Re: [PATCH net-next 1/2] net: stmmac: dwmac4: Read the UC filter size from hardware capabilities

[Nicolai Buchwitz]

Hi Maxime

On 31.8.2026 09:01, Maxime Chevallier wrote:
> dwmac4 has multiple banks of perfect filter entries, independently
> configurable during IP integration.
>
> The multi_addr bank reports a number between 0 and 31 corresponding to
> the actual number of entries in that bank, while the 32 and 64 banks
> are all-or-nothing.
>
> Expose these caps over debugfs as well.
>
> Signed-off-by: Maxime Chevallier <maxime.chevallier@xxxxxxxxxxx>
> ---

> [...]

> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4.h 
> b/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
> index 6382836828ba..89368e34a388 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
> @@ -176,7 +176,9 @@ enum power_event {
>
>  /* MAC HW features0 bitmap */
>  #define GMAC_HW_FEAT_SAVLANINS		BIT(27)
> -#define GMAC_HW_FEAT_ADDMAC		BIT(18)
> +#define GMAC_HW_FEAT_MACADR64SEL	BIT(24)
> +#define GMAC_HW_FEAT_MACADR32SEL	BIT(23)
> +#define GMAC_HW_FEAT_ADDMAC		GENMASK(22, 18)
>  #define GMAC_HW_FEAT_RXCOESEL		BIT(16)
>  #define GMAC_HW_FEAT_TXCOSEL		BIT(14)
>  #define GMAC_HW_FEAT_EEESEL		BIT(13)
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c 
> b/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c
> index 23ffe1adcd0d..14ac3f0e51f7 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c
> @@ -388,6 +388,8 @@ static int dwmac4_get_hw_feature(void __iomem 
> *ioaddr,
>  	dma_cap->half_duplex = (hw_cap & GMAC_HW_FEAT_HDSEL) >> 2;
>  	dma_cap->vlhash = (hw_cap & GMAC_HW_FEAT_VLHASH) >> 4;
>  	dma_cap->multi_addr = (hw_cap & GMAC_HW_FEAT_ADDMAC) >> 18;

Now that ADDMAC has grown from single bit to a mask, the hardcoded 18 
has to match
dwmac4.h. So IMHO it would make sense to use FIELD_GET() here (like 
actphyif)?

> +	dma_cap->additional_32_addr = (hw_cap & GMAC_HW_FEAT_MACADR32SEL) >> 
> 23;
> +	dma_cap->additional_64_addr = (hw_cap & GMAC_HW_FEAT_MACADR64SEL) >> 
> 24;
>  	dma_cap->pcs = (hw_cap & GMAC_HW_FEAT_PCSSEL) >> 3;
>  	dma_cap->sma_mdio = (hw_cap & GMAC_HW_FEAT_SMASEL) >> 5;
>  	dma_cap->pmt_remote_wake_up = (hw_cap & GMAC_HW_FEAT_RWKSEL) >> 6;
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c 
> b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index f2fc89176654..a885f8cfef21 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -6580,6 +6580,18 @@ static int stmmac_dma_cap_show(struct seq_file 
> *seq, void *v)
>  		seq_printf(seq,
>  			   "\tNumber of Additional MAC address registers: %d\n",
>  			   priv->dma_cap.multi_addr);
> +	} else if (priv->plat->core_type == DWMAC_CORE_GMAC4) {
> +		seq_printf(seq,
> +			   "\tNumber of MAC address registers (1-31): %d\n",
> +			   priv->dma_cap.multi_addr);
> +		seq_printf(seq,
> +			   "\tAdditional 32 MAC address registers (32-63): %s\n",
> +			   priv->dma_cap.additional_32_addr ? "Y" : "N");
> +		seq_printf(seq,
> +			   "\tAdditional 64 MAC address registers (64-127): %s\n",
> +			   priv->dma_cap.additional_64_addr ? "Y" : "N");
> +		seq_printf(seq, "\tHash Filter: %s\n",
> +			   (priv->dma_cap.hash_filter) ? "Y" : "N");

hash_filter seems to be only set in dwmac1000_dma.c? So on dwmac4 it 
would always print N?

>  	} else {
>  		seq_printf(seq, "\tHash Filter: %s\n",
>  			   (priv->dma_cap.hash_filter) ? "Y" : "N");

Thanks,
Nicolai