Date:   Fri,  1 Dec 2023 12:40:36 +0000 (UTC)
From:   Kalle Valo <kvalo@...nel.org>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
        jernej.skrabec@...il.com, pkshih@...ltek.com,
        ulf.hansson@...aro.org, tony0620emma@...il.com, lukas@...re.com,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: Re: [PATCH v3] wifi: rtw88: sdio: Honor the host max_req_size in the
 RX
 path

Martin Blumenstingl <martin.blumenstingl@...glemail.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@...re.com>
> Closes: https://lore.kernel.org/linux-wireless/CAFBinCBaXtebixKbjkWKW_WXc5k=NdGNaGUjVE8NCPNxOhsb2g@mail.gmail.com/
> Suggested-by: Ping-Ke Shih <pkshih@...ltek.com>
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
> Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>
> Acked-by: Ping-Ke Shih <pkshih@...ltek.com>
> Tested-by: Lukas F. Hartmann <lukas@...re.com>
> Reported-by: Lukas F. Hartmann <lukas@...re.com>
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
> Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>
> Acked-by: Ping-Ke Shih <pkshih@...ltek.com>
> Tested-by: Lukas F. Hartmann <lukas@...re.com>

Patch applied to wireless-next.git, thanks.

00384f565a91 wifi: rtw88: sdio: Honor the host max_req_size in the RX path

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20231120115726.1569323-1-martin.blumenstingl@googlemail.com/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches

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