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Date: Thu, 9 Jan 2025 16:31:59 +0000
From: Simon Horman <horms@kernel.org>
To: Paul Barker <paul.barker.ct@bp.renesas.com>
Cc: Niklas =?utf-8?Q?S=C3=B6derlund?= <niklas.soderlund@ragnatech.se>,
	Andrew Lunn <andrew+netdev@lunn.ch>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>, Paolo Abeni <pabeni@redhat.com>,
	Sergey Shtylyov <s.shtylyov@omp.ru>, netdev@vger.kernel.org,
	linux-renesas-soc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [net PATCH] net: ravb: Fix max TX frame size for RZ/V2M
Message-ID: <20250109163159.GL7706@kernel.org>
References: <20250109113706.1409149-1-paul.barker.ct@bp.renesas.com>
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In-Reply-To: <20250109113706.1409149-1-paul.barker.ct@bp.renesas.com>

On Thu, Jan 09, 2025 at 11:37:06AM +0000, Paul Barker wrote:
> When tx_max_frame_size was added to struct ravb_hw_info, no value was
> set in ravb_rzv2m_hw_info so the default value of zero was used.
> 
> The maximum MTU is set by subtracting from tx_max_frame_size to allow
> space for headers and frame checksums. As ndev->max_mtu is unsigned,
> this subtraction wraps around leading to a ridiculously large positive
> value that is obviously incorrect.
> 
> Before tx_max_frame_size was introduced, the maximum MTU was based on
> rx_max_frame_size. So, we can restore the correct maximum MTU by copying
> the rx_max_frame_size value into tx_max_frame_size for RZ/V2M.
> 
> Fixes: 1d63864299ca ("net: ravb: Fix maximum TX frame size for GbEth devices")
> Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>

Reviewed-by: Simon Horman <horms@kernel.org>

...