linux-kernel - Re: [PATCH 4/7] x86/pci: use pcie

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Message-ID: <522825E3.9050806@huawei.com>
Date:	Thu, 5 Sep 2013 14:34:11 +0800
From:	Yijing Wang <wangyijing@...wei.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
CC:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Gavin Shan <shangw@...ux.vnet.ibm.com>,
	"James E.J. Bottomley" <JBottomley@...allels.com>,
	"David S. Miller" <davem@...emloft.net>,
	<linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>,
	Hanjun Guo <guohanjun@...wei.com>
Subject: Re: [PATCH 4/7] x86/pci: use pcie_cap to simplify code

On 2013/9/4 10:59, Bjorn Helgaas wrote:
> On Tue, Sep 03, 2013 at 03:35:12PM +0800, Yijing Wang wrote:
>> PCI core saves PCIe Cap offset in pcie_cap,
>> use pcie_cap to simplify code.
>>
>> Signed-off-by: Yijing Wang <wangyijing@...wei.com>
>> ---
>>  arch/x86/pci/fixup.c |    2 +-
>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/arch/x86/pci/fixup.c b/arch/x86/pci/fixup.c
>> index f5809fa..ee8330d 100644
>> --- a/arch/x86/pci/fixup.c
>> +++ b/arch/x86/pci/fixup.c
>> @@ -288,7 +288,7 @@ static void pcie_rootport_aspm_quirk(struct pci_dev *pdev)
>>  		 */
>>  		list_for_each_entry(dev, &pbus->devices, bus_list) {
>>  			/* There are 0 to 8 devices attached to this bus */
>> -			cap_base = pci_find_capability(dev, PCI_CAP_ID_EXP);
>> +			cap_base = dev->pcie_cap;
>>  			quirk_aspm_offset[GET_INDEX(pdev->device, dev->devfn)] = cap_base + 0x10;
> 
> This should use PCI_EXP_LNKCTL instead of "0x10".
> 
>>  		}
>>  		pbus->ops = &quirk_pcie_aspm_ops;

Hi Bjorn,
   Thanks for your review and comments!

> 
> This quirk replaces the config accessors with ones that silently ignore
> writes to ASPM control bits.  That really warrants at least a dev_info()
> note here, and we should be using pci_bus_set_ops().

Good idea, I will update it, thanks!

> 
> Even that is a little bit dubious because I don't think this is really
> safe -- what happens if this quirk replaces the ops, then somebody
> else replaces the ops again?  aer_inject.c at least keeps track of
> the old ops and seems to fall back to them, but it seems fragile to
> depend on every caller of pci_bus_set_ops() to do the right thing
> there.
> 
> But this is beyond the scope of your patch, so if you just
> add a dev_info() note and use pci_bus_set_ops(), that should be
> enough for now.
> 
> 


-- 
Thanks!
Yijing

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