linux-kernel - Re: wifi: rtw88: question about SDIO RX aggregation limiting

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Message-ID: <CAFBinCBsg8jPhpqSOr9w2JhwN5YjPeME1Uye7meSY8h=b_N4Qg@mail.gmail.com>
Date:   Mon, 19 Jun 2023 22:38:24 +0200
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     Ping-Ke Shih <pkshih@...ltek.com>
Cc:     "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "Lukas F. Hartmann" <lukas@...re.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tony0620emma@...il.com" <tony0620emma@...il.com>,
        "jernej.skrabec@...il.com" <jernej.skrabec@...il.com>
Subject: Re: wifi: rtw88: question about SDIO RX aggregation limiting

Hello Ping-Ke,

apologies for the long delay.

On Tue, Jun 13, 2023 at 4:20 AM Ping-Ke Shih <pkshih@...ltek.com> wrote:
[...]
> The unit of BIT_RXDMA_AGG_PG_TH is 1k bytes, so I think you can
> set mmc_host->max_req_size/1024.
I tried this but I got a result that I don't understand.
I've been testing with three BIT_RXDMA_AGG_PG_TH values on a SoC that
can handle 255 * 1024 bytes. Each time I connected to the same AP and
downloaded a bigger file over http(s).
BIT_RXDMA_AGG_PG_TH: biggest observed rx_len in rtw_sdio_rxfifo_recv()
255: 20968
6: 5122
1: 1602

The biggest rx_len I have observed for BIT_RXDMA_AGG_PG_TH 1 looks suspicious:
My understanding is that I shouldn't be seeing rx_len larger than
BIT_RXDMA_AGG_PG_TH * 1024.
BIT_RXDMA_AGG_PG_TH = 6 is within this limit but BIT_RXDMA_AGG_PG_TH =
1 isn't (I'm seeing 578 extra bytes in addition to the 1024 bytes that
I was expecting).
Do you have any idea where this is coming from? I'm worried that we
can still end up with the problem that Lukas described but seems to
not have hit in his testing with BIT_RXDMA_AGG_PG_TH = 6

> I wonder why 0x6 works on Amlogic SoCs. Could you or Lukas compare performance
> between the settings of 0x1 and 0x6?
I can do this later this week but I'd like to understand the above
results first.


Best regards,
Martin