Re: [PATCH net v2 2/3] net: stmmac: Limit FIFO size by hardware capability

[Huacai Chen]

On Wed, Jan 22, 2025 at 1:15 AM Yanteng Si <si.yanteng@xxxxxxxxx> wrote:
>
> 在 1/21/25 12:41, Kunihiko Hayashi 写道:
> > Tx/Rx FIFO size is specified by the parameter "{tx,rx}-fifo-depth" from
> > stmmac_platform layer.
> >
> > However, these values are constrained by upper limits determined by the
> > capabilities of each hardware feature. There is a risk that the upper
> > bits will be truncated due to the calculation, so it's appropriate to
> > limit them to the upper limit values and display a warning message.
> >
> > Fixes: e7877f52fd4a ("stmmac: Read tx-fifo-depth and rx-fifo-depth from the devicetree")
> > Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@xxxxxxxxxxxxx>
> > ---
> >   drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 13 +++++++++++++
> >   1 file changed, 13 insertions(+)
> >
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > index 251a8c15637f..da3316e3e93b 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > @@ -7245,6 +7245,19 @@ static int stmmac_hw_init(struct stmmac_priv *priv)
> >               priv->plat->tx_queues_to_use = priv->dma_cap.number_tx_queues;
> >       }
> >
>
> > +     if (priv->plat->rx_fifo_size > priv->dma_cap.rx_fifo_size) {
>
> > +             dev_warn(priv->device,
> > +                      "Rx FIFO size exceeds dma capability (%d)\n",
> > +                      priv->plat->rx_fifo_size);
> > +             priv->plat->rx_fifo_size = priv->dma_cap.rx_fifo_size;
> I executed grep and found that only dwmac4 and dwxgmac2 have initialized
> dma_cap.rx_fifo_size. Can this code still work properly on hardware
> other than these two?
Agree, this will make my below patch not work again, because
dwmac-loongson is based on dwmac1000.

https://lore.kernel.org/netdev/20250121093703.2660482-1-chenhuacai@xxxxxxxxxxx/T/#u

Huacai

>
>
> Thanks,
> Yanteng
>