Loongson-make-_rdmsr-_wrmsr-be-atomic.patch

From a6310a884cd9bb469c6267554c3913ad8300b55c Mon Sep 17 00:00:00 2001
From: Wu Zhangjin <wuzhangjin@gmail.com>
Date: Wed, 10 Mar 2010 21:52:07 +0800
Subject: [PATCH] Loongson: make _rdmsr, _wrmsr be atomic

commit a6310a884cd9bb469c6267554c3913ad8300b55c in tip.

The _rdmsr, _wrdmsr operation must be atomic to ensure accessing the
right msr address we want.

Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>

diff --git a/arch/mips/pci/ops-loongson2.c b/arch/mips/pci/ops-loongson2.c
index aa5d3da..98aa2f3 100644
--- a/arch/mips/pci/ops-loongson2.c
+++ b/arch/mips/pci/ops-loongson2.c
@@ -182,15 +182,22 @@ struct pci_ops loongson_pci_ops = {
 };
 
 #ifdef CONFIG_CS5536
+
+DEFINE_RAW_SPINLOCK(msr_lock);
+
 void _rdmsr(u32 msr, u32 *hi, u32 *lo)
 {
 	struct pci_bus bus = {
 		.number = PCI_BUS_CS5536
 	};
 	u32 devfn = PCI_DEVFN(PCI_IDSEL_CS5536, 0);
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&msr_lock, flags);
 	loongson_pcibios_write(&bus, devfn, PCI_MSR_ADDR, 4, msr);
 	loongson_pcibios_read(&bus, devfn, PCI_MSR_DATA_LO, 4, lo);
 	loongson_pcibios_read(&bus, devfn, PCI_MSR_DATA_HI, 4, hi);
+	raw_spin_unlock_irqrestore(&msr_lock, flags);
 }
 EXPORT_SYMBOL(_rdmsr);
 
@@ -200,9 +207,13 @@ void _wrmsr(u32 msr, u32 hi, u32 lo)
 		.number = PCI_BUS_CS5536
 	};
 	u32 devfn = PCI_DEVFN(PCI_IDSEL_CS5536, 0);
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&msr_lock, flags);
 	loongson_pcibios_write(&bus, devfn, PCI_MSR_ADDR, 4, msr);
 	loongson_pcibios_write(&bus, devfn, PCI_MSR_DATA_LO, 4, lo);
 	loongson_pcibios_write(&bus, devfn, PCI_MSR_DATA_HI, 4, hi);
+	raw_spin_unlock_irqrestore(&msr_lock, flags);
 }
 EXPORT_SYMBOL(_wrmsr);
 #endif
-- 
1.7.1.1