Re: [RFC PATCH] usb: dwc3: wait for USB2 PHY clock recovery during role switch

[sashiko-bot@kernel.org]

> During a device-to-host role switch, the USB2 PHY may still be
> suspended from the previous gadget session. After clearing SUSPHY,
> the PHY requires up to 1.5 ms before the UTMI clock is stable.
> This was observed during a device-to-host role switch with
> a USB earphone attached. Traces showed that SUSPHY remained asserted
> until __dwc3_set_mode() cleared it, after which host initialization
> immediately started accessing the xHCI PORTSC registers.
> The USB2 PHY specification requires up to 1.5 ms for clock recovery
> after exiting suspend. Accessing the controller before the UTMI clock has
> stabilized can therefore occur during this recovery interval.
> Wait for the PHY clock recovery when SUSPHY was set before switching
> to host mode. Avoid the delay when the PHY was already active.
> This change is limited to the role-switch path. Runtime suspend
> requires separate handling
> 
> Signed-off-by: Uttkarsh Aggarwal <uttkarsh.aggarwal@oss.qualcomm.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261030062509.3475322-1-uttkarsh.aggarwal@oss.qualcomm.com?part=1