Date:	Tue, 3 Jun 2014 17:00:45 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Adam Radford <aradford@...il.com>
Subject: Re: [PATCH] PCI: add quirk for 3ware 9650SE controller

On Tue, Nov 5, 2013 at 11:44 AM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> On Tue, Nov 5, 2013 at 6:06 AM, Jiri Kosina <jkosina@...e.cz> wrote:
>> On Thu, 31 Oct 2013, Bjorn Helgaas wrote:
>>
>>> > Attached is dmesg output leading to timeouts (that are cured by my
>>> > original patch in this thread) and lspci.
>>>
>>> I opened https://bugzilla.kernel.org/show_bug.cgi?id=64141 for this
>>> issue and attached your dmesg log and lspci output.
>>>
>>> > Please let me know if there is anything else I could do, or if you are
>>> > going to proceed with my patch adding the quirk.
>>>
>>> Your quirk keeps us from disabling MSIs on the device during
>>> enumeration.  But even if the BIOS left MSIs enabled, there's nothing
>>> to field the MSI until after the driver claims the device.  So I don't
>>> believe this has to be done as a quirk.  It should work just as well
>>> to do something in the driver when it claims the device.
>>>
>>> I guess another way to say this is that I don't think we understand
>>> what the real problem is, and if we just add a quirk to work around
>>> it, we might miss the chance to fix the real problem, and we may never
>>> be able to remove the special-case code we're adding in the generic
>>> path.
>>>
>>> I know you said you tried doing something in the driver, and it didn't
>>> work.  I don't know exactly what you tried, but twa_probe() looks
>>> strange to me.  The other drivers I looked at do all their PCI
>>> initialization before the scsi_host_alloc() / scsi_add_host() /
>>> scsi_scan_host() stuff.  But twa_probe() has PCI stuff scattered
>>> around between those three SCSI calls.  In particular, it does the MSI
>>> setup way down near the end, after scsi_add_host(), which seems like
>>> just the sort of thing that could explain this problem.
>>
>> What I tried was patch below, but it didn't have any observable effect --
>> the commands sent to the controller would still time out the same way.
>>
>> Debugging this is not really straightforward for me unfortunately, as I
>> don't own the system myself.
>>
>> I agree that we don't fully understand what is happening, but the quirk
>> was the only way I have been able to come up with to make the device
>> functioning again (apart from reverting d5dea7d95).
>>
>> Any other ideas are welcome.
>
> This patch looks like a good start, but there's a whole lot of other
> PCI-related initialization that I would suggest moving as well --
> pci_request_regions(), ioremap(), pci_set_drvdata(), pci_enable_msi,
> request_irq(), etc.  I would do this myself, but there are some pieces
> that don't look completely trivial, e.g., things like
> TW_DISABLE_INTERRUPTS() and twa_reset_sequence() don't look like
> they're SCSI-specific, but they are currently implemented using
> tw_dev, which looks like it's allocated by scsi_host_alloc().
> Untangling all this looks like more work than I want to sign up to.
>
> But I really don't want to put the quirk in because it's just a quick
> hack that apparently just covers up bugs in the driver, and it will be
> an annoyance in the PCI core forever.

Just FYI, I reassigned
https://bugzilla.kernel.org/show_bug.cgi?id=64141 from PCI to SCSI,
since I don't think there's a PCI core problem here.  I don't know if
SCSI pay attention to bugzilla at all; I'm just mentioning it here in
case anybody still cares about this problem and was hoping that I was
going to do something.

Bjorn

>> ---
>>  drivers/scsi/3w-9xxx.c |   10 +++++-----
>>  1 files changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/scsi/3w-9xxx.c b/drivers/scsi/3w-9xxx.c
>> index ba754c3..bad7faf 100644
>> --- a/drivers/scsi/3w-9xxx.c
>> +++ b/drivers/scsi/3w-9xxx.c
>> @@ -2055,6 +2055,11 @@ static int __devinit twa_probe(struct pci_dev *pdev, const struct pci_device_id
>>                         goto out_disable_device;
>>                 }
>>
>> +       /* Try to enable MSI */
>> +       if (use_msi && (pdev->device != PCI_DEVICE_ID_3WARE_9000) &&
>> +           !pci_enable_msi(pdev))
>> +               set_bit(TW_USING_MSI, &tw_dev->flags);
>> +
>>         host = scsi_host_alloc(&driver_template, sizeof(TW_Device_Extension));
>>         if (!host) {
>>                 TW_PRINTK(host, TW_DRIVER, 0x24, "Failed to allocate memory for device extension");
>> @@ -2134,11 +2139,6 @@ static int __devinit twa_probe(struct pci_dev *pdev, const struct pci_device_id
>>                le32_to_cpu(*(int *)twa_get_param(tw_dev, 2, TW_INFORMATION_TABLE,
>>                                      TW_PARAM_PORTCOUNT, TW_PARAM_PORTCOUNT_LENGTH)));
>>
>> -       /* Try to enable MSI */
>> -       if (use_msi && (pdev->device != PCI_DEVICE_ID_3WARE_9000) &&
>> -           !pci_enable_msi(pdev))
>> -               set_bit(TW_USING_MSI, &tw_dev->flags);
>> -
>>         /* Now setup the interrupt handler */
>>         retval = request_irq(pdev->irq, twa_interrupt, IRQF_SHARED, "3w-9xxx", tw_dev);
>>         if (retval) {
>>
>>
>> --
>> Jiri Kosina
>> SUSE Labs
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