mccomphy: add support for YT8531

[mhorne]

Summary

Attempt #2, this time with proper conditional FDT.

Co-authored-by: mhorne

[mhorne]

@jsihv_gmx.com you might have seen, I merged this functionality but had to revert as it broke the build on amd64 (!FDT). Here is an updated version which addresses this.

sys/dev/mii/mcommphy.c

256–266

I attempted to simplify this delay logic, from your previous version. Notably we do not need to validate that the value is divisible by 150; the division operation will round down.

Does this look sane/correct? Maybe the values need an upper bound.

From sys/contrib/device-tree/Bindings/net/motorcomm,yt8xxx.yaml:

rx-internal-delay-ps:
  description: |
    RGMII RX Clock Delay used only when PHY operates in RGMII mode with
    internal delay (phy-mode is 'rgmii-id' or 'rgmii-rxid') in pico-seconds.
  enum: [ 0, 150, 300, 450, 600, 750, 900, 1050, 1200, 1350, 1500, 1650,
          1800, 1900, 1950, 2050, 2100, 2200, 2250, 2350, 2500, 2650, 2800,
          2950, 3100, 3250, 3400, 3550, 3700, 3850, 4000, 4150 ]
  default: 1950

tx-internal-delay-ps:
  description: |
    RGMII TX Clock Delay used only when PHY operates in RGMII mode with
    internal delay (phy-mode is 'rgmii-id' or 'rgmii-txid') in pico-seconds.
  enum: [ 0, 150, 300, 450, 600, 750, 900, 1050, 1200, 1350, 1500, 1650, 1800,
          1950, 2100, 2250 ]
  default: 1950

268–383

I split the FDT parsing code into a separate function here, which is called before the other setup logic.

[mhorne]

sys/dev/mii/mcommphy.c

245

will drop this.

[jsihv_gmx.com]

sys/dev/mii/mcommphy.c

49

For building on AMD64 also this #include of mii_fdt.h header requires to be omitted with #ifdef FDT

256–266

I confirm these changes are correct. Checking is not needed here though a sane FDT probably gives values divisible by 150.

268–383

My own solution (in case you missed it) was simply to put #ifdef FDT around functions mcommphy_yt8531_setup_delay() and mcommphy_yt8531_setup() (so that function's opening and closing brackets with closing return instructions are included but the rest of the content not). Anyway, I'm fine with this solution too.

[mhorne]

sys/dev/mii/mcommphy.c

49

Oh yes. It does not break the build on amd64 but it is clearly not needed there.

268–383

I did miss that...

I will exclude mcommphy_yt8531_setup_delay() from the !FDT case, since I am unsure what the implications of writing a delay value of zero would be. Especially when the default is listed as 1950 in the dts spec above...

[mhorne]

Add #ifdef FDT conditionals around mii_fdt.h inclusion and the call to mcommphy_yt8531_setup_delay().