Re: [PATCH net-next 05/13] net: macb: add no LSO capability (MACB_CAPS_NO_LSO)

[Théo Lebrun]

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@xxxxxxxxxxx>
>> ---
>>  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