RFC: stmmac RSS support

RFC: stmmac RSS support

[Russell King (Oracle)]

Hi,

While looking at the possibilities of minimising the memory that
struct plat_stmmacenet_data consumes (880 bytes presently on
aarch64), I came across the RSS feature in stmmac.

In commit 76067459c686 ("net: stmmac: Implement RSS and enable it in
XGMAC core"), support was added for RSS to the core stmmac driver for
the dwxgmac2 core. I can only find socfpga and tegra as the two
platform glues that use the dwxgmac2 core.

RSS support is only enabled when both the core supports it, and the
platform glue sets priv->plat->rss_en.

However, the stmmac-related results of grepping for this member do not
show any platform glues which set this flag:

$ git grep '\<rss_en\>'
Documentation/networking/device_drivers/ethernet/stmicro/stmmac.rst:        int rss_en;
drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:      if (!priv->dma_cap.rssen || !priv->plat->rss_en) {
drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:      if (priv->dma_cap.rssen && priv->plat->rss_en)

So, as no one has decided to enable this feature during the intervening
six years, is there any benefit to having this code in the mainline
kernel, or should this feature be dropped?

If a user appears, the code will remain in git history and could be
restored.

Thoughts?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!

Re: RFC: stmmac RSS support

[Qingfang Deng]

On Sat, 7 Feb 2026 17:36:06 +0000, Russell King (Oracle) wrote:
> Hi,
> 
> While looking at the possibilities of minimising the memory that
> struct plat_stmmacenet_data consumes (880 bytes presently on
> aarch64), I came across the RSS feature in stmmac.
> 
> In commit 76067459c686 ("net: stmmac: Implement RSS and enable it in
> XGMAC core"), support was added for RSS to the core stmmac driver for
> the dwxgmac2 core. I can only find socfpga and tegra as the two
> platform glues that use the dwxgmac2 core.
> 
> RSS support is only enabled when both the core supports it, and the
> platform glue sets priv->plat->rss_en.
> 
> However, the stmmac-related results of grepping for this member do not
> show any platform glues which set this flag:
> 
> $ git grep '\<rss_en\>'
> Documentation/networking/device_drivers/ethernet/stmicro/stmmac.rst:        int rss_en;
> drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:      if (!priv->dma_cap.rssen || !priv->plat->rss_en) {
> drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:      if (priv->dma_cap.rssen && priv->plat->rss_en)
> 
> So, as no one has decided to enable this feature during the intervening
> six years, is there any benefit to having this code in the mainline
> kernel, or should this feature be dropped?
> 
> If a user appears, the code will remain in git history and could be
> restored.
> 
> Thoughts?

As someone who has worked on both DWC GMAC and DWC XGMAC, I think the
whole XGMAC code needs to be uncoupled from the stmmac driver. They're
completely different IP cores.

> 
> -- 
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
>