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

Théo Lebrun
2025-03-26T10:04:27Z

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@bootlin.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