Re: [PATCH] net: stmmac: set multicast filter to zero if feature is unsupported

[Nikunj Kela <nikunj.kela@sima.ai>]

On 5/25/25 7:09 PM, Yanteng Si wrote:
> 在 5/24/25 6:19 AM, Nikunj Kela 写道:
>> Hash based multicast filtering is an optional feature. Currently,
>> driver overrides the value of multicast_filter_bins based on the hash
>> table size. If the feature is not supported, hash table size reads 0
>> however the value of multicast_filter_bins remains set to default
>> HASH_TABLE_SIZE which is incorrect. Let's override it to 0 if the
>> feature is unsupported.
>>
>> Signed-off-by: Nikunj Kela <nikunj.kela@sima.ai>
>> ---
>>   drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c 
>> b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> index 085c09039af4..ccea9f811a05 100644
>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> @@ -7241,6 +7241,9 @@ static int stmmac_hw_init(struct stmmac_priv 
>> *priv)
>>                       (BIT(priv->dma_cap.hash_tb_sz) << 5);
>>               priv->hw->mcast_bits_log2 =
>> ilog2(priv->hw->multicast_filter_bins);
>> +        } else {
>> +            priv->hw->multicast_filter_bins = 0;
>> +            priv->hw->mcast_bits_log2 = 0;
>>           }
>
> I didn't read the code carefully, just did a simple search：
>
> ❯ grep -rn multicast_filter_bins drivers/net/
> drivers/net/ethernet/stmicro/stmmac/common.h:611:    unsigned int 
> multicast_filter_bins;
> drivers/net/ethernet/stmicro/stmmac/dwmac-sophgo.c:26: 
> plat_dat->multicast_filter_bins = 0;
> ***
> drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c:512: 
> plat->multicast_filter_bins = HASH_TABLE_SIZE;
> ***
> drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c:536: 
> &plat->multicast_filter_bins);
> drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c:541: 
> plat->multicast_filter_bins = dwmac1000_validate_mcast_bins(
> drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c:542: &pdev->dev, 
> plat->multicast_filter_bins);
> drivers/net/ethernet/stmicro/stmmac/dwmac1000_core.c:523: 
> mac->multicast_filter_bins = priv->plat->multicast_filter_bins;
> drivers/net/ethernet/stmicro/stmmac/dwmac1000_core.c:527:    if 
> (mac->multicast_filter_bins)
> drivers/net/ethernet/stmicro/stmmac/dwmac1000_core.c:528: 
> mac->mcast_bits_log2 = ilog2(mac->multicast_filter_bins);
> drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c:516: 
> (netdev_mc_count(dev) > hw->multicast_filter_bins)) {
> drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c:1527: 
> mac->multicast_filter_bins = priv->plat->multicast_filter_bins;
> drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c:1531:    if 
> (mac->multicast_filter_bins)
> drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c:1532: 
> mac->mcast_bits_log2 = ilog2(mac->multicast_filter_bins);
> drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c:1568: 
> mac->multicast_filter_bins = priv->plat->multicast_filter_bins;
> drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c:1572:    if 
> (mac->multicast_filter_bins)
> drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c:1573: 
> mac->mcast_bits_log2 = ilog2(mac->multicast_filter_bins);
> drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c:543:    if 
> (netdev_mc_count(priv->dev) >= priv->hw->multicast_filter_bins)
> drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c:633:    if 
> (netdev_mc_count(priv->dev) >= priv->hw->multicast_filter_bins)
> drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c:679:    if 
> (netdev_mc_count(priv->dev) >= priv->hw->multicast_filter_bins)
> drivers/net/ethernet/stmicro/stmmac/stmmac_pci.c:31: 
> plat->multicast_filter_bins = HASH_TABLE_SIZE;
> drivers/net/ethernet/stmicro/stmmac/stmmac_pci.c:84: 
> plat->multicast_filter_bins = HASH_TABLE_SIZE;
> drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c:98: 
> plat->multicast_filter_bins = 256;
> drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c:365: 
> mac->multicast_filter_bins = priv->plat->multicast_filter_bins;
> drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c:369:    if 
> (mac->multicast_filter_bins)
> drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c:370: 
> mac->mcast_bits_log2 = ilog2(mac->multicast_filter_bins);
> drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:7240: 
> priv->hw->multicast_filter_bins =
> drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:7243: 
> ilog2(priv->hw->multicast_filter_bins);
> drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c:570: 
> plat->multicast_filter_bins = HASH_TABLE_SIZE;
> drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c:707: 
> plat->multicast_filter_bins = HASH_TABLE_SIZE;
> drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c:479: 
> plat_dat->multicast_filter_bins = 0;
> drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c:456:    int 
> numhashregs = (hw->multicast_filter_bins >> 5);
> drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c:485: 
> (netdev_mc_count(dev) > hw->multicast_filter_bins)) {
> drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c:1057: 
> mac->multicast_filter_bins = priv->plat->multicast_filter_bins;
> drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c:1061:    if 
> (mac->multicast_filter_bins)
> drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c:1062: 
> mac->mcast_bits_log2 = ilog2(mac->multicast_filter_bins);
> drivers/net/ethernet/stmicro/stmmac/dwmac-generic.c:43: 
> plat_dat->multicast_filter_bins = HASH_TABLE_SIZE;
>
> and
>
> drivers/net/ethernet/stmicro/stmmac/common.h:265:#define 
> HASH_TABLE_SIZE 64
>
>
> From the search results, the default value of multicast_filter_bins
> may be meaningful. And I think that even if some hardware does not
> support this feature, it should still be overridden in its own directory.

There is a DT property 'snps,multicast-filter-bins' available to 
override the default value for a platform however this property is not 
taken into consideration in case of xgmac. That being said, 
stmmac_platform.c logic can be modified to extend the property use for 
xgmac also however the value will be overridden later based on hash 
table size read from the HW Feature register. So only zero value will be 
usable via DT in that case. Hence I thought of setting it to 0 in the 
else part of the code I modified in this patch. If you think I should 
extend the DT property for xgmac, I can modify the patch too.

Thanks,

-Nikunj

>
>
> Thanks,
> Yanteng
>