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From: Michael Grzeschik <mgr@pengutronix.de>
To: Ahmad Fatoum <a.fatoum@pengutronix.de>
Cc: Ahmad Fatoum <ahmad@a3f.at>, Sascha Hauer <sha@pengutronix.de>,
	barebox@lists.infradead.org
Subject: Re: [PATCH 1/2] fixup! usb: dwc2: Add support for optional usb phy
Date: Tue, 22 Mar 2022 09:19:05 +0100	[thread overview]
Message-ID: <20220322081905.GK11246@pengutronix.de> (raw)
In-Reply-To: <4bbe2758-ff16-6694-8bad-b8df2c254a48@pengutronix.de>


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On Tue, Mar 22, 2022 at 06:35:22AM +0100, Ahmad Fatoum wrote:
>On 21.03.22 23:17, Michael Grzeschik wrote:
>> On Wed, Jan 06, 2021 at 11:05:43AM +0100, Sascha Hauer wrote:
>>> On Mon, Dec 21, 2020 at 01:32:50AM +0100, Ahmad Fatoum wrote:
>>>> Linux doesn't seem to enforce a fixed order between phy_init and
>>>> phy_power_on. The Linux dwc2 driver does power_on and then phy_init,
>>>> which is the inverse of what barebox is currently doing.
>>>>
>>>> The PHYs normally used with dwc2 are written with this in mind.
>>>> For example, our stm32-usbphyc driver fails to disable:
>>>>
>>>>   ERROR: stm32-usbphyc 5a006000.usbphyc@5a006000.of: PLL not reset
>>>>   ERROR: phy1: phy exit failed --> -5
>>>>
>>>> Because Linux does exit -> power_off, but barebox does power_off ->
>>>> exit.
>>>>
>>>> Issue was raised upstream:
>>>> https://lore.kernel.org/lkml/6cd01e79-fdc0-3bd4-32b5-a85142533f8a@pengutronix.de/T/#t
>>>>
>>>> Until this is settled, swap the order to follow what Linux does.
>>>> This is suboptimal, because it means controller drivers have different
>>>> order of the operations and that you can't combine arbitrary PHYs and
>>>> controllers, but it seems unlikely we will support combinations that
>>>> aren't supported by Linux in the first place anyway.
>>>
>>> This is valuable information and I don't want it to be lost, so instead
>>> of applying this as a fixup I rewrote the subject to:
>>>
>>> usb: dwc2: swap order of phy_init and phy_power_on to what Linux does
>>>
>>> and applied it as a separate patch.
>>
>> With this patch applied, some stm32mp1 do seem to timeout when
>> addressing the core.
>>
>> WARNING: dwc2 49000000.usb-otg@49000000.of: dwc2_core_reset: Timeout! Waiting for Core Soft Reset
>> ERROR: dwc2 49000000.usb-otg@49000000.of: probe failed: Connection timed out
>>
>> When I revert this patch. Everything works fine again.
>>
>> Is it possible that we can revert it in mainline now?
>
>Since 0e37f94fbe1b ("phy: stm32: sync with upstream"), the phy-stm32-usbphyc now
>has no poweron/poweroff callbacks, so a revert seems to only slightly change
>timing. I'd suggest you dig some more.

That is not true. phy_power_on also enables the phy_regulator. Changing
this order has the effect that the regulator is enabled after or before
phy_init call.

>> How can I reproduce the case this was fixing in the first place?
>
>The case was that barebox calls poweron/init in a different order than Linux.
>This point is moot now though because poweron is no longer provided by the
>driver.

Still not true, though.

Regards,
Michael

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  reply	other threads:[~2022-03-22  8:20 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-21  0:32 [PATCH 0/2] usb: dwc2: gadget: fix stm32mp1 hang on barebox shutdown Ahmad Fatoum
2020-12-21  0:32 ` [PATCH 1/2] fixup! usb: dwc2: Add support for optional usb phy Ahmad Fatoum
2021-01-06 10:05   ` Sascha Hauer
2022-03-21 22:17     ` Michael Grzeschik
2022-03-22  5:35       ` Ahmad Fatoum
2022-03-22  8:19         ` Michael Grzeschik [this message]
2022-03-22  8:25           ` Ahmad Fatoum
2022-03-22  8:29             ` Michael Grzeschik
2022-03-22  9:23               ` Jules Maselbas
2020-12-21  0:32 ` [PATCH 2/2] regulator: stm32-pwr: don't propagate regulator turn-off to supply Ahmad Fatoum

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