Re: [PATCH] pciehp: Acknowledge the spurious "cmd completed" event.

On Thu, Feb 20, 2014 at 2:20 PM, Bjorn Helgaas <[email protected]> wrote:
> On Thu, Feb 20, 2014 at 12:42 AM, Rajat Jain <[email protected]> wrote:
>> Hello Bjorn,
>>
>>>>
>>>> On Mon, Nov 25, 2013 at 07:03:11PM +0000, Rajat Jain wrote:
>>>> > Hello,
>>>> >
>>>> > > > On a different note, I feel there is still a need to apply my
>>>> > > > original
>>>> > > patch. There is still an open problem in case of spurious interrupts
>>>> > > (or in any case where the condition "if (slot_status &
>>>> PCI_EXP_SLTSTA_CC)"
>>>> > > becomes true in pcie_write_cmd()). That is because once that
>>>> > > happens, we never clear that interrupt, and no further hotplug
>>>> > > interrupts shall be received unless we do that.
>>>> > >
>>>> > > I agree this is an issue and we should address it somehow.  My
>>>> > > hesitation is just that I'd prefer to do some more aggressive
>>>> > > restructuring rather than apply a point fix.  For example:
>>>> >
>>>> > OK, I'll attempt to fix it that way when I get time.
>>>> >
>>>> > >
>>>> > > - We currently look at PCI_EXP_SLTSTA_CC in pcie_isr(),
>>>> > > pcie_poll_cmd(), and pcie_write_cmd().  I think it would be better
>>>> > > to look at it only in pcie_isr().
>>>> > >
>>>> > > - I don't think pcie_poll_cmd() should exist at all; we should poll
>>>> > > by calling pcie_isr() instead.
>>>> > >
>>>> > > - We need pcie_write_cmd(), but I think the way it waits is
>>>> backwards.
>>>> > >  Currently we issue the command, then wait for it to complete.  I
>>>> > > think we should issue the command, note the current time, and return
>>>> > > without waiting.  The *next* time we need to issue a command, we can
>>>> > > wait for completion of the previous one (or timeout) if necessary.
>>>> > >
>>>> > > But maybe we need the point fix in the interim, especially if
>>>> > > anybody can actually produce the scenario you mention.
>>>> >
>>>> > Ok.
>>>>
>>>> This patch is still in patchwork, but I've lost track of where we are.
>>>> Did you resolve this in the series that I just applied, or is it still
>>>> an outstanding issue?
>>>
>>> No, I did not solve it. It is still an outstanding issue. So far I am using your patch to overcome this:
>>>
>>> http://www.spinics.net/lists/hotplug/msg05830.html
>>>
>>> I'll just attempt to conclude the status on this issue so that you can make the decision on the course of action. IMHO there are 2 independent issues that we discussed in this thread:
>>>
>>> 1) PCIe compliant HW (that generates cmd completed interrupts at every write of Slot_ctrl register) being penalized with 1 second delay during the boot up. Your patch solves this.
>>>
>>> 2) If there is a genuine spurious interrupt, it does not get acknowledged. I had originally posted a patch for THIS problem.
>>> http://www.spinics.net/lists/hotplug/msg05815.html
>>>
>>> You had indicated that you would rather want a bigger restructuring of the driver to solve (2).
>>>
>>> My observation: MY problem (in my setup) is not seen if I use either of the patches (yours or mine).
>>>
>>> My opinion: I think my patch solves (2) but might not solve (1) for all corner cases. Also your patch solves (1) but may not solve (2) for all corner cases -Thus we should probably solve both of these problems individually.
>>>
>>
>> Just wondering if you decided on how to solve this problem?
>>
>> Are you planning this for 3.15?
>
> Sorry, I haven't had a chance to work on this, so I don't think *I*
> will get anything done for v3.15.  To make forward progress, maybe we
> should merge your original patch?  Would you mind posting it again so
> it gets into patchwork again?

Just sent it again, Thanks!
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