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SubjectRe: [PATCH 3/3] usb: dwc2: prevent core phy initialisation
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Hi Greg,

On 12/8/22 16:53, Greg Kroah-Hartman wrote:
> On Wed, Dec 07, 2022 at 02:19:18PM +0100, Quentin Schulz wrote:
>> From: Bin Yang <yangbin@rock-chips.com>
>>
>> The usb phys need to be controlled dynamically on some Rockchip SoCs.
>> So set the new HCD flag which prevents USB core from trying to manage
>> our phys.
>>
>> Signed-off-by: Bin Yang <yangbin@rock-chips.com>
>> Signed-off-by: Frank Wang <frank.wang@rock-chips.com>
>> Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
>> ---
>> drivers/usb/dwc2/hcd.c | 7 +++++++
>> 1 file changed, 7 insertions(+)
>>
>> diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
>> index 657f1f659ffaf..757a66fa32fa8 100644
>> --- a/drivers/usb/dwc2/hcd.c
>> +++ b/drivers/usb/dwc2/hcd.c
>> @@ -5315,6 +5315,13 @@ int dwc2_hcd_init(struct dwc2_hsotg *hsotg)
>> if (!IS_ERR_OR_NULL(hsotg->uphy))
>> otg_set_host(hsotg->uphy->otg, &hcd->self);
>>
>> + /*
>> + * do not manage the PHY state in the HCD core, instead let the driver
>> + * handle this (for example if the PHY can only be turned on after a
>> + * specific event)
>> + */
>> + hcd->skip_phy_initialization = 1;
>
> Wait, doesn't this mess with the phy logic for all other chips that use
> this IP block? Have you tested this on other systems?
>

I have not. I asked this in the cover-letter but I guess I should have
made the patch series an RFC for this reason?

> I'd like some verification first before taking this change as it seems
> very specific-platform.
>

There's already some platform-specific callbacks for the driver (see
dwc2_set_rk_params in drivers/usb/dwc2/params.c) but this gets called
too early, before hcd structure is actually allocated. So we either need
to use some "proxy"/shadow variable in dwc2_core_params and then update
it right after hcd gets allocated or have another platform-specific
callback only for hcd (post-)initialization.

Nothing too fancy so shouldn't take too long to implement. Any
preference? Something else?

Also on a side note, after further testing, USB peripheral mode in
dual-role mode does not seem to be entirely fixed with this patch
series, I still have occasional locks. But considering that it
absolutely didn't work before, it is some kind of progress.
There are also some issues related to USB host mode in dual-role mode
but I saw those happening before the patch series too. I'll see what I
can do, really frustrating to work with IPs for which there's no
documentation :/

Cheers,
Quentin

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