Re: [PATCH v2 1/1] phy: sun4i-usb: fix phy write on H3 and newer

[Evgeny Boger <boger@wirenboard.com>]

> On 1/11/22 10:51 AM, Evgeny Boger wrote:
>> We noticed that USB hosts won't reliably enumerate USB HS (480Mb/s) devices
>> in our custom A40i-based design. What we observe is that after several
>> attempts USB device would fail to enumerate on EHCI port (HS) and will be
>> enumerated instead on OHCI (FS, 12Mb/s) only:
>>
>> [    6.368009] usb 1-1: new high-speed USB device number 5 using ehci-platform
>> [    6.818008] usb 1-1: device not accepting address 5, error -71
>> [    6.823868] usb usb1-port1: unable to enumerate USB device
>> [    7.308013] usb 3-1: new full-speed USB device number 2 using ohci-platform
>> [    7.575045] usb 3-1: not running at top speed; connect to a high speed hub
>>
>> On some boards one of the ports would work in high-speed mode, but
>> on most of the boards all three USB ports would only work in FS mode.
>>
>> At the same time, USB work flawlessly in high-speed mode in vendor kernel.
>>
>> Looking for the differences in USB code, we found the issue with USB PHY
>> register initialization. Basically, USB PHY driver sets a couple of
>> internal undocumented PHY registers to the predefined constants. These PHY
>> registers are accessed in a very (and I mean VERY) weird way by shifting
>> register addresses and values bit-by-bit. This access method was slightly
>> changed starting from H3 SoC, according to the BSP source for different
>> SoCs.
>>
>> As a result, mainline PHY driver won't set these PHY registers properly
>> resulting in unreliable enumeration in high-speed mode.
>>
>> We don't know whether this issue will result in broken HS mode on all
>> affected SoCs or instead the A40i is an unfortunate exception. What we
>> indeed verified, is that BSPs for all affected SoCs write these registers
>> properly while mainline kernel don't. We also were able to reproduce the
>> USB issue on a couple of A40i boards from other vendors, so we are pretty
>> sure these registers have to always be properly set, regardlress of
> typo: regardless
>
>> a hardware layout.
>>
>> The proposed patch is tested on A40i-based Wiren Board 7 building
>> automation controller. More details are below.
>>
>> On older SoCs (prior to H3) PHY register are accessed by manipulating
>> the common register for all PHYs. PHY index is specified by pulsing
>> usbc bit.
>>
>> Newer SoCs leave the access procedure mostly unchanged, the
>> difference being that the latch registers are separate for each PHY.
>>
>> Additionally, accessing USB PHY registers is only possible if phy0 is
>> routed to musb IP instead of HCI.
>>
>> Introduce phy_reg_access_v2 cfg flag for H3 (H2+, H5),
>> R40 (V40, A40i, T3), V3s (V3, S3) and A64 SoCs.
>>
>> On A83t, H6, H616, T507 and probably on more recent hardware,
>> these PHY registers are not used in vendor BSP.
>> So don't set v2 flag for these even newer SoCs as a precaution.
>>
>> Signed-off-by: Evgeny Boger <boger@wirenboard.com>
> Tested-by: Samuel Holland <samuel@sholland.org> # A40i, H3
>
> I tested this patch on a Banana Pi M2 Berry (A40i) board. My board did not have
> any USB reliability problems without this patch, but the patch didn't break
> anything either. So since it fixes USB for you, the patch looks like a net
> improvement.
Samuel, thank you for testing this!
>
> And with Maxime's comments resolved:
>
> Reviewed-by: Samuel Holland <samuel@sholland.org>


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