On Fri, Nov 8, 2013 at 10:30 AM, Rajat Jain <rajatjain.linux@xxxxxxxxx> wrote:
> On Thu, Nov 7, 2013 at 5:23 PM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote:
>> Where does this delay happen on your system? I tried to work through
>> the path but I don't see it yet. Here's what I expect to happen on your
>> system:
>>
>> pciehp_probe
>> pcie_init
>> readl(SLTCAP)
>> if (NO_CMD_CMPL || !(POWER_CTRL | ATTN_LED | PWR_LED | EMI)) # true
>> ctrl->no_cmd_complete = 1 # set (condition above is true)
>> writew(SLTSTA, 0x1f) # clear ABP PFD MRLSC PDC CC
>> pcie_disable_notification
>> pcie_write_cmd(0, PDCE | ABPE | MRLSCE | PFDE | HPIE | CCIE | DLLSCE)
>> readw(SLTSTA) # CC == 0 (was cleared above)
>> writew(SLTCTL)
>> ...
>> # no waiting here because no_cmd_complete == 1
>> ...
>> hardware sets SLTSTA.CC
>> ...
>> pcie_init_notification
>> pcie_enable_notification
>> pcie_write_cmd
>> readw(SLTSTA) # CC == 1 (was set by HW above)
>> if (SLTSTA.CC) # true
>> if (!NO_CMD_CMPL)) # true
>> dbg("Unexpected CMD_COMPLETED. ...")
>> ctrl->no_cmd_complete = 0
>> writew(SLTCTL)
>> ...
>> # this time we wait because no_cmd_complete == 0
>> ...
>> pcie_wait_cmd(..., poll == 1) # now no_cmd_complete == 0
>
> Actually pcie_wait_cmd() shall be called with poll=0. That is because
> the following conditions are both false (we just enabled both the
> interrupts while enabling notifications):
>
> if (!(slot_ctrl & PCI_EXP_SLTCTL_HPIE) ||
> !(slot_ctrl & PCI_EXP_SLTCTL_CCIE))
> poll = 1;
>
> Thus it does not poll, but waits for interrupt. Which does not happen
> because the CC bit in the slot status register was not cleared.
Right, of course. Thanks for pointing out my error.
> As a
> result, we get the following messages on the console for each
> controller (and 1 second delay):
> ===========================
> Unexpected CMD_COMPLETED. Need to wait for command completed event.
> Command not completed in 1000 msec
> ===========================
> With my patch, we'd eliminate the 1 second delay and the second line
> of output above. If we also want to get rid of the first line
> "Unexpected CMD_COMPLETED..." also, that would probably have to be
> solved by changing the behavior to assume that CC shall be generated
> for every SLOTCTRL register write.
I *do* want to get rid of the "Unexpected CMD_COMPLETED" complaint.
We shouldn't complain about hardware that is working perfectly fine.
I don't know the best way to do that yet. I have found a box with the
same hardware that was fixed by 5808639bfa98, so I hope to play with
it and figure out something that will work nicely for both scenarios.
BTW, can you open a report at bugzilla.kernel.org and attach your
"lspci -vvxxx" and dmesg output? When we eventually merge a fix, I'd
like to have the details archived somewhere.
Bjorn
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