Subject: Re: [PATCH iwl-net] igc: Fix hicredit calculation

From: Vinicius Costa Gomes <[email-masked]>
Date: Fri, 08 Dec 2023 16:54:17 -0800

Rodrigo Cataldo via B4 Relay
<[email-masked]> writes:

> From: Rodrigo Cataldo <[email-masked]>
>
> According to the Intel Software Manual for I225, Section 7.5.2.7,
> hicredit should be multiplied by the constant link-rate value, 0x7736.
>
> Currently, the old constant link-rate value, 0x7735, from the boards
> supported on igb are being used, most likely due to a copy'n'paste, as
> the rest of the logic is the same for both drivers.
>
> Update hicredit accordingly.
>
> Fixes: 1ab011b0bf07 ("igc: Add support for CBS offloading")
> Reviewed-by: Kurt Kanzenbach <[email-masked]>
> Signed-off-by: Rodrigo Cataldo <[email-masked]>
> ---

Very good catch.

Acked-by: Vinicius Costa Gomes <[email-masked]>

Just for curiosity, my test machines are busy right now, what kind of
difference are you seeing?

> This is a simple fix for the credit calculation on igc devices
> (i225/i226) to match the Intel software manual.
>
> This is my first contribution to the Linux Kernel. Apologies for any
> mistakes and let me know if I improve anything.
> ---
>  drivers/net/ethernet/intel/igc/igc_tsn.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/intel/igc/igc_tsn.c b/drivers/net/ethernet/intel/igc/igc_tsn.c
> index a9c08321aca9..22cefb1eeedf 100644
> --- a/drivers/net/ethernet/intel/igc/igc_tsn.c
> +++ b/drivers/net/ethernet/intel/igc/igc_tsn.c
> @@ -227,7 +227,7 @@ static int igc_tsn_enable_offload(struct igc_adapter *adapter)
>  			wr32(IGC_TQAVCC(i), tqavcc);
>  
>  			wr32(IGC_TQAVHC(i),
> -			     0x80000000 + ring->hicredit * 0x7735);
> +			     0x80000000 + ring->hicredit * 0x7736);
>  		} else {
>  			/* Disable any CBS for the queue */
>  			txqctl &= ~(IGC_TXQCTL_QAV_SEL_MASK);
>
> ---
> base-commit: 2078a341f5f609d55667c2dc6337f90d8f322b8f
> change-id: 20231206-igc-fix-hicredit-calc-028bf73c50a8
>
> Best regards,
> -- 
> Rodrigo Cataldo <[email-masked]>
>

Cheers,
-- 
Vinicius