Re: [PATCH net] net: airoha: Add retry mechanism to airoha_qdma_set_trtcm_param()

[Lorenzo Bianconi <lorenzo@kernel.org>]

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> From: Brown Huang <brown.huang@airoha.com>
> 
> CPU accesses QDMA via the bus. When multiple modules are using the bus
> simultaneously, CPU access to QDMA may encounter bus timeouts and fails,
> resulting in QDMA configuration failures and potentially causing packet
> transmission issues. In order to mitigate the issue, introduce a retry
> mechanism to airoha_qdma_set_trtcm_param routine in order to ensure the
> configuration is correctly applied to the hardware.
> 
> Fixes: ef1ca9271313b ("net: airoha: Add sched HTB offload support")
> Signed-off-by: Brown Huang <brown.huang@airoha.com>
> Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> ---
>  drivers/net/ethernet/airoha/airoha_eth.c | 21 +++++++++++++++------
>  1 file changed, 15 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
> index eab6a98d62b9..aaf7d8c8ccd3 100644
> --- a/drivers/net/ethernet/airoha/airoha_eth.c
> +++ b/drivers/net/ethernet/airoha/airoha_eth.c
> @@ -2493,14 +2493,23 @@ static int airoha_qdma_set_trtcm_param(struct airoha_qdma *qdma, int channel,
>  		     FIELD_PREP(TRTCM_METER_GROUP_MASK, group) |
>  		     FIELD_PREP(TRTCM_PARAM_INDEX_MASK, idx) |
>  		     FIELD_PREP(TRTCM_PARAM_RATE_TYPE_MASK, mode);
> +	int i;
>  
> -	airoha_qdma_wr(qdma, REG_TRTCM_DATA_LOW(addr), val);
> -	airoha_qdma_wr(qdma, REG_TRTCM_CFG_PARAM(addr), config);
> +	for (i = 0; i < 100; i++) {
> +		u32 data;
>  
> -	return read_poll_timeout(airoha_qdma_rr, val,
> -				 val & TRTCM_PARAM_RW_DONE_MASK,
> -				 USEC_PER_MSEC, 10 * USEC_PER_MSEC, true,
> -				 qdma, REG_TRTCM_CFG_PARAM(addr));
> +		airoha_qdma_wr(qdma, REG_TRTCM_DATA_LOW(addr), val);
> +		wmb();
> +		airoha_qdma_wr(qdma, REG_TRTCM_CFG_PARAM(addr), config);
> +		if (airoha_qdma_get_trtcm_param(qdma, channel, addr, param,
> +						mode, &data, NULL))
> +			continue;
> +
> +		if (data == val)
> +			break;
> +	}
> +
> +	return i == 100 ? -EBUSY : 0;
>  }
>  
>  static int airoha_qdma_set_trtcm_config(struct airoha_qdma *qdma, int channel,
> 
> ---
> base-commit: 4aacf509e537a711fa71bca9f234e5eb6968850e
> change-id: 20260605-airoha_qdma_set_trtcm_param-retry-fix-a9d2956b9b2f
> 
> Best regards,
> -- 
> Lorenzo Bianconi <lorenzo@kernel.org>

I think the issue reported by sashiko in [0] is valid and it needs to be
addressed in v2, but since I am not the original author of the patch, I will
let Brown or Leto comment on it.

Regards,
Lorenzo

[0] https://sashiko.dev/#/patchset/20260608-airoha_qdma_set_trtcm_param-retry-fix-v1-1-f07704f0d8c5%40kernel.org

> 

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