> From: Chad Monroe <chad@monroe.io>
> 
> With flow stats enabled, PPE offload setup requests flow statistics
> from the NPU. If the running NPU firmware does not support flow
> counters, the request fails and the current setup path aborts PPE
> offload.
> 
> Treat flow statistics as an optional capability so that a failure to
> set up the counters does not prevent normal PPE offload. Continue PPE
> initialization when the NPU refuses the flow-statistics request.
> 
> Also treat a zero NPU statistics address returned by the firmware as a
> refusal. The host-side DMA buffer (foe_stats_dma) is allocated by
> dmam_alloc_coherent() in airoha_ppe_init() from system memory. The NPU
> statistics address (npu_stats_addr) is a separate allocation from the
> NPU firmware's internal SRAM pool. When that pool is exhausted, the
> firmware replies with success and npu_stats_addr = 0. A zero address
> does not provide a usable counter region and must not be passed to
> devm_ioremap().
> 
> When flow stats entries are available, clear PSE_PORT6_SHARE_DIS so
> that PSE port 6 (CDM3 path to the NPU) participates in shared-buffer
> flow control. PSE_FC_CFG bits 26:16 control per-port whether flow
> control considers the shared buffer pool. Bit 22 is port 6.
> 
> When flow statistics are unavailable, PPE continues to operate without
> NPU flow counters while retaining normal offload functionality.
> 
> This combines the original SmartRG/Airoha fixes for:
> - keeping PPE offload active when the NPU refuses flow statistics
> - treating a zero NPU statistics address as a flow-statistics refusal
> 
> Based on the original SmartRG/Airoha work by Chad Monroe:
> 5ce96ab ("SDG-9458: keep PPE offload when NPU refuses flow stats")
> 0ad8528 ("SDG-9458: airoha: treat a zero NPU stats address as a refusal")
> Fixes: b81e0f2b58be ("net: airoha: Add FLOW_CLS_STATS callback support")
> Tested-on: AN7581 with MT7992
> Signed-off-by: Chad Monroe <chad@monroe.io>
> Signed-off-by: SAYANTAN NANDY <sayantann11@gmail.com>

Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>

> ---
> 
> Changes since v2:
> - Drop flow_stats_cap entirely (Lorenzo).
> - Keep the original airoha_ppe_get_num_stats_entries() checks (Lorenzo).
> - Guard airoha_fe_clear() with sram_num_stats_entries > 0 (Lorenzo).
> - Replace the error assignment and goto with a direct if check and
>   dev_warn() (Lorenzo).
> 
> Changes since v1:
> - Explain the NPU SRAM allocation separately from the host-side DMA
>   buffer (Lorenzo).
> - Use airoha_fe_clear() and shorten the warning message (Lorenzo).
> - Include hardware testing information requested by netdev-bot.
> 
>  drivers/net/ethernet/airoha/airoha_npu.c  |  8 ++++++++
>  drivers/net/ethernet/airoha/airoha_ppe.c  | 10 ++++++----
>  drivers/net/ethernet/airoha/airoha_regs.h |  2 ++
>  3 files changed, 16 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/airoha/airoha_npu.c b/drivers/net/ethernet/airoha/airoha_npu.c
> index 4d3195eb00f7..b32a01dbe06b 100644
> --- a/drivers/net/ethernet/airoha/airoha_npu.c
> +++ b/drivers/net/ethernet/airoha/airoha_npu.c
> @@ -450,6 +450,14 @@ static int airoha_npu_ppe_stats_setup(struct airoha_npu *npu,
>  	if (err)
>  		goto out;
>  
> +	/* The firmware reports success with a zero address when its SRAM
> +	 * pool has no room left for the counters.
> +	 */
> +	if (!ppe_data->stats_info.npu_stats_addr) {
> +		err = -ENOSPC;
> +		goto out;
> +	}
> +
>  	npu->stats = devm_ioremap(npu->dev,
>  				  ppe_data->stats_info.npu_stats_addr,
>  				  size);
> diff --git a/drivers/net/ethernet/airoha/airoha_ppe.c b/drivers/net/ethernet/airoha/airoha_ppe.c
> index 92611802801e..74ac3791cb63 100644
> --- a/drivers/net/ethernet/airoha/airoha_ppe.c
> +++ b/drivers/net/ethernet/airoha/airoha_ppe.c
> @@ -144,6 +144,9 @@ static void airoha_ppe_hw_init(struct airoha_ppe *ppe)
>  	sram_ppe_num_data_entries =
>  		PPE_RAM_NUM_ENTRIES_SHIFT(sram_ppe_num_data_entries);
>  
> +	if (sram_num_stats_entries > 0)
> +		airoha_fe_clear(eth, PSE_FC_CFG, PSE_PORT6_SHARE_DIS);
> +
>  	for (i = 0; i < eth->soc->num_ppe; i++) {
>  		airoha_fe_wr(eth, REG_PPE_TB_BASE(i),
>  			     ppe->foe_dma + sram_tb_size);
> @@ -1454,10 +1457,9 @@ static int airoha_ppe_offload_setup(struct airoha_eth *eth)
>  
>  	ppe_num_stats_entries = airoha_ppe_get_total_num_stats_entries(ppe);
>  	if (ppe_num_stats_entries > 0) {
> -		err = npu->ops.ppe_init_stats(npu, ppe->foe_stats_dma,
> -					      ppe_num_stats_entries);
> -		if (err)
> -			goto error_npu_put;
> +		if (npu->ops.ppe_init_stats(npu, ppe->foe_stats_dma,
> +					    ppe_num_stats_entries))
> +			dev_warn(eth->dev, "NPU refused flow stats\n");
>  	}
>  
>  	airoha_ppe_hw_init(ppe);
> diff --git a/drivers/net/ethernet/airoha/airoha_regs.h b/drivers/net/ethernet/airoha/airoha_regs.h
> index 442b48c9b991..aee06c058586 100644
> --- a/drivers/net/ethernet/airoha/airoha_regs.h
> +++ b/drivers/net/ethernet/airoha/airoha_regs.h
> @@ -72,6 +72,8 @@
>  #define PSE_CFG_OQ_RSV_MASK		GENMASK(13, 0)
>  
>  #define PSE_FQ_CFG			0x008c
> +#define PSE_FC_CFG			0x0098
> +#define PSE_PORT6_SHARE_DIS		BIT(22)
>  #define PSE_FQ_LIMIT_MASK		GENMASK(14, 0)
>  
>  #define REG_FE_PSE_BUF_SET		0x0090
> -- 
> 2.43.0
>