[PATCH net v2] net: airoha: Fix TX scheduler queue mask loop upper bound

[Lorenzo Bianconi]

> In airoha_qdma_set_chan_tx_sched(), the loop clearing queue mask was
> using AIROHA_NUM_TX_RING (32) instead of AIROHA_NUM_QOS_QUEUES (8).
> 
> Each channel has 8 queues, and TXQ_DISABLE_CHAN_QUEUE_MASK(channel, i)
> computes BIT(i + (channel * 8)). With i ranging 0..31, this causes:
> - channel 0: clears bit 0..31 (all 4 channels) instead of 0..7
> - channel 1: clears bit 8..31 (channels 1-3) instead of 8..15
> - channel 2: clears bit 16..31 (channels 2-3) instead of 16..23
> - channel 3: clears bit 24..31 (channel 3 only) - correct by accident
> 
> While BIT(32+) on arm64 produces 64-bit values truncated to 0 in u32
> mask parameter, the loop still incorrectly clears queues within the
> same channel beyond queue 7.
> 
> Even though this is functionally harmless (the register resets to 0
> and is only ever cleared, never set — so clearing extra bits is a
> no-op), the loop bound is semantically wrong and should be fixed for
> correctness and clarity.
> 
> Fix by using AIROHA_NUM_QOS_QUEUES (8) as the loop upper bound.
> 
> Fixes: ef1ca9271313 ("net: airoha: Add sched HTB offload support")
> Acked-by: Lorenzo Bianconi <lorenzo at kernel.org>
> Signed-off-by: Wayen Yan <win847 at gmail.com>
> ---
> Changes in v2:
> - Add Lorenzo's Acked-by tag.
> - Clarify in commit message that this is semantically wrong but
>   functionally harmless (register resets to 0, only cleared), as
>   Lorenzo pointed out in review.
> - Rebase on current net tree.
> 
> Link: https://lore.kernel.org/netdev/ajJIWMs4dVbfkHZ5@lore-desk/
> Link: https://lore.kernel.org/netdev/CAL_ptrs6J3Ryw_4mVTq5VgzkB4RreF5S0huHyLvd9YwWr1m6jAA@mail.gmail.com/
> 
>  drivers/net/ethernet/airoha/airoha_eth.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
> index d0c0c0ec8a..ca77747b44 100644
> --- a/drivers/net/ethernet/airoha/airoha_eth.c
> +++ b/drivers/net/ethernet/airoha/airoha_eth.c
> @@ -2212,7 +2212,7 @@ static int airoha_qdma_set_chan_tx_sched(struct net_device *dev,
>  	struct airoha_gdm_port *port = netdev_priv(dev);

it seems you have not rebased on top of net tree.

Regards,
Lorenzo

>  	int i;
>  
> -	for (i = 0; i < AIROHA_NUM_TX_RING; i++)
> +	for (i = 0; i < AIROHA_NUM_QOS_QUEUES; i++)
>  		airoha_qdma_clear(port->qdma, REG_QUEUE_CLOSE_CFG(channel),
>  				  TXQ_DISABLE_CHAN_QUEUE_MASK(channel, i));
>  
> -- 
> 2.51.0
> 
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