netdev - Re: [RFC PATCH v1 00/19] rtw88: Add SDIO support

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Date:   Fri, 30 Dec 2022 00:18:39 +0100
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>,
        Yan-Hsuan Chuang <tony0620emma@...il.com>,
        Kalle Valo <kvalo@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Chris Morgan <macroalpha82@...il.com>,
        Nitin Gupta <nitin.gupta981@...il.com>,
        Neo Jou <neojou@...il.com>,
        Jernej Skrabec <jernej.skrabec@...il.com>
Subject: Re: [RFC PATCH v1 00/19] rtw88: Add SDIO support

Hi Ping-Ke,

thanks again for all your input!

On Thu, Dec 29, 2022 at 5:19 AM Ping-Ke Shih <pkshih@...ltek.com> wrote:
[...]
> > - RX throughput on a 5GHz network is at 19 Mbit/s
>
> I have a suggestion about RX throughput, please check below registers with
> vendor driver:
>
> REG_RXDMA_AGG_PG_TH
> REG_TXDMA_PQ_MAP(0x10c) BIT_RXDMA_AGG_EN (bit2)
> REG_RXDMA_MODE(0290)  BIT_DMA_MODE (bit1)
Unfortunately I didn't manage to get the vendor driver to work with
mainline Linux.
The Android installation on my board (which is how it was shipped)
uses the vendor driver but unlike some Amlogic code the Realtek
(vendor) wireless driver does not allow reading arbitrary registers
through sysfs.
So I can't check the values that the vendor driver uses.

> Try to adjust AGG_PG_TH to see if it can help.
I tried a few values and I can say that it does change the RX
throughput, but the result is always lower than 19 Mbit/s, meaning
that it's worse than RX aggregation disabled (on my RTL8822CS).
Currently we're disabling RX aggregation in the driver. But Jernej
mentioned previously that for his RTL8822BS he found that RX
aggregation seems to improve performance.

Independent of this I did some investigation on my own and found that
when reducing the TX throughput the RX throughput increases.
For this I tried using ieee80211_{stop,wake}_queue() in the sdio.c HCI
sub-driver.
RX throughput is now at 23.5 Mbit/s (that +25% compared to before) on
my RTL8822CS (with RX aggregation still disabled, just like in the 19
Mbit/s test).
Unfortunately TX throughput is now way below 10 Mbit/s.

Additionally I think that the antenna of my board is worse than my
access point's antenna. So TX from rtw88 to my AP may be faster
(because the AP can "hear better") than RX (rtw88 "hearing is worse").

For today I'm tired and will stop here.


Best regards,
Martin


[0] https://github.com/xdarklight/linux/commit/3f2e6b9cd40dc785b5c72dbc9c8b471a2e205344