Hi Andrew, I set phy-id registers to 30 and 31 and found the read-back values of mdio read commands from CPU are all 0x0000. I consulted with an ASIC engineer. She confirmed that if phy-id of a mdio command from CPU does not match any phy-id registers, the mdio command will not be sent out. She explained if phy-id of a mdio command does not match any phy-id registers (represent addresses of external PHYs), why MAC needs to send a command to non-existing PHY? Best regards, Wells Lu 呂芳騰 智能運算專案/Smart Computing Program 家庭平台事業群/Home Entertainment Business Unit 凌陽科技/Sunplus Technology Co., Ltd. 地址：300新竹科學園區創新一路19號 19, Innovation 1st Road, Science-based Industrial Park Hsin-Chu, Taiwan 300 TEL：886-3-5786005 ext. 2580 > -----Original Message----- > From: Andrew Lunn <andrew@xxxxxxx> > Sent: Thursday, November 25, 2021 11:21 PM > To: Wells Lu 呂芳騰 <wells.lu@xxxxxxxxxxx> > Cc: Wells Lu <wellslutw@xxxxxxxxx>; davem@xxxxxxxxxxxxx; kuba@xxxxxxxxxx; > robh+dt@xxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; > linux-kernel@xxxxxxxxxxxxxxx; p.zabel@xxxxxxxxxxxxxx; Vincent Shih 施錕鴻 > <vincent.shih@xxxxxxxxxxx> > Subject: Re: [PATCH v2 2/2] net: ethernet: Add driver for Sunplus SP7021 > > > Due to hardware design, we still need to set PHY address, because MDIO > > controller of SP7021 only sends out MDIO commands with the same > > address listed in PHY address registers. The function below needs to > > be kept. > > I suggest you actually set it to some other address. One of the good/bad things about MDIO > is you have no idea if the device is there. A read to a device which does not exist just > returns 0xffff, not an error. So i would set the address of 0x1f. I've never seen a PHY > actually use that address. > > Andrew
