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

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Message-Id: <D8Q42H2O4AC0.1HV63W6F5L45U@bootlin.com>
Date: Wed, 26 Mar 2025 11:04:14 +0100
From: Théo Lebrun <theo.lebrun@...tlin.com>
To: "Claudiu Beznea" <claudiu.beznea@...on.dev>, "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)

Hello Claudiu,

On Mon Mar 24, 2025 at 9:18 AM CET, Claudiu Beznea wrote:
> 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.

Proposal:

+  /* Check LSO capability; runtime detection can be overridden by a cap
+   * flag if the hardware is known to be buggy */

I'll use that in V2, or feel free to reply if it's still unclear.

Thanks,

--
Théo Lebrun, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com