linux-kernel - Re: [PATCH 3/3] usb: dwc2: prevent core phy initialisation

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Message-ID: <28b4be7d-1bad-b16f-9445-620d7ac0c07a@theobroma-systems.com>
Date:   Fri, 9 Dec 2022 13:38:55 +0100
From:   Quentin Schulz <quentin.schulz@...obroma-systems.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Quentin Schulz <foss+kernel@...il.net>,
        Minas Harutyunyan <hminas@...opsys.com>,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        William Wu <william.wu@...k-chips.com>,
        Bin Yang <yangbin@...k-chips.com>,
        Frank Wang <frank.wang@...k-chips.com>
Subject: Re: [PATCH 3/3] usb: dwc2: prevent core phy initialisation

Hi Greg,

On 12/9/22 13:13, Greg Kroah-Hartman wrote:
> On Fri, Dec 09, 2022 at 12:15:34PM +0100, Quentin Schulz wrote:
>> 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@...k-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@...k-chips.com>
>>>> Signed-off-by: Frank Wang <frank.wang@...k-chips.com>
>>>> Signed-off-by: Quentin Schulz <quentin.schulz@...obroma-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?
> 
> Ah, should I drop the first 2 in this series that I already applied?
> 

Up to you. I need the three patches to have it (somewhat) working, so 
only merging the first two isn't going to improve the current situation 
much for me. I don't mind carrying them over for a v2 (or how many 
versions are needed).

>>> 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?
> 
> Which ever you think would be simplest.
> 

Got it.

Cheers,
Quentin