linux-kernel - Re: [PATCH 1/1] ia64/pci: set mmio decoding on for some host bridge

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Date:	Tue, 09 Jul 2013 13:43:46 +0800
From:	ZhenHua <zhen-hual@...com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
CC:	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Li, Zhen-Hua" <zhen-hual@...com>
Subject: Re: [PATCH 1/1] ia64/pci: set mmio decoding on for some host bridge

Hi Bjorn,
Thank you for reviewing this patch. I have created a new one and sent it 
out.
And your questions are answered in that new wmail.

Regards
ZhenHua

On 07/09/2013 04:35 AM, Bjorn Helgaas wrote:
> On Sun, Jul 7, 2013 at 6:16 PM, Li, Zhen-Hua <zhen-hual@...com> wrote:
>> On some IA64 platforms with intel PCI bridge, for example, HP BL890c i2
>> with  Intel Corporation 5520/5500/X58 I/O Hub PCI Express Root Port,
>> when kernel tries to disable the mmio decoding on the PCI bridge devices,
>> kernel may crash.
>>
>> And in the comment of function quirk_mmio_always_on, it also says:
>> "But doing so (disable the mmio decoding) may cause problems on host bridge
>>   and perhaps other key system devices"
>>
>> So, for these PCI bridges,  dev->mmio_always_on bit should be set to 1.
>>
>>
>> Signed-off-by: Li, Zhen-Hua <zhen-hual@...com>
>> ---
>>   drivers/pci/quirks.c |   15 +++++++++++++++
>>   1 file changed, 15 insertions(+)
>>
>> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
>> index e85d230..24b8024 100644
>> --- a/drivers/pci/quirks.c
>> +++ b/drivers/pci/quirks.c
>> @@ -44,6 +44,21 @@ static void quirk_mmio_always_on(struct pci_dev *dev)
>>   DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_ANY_ID, PCI_ANY_ID,
>>                                  PCI_CLASS_BRIDGE_HOST, 8, quirk_mmio_always_on);
>>
>> +#ifdef CONFIG_IA64
>> +/*
>> + * On some IA64 platforms, for some intel PCI bridge devices, for example,
>> + * the Intel Corporation 5520/5500/X58 I/O Hub PCI Express Root Port,
>> + * disable the mmio decoding on these devices may cause system crash.
>> + * So dev->mmio_always_on bit should be set to 1.
>> + */
>> +static void quirk_mmio_on_intel_pcibridge(struct pci_dev *dev)
>> +{
>> +       dev->mmio_always_on = 1;
>> +}
>> +DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_ANY_ID, PCI_ANY_ID,
>> +                       PCI_CLASS_BRIDGE_PCI, 8, quirk_mmio_on_intel_pcibridge);
>> +#endif
> The changelog and comment suggest an issue specific to Intel
> 5520/5500/X58, but the patch sets mmio_always_on for *all* PCI
> bridges.
>
> It claims to be specific to ia64 (and is only compiled there), but the
> chipset is also used for x86.  You need to explain why the problem
> only affects ia64.
>
> Bjorn

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