Re: [PATCH iwl-next v8 06/11] igc: set the RX packet buffer size for TSN mode

Vladimir Oltean
2025-03-05T23:16:09Z

On Wed, Mar 05, 2025 at 08:00:21AM -0500, Faizal Rahim wrote:
> In preparation for supporting frame preemption, when entering TSN mode
> set the receive packet buffer to 16KB for the Express MAC, 16KB for
> the Preemptible MAC and 2KB for the BMC, according to the datasheet
> section 7.1.3.2.
>
> Co-developed-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
> Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
> Signed-off-by: Faizal Rahim <faizal.abdul.rahim@linux.intel.com>
> ---
> drivers/net/ethernet/intel/igc/igc_defines.h | 3 +++
> drivers/net/ethernet/intel/igc/igc_tsn.c | 13 +++++++++++--
> 2 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/igc/igc_defines.h b/drivers/net/ethernet/intel/igc/igc_defines.h
> index 516ef70c98e9..b19ac6f30dac 100644
> --- a/drivers/net/ethernet/intel/igc/igc_defines.h
> +++ b/drivers/net/ethernet/intel/igc/igc_defines.h
> @@ -402,6 +402,9 @@
>
> /* 7KB bytes buffer for each tx queue (total 4 queues) + 4KB for BMC*/
> #define IGC_TXPBSIZE_TSN 0x041c71c7
> +/* 15KB for EXP + 15KB for BE + 2KB for BMC */
> +#define IGC_RXPBSIZE_TSN 0x0000f08f
> +#define IGC_RXPBSIZE_SIZE_MASK 0x0001FFFF

Does 0x0000f08f have any further meaning, does it represent anything
bitwise? (similar question for IGC_TXPBSIZE_TSN in the previous patch).
I don't see the correlation between the values mentioned in the comment
and the magic constant. If RXPBPSIZE has a bitwise meaning, maybe you
could rewrite the magic value with macros for each field.