Re: [PATCH net-next v2 1/2] net: stmmac: Return early if invalid in loongson_dwmac_fix_reset()

[Tiezhu Yang]

On 2025/7/23 下午10:53, Andrew Lunn wrote:
> On Wed, Jul 23, 2025 at 06:00:55PM +0800, Tiezhu Yang wrote:
> > If the MAC controller does not connect to any PHY interface, there is a
> > missing clock, then the DMA reset fails.
> >
> > For this case, the DMA_BUS_MODE_SFT_RESET bit is 1 before software reset,
> > just return -EINVAL immediately to avoid waiting for the timeout when the
> > DMA reset fails in loongson_dwmac_fix_reset().
> >
> > Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
> > ---
> >   drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c | 3 +++
> >   1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c
> > index e1591e6217d4..6d10077666c7 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c
> > @@ -513,6 +513,9 @@ static int loongson_dwmac_fix_reset(void *priv, void __iomem *ioaddr)
> >   {
> >   	u32 value = readl(ioaddr + DMA_BUS_MODE);
> >   
> > +	if (value & DMA_BUS_MODE_SFT_RESET)
> > +		return -EINVAL;
>
> What happens with this return value? Do you get an error message which
> gives a hint the PHY clock is missing? Would a netdev_err() make sense
> here?

Yes, I will use dev_err() rather than netdev_err() (because there is no
net_device member here) to do something like this:

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c 
b/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c
index 6d10077666c7..4a7b2b11ecce 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c
@@ -513,8 +513,11 @@ static int loongson_dwmac_fix_reset(void *priv, 
void __iomem *ioaddr)
 {
        u32 value = readl(ioaddr + DMA_BUS_MODE);

-       if (value & DMA_BUS_MODE_SFT_RESET)
+       if (value & DMA_BUS_MODE_SFT_RESET) {
+               struct plat_stmmacenet_data *plat = priv;
+               dev_err(&plat->pdev->dev, "the PHY clock is missing\n");
                return -EINVAL;
+       }

        value |= DMA_BUS_MODE_SFT_RESET;
        writel(value, ioaddr + DMA_BUS_MODE);

Thanks,
Tiezhu