linux-kernel - Re: [PATCH v1] usb: chipidea: tegra: Delay PHY suspending

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Date:   Wed, 9 Jun 2021 15:07:31 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Felipe Balbi <balbi@...nel.org>,
        Maxim Schwalm <maxim.schwalm@...il.com>,
        Peter Chen <peter.chen@...nel.org>
Cc:     linux-tegra@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] usb: chipidea: tegra: Delay PHY suspending

09.06.2021 15:04, Dmitry Osipenko пишет:
> The ChipIdea driver enters into suspend immediately after seeing a
> VBUS disconnection. Some devices need an extra delay after losing
> VBUS, otherwise VBUS may be floating, preventing the PHY's suspending
> by the VBUS detection sensors. This problem was found on Tegra30 Asus
> Transformer TF700T tablet device, where the USB PHY wakes up immediately
> from suspend because VBUS sensor continues to detect VBUS as active after
> disconnection. A minimum delay of 20ms is needed in order to fix this
> issue, hence add 25ms delay before suspending the PHY.
> 
> Reported-by: Maxim Schwalm <maxim.schwalm@...il.com> # Asus TF700T
> Tested-by: Maxim Schwalm <maxim.schwalm@...il.com> # Asus TF700T
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/usb/chipidea/ci_hdrc_tegra.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/usb/chipidea/ci_hdrc_tegra.c b/drivers/usb/chipidea/ci_hdrc_tegra.c
> index 60361141ac04..d1359b76a0e8 100644
> --- a/drivers/usb/chipidea/ci_hdrc_tegra.c
> +++ b/drivers/usb/chipidea/ci_hdrc_tegra.c
> @@ -4,6 +4,7 @@
>   */
>  
>  #include <linux/clk.h>
> +#include <linux/delay.h>
>  #include <linux/io.h>
>  #include <linux/module.h>
>  #include <linux/of_device.h>
> @@ -255,6 +256,13 @@ static int tegra_ehci_hub_control(struct ci_hdrc *ci, u16 typeReq, u16 wValue,
>  
>  static void tegra_usb_enter_lpm(struct ci_hdrc *ci, bool enable)
>  {
> +	/*
> +	 * Give hardware time to settle down after VBUS disconnection,
> +	 * otherwise PHY may wake up from suspend immediately.
> +	 */
> +	if (enable)
> +		msleep(25);
> +
>  	/*
>  	 * Touching any register which belongs to AHB clock domain will
>  	 * hang CPU if USB controller is put into low power mode because
> 

I missed that Peter's email address changed. Making this reply to the
new address for visibility.