RE: [PATCH iwl-net] igc: Fix hicredit calculation

[Vinicius Costa Gomes <vinicius.gomes@intel.com>]

Rodrigo CADORE CATALDO <rodrigo.cadore@l-acoustics.com> writes:

>> -----Original Message-----
>> From: Vinicius Costa Gomes <vinicius.gomes@intel.com>
>> 
>> Rodrigo Cataldo via B4 Relay
>> <devnull+rodrigo.cadore.l-acoustics.com@kernel.org> writes:
>> 
>> > From: Rodrigo Cataldo <rodrigo.cadore@l-acoustics.com>
>> >
>> > 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 <kurt@linutronix.de>
>> > Signed-off-by: Rodrigo Cataldo <rodrigo.cadore@l-acoustics.com>
>> > ---
>> 
>> Very good catch.
>> 
>> Acked-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
>> 
>> Just for curiosity, my test machines are busy right now, what kind of
>> difference are you seeing?
>> 
>
> Hello Vinicius, thank you for the ACK.
>
> For our internal setup, this does not make a difference. My understanding is 
> that hicredit is used for non-SR traffic mixed with SR traffic (i.e., hicredit is
> directly related to the max non-SR frame size). But our setup does not mix
> them (q0 is used only for milan audio/clock SR class A).

I see.

>
> Let me know if you think we need a testcase for this.
>

It was just curiority. No need. Thanks.

>> > 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 <rodrigo.cadore@l-acoustics.com>
>> >
>> 
>> Cheers,
>> --
>> Vinicius
>
> Best Regards,
> Rodrigo Cataldo


Cheers,
-- 
Vinicius