linux-kernel - Re: [PATCH net-next 05/13] net: macb: add no LSO capability (MACB_CAPS_NO

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Message-ID: <3e6cb322-bc8d-471c-87c8-286b98f12ad9@tuxon.dev>
Date: Mon, 24 Mar 2025 10:18:44 +0200
From: Claudiu Beznea <claudiu.beznea@...on.dev>
To: Théo Lebrun <theo.lebrun@...tlin.com>,
 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>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Nicolas Ferre <nicolas.ferre@...rochip.com>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Alexandre Ghiti <alex@...ti.fr>, Samuel Holland <samuel.holland@...ive.com>,
 Richard Cochran <richardcochran@...il.com>,
 Russell King <linux@...linux.org.uk>,
 Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
 Vladimir Kondratiev <vladimir.kondratiev@...ileye.com>,
 Gregory CLEMENT <gregory.clement@...tlin.com>
Cc: netdev@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
 linux-mips@...r.kernel.org, Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
 Tawfik Bayouk <tawfik.bayouk@...ileye.com>
Subject: Re: [PATCH net-next 05/13] net: macb: add no LSO capability
 (MACB_CAPS_NO_LSO)

Hi, Theo,

On 21.03.2025 21:09, Théo Lebrun wrote:
> LSO is runtime-detected using the PBUF_LSO field inside register
> designcfg_debug6/GEM_DCFG6. Allow disabling that feature if it is
> broken by using struct macb_config->caps.
> 
> Signed-off-by: Théo Lebrun <theo.lebrun@...tlin.com>
> ---
>  drivers/net/ethernet/cadence/macb.h      | 1 +
>  drivers/net/ethernet/cadence/macb_main.c | 5 +++--
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
> index 3b43cb9468e3618754ff2bc6c5f360447bdeeed0..e9da6e3b869fc772613a0d6b86308917c9bff7fe 100644
> --- a/drivers/net/ethernet/cadence/macb.h
> +++ b/drivers/net/ethernet/cadence/macb.h
> @@ -739,6 +739,7 @@
>  #define MACB_CAPS_MIIONRGMII			BIT(9)
>  #define MACB_CAPS_NEED_TSUCLK			BIT(10)
>  #define MACB_CAPS_QUEUE_DISABLE			BIT(11)
> +#define MACB_CAPS_NO_LSO			BIT(12)
>  #define MACB_CAPS_PCS				BIT(24)
>  #define MACB_CAPS_HIGH_SPEED			BIT(25)
>  #define MACB_CAPS_CLK_HW_CHG			BIT(26)
> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
> index b5797c1ac0a41e9472883b013c1e44a01092f257..807f7abbd9941bf624f14a5ddead68dad1c8deb2 100644
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -4373,8 +4373,9 @@ static int macb_init(struct platform_device *pdev)
>  	/* Set features */
>  	dev->hw_features = NETIF_F_SG;
>  
> -	/* Check LSO capability */
> -	if (GEM_BFEXT(PBUF_LSO, gem_readl(bp, DCFG6)))
> +	/* Check LSO capability; capability is for buggy HW */

The comment here is a bit confusing to me.

> +	if (!(bp->caps & MACB_CAPS_NO_LSO) &&
> +	    GEM_BFEXT(PBUF_LSO, gem_readl(bp, DCFG6)))
>  		dev->hw_features |= MACB_NETIF_LSO;
>  
>  	/* Checksum offload is only available on gem with packet buffer */
>