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SubjectRe: [PATCH] PCI: add quirk for 3ware 9650SE controller
On Tue, Nov 5, 2013 at 6:06 AM, Jiri Kosina <> 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 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.


> ---
> 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,
> - /* 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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