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

[David Daney <ddaney@caviumnetworks.com>]

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