linux-kernel - Re: [PATCH net-next v3] net: ethernet: mtk_eth_soc: convert cap_bit in mtk_eth

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Message-ID: <20250424184311.GM3042781@horms.kernel.org>
Date: Thu, 24 Apr 2025 19:43:11 +0100
From: Simon Horman <horms@...nel.org>
To: Daniel Golle <daniel@...rotopia.org>
Cc: Felix Fietkau <nbd@....name>, Sean Wang <sean.wang@...iatek.com>,
	Lorenzo Bianconi <lorenzo@...nel.org>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH net-next v3] net: ethernet: mtk_eth_soc: convert cap_bit
 in mtk_eth_muxc struct to u64

On Wed, Apr 23, 2025 at 01:48:02AM +0100, Daniel Golle wrote:
> From: Bo-Cun Chen <bc-bocun.chen@...iatek.com>
> 
> With commit 51a4df60db5c2 ("net: ethernet: mtk_eth_soc: convert caps in
> mtk_soc_data struct to u64") the capabilities bitfield was converted to
> a 64-bit value, but a cap_bit in struct mtk_eth_muxc which is used to
> store a full bitfield (rather than the bit number, as the name would
> suggest) still holds only a 32-bit value.
> 
> Change the type of cap_bit to u64 in order to avoid truncating the
> bitfield which results in path selection to not work with capabilities
> above the 32-bit limit.
> 
> The values currently stored in the cap_bit field are
> MTK_ETH_MUX_GDM1_TO_GMAC1_ESW:
>  BIT_ULL(18) | BIT_ULL(5)
> 
> MTK_ETH_MUX_GMAC2_GMAC0_TO_GEPHY:
>  BIT_ULL(19) | BIT_ULL(5) | BIT_ULL(6)
> 
> MTK_ETH_MUX_U3_GMAC2_TO_QPHY:
>  BIT_ULL(20) | BIT_ULL(5) | BIT_ULL(6)
> 
> MTK_ETH_MUX_GMAC1_GMAC2_TO_SGMII_RGMII:
>  BIT_ULL(20) | BIT_ULL(5) | BIT_ULL(7)
> 
> MTK_ETH_MUX_GMAC12_TO_GEPHY_SGMII:
>  BIT_ULL(21) | BIT_ULL(5)
> 
> While all those values are currently still within 32-bit boundaries,
> the addition of new capabilities of MT7988 as well as future SoC's
> like MT7987 will exceed them. Also, the use of a 32-bit 'int' type to
> store the result of a BIT_ULL(...) is misleading.
> 
> Signed-off-by: Bo-Cun Chen <bc-bocun.chen@...iatek.com>
> Signed-off-by: Daniel Golle <daniel@...rotopia.org>
> ---
> v3: don't use Fixes: tag
> v2: improve commit message

Thanks for the updates.

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