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Re: [PATCH] Loongson: Lemote-2F: Fixup of _rdmsr and _wrmsr

To: Wu Zhangjin <wuzhangjin@gmail.com>, Ralf Baechle <ralf@linux-mips.org>
Subject: Re: [PATCH] Loongson: Lemote-2F: Fixup of _rdmsr and _wrmsr
From: David Daney <ddaney@caviumnetworks.com>
Date: Wed, 10 Mar 2010 16:17:35 -0800
Cc: linux-mips@linux-mips.org
In-reply-to: <7c2dec50764082fafa83895b740f644fc592afa4.1268235182.git.wuzhangjin@gmail.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <7c2dec50764082fafa83895b740f644fc592afa4.1268235182.git.wuzhangjin@gmail.com>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.8) Gecko/20100301 Fedora/3.0.3-1.fc12 Thunderbird/3.0.3
On 03/10/2010 07:41 AM, Wu Zhangjin wrote:
From: Wu Zhangjin<wuzhangjin@gmail.com>

The _rdmsr, _wrmsr operation must be atomic to ensure the accessing to msr
address is what we want.

Without this patch, in some cases, the reboot operation(fs2f_reboot) defined in
arch/mips/loongson/lemote-2f/reset.c may fail for it called _rdmsr, _wrmsr but
may be interrupted/preempted by the other related operations and make the
_rdmsr get the wrong value or make the _wrmsr write a wrong value to an
unexpected target.

Signed-off-by: Wu Zhangjin<wuzhangjin@gmail.com>
---
  arch/mips/pci/ops-loongson2.c |    9 +++++++++
  1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/arch/mips/pci/ops-loongson2.c b/arch/mips/pci/ops-loongson2.c
index 2bb4057..1f93dfb 100644
--- a/arch/mips/pci/ops-loongson2.c
+++ b/arch/mips/pci/ops-loongson2.c
@@ -180,15 +180,20 @@ struct pci_ops loongson_pci_ops = {
  };

  #ifdef CONFIG_CS5536
+DEFINE_SPINLOCK(msr_lock);


Should this be DEFINE_RAW_SPINLOCK instead?

David Daney


  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;
+
+       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);
+       spin_unlock_irqrestore(&msr_lock, flags);
  }
  EXPORT_SYMBOL(_rdmsr);

@@ -198,9 +203,13 @@ void _wrmsr(u32 msr, u32 hi, u32 lo)
                .number = PCI_BUS_CS5536
        };
        u32 devfn = PCI_DEVFN(PCI_IDSEL_CS5536, 0);
+       unsigned long flags;
+
+       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);
+       spin_unlock_irqrestore(&msr_lock, flags);
  }
  EXPORT_SYMBOL(_wrmsr);
  #endif


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