linux-kernel - Re: [PATCH v2 3/6] powerpc/pci: use pci_is

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Message-ID: <52579BD6.40802@huawei.com>
Date:	Fri, 11 Oct 2013 14:33:58 +0800
From:	Yijing Wang <wangyijing@...wei.com>
To:	Gavin Shan <shangw@...ux.vnet.ibm.com>
CC:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"James E.J. Bottomley" <JBottomley@...allels.com>,
	<linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>,
	Hanjun Guo <guohanjun@...wei.com>,
	Paul Mackerras <paulus@...ba.org>,
	<linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH v2 3/6] powerpc/pci: use pci_is_pcie() to simplify code

On 2013/10/11 14:16, Gavin Shan wrote:
> On Fri, Oct 11, 2013 at 04:49:56PM +1100, Benjamin Herrenschmidt wrote:
>> On Fri, 2013-09-06 at 14:30 -0600, Bjorn Helgaas wrote:
>>> On Thu, Sep 05, 2013 at 03:55:27PM +0800, Yijing Wang wrote:
>>>> Use pci_is_pcie() to simplify code.
>>>>
>>>> Acked-by: Kumar Gala <galak@...nel.crashing.org>
>>>> Reviewed-by: Gavin Shan <shangw@...ux.vnet.ibm.com>
>>>> Signed-off-by: Yijing Wang <wangyijing@...wei.com>
>>>> Cc: Gavin Shan <shangw@...ux.vnet.ibm.com>
>>>> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
>>>> Cc: Paul Mackerras <paulus@...ba.org>
>>>> Cc: linuxppc-dev@...ts.ozlabs.org
>>>> Cc: linux-kernel@...r.kernel.org
>>>> ---
>>>>  arch/powerpc/kernel/eeh.c     |    3 +--
>>>>  arch/powerpc/sysdev/fsl_pci.c |    2 +-
>>>>  2 files changed, 2 insertions(+), 3 deletions(-)
>>>
>>> Ben, Paul, this has no dependencies on anything new to PCI or any
>>> other patches in this series, so you can take it through the POWERPC
>>> tree.  If you don't want to do that, let me know and I can take it.
>>>
>>> If you want it:
>>>
>>> Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
>>
>> It's also quite broken :-)
>>
>> See below:
>>
>>>> diff --git a/arch/powerpc/kernel/eeh.c b/arch/powerpc/kernel/eeh.c
>>>> index 55593ee..6ebbe54 100644
>>>> --- a/arch/powerpc/kernel/eeh.c
>>>> +++ b/arch/powerpc/kernel/eeh.c
>>>> @@ -189,8 +189,7 @@ static size_t eeh_gather_pci_data(struct eeh_dev *edev, char * buf, size_t len)
>>>>  	}
>>>>  
>>>>  	/* If PCI-E capable, dump PCI-E cap 10, and the AER */
>>>> -	cap = pci_find_capability(dev, PCI_CAP_ID_EXP);
>>>> -	if (cap) {
>>>> +	if (pci_is_pcie(dev)) {
>>>>  		n += scnprintf(buf+n, len-n, "pci-e cap10:\n");
>>>>  		printk(KERN_WARNING
>>>>  		       "EEH: PCI-E capabilities and status follow:\n");
>>
>> So we remove reading of "cap", but slightly further down the code does:
>>
>> 		for (i=0; i<=8; i++) {
>> 			eeh_ops->read_config(dn, cap+4*i, 4, &cfg);
>> 			n += scnprintf(buf+n, len-n, "%02x:%x\n", 4*i, cfg);
>> 			printk(KERN_WARNING "EEH: PCI-E %02x: %08x\n", i, cfg);
>> 		}
>>
>> Which actually *uses* the value of "cap" ... oops :-)
>>
> 
> It's my fault and I should have looked into the changes more closely.
> How about changing it like this:
> 
> 	cap = pci_is_pcie(dev) ? pci_pcie_cap(dev) :
> 	      pci_find_capability(dev, PCI_CAP_ID_EXP);
> 	if (cap) {
> 		...
> 	}
> 
> It would save some PCI-CFG access cycles for most cases :-)

Hi Gavin,  it's not your fault, it's my fault. :)

Because pci_pcie_cap(dev) == dev->pcie_cap == pci_find_capability(dev, PCI_CAP_ID_EXP);

so I think it's ok to use dev->pcie_cap instead of stale "cap".

I have updated this patch.

Thanks for your review and comments!

Thanks!
Yijing.


> 
>>>> diff --git a/arch/powerpc/sysdev/fsl_pci.c b/arch/powerpc/sysdev/fsl_pci.c
>>>> index 46ac1dd..5402a1d 100644
>>>> --- a/arch/powerpc/sysdev/fsl_pci.c
>>>> +++ b/arch/powerpc/sysdev/fsl_pci.c
>>>> @@ -41,7 +41,7 @@ static void quirk_fsl_pcie_header(struct pci_dev *dev)
>>>>  	u8 hdr_type;
>>>>  
>>>>  	/* if we aren't a PCIe don't bother */
>>>> -	if (!pci_find_capability(dev, PCI_CAP_ID_EXP))
>>>> +	if (!pci_is_pcie(dev))
>>>>  		return;
>>>>  
>>>>  	/* if we aren't in host mode don't bother */
> 
> Thanks,
> Gavin
> 
> 
> .
> 


-- 
Thanks!
Yijing

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