netdev - Re: [PATCH net-next v2 1/2] net: stmmac: Return early if invalid in loongson_dwmac_fix

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Message-ID: <b98a5351-f711-ecb1-75fa-68c69263e950@loongson.cn>
Date: Thu, 24 Jul 2025 10:26:00 +0800
From: Tiezhu Yang <yangtiezhu@...ngson.cn>
To: Andrew Lunn <andrew@...n.ch>
Cc: Andrew Lunn <andrew+netdev@...n.ch>,
 "David S . Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>,
 Maxime Chevallier <maxime.chevallier@...tlin.com>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2 1/2] net: stmmac: Return early if invalid in
 loongson_dwmac_fix_reset()

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@...ngson.cn>
>> ---
>>   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