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From:   Justin Capella <justincapella@gmail.com>
Date:   Sun, 1 Dec 2019 20:28:12 -0800
Message-ID: <CAMrEMU89NCJ4HKVqirYrNTC83Hv8HpT7uKrvQ-3p3Bvju=8_-Q@mail.gmail.com>
Subject: Re: [PATCH] ath10k: set max mtu to 1500 for sdio chip
To:     Wen Gong <wgong@codeaurora.org>
Cc:     ath10k <ath10k@lists.infradead.org>, linux-wireless@vger.kernel.org
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So I understand the reasoning behind using ETH_DATA_LEN, but would it
be more future proof / obvious to the next dev to calculate the size
given the interface's parameters/defines--- I get that the values were
chosen to align with this but just worried if things were to change
over time this would not be resilient/obvious thing to fix up?

I was curious if these changes would have any impact on things like
WEP where the frames are a little larger? I came across a random post
about 80211 mdsu/mtus here
https://www.cwnp.com/forums/posts?postNum=307311 and they had
mentioned it, so it got me curious

On Tue, Nov 26, 2019 at 7:00 PM Wen Gong <wgong@codeaurora.org> wrote:
>
> For sdio chip, the max credit size in firmware is 1556, the 1556
> include payload, ieee80211 header, htt header, htc header. So it
> need to set the max mtu to 1500 to forbidden TX packet which exceed
> 1500 form application.
>
> Tested with QCA6174 SDIO with firmware
> WLAN.RMH.4.4.1-00017-QCARMSWP-1.
>
> Signed-off-by: Wen Gong <wgong@codeaurora.org>
> ---
>  drivers/net/wireless/ath/ath10k/sdio.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/net/wireless/ath/ath10k/sdio.c b/drivers/net/wireless/ath/ath10k/sdio.c
> index 60849ab8088f..8aa8ebc1d8e9 100644
> --- a/drivers/net/wireless/ath/ath10k/sdio.c
> +++ b/drivers/net/wireless/ath/ath10k/sdio.c
> @@ -2185,6 +2185,8 @@ static int ath10k_sdio_probe(struct sdio_func *func,
>         bus_params.chip_id = 0;
>         bus_params.hl_msdu_ids = true;
>
> +       ar->hw->max_mtu = ETH_DATA_LEN;
> +
>         ret = ath10k_core_register(ar, &bus_params);
>         if (ret) {
>                 ath10k_err(ar, "failed to register driver core: %d\n", ret);
> --
> 2.23.0
>