compatible mode to fix booting on
systems with such firmware before we have an actual driver for
EXTIMER.

Cc: stable@...r.kernel.org
Signed-off-by: Jiaxun Yang <jiaxun.yang@...goat.com>
---
Please take this patch via fixes (or second 6.11 PR) tree so it can
reach stable faster.

Thansks!
---
 arch/mips/kernel/cpu-probe.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index bda7f193baab..af7412549e6e 100644
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -1724,12 +1724,16 @@ static inline void cpu_probe_loongson(struct cpuinfo_mips *c, unsigned int cpu)
 		c->ases |= (MIPS_ASE_LOONGSON_MMI | MIPS_ASE_LOONGSON_CAM |
 			MIPS_ASE_LOONGSON_EXT | MIPS_ASE_LOONGSON_EXT2);
 		c->ases &= ~MIPS_ASE_VZ; /* VZ of Loongson-3A2000/3000 is incomplete */
+		change_c0_config6(LOONGSON_CONF6_EXTIMER | LOONGSON_CONF6_INTIMER,
+				  LOONGSON_CONF6_INTIMER);
 		break;
 	case PRID_IMP_LOONGSON_64G:
 		__cpu_name[cpu] = "ICT Loongson-3";
 		set_elf_platform(cpu, "loongson3a");
 		set_isa(c, MIPS_CPU_ISA_M64R2);
 		decode_cpucfg(c);
+		change_c0_config6(LOONGSON_CONF6_EXTIMER | LOONGSON_CONF6_INTIMER,
+				  LOONGSON_CONF6_INTIMER);
 		break;
 	default:
 		panic("Unknown Loongson Processor ID!");

---
base-commit: dee7f101b64219f512bb2f842227bd04c14efe30
change-id: 20240723-loongson-exttimer-14b48e7ad5d6

Best regards,
-- 
Jiaxun Yang <jiaxun.yang@...goat.com>