[PATCH] ARM: dts: BCM5301X: Add DT for Asus RT-AC88U

[Arınç ÜNAL]

On 22/09/2021 21:15, Florian Fainelli wrote:
> On 9/21/21 5:19 AM, Arınç ÜNAL wrote:
>> Hardware Info
>> -------------
>>
>> Processor	- Broadcom BCM4709C0KFEBG dual-core @ 1.4 GHz
>> Switch		- BCM53012 in BCM4709C0KFEBG & external RTL8365MB
> 
> There is no Device Tree description of the RTL8365MB switch, can it be
> driven/controlled via MDIO, SPI or GPIOs by any chance? This is not a
> show stopper for accepting the patch, just wondering if you are somehow
> trying to get that switch controlled by the rtl8366 DSA driver as well?
> 
There's a v1 patch on net-next adding DSA support for RTL8365MB by Alvin 
Šipraga, CC'ing them. There's also a v2 patch coming.
https://lore.kernel.org/netdev/20210822193145.1312668-1-alvin@pqrs.dk/

I've been mailing Alvin to figure out how to define it on the device 
tree. They have provided very useful information. Quoting a few:

 >> I'm trying to write the device tree to support this switch. I'm not sure
 >> whether the default GPIO IDs of mdc-gpios, mdio-gpios, reset-gpios &
 >> interrupts on realtek-smi.txt kernel documentation are correct.
 >> 
https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/bindings/net/dsa/realtek-smi.txt
 >
 > These gpios are just an example. It really depends how your board is
 > wired up. You have to figure out which SoC pad is wired to the MDC,
 > MDIO, and RESET pins on the RTL8365MB. Then you have to make sure the
 > pinmux is set up correctly so that these pads correspond to some GPIO
 > with a given ID, and then pick the right GPIO controller (&chipcommon?)
 > and put the ID after that. It will not necessarily be 21, 22, 14.

 > In summary:
 >
 > - figure out which pads are wired to MDC, MDIO, RESET
 > - figure out pinmux to make them into gpios
 > - figure out gpio ID and describe that in the device tree
 >

I have backported the v1 patch to kernel 5.10 and tried an example 
definition on the device tree to test it out on RT-AC88U. It's on this 
branch:
https://github.com/arinc9/openwrt/commits/realtek-work-asus_rt-ac88u

It doesn't work as is, likely missing further configuration, which I'm 
clueless to figure out myself. I'd very appreciate it if you could weigh in.

[    1.598858] realtek-smi switch at 1: failed to get RESET GPIO
---
[    3.015528] realtek-smi switch at 1: deasserted RESET
[    3.021171] realtek-smi switch at 1: found an RTL8365MB-VC switch 
(ver=0x0040)
[    3.028193] realtek-smi switch at 1: unable to register switch ret = -517
---
[    3.405527] realtek-smi switch at 1: deasserted RESET
[    3.411165] realtek-smi switch at 1: found an RTL8365MB-VC switch 
(ver=0x0040)
[    3.418449] DSA: tree 0 already setup! Disjoint trees?
[    3.423607] realtek-smi switch at 1: unable to register switch ret = -17
[    3.430137] realtek-smi: probe of switch at 1 failed with error -17

---

I was thinking, we figure out how to define it properly on the device 
tree and make the driver work whilst the v2 patch is applied to 
net-next. Then we could send another patch defining the switch on the 
device tree.
There's the "compatible = "realtek,rtl8365mb";" property, which would be 
undefined until the driver is added.

Cheers.
Arınç