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From:   Kalle Valo <kvalo@codeaurora.org>
To:     Dmitry Osipenko <digetx@gmail.com>
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
References: <20200610152106.175257-1-chi-hsien.lin@cypress.com>
        <20200610152106.175257-4-chi-hsien.lin@cypress.com>
        <f0910f96-1d23-daf1-b517-363e59bff105@gmail.com>
        <875z9yr7lg.fsf@codeaurora.org>
        <ffcf55cc-b27d-78ec-ff4f-e7efa3087712@gmail.com>
Date:   Tue, 04 Aug 2020 20:22:22 +0300
In-Reply-To: <ffcf55cc-b27d-78ec-ff4f-e7efa3087712@gmail.com> (Dmitry
        Osipenko's message of "Tue, 4 Aug 2020 18:53:20 +0300")
Message-ID: <87a6zapbqp.fsf@codeaurora.org>
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Dmitry Osipenko <digetx@gmail.com> writes:

> 04.08.2020 14:08, Kalle Valo =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
>> Dmitry Osipenko <digetx@gmail.com> writes:
>>=20
>>> 10.06.2020 18:21, Chi-Hsien Lin =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
>>>> 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>
>>=20
>> [...]
>>=20
>>> 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             s=
ender
>>> [  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             s=
ender
>>> [  5]   0.00-14.01  sec   959 KBytes   561 Kbits/sec
>>> receiver
>>=20
>> Can someone please send a revert patch (with the explanation above) if a
>> fix is not quickly found? The commit id is:
>>=20
>> 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
>>=20
>>     brcmfmac: reserve 2 credits for host tx control path
>>=20
>
> Hello Kalle,
>
> I'll send the revert if nobody will stand up to address the problem in a
> two weeks, thanks.

Thanks. Then I should be able to get the revert to v5.9 so that the
release won't be broken. (v5.8 is unaffected)

--=20
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatc=
hes