On 5/23/22 13:46, Rasmus Villemoes wrote:
On 23/05/2022 12.57, Marek Vasut wrote:
On 5/23/22 11:17, Rasmus Villemoes wrote:
Hi
Hi,
I'm looking at switching the dwc_eth_qos driver over to use
dm_eth_phy_connect(). However, I'm a little puzzled by the code for the
tegra variant. The comment at the top of the file, as well as
tegra186.dtsi, says
phy-mode = "rgmii";
But eqos_get_interface_tegra186() returns a hard-coded
PHY_INTERFACE_MODE_MII. Now the commit which introduced the ->interface
abstraction, ac2d4efb16e (net: dwc_eth_qos: add Ethernet stm32mp1
support), and that eqos_get_interface_tegra186() function, changed
- eqos->phy = phy_connect(eqos->mii, 0, dev, 0);
to
+ eqos->phy = phy_connect(eqos->mii, 0, dev,
+ eqos->config->interface(dev));
and that last hard-coded 0 in the former phy_connect() is indeed
equivalent to PHY_INTERFACE_MODE_MII.
So which is it? It would be nice if one could just rely on
dm_eth_phy_connect() picking up the correct value from device tree, and
drop all the code which duplicates parsing of phy-mode from the ethernet
driver.
linux-2.6$ git grep mii arch/arm64/boot/dts/nvidia/tegra186*
arch/arm64/boot/dts/nvidia/tegra186-p3310.dtsi: phy-mode = "rgmii";
arch/arm64/boot/dts/nvidia/tegra186-p3509-0000+p3636-0001.dts: phy-mode
= "rgmii-id";
So probably RGMII ?
Well, yes, I also did check the linux device tree files which also says
rgmii, but that doesn't explain why the U-Boot driver code seems to
ignore that entirely and use mii hardcoded, both before and after
ac2d4efb16e.
So another way of asking: does this driver actually work today, and/or
has it worked at some point? I assume the answer is yes - after all, the
very first commit "supports the specific configuration used in NVIDIA's
Tegra186 chip", but that commit also did that phy_connect() with a last
argument of 0 aka PHY_INTERFACE_MODE_MII.
And would it break if one started taking the phy-mode from device tree?
If so, should device tree be updated to say "mii"?
I think we wait for nvidia to answer all this, I don't have that SoC
available.
