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Subject: Re: [PATCH V2 3/6] brcmfmac: reserve 2 credits for host tx control
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To:     Dmitry Osipenko <digetx@gmail.com>,
        Chi-Hsien Lin <chi-hsien.lin@cypress.com>,
        Kalle Valo <kvalo@codeaurora.org>
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        Hante Meuleman <hante.meuleman@broadcom.com>,
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From:   Wright Feng <wright.feng@cypress.com>
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Dmitry Osipenko 於 8/12/2020 10:22 PM 寫道:
> 12.08.2020 07:03, Wright Feng пишет:
> ...
>> Hi Dmitry,
>>
>> The last time the drivers I used is v5.4 and I was not able to see low
>> throughput issue as you saw.
>> At this time, I changed the base to tag wt-2020-0727 and I am able to
>> reproduce the issue as you did.
>> TX throughput with wt-2020-07-27 FMAC is 190 Kbits/sec
>>
>>
>> The root cause should be that tx_max and tx_seq are circle positive
>> numbers, it should not use ">" to check if it still exists available TX
>> credit.
>> With the solution below, I am able to get the normal throughput.
>> TX throughput with wt-2020-07-27+patch FMAC is 40.0 Mbits/sec
>>
>> Regarding another case about 40Mbit/s, I am using 4329b0(4329/2) chip to
>> verify the throughput because we are not able to find 4329b1(4329/3)
>> which is very old product around 10 years ago.
>> The firmware I am using is the same version but the build is for 4329b0.
>> (private internal build - 4.220.48). My host platform is x86_64 with 4
>> cores on Linux kernel 4.12. I will try your NVRAM when I have time to
>> see if I can find anything.
>>
>> ---
>> diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c
>> b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c
>> index e8712ad..50c8107 100644
>> --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c
>> +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c
>> @@ -664,9 +664,14 @@ static void pkt_align(struct sk_buff *p, int len,
>> int align)
>>   /* To check if there's window offered */
>>   static bool data_ok(struct brcmf_sdio *bus)
>>   {
>> -    /* Reserve TXCTL_CREDITS credits for txctl */
>> -    return (bus->tx_max - bus->tx_seq) > TXCTL_CREDITS &&
>> -           ((bus->tx_max - bus->tx_seq) & 0x80) == 0;
>> +    u8 tx_rsv = 0;
>> +
>> +    /* Reserve TXCTL_CREDITS credits for txctl when it is ready to send */
>> +    if (bus->ctrl_frame_stat)
>> +        tx_rsv = TXCTL_CREDITS;
>> +
>> +    return (bus->tx_max - bus->tx_seq - tx_rsv) != 0 &&
>> +           ((bus->tx_max - bus->tx_seq - tx_rsv) & 0x80) == 0;
>>   }
>>
>>   /* To check if there's window offered */
>> ---
> 
> Wright, thank you very much for the patch! It fixes the problem!
> 
> Tested-by: Dmitry Osipenko <digetx@gmail.com>
> 
> The 4329/3 is indeed an older chip, but it's also an "old" device (Acer
> A500 tablet from 2011/12) that I'm using. Upstream v5.9 kernel just got
> support for the A500. There are quite a lot of other older devices with
> 4329/3 in a wild that are still very usable if user can wipe off ancient
> Android and put a modern Linux distro on them. Today that A500 tablet is
> still rocking hard running a modern upstream kernel, opensource drivers
> and KDE Plasma 5. The 15Mbit is a good enough speed for a lot of things,
> but of course 40Mbit will be better. Would be great if you could try to
> help with improving the speed :) Please feel free to contact me at any
> time if you'll have patches to try!
> 
Dmitry,
Thanks for the verification. The patch will be submitted to upstream 
within two days.
And with regards to low THP problem on Acer A500 tablet, I will create 
another mail thread to discuss with you.