linux-kernel - Re: [PATCH v1 1/8] usb: phy: tegra: Add delay after power up

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Date:   Wed, 16 Dec 2020 12:09:24 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sergei Shtylyov <sergei.shtylyov@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Peter Chen <Peter.Chen@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Felipe Balbi <balbi@...nel.org>,
        Matt Merhar <mattmerhar@...tonmail.com>,
        Nicolas Chauvet <kwizart@...il.com>,
        Peter Geis <pgwipeout@...il.com>
Cc:     linux-tegra@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/8] usb: phy: tegra: Add delay after power up

16.12.2020 11:51, Sergei Shtylyov пишет:
> Hello!
> 
> On 15.12.2020 23:21, Dmitry Osipenko wrote:
> 
>> The PHY hardware needs the delay of 2ms after power up, otherwise initial
>> interrupt may be lost if USB controller is accessed before PHY is settled
>> down. Previously this issue was masked by implicit delays, but now it
>> pops
>> up after squashing the older ehci-tegra driver into the ChipIdea driver.
>>
>> Tested-by: Matt Merhar <mattmerhar@...tonmail.com>
>> Tested-by: Nicolas Chauvet <kwizart@...il.com>
>> Tested-by: Peter Geis <pgwipeout@...il.com>
>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>> ---
>>   drivers/usb/phy/phy-tegra-usb.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/usb/phy/phy-tegra-usb.c
>> b/drivers/usb/phy/phy-tegra-usb.c
>> index 03a333797382..cee9c9dbb775 100644
>> --- a/drivers/usb/phy/phy-tegra-usb.c
>> +++ b/drivers/usb/phy/phy-tegra-usb.c
>> @@ -784,6 +784,9 @@ static int tegra_usb_phy_power_on(struct
>> tegra_usb_phy *phy)
>>         phy->powered_on = true;
>>   +    /* let PHY to settle down */
> 
>    Let the PHY settle down.

Hi,

I'll improve the comments in v2, thanks.