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Date: Tue, 28 Aug 2012 16:10:07 -0700 From: "Franky Lin" <frankyl@...adcom.com> To: "Stephen Warren" <swarren@...dotorg.org> cc: "Wei Ni" <wni@...dia.com>, "Arend van Spriel" <arend@...adcom.com>, "rvossen@...adcom.com" <rvossen@...adcom.com>, "Rakesh Kumar" <krakesh@...dia.com>, "Laxman Dewangan" <ldewangan@...dia.com>, "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>, "brcm80211-dev-list@...adcom.com" <brcm80211-dev-list@...adcom.com> Subject: Re: [PATCH 2/6] brcmfmac: Handling the interrupt in ISR directly for non-OOB 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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