On 8/2/2017 1:49 PM, Alex Williamson wrote:
> On Wed, 2 Aug 2017 13:18:24 -0400
[snip]
>> static void pci_flr_wait(struct pci_dev *dev)
>> {
>> - int i = 0;
>> + u32 sleep = 1000, total = 0;
>> u32 id;
>> + bool ret;
>>
>> if (dev->is_virtfn) {
>> msleep(100);
>> return;
>> }
>>
>> + /* don't touch the HW before waiting 100ms */
>> + msleep(100);
>> +
>
>
> Wouldn't it be better as:
>
Sure, that looks reasonable.
> msleep(100);
>
> if (dev->is_virtfn)
> return;
>
> Perhaps with a spec reference in a comment why we don't care about
> checking config space for the vf.
The spec reference is in the commit message of
"PCI: limit FLR wait time to 100ms maximum"
where I introduce this check. Do you prefer a reference in the code?
I was under the impression that commit messages are used for these
kind of documentation.
>
>> do {
>> - msleep(100);
>> - pci_read_config_dword(dev, PCI_COMMAND, &id);
>> - } while (i++ < 10 && id == ~0);
>> -
>> - if (id == ~0)
>> - dev_warn(&dev->dev, "Failed to return from FLR\n");
>> - else if (i > 1)
>> - dev_info(&dev->dev, "Required additional %dms to return from
>> FLR\n",
>> - (i - 1) * 100);
>> + ret = pci_bus_read_dev_vendor_id(dev->bus, dev->devfn, &id,
>> + sleep);
>> + if (ret)
>> + break;
>> + total += sleep;
>> + sleep *= 2;
>> + } while (total < 60000 && !ret);
>> +
>> + if (!ret)
>> + dev_warn(&dev->dev, "Failed to return from FLR after %ds\n",
>> + total);
>> + else if (total)
>> + dev_info(&dev->dev, "Required additional %ds to return from
>> FLR\n",
>> + total);
>> }
>
> I'm not a big fan. Nested exponential backoff is pretty nasty. Are
> there users of pci_bus_read_dev_vendor_id() that don't want a "still
> trying" message? It seems better to add that to the function than try
> to wrap this bandage around it. Thanks,
I can work towards that if Bjorn doesn't have any objections.
>
> Alex
>
--
Sinan Kaya
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm
Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux
Foundation Collaborative Project.
