Re: [PATCH net RESEND v2] net: macb: configure ENST registers for all queues

[Jacob Keller]

On 10/5/2026 4:08 AM, Vineeth Karumanchi wrote:
> When a taprio config only covered a subset of queues, the driver
> programmed the ENST registers only for the queues named in the config
> and left the remaining queues holding stale register values. This
> produced an inconsistent hardware setup that affected the scheduling
> of the configured queues.
> 
> This was observed on a GEM instance with four hardware queues, all
> enabled:
> 
> Initial configuration:
> - All four queues are enabled.
> - enst_on_time_qX registers are left at their reset value (0x0001FFFF).
> - Only q0 and q1 are configured with valid, non-overlapping ENST
>   schedules (T0 and T1 respectively).
> - Traffic streams p0 and p1 are bound to q0 and q1.
> - ENST is enabled only on q0 and q1.
> 
> Observed behavior:
> - During T0 on-time, both p0 and p1 packets are transmitted.
> - During T1 on-time, both p0 and p1 packets are transmitted.
> 
> With the unused queues (q2 and q3) explicitly programmed with
> enst_on_time = 0x0:
> - During T0 on-time, only p0 packets are transmitted.
> - During T1 on-time, only p1 packets are transmitted.
> 
> Leaving the ENST on-time registers of unused queues at their reset
> value (0x0001FFFF) disrupts the scheduling of the configured queues,
> whereas programming them with 0x0 yields the expected ENST operation.
> 
> Program the ENST registers for every queue unconditionally. The
> per-queue configuration array is now allocated for bp->num_queues and
> indexed directly by queue_id; unconfigured queues are left
> zero-initialized by kzalloc_objs(), so their registers are cleared.
> Indexing the array by queue_id also makes the queue_id field in
> struct macb_queue_enst_config redundant, so drop it.
> 
> Fixes: 89934dbf169e ("net: macb: Add TAPRIO traffic scheduling support")
> Reviewed-by: Théo Lebrun <theo.lebrun@xxxxxxxxxxx>
> Signed-off-by: Vineeth Karumanchi <vineeth.karumanchi@xxxxxxx>
> ---

Reviewed-by: Jacob Keller <jacob.e.keller@xxxxxxxxx>