Re: [PATCH net-next 2/2] net: stmmac: dwmac4: Use the full perfect filter ability for UC filter

[Nicolai Buchwitz]

Hi Maxime

On 31.8.2026 09:01, Maxime Chevallier wrote:
> Contrary to dwmac1000 that gets its number of perfect filter entries
> through the 'snps,perfect-filter-entries' property, dwmac4 allows
> reading the filter size from the HW features registers.
>
> Perfect filter is used for Unicast filtering, and can contain up to 128
> entries, each having its own set of registers to access it.
>
> The registers are always at the same location in the map, regardless
> whether or not the entry is implemented in hardware. Accessing a 
> register
> for an un-implemented entry just doesn't do anything.
>
> The filter is made of one always-available entry, and 3 configurable
> banks :
>
>  Entry 0 : Always implemented, stores the primary MAC address
>
>  Entry 1  \
>   ...     + -- Can contain between 0 and 31 entries. Number of 
> available
>  Entry 31 /    entries in HW_Features0[18:22].
>
>  Entry 32 \
>   ...     + -- Additional 32 entries, all or nothing. Availability is
>  Entry 63 /    specified by HW_Features0[23]
>
>  Entry 64  \
>   ...      + - Additional 64 entries, all or nothing. Availability is
>  Entry 127 /   specified by HW_Features0[24].
>
> Each of the 3 configurable banks are independently selectable, meaning
> we can have gaps in the register banks.
>
> For instance, a setup with 50 addresses enabled will have 17 entries in
> the first bank and the additional 32 bank enabled (50 = 32 + 17 + 1).
>
> Another example with 70 addresses : 64 addr bank on, 5 addresses in the
> first bank (70 = 64 + 5 + 1).
>
> While I haven't seen HW with gaps in the banks, Synopsys confirmed this
> is a real possibility.
>
> Let's therefore introduce a dwmac4 helper to get the physical slot
> number of a given entry, allowing to configure the correct bank when
> populating the filter. As we need the HW feature-set to compute the
> index, store the bank info in the mac_device_info struct.
>
> The total number of available entries is computed based on the
> discovered parameters, instead of using the default value of 1.
>
> Results on HW that uses dwmac4 :
>
>  - imx8mp   : goes from 1 entry to 64 (1 + 31 + 32)
>  - stm32mp1 : goes from 1 entry to 4 (1 + 3)
>  - jh7110   : goes from 1 entry to 9 (1 + 8)
>  - yt6801   : goes from 1 entry to hum, 1 entry (no extra addresses)
>
> Signed-off-by: Maxime Chevallier <maxime.chevallier@xxxxxxxxxxx>
> ---

> [...]

Reviewed-by: Nicolai Buchwitz <nb@xxxxxxxxxxx>

Thanks,
Nicolai