linux-kernel - [PATCH] mips: smp-bmips: fix CPU mappings

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Message-Id: <20210223124817.26486-1-noltari@gmail.com>
Date:   Tue, 23 Feb 2021 13:48:17 +0100
From:   Álvaro Fernández Rojas 
        <noltari@...il.com>
To:     jonas.gorski@...il.com, Florian Fainelli <f.fainelli@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        bcm-kernel-feedback-list@...adcom.com, linux-mips@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Álvaro Fernández Rojas 
        <noltari@...il.com>
Subject: [PATCH] mips: smp-bmips: fix CPU mappings

When booting bmips with SMP enabled on a BCM6358 running on CPU #1 instead of
CPU #0, the current CPU mapping code produces the following:
- smp_processor_id(): 0
- cpu_logical_map(): 1
- cpu_number_map(): 1

This is because SMP isn't supported on BCM6358 since it has a shared TLB, so
it is disabled and max_cpus is decreased from 2 to 1.

Signed-off-by: Álvaro Fernández Rojas <noltari@...il.com>
---
 arch/mips/kernel/smp-bmips.c | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/arch/mips/kernel/smp-bmips.c b/arch/mips/kernel/smp-bmips.c
index 359b176b665f..c4760cb48a67 100644
--- a/arch/mips/kernel/smp-bmips.c
+++ b/arch/mips/kernel/smp-bmips.c
@@ -134,17 +134,24 @@ static void __init bmips_smp_setup(void)
 	if (!board_ebase_setup)
 		board_ebase_setup = &bmips_ebase_setup;
 
-	__cpu_number_map[boot_cpu] = 0;
-	__cpu_logical_map[0] = boot_cpu;
-
-	for (i = 0; i < max_cpus; i++) {
-		if (i != boot_cpu) {
-			__cpu_number_map[i] = cpu;
-			__cpu_logical_map[cpu] = i;
-			cpu++;
+	if (max_cpus > 1) {
+		__cpu_number_map[boot_cpu] = 0;
+		__cpu_logical_map[0] = boot_cpu;
+
+		for (i = 0; i < max_cpus; i++) {
+			if (i != boot_cpu) {
+				__cpu_number_map[i] = cpu;
+				__cpu_logical_map[cpu] = i;
+				cpu++;
+			}
+			set_cpu_possible(i, 1);
+			set_cpu_present(i, 1);
 		}
-		set_cpu_possible(i, 1);
-		set_cpu_present(i, 1);
+	} else {
+		__cpu_number_map[0] = boot_cpu;
+		__cpu_logical_map[0] = 0;
+		set_cpu_possible(0, 1);
+		set_cpu_possible(0, 1);
 	}
 }
 
-- 
2.20.1