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From: Lukas F. Hartmann <lukas@mntre.com>
To: Kalle Valo <kvalo@kernel.org>, Martin Blumenstingl
 <martin.blumenstingl@googlemail.com>
Cc: linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org,
 jernej.skrabec@gmail.com, pkshih@realtek.com, ulf.hansson@linaro.org,
 tony0620emma@gmail.com, Martin Blumenstingl
 <martin.blumenstingl@googlemail.com>
Subject: Re: [PATCH v3] wifi: rtw88: sdio: Honor the host max_req_size in
 the RX path
In-Reply-To: <170137159397.1963309.4329648460865757143.kvalo@kernel.org>
References: <20231120115726.1569323-1-martin.blumenstingl@googlemail.com>
 <170137159397.1963309.4329648460865757143.kvalo@kernel.org>
Date: Thu, 30 Nov 2023 20:30:33 +0100
Message-ID: <87edg7ujhi.fsf@mntre.com>
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MIME-Version: 1.0
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Hi Ping-Ke, Kalle, Martin,

sorry for my late reply. Yes, this patch fixes my original problems and
I have usable WiFi now. There are still some remaining problems like
connection dropouts every minute or so, but it's unrelated and a topic
of further investigation. 

Tested-by: Lukas F. Hartmann <lukas@mntre.com>

Best
Lukas
-- 
Lukas F. Hartmann, CEO
MNT Research GmbH
https://mntre.com

Kalle Valo <kvalo@kernel.org> writes:

> Martin Blumenstingl <martin.blumenstingl@googlemail.com> wrote:
>
>> Lukas reports skb_over_panic errors on his Banana Pi BPI-CM4 which comes
>> with an Amlogic A311D (G12B) SoC and a RTL8822CS SDIO wifi/Bluetooth
>> combo card. The error he observed is identical to what has been fixed
>> in commit e967229ead0e ("wifi: rtw88: sdio: Check the HISR RX_REQUEST
>> bit in rtw_sdio_rx_isr()") but that commit didn't fix Lukas' problem.
>> 
>> Lukas found that disabling or limiting RX aggregation works around the
>> problem for some time (but does not fully fix it). In the following
>> discussion a few key topics have been discussed which have an impact on
>> this problem:
>> - The Amlogic A311D (G12B) SoC has a hardware bug in the SDIO controller
>>   which prevents DMA transfers. Instead all transfers need to go through
>>   the controller SRAM which limits transfers to 1536 bytes
>> - rtw88 chips don't split incoming (RX) packets, so if a big packet is
>>   received this is forwarded to the host in it's original form
>> - rtw88 chips can do RX aggregation, meaning more multiple incoming
>>   packets can be pulled by the host from the card with one MMC/SDIO
>>   transfer. This Depends on settings in the REG_RXDMA_AGG_PG_TH
>>   register (BIT_RXDMA_AGG_PG_TH limits the number of packets that will
>>   be aggregated, BIT_DMA_AGG_TO_V1 configures a timeout for aggregation
>>   and BIT_EN_PRE_CALC makes the chip honor the limits more effectively)
>> 
>> Use multiple consecutive reads in rtw_sdio_read_port() and limit the
>> number of bytes which are copied by the host from the card in one
>> MMC/SDIO transfer. This allows receiving a buffer that's larger than
>> the hosts max_req_size (number of bytes which can be transferred in
>> one MMC/SDIO transfer). As a result of this the skb_over_panic error
>> is gone as the rtw88 driver is now able to receive more than 1536 bytes
>> from the card (either because the incoming packet is larger than that
>> or because multiple packets have been aggregated).
>> 
>> In case of an receive errors (-EILSEQ has been observed by Lukas) we
>> need to drain the remaining data from the card's buffer, otherwise the
>> card will return corrupt data for the next rtw_sdio_read_port() call.
>> 
>> Fixes: 65371a3f14e7 ("wifi: rtw88: sdio: Add HCI implementation for SDIO based chipsets")
>> Reported-by: Lukas F. Hartmann <lukas@mntre.com>
>> Closes: https://lore.kernel.org/linux-wireless/CAFBinCBaXtebixKbjkWKW_WXc5k=NdGNaGUjVE8NCPNxOhsb2g@mail.gmail.com/
>> Suggested-by: Ping-Ke Shih <pkshih@realtek.com>
>> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
>> Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
>> Acked-by: Ping-Ke Shih <pkshih@realtek.com>
>
> Did this fix Lukas' problem? I couldn't see any answer to Ping's
> question.
>
> Patch set to Deferred.
>
> -- 
> https://patchwork.kernel.org/project/linux-wireless/patch/20231120115726.1569323-1-martin.blumenstingl@googlemail.com/
>
> https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
>