linux-kernel - Re: [RFT PATCH 1/2] usb: dwc2: Add a 10 ms delay to dwc2_core

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Date:	Sat, 5 Mar 2016 21:41:20 +0100
From:	Michael Niewoehner <linux@...ewoehner.de>
To:	Doug Anderson <dianders@...omium.org>,
	John Youn <johnyoun@...opsys.com>
Cc:	Felipe Balbi <balbi@...nel.org>, Heiko Stuebner <heiko@...ech.de>,
	Caesar Wang <caesar.upstream@...il.com>,
	Tao Huang <huangtao@...k-chips.com>,
	Remi Pommarel <repk@...plefau.lt>,
	Stefan Wahren <stefan.wahren@...e.com>,
	Julius Werner <jwerner@...omium.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFT PATCH 1/2] usb: dwc2: Add a 10 ms delay to dwc2_core_reset()

Hi Douglas,
Hi John,

Am 05.03.2016 um 01:33 schrieb Doug Anderson <dianders@...omium.org>:

> Michael,
> 
> On Fri, Mar 4, 2016 at 4:09 PM, Michael Niewoehner <linux@...ewoehner.de> wrote:
>>>> From testing and trying to make sense of the documentation, it appears
>>>> that a 10 ms delay is needed after resetting the core to make sure that
>>>> everything is stable and consistent.  Let's add it.
>>>> 
>>>> In my testing (on rk3288) this allows us to revert commit
>>>> 192cb07f7928 ("usb: dwc2: Fix probe problem on bcm2835").  Though I
>>>> could never reproduce the problems on my board, this might also allow us
>>>> to revert commit bd84f4ae9986 ("usb: dwc2: Add extra delay when forcing
>>>> dr_mode").
>>>> 
>>>> Signed-off-by: Douglas Anderson <dianders@...omium.org>
>>> 
>>> Tested-by: Michael Niewoehner <linux@...ewoehner.de>
> 
> Thanks!  That's great news!
> 
> 
>>> I’m a bit confused since git log says bd84f4ae9986 has been merged in 62718e304aa6 but looking at drivers/usb/dwc2/core.c it seems the patch has not been applied anyways ...
>>> However, I tested you your two patches with „magically reverted“ bd84f4ae9986 (msleep 50) on rk3188.
>>> The sdcard keeps being detected and boots just fine.
>> I meant usb stick of course… too much sdcards in my head today \o/.
> 
> Odd.  It looks to be there for me...
> 
> $ git checkout 62718e304aa6
> HEAD is now at 62718e304aa6... Merge tag 'usb-4.5-rc6' of
> git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb
> 
> $ git grep -C3 "NOTE: This is required" -- drivers/usb/dwc2/core.c
> drivers/usb/dwc2/core.c-        }
> drivers/usb/dwc2/core.c-
> drivers/usb/dwc2/core.c-        /*
> drivers/usb/dwc2/core.c:         * NOTE: This is required for some
> rockchip soc based
> drivers/usb/dwc2/core.c-         * platforms.
> drivers/usb/dwc2/core.c-         */
> drivers/usb/dwc2/core.c-        msleep(50);

I unfortunately have bad news.
After some more testing it turned out that usb does NOT work (always) on rk3188 when reverting bd84f4ae9986.
It looks like that is dependent on which device / vendor is plugged in.
The usb stick I tested yesterday worked once but today just blinks shortly and then stops working.
Another usb stick I tested today doesn’t blink or work at all. Maybe I should have tested booting some more times :-(

Best regards
Michael