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

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Date:   Wed, 16 Dec 2020 11:51:14 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...il.com>
To:     Dmitry Osipenko <digetx@...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

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.

> +	usleep_range(2000, 2500);
> +
>   	return 0;
>   }
>   

MBR, Sergei