linux-kernel - Re: [PATCH -next] tile/PCI: use for_each_pci

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Message-ID: <CAErSpo4_mUBk+UXHUsRPzqUWENxgUqp27rf5QhFtgOFv-2AacQ@mail.gmail.com>
Date:	Tue, 4 Dec 2012 13:57:46 -0700
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Chris Metcalf <cmetcalf@...era.com>
Cc:	Wei Yongjun <weiyj.lk@...il.com>, yongjun_wei@...ndmicro.com.cn,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH -next] tile/PCI: use for_each_pci_dev to simplify the code

On Tue, Dec 4, 2012 at 1:05 PM, Chris Metcalf <cmetcalf@...era.com> wrote:
> On 12/4/2012 2:57 PM, Bjorn Helgaas wrote:
>> On Mon, Dec 3, 2012 at 6:28 AM, Wei Yongjun <weiyj.lk@...il.com> wrote:
>>> From: Wei Yongjun <yongjun_wei@...ndmicro.com.cn>
>>>
>>> Use for_each_pci_dev to simplify the code.
>>>
>>> Signed-off-by: Wei Yongjun <yongjun_wei@...ndmicro.com.cn>
>>> ---
>>>  arch/tile/kernel/pci.c | 4 ++--
>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/arch/tile/kernel/pci.c b/arch/tile/kernel/pci.c
>>> index 7598226..aac1cd5 100644
>>> --- a/arch/tile/kernel/pci.c
>>> +++ b/arch/tile/kernel/pci.c
>>> @@ -245,7 +245,7 @@ static void __devinit fixup_read_and_payload_sizes(void)
>>>         u16 new_values;
>>>
>>>         /* Scan for the smallest maximum payload size. */
>>> -       while ((dev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, dev)) != NULL) {
>>> +       for_each_pci_dev(dev) {
>>>                 u32 devcap;
>>>                 int max_payload;
>>>
>>> @@ -260,7 +260,7 @@ static void __devinit fixup_read_and_payload_sizes(void)
>>>
>>>         /* Now, set the max_payload_size for all devices to that value. */
>>>         new_values = (max_read_size << 12) | (smallest_max_payload << 5);
>>> -       while ((dev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, dev)) != NULL)
>>> +       for_each_pci_dev(dev)
>>>                 pcie_capability_clear_and_set_word(dev, PCI_EXP_DEVCTL,
>>>                                 PCI_EXP_DEVCTL_PAYLOAD | PCI_EXP_DEVCTL_READRQ,
>>>                                 new_values);
>>>
>>>
>> This patch looks correct to me, as far as it goes.
>>
>> Of course, any time we use for_each_pci_dev(), it's a good clue that
>> this code won't work for hotplug, so presumably you don't care about
>> hotplug on this system.
>
> Hotplug development is under way at the moment.
>
>> tile/kernel/pci_gx.c has a function of the same name, implemented
>> completely differently, which suggests that some unification or
>> refactoring might be possible.
>
> Sorry, which function are you referring to?  You mention MPS/MRS so perhaps you're talking about fixup_read_and_payload_sizes()?

Yes, sorry I didn't make that more clear.  Both tile and tile-gx have
fixup_read_and_payload_sizes() implementations.

>> In general, I think the PCI_EXP_DEVCAP and PCI_EXP_DEVCTL code for MPS
>> and MRRS management belongs in the PCI core, not in drivers or
>> architectures (it's fine if they provide device- or platform-specific
>> constraints), so anything you can do to move in that direction would
>> be good.
>>
>> Bjorn
>
> Thanks!
>
> --
> Chris Metcalf, Tilera Corp.
> http://www.tilera.com
>
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