[PATCH RFC 05/22] usb: dwc3: apple: Do not use host-vbus-glitches workaround

[Sven Peter]

On 22.08.25 00:28, Thinh Nguyen wrote:
> On Thu, Aug 21, 2025, Sven Peter wrote:
>> From: Janne Grunau <j at jannau.net>

[...]

>>   	/*
>>   	 * Some platforms need to power off all Root hub ports immediately after DWC3 set to host
>>   	 * mode to avoid VBUS glitch happen when xhci get reset later.
>> +	 * On Apple platforms we must not touch any MMIO yet because dwc3
>> +	 * will not work correctly before its PHY has been initialized.
> 
> This doesn't make sense, the phy should've been initialized by this
> point. We already access MMIO before this. Even your [PATCH RFC 7/22]
> attempts to access MMIO before this, yet accessing here causes problem.
> Do we know when the phy get initialized then?

You're absolutely right, this doesn't make any sense!

dwc3_power_off_all_roothub_ports uses ioremap which will map the XHCI 
region as Device-nGnRE. That just doesn't work on these machines and 
actually explains the SErrors.
Resources on these machines generally have the IORESOURCE_MEM_NONPOSTED 
flag set (via the nonposted-mmio dt property) and then use ioremap_np to 
map them using Device-nGnRnE.


Best,


Sven