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SubjectRe: [PATCH] PCI: add quirk for 3ware 9650SE controller
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.

---
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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