Michael Ellerman wrote:
> On Fri, 2009-05-08 at 07:13 -0600, Matthew Wilcox wrote:
>> The NIU device refuses to allow accesses to MSI-X registers before MSI-X
>> is enabled. This patch fixes the problem by moving the read of the mask
>> register to after MSI-X is enabled.
>>
>> Reported-by: David S. Miller <davem@xxxxxxxxxxxxx>
>> Tested-by: David S. Miller <davem@xxxxxxxxxxxxx>
>> Reviewed-by: David S. Miller <davem@xxxxxxxxxxxxx>
>> Signed-off-by: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
>>
>> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
>> index 6f2e629..3627732 100644
>> --- a/drivers/pci/msi.c
>> +++ b/drivers/pci/msi.c
>> @@ -455,8 +455,6 @@ static int msix_capability_init(struct pci_dev *dev,
>> entry->msi_attrib.default_irq = dev->irq;
>> entry->msi_attrib.pos = pos;
>> entry->mask_base = base;
>> - entry->masked = readl(base + j * PCI_MSIX_ENTRY_SIZE +
>> - PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET);
>> msix_mask_irq(entry, 1);
>
> 158 static void msix_mask_irq(struct msi_desc *desc, u32 flag)
> 159 {
> 160 u32 mask_bits = desc->masked;
> ...
> 165 writel(mask_bits, desc->mask_base + offset);
>
>
> So I guess this device is just silently ignoring that write?
I guess that write can be ignored while reads are not.
It seems that this issue was introduced by Matthew's commit:
commit f2440d9acbe866b917b16cc0f927366341ce9215
<quote>
@@ -435,11 +432,12 @@ static int msix_capability_init(struct pci_dev *dev,
entry->msi_attrib.is_msix = 1;
entry->msi_attrib.is_64 = 1;
entry->msi_attrib.entry_nr = j;
- entry->msi_attrib.maskbit = 1;
- entry->msi_attrib.masked = 1;
entry->msi_attrib.default_irq = dev->irq;
entry->msi_attrib.pos = pos;
entry->mask_base = base;
+ entry->masked = readl(base + j * PCI_MSIX_ENTRY_SIZE +
+ PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET);
+ msix_mask_irq(entry, 1);
list_add_tail(&entry->list, &dev->msi_list);
}
</quote>
I'm not sure why Matthew changed it to read/write...
> And aren't we violating the spec by writing 0x1 into the device there
> (assuming desc->masked is 0x0 from the kzalloc), ie. we're supposed to
> read and write back the reserved bits unchanged. (§ 6.8.2.9?)
Spec says:
"This bit's state after reset is 1 (entry is masked).
This bit is read/write."
>> @@ -493,6 +491,12 @@ static int msix_capability_init(struct pci_dev *dev,
>> msix_set_enable(dev, 1);
>> dev->msix_enabled = 1;
>
> Are we safe if we take an interrupt here?
If reset was properly done on the device, we will be safe since entries are
masked. Otherwise, ... I'm not sure.
>> + list_for_each_entry(entry, &dev->msi_list, list) {
>> + int vector = entry->msi_attrib.entry_nr;
>> + entry->masked = readl(base + vector * PCI_MSIX_ENTRY_SIZE +
>> + PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET);
>> + }
>> +
>> return 0;
>> }
I think we can remove read/write here because it was same as before the
Matthew's change above.
If we really need read/write here, then I believe Matthew can provide
an incremental patch for that.
Thanks,
H.Seto
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