Re: [PATCH V2 3/6] brcmfmac: reserve 2 credits for host tx control path

From: Dmitry Osipenko <digetx@gmail.com>
To: Kalle Valo <kvalo@codeaurora.org>
Cc: Chi-Hsien Lin <chi-hsien.lin@cypress.com>,
	linux-wireless@vger.kernel.org, brcm80211-dev-list@broadcom.com,
	brcm80211-dev-list@cypress.com,
	Arend van Spriel <arend.vanspriel@broadcom.com>,
	Franky Lin <franky.lin@broadcom.com>,
	Hante Meuleman <hante.meuleman@broadcom.com>,
	Wright Feng <wright.feng@cypress.com>,
	Amar Shankar <amsr@cypress.com>,
	Jia-Shyr Chuang <joseph.chuang@cypress.com>
Subject: Re: [PATCH V2 3/6] brcmfmac: reserve 2 credits for host tx control path
Date: Tue, 4 Aug 2020 18:53:20 +0300	[thread overview]
Message-ID: <ffcf55cc-b27d-78ec-ff4f-e7efa3087712@gmail.com> (raw)
In-Reply-To: <875z9yr7lg.fsf@codeaurora.org>

04.08.2020 14:08, Kalle Valo пишет:
> Dmitry Osipenko <digetx@gmail.com> writes:
> 
>> 10.06.2020 18:21, Chi-Hsien Lin пишет:
>>> From: Amar Shankar <amsr@cypress.com>
>>>
>>> It is observed that sometimes when sdiod is low in tx credits in low
>>> rssi scenarios, the data path consumes all sdiod rx all credits and
>>> there is no sdiod rx credit available for control path causing host
>>> and card to go out of sync resulting in link loss between host and
>>> card. So in order to prevent it some credits are reserved for control
>>> path.
>>>
>>> Note that TXCTL_CREDITS can't be larger than the firmware default
>>> credit update threshold 2; otherwise there will be a deadlock for both
>>> side waiting for each other.
>>>
>>> Signed-off-by: Amar Shankar <amsr@cypress.com>
>>> Signed-off-by: Jia-Shyr Chuang <joseph.chuang@cypress.com>
>>> Signed-off-by: Chi-Hsien Lin <chi-hsien.lin@cypress.com>
> 
> [...]
> 
>> This patch causes a severe WiFi performance regression on BCM4329.
>> Please fix or revert this patch, thanks in advance.
>>
>> Before this patch:
>> - - - - - - - - - - - - - - - - - - - - - - - - -
>> [ ID] Interval           Transfer     Bitrate         Retr
>> [  5]   0.00-10.00  sec  17.2 MBytes  14.4 Mbits/sec    0             sender
>> [  5]   0.00-10.04  sec  16.9 MBytes  14.1 Mbits/sec
>> receiver
>>
>>
>> After this patch:
>> - - - - - - - - - - - - - - - - - - - - - - - - -
>> [ ID] Interval           Transfer     Bitrate         Retr
>> [  5]   0.00-10.00  sec  1.05 MBytes   881 Kbits/sec    3             sender
>> [  5]   0.00-14.01  sec   959 KBytes   561 Kbits/sec
>> receiver
> 
> Can someone please send a revert patch (with the explanation above) if a
> fix is not quickly found? The commit id is:
> 
> commit b41c232d33666191a1db11befc0f040fcbe664e9
> Author:     Amar Shankar <amsr@cypress.com>
> AuthorDate: Wed Jun 10 10:21:03 2020 -0500
> Commit:     Kalle Valo <kvalo@codeaurora.org>
> CommitDate: Tue Jul 14 12:46:43 2020 +0300
> 
>     brcmfmac: reserve 2 credits for host tx control path
> 

Hello Kalle,

I'll send the revert if nobody will stand up to address the problem in a
two weeks, thanks.