Re: [PATCH 2/6] brcmfmac: Handling the interrupt in ISRdirectly for non-OOB

[Franky Lin]

On 08/28/2012 04:04 PM, Stephen Warren wrote:
> On 08/28/2012 04:01 PM, Franky Lin wrote:
> > On 08/28/2012 03:39 PM, Stephen Warren wrote:
> > > On 08/28/2012 09:45 AM, Franky Lin wrote:
> > > > On 08/28/2012 04:13 AM, Wei Ni wrote:
> > > > > On Tue, 2012-08-28 at 04:06 +0800, Stephen Warren wrote:
> > > > > > On 08/27/2012 09:24 AM, Arend van Spriel wrote:
> > > > > > > On 08/27/2012 12:25 PM, Wei Ni wrote:
> > > > > > > > In case of inband interrupts, if we handle the interrupt in dpc
> > > > > > > > thread,
> > > > > > > > two level of thread switching takes place to process wifi
> > > > > > > > interrupts.
> > > > > > > > One in SDHCI driver and the other in Wifi driver. This may cause the
> > > > > > > > system
> > > > > > > > instability.
> > > ...
> > > > > > > Not sure if I can follow this explanation. The isr is called with
> > > > > > > host
> > > > > > > claimed (by sdio_irq_thread) and all it does is at a linked list
> > > > > > > member
> > > > > > > and signal the dpc thread. After doing this the host is released.
> > > > > >
> > > > > > Is the issue something like the ISR handler or first level of
> > > > > > threading
> > > > > > does:
> > > > > >
> > > > > > * Trigger DPC
> > > > > > * Re-enable interrupt
> > > > > >
> > > > > > So that the interrupt then fires again before the triggered DPC can
> > > > > > run
> > > > > > to handle/clear it, thus causing an interrupt storm?
> > > > > >
> > > > > > Whereas handling the interrupt directly prevents this race condition?
> > > > >
> > > > > Above is my understanding.
> > > >
> > > > I understand the issue here and totally agree that we should treat
> > > > in-band and out-band interrupts differently. But my concern is that the
> > > > behavior of releasing the host before calling brcmf_sdbrcm_isr and grab
> > > > it after is likely error prone. Also we are restructuring the dpc
> > > > routine internally and it's almost done. I will find a better solution
> > > > for in-band interrupt and get it the queue as well. So I suggest
> > > > dropping this patch.
> > >
> > > Franky, do you know which kernel release the DPC restructuring will make
> > > it into? I ask because I can't apply the rest of the patches in this
> > > series without first resolving the stability issues with the Broadcom
> > > WiFi enabled, since that'd de-stabilize the Tegra platform
> > > significantly, and I'd like to plan when we can apply these patches to
> > > Tegra. Thanks!
> >
> > Hi Stephen,
> >
> > Since we submit patches through linux-wireless tree, you may only be
> > able to pick it up at 3.7-rc1. It's quite a big change so I don't think
> > it will qualify as a bug fix to get into 3.6-rcX.
>
> That's as quick as I expected it to show up, so that's great. I don't
> suppose you could mail Wei and myself once the patch gets into the
> linux-wireless tree, so we can test it out on Tegra. If the patch could
> possibly go into a topic branch in the wireless tree so it can be merged
> into the Tegra tree before this series, that would be awesome. Thanks.

Will keep you posted.

Franky

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