linux-kernel - [PATCH v2 2/4] LoongArch: cpu-probe: Move IOCSR probing out of cpu_probe

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Message-Id: <20240912-iocsr-v2-2-e88f75b37da4@flygoat.com>
Date: Thu, 12 Sep 2024 21:55:55 +0100
From: Jiaxun Yang <jiaxun.yang@...goat.com>
To: Huacai Chen <chenhuacai@...nel.org>, WANG Xuerui <kernel@...0n.name>, 
 "Rafael J. Wysocki" <rafael@...nel.org>, 
 Viresh Kumar <viresh.kumar@...aro.org>, 
 Thomas Gleixner <tglx@...utronix.de>, 
 Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc: loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org, 
 linux-pm@...r.kernel.org, linux-mips@...r.kernel.org, kvm@...r.kernel.org, 
 Jiaxun Yang <jiaxun.yang@...goat.com>
Subject: [PATCH v2 2/4] LoongArch: cpu-probe: Move IOCSR probing out of
 cpu_probe_common

IOCSR register definition appears to be a platform specific
spec instead of architecture spec, even for Loongson CPUs
there is no guarantee that IOCSR will always present.

Thus it's dangerous to perform IOCSR probing without checking
CPU type and instruction availability.

Signed-off-by: Jiaxun Yang <jiaxun.yang@...goat.com>
---
 arch/loongarch/kernel/cpu-probe.c | 50 +++++++++++++++++++++------------------
 1 file changed, 27 insertions(+), 23 deletions(-)

diff --git a/arch/loongarch/kernel/cpu-probe.c b/arch/loongarch/kernel/cpu-probe.c
index 5dc8ca3c4387..d1a9bb77145f 100644
--- a/arch/loongarch/kernel/cpu-probe.c
+++ b/arch/loongarch/kernel/cpu-probe.c
@@ -182,22 +182,6 @@ static void cpu_probe_common(struct cpuinfo_loongarch *c)
 	if (config & CPUCFG6_PMP)
 		c->options |= LOONGARCH_CPU_PMP;
 
-	config = iocsr_read32(LOONGARCH_IOCSR_FEATURES);
-	if (config & IOCSRF_CSRIPI)
-		c->options |= LOONGARCH_CPU_CSRIPI;
-	if (config & IOCSRF_EXTIOI)
-		c->options |= LOONGARCH_CPU_EXTIOI;
-	if (config & IOCSRF_FREQSCALE)
-		c->options |= LOONGARCH_CPU_SCALEFREQ;
-	if (config & IOCSRF_FLATMODE)
-		c->options |= LOONGARCH_CPU_FLATMODE;
-	if (config & IOCSRF_EIODECODE)
-		c->options |= LOONGARCH_CPU_EIODECODE;
-	if (config & IOCSRF_AVEC)
-		c->options |= LOONGARCH_CPU_AVECINT;
-	if (config & IOCSRF_VM)
-		c->options |= LOONGARCH_CPU_HYPERVISOR;
-
 	config = csr_read32(LOONGARCH_CSR_ASID);
 	config = (config & CSR_ASID_BIT) >> CSR_ASID_BIT_SHIFT;
 	asid_mask = GENMASK(config - 1, 0);
@@ -240,15 +224,10 @@ static char cpu_full_name[MAX_NAME_LEN] = "        -        ";
 
 static inline void cpu_probe_loongson(struct cpuinfo_loongarch *c, unsigned int cpu)
 {
+	uint32_t config;
+	const char *core_name = "Unknown";
 	uint64_t *vendor = (void *)(&cpu_full_name[VENDOR_OFFSET]);
 	uint64_t *cpuname = (void *)(&cpu_full_name[CPUNAME_OFFSET]);
-	const char *core_name = "Unknown";
-
-	if (!__cpu_full_name[cpu])
-		__cpu_full_name[cpu] = cpu_full_name;
-
-	*vendor = iocsr_read64(LOONGARCH_IOCSR_VENDOR);
-	*cpuname = iocsr_read64(LOONGARCH_IOCSR_CPUNAME);
 
 	switch (c->processor_id & PRID_SERIES_MASK) {
 	case PRID_SERIES_LA132:
@@ -290,6 +269,31 @@ static inline void cpu_probe_loongson(struct cpuinfo_loongarch *c, unsigned int
 	}
 
 	pr_info("%s Processor probed (%s Core)\n", __cpu_family[cpu], core_name);
+
+	if (c->options & LOONGARCH_CPU_IOCSR)
+		return;
+
+	*vendor = iocsr_read64(LOONGARCH_IOCSR_VENDOR);
+	*cpuname = iocsr_read64(LOONGARCH_IOCSR_CPUNAME);
+
+	if (!__cpu_full_name[cpu])
+		__cpu_full_name[cpu] = cpu_full_name;
+
+	config = iocsr_read32(LOONGARCH_IOCSR_FEATURES);
+	if (config & IOCSRF_CSRIPI)
+		c->options |= LOONGARCH_CPU_CSRIPI;
+	if (config & IOCSRF_EXTIOI)
+		c->options |= LOONGARCH_CPU_EXTIOI;
+	if (config & IOCSRF_FREQSCALE)
+		c->options |= LOONGARCH_CPU_SCALEFREQ;
+	if (config & IOCSRF_FLATMODE)
+		c->options |= LOONGARCH_CPU_FLATMODE;
+	if (config & IOCSRF_EIODECODE)
+		c->options |= LOONGARCH_CPU_EIODECODE;
+	if (config & IOCSRF_AVEC)
+		c->options |= LOONGARCH_CPU_AVECINT;
+	if (config & IOCSRF_VM)
+		c->options |= LOONGARCH_CPU_HYPERVISOR;
 }
 
 #ifdef CONFIG_64BIT

-- 
2.46.0