Re: [PATCH net-next v2 2/3] net: stmmac: Add glue driver for Motorcomm YT6801 ethernet controller

On Sun, Nov 16, 2025 at 02:50:48PM +0800, Xi Ruoyao wrote:

On Sat, 2025-11-15 at 11:46 +0000, Yao Zi wrote:

quoted

On Tue, Nov 11, 2025 at 12:32:56PM +0000, Russell King (Oracle) wrote:

quoted

On Tue, Nov 11, 2025 at 10:52:51AM +0000, Yao Zi wrote:

quoted

+	plat->bus_id		= pci_dev_id(pdev);
+	plat->phy_addr		= -1;
+	plat->phy_interface	= PHY_INTERFACE_MODE_GMII;
+	plat->clk_csr		= STMMAC_CSR_20_35M;

Could you include a comment indicating what the stmmac clock rate
actually is (the rate which is used to derive this divider) ? As
this is PCI, I'm guessing it's 33MHz, which fits with your divider
value.

The divider is taken from vendor driver, and the clock path isn't
mentioned in the datasheet, either. I don't think it's 33MHz since
it's
a PCIe chip, and there's no 33MHz clock supplied by PCIe.

The datasheet[1] (Chinese website, requires login) mentions that the
controller requires a 25MHz external clock input/oscillator to
function,

quoted

25MHz Crystal Input pin.

If use external oscillator or clock from another device.
  1. When connect an external 25MHz oscillator or clock from another
  device to XTAL_O pin, XTAL_I must be shorted to GND.
  2. When connect an external 25MHz oscillator or clock from another
  device to XTAL_I pin, keep the XTAL_O floating.

25MHz fits in STMMAC_CSR_20_35M, too, so it's more likely the clock
source.

I don't think this guess could be confirmed without vendor's help,
should the information be included as comment.

I used the "beep" function of a multimeter to "probe" the connectivity
of the two YT6801 chips on a XB612B0 V1.1 board.  There are two 25 MHz
oscillators on the board, each connected to a YT6801.

Sorry for not being clear here, I'm sure the controller requires an
oscillators to function (since the datasheet states so). What's unclear
here is whether the 20~35MHz clock provided for internal MDIO bus is
dervided from it.

Anyway, I would add a comment to mention this in v3. Thanks.

Best regards,
Yao Zi

-- 
Xi Ruoyao [off-list ref]