linux-kernel - Re: [PATCH 13/15] usb: dwc2: Add exit hibernation mode before removing drive

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Date:   Thu, 15 Apr 2021 12:24:19 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...il.com>
To:     Artur Petrosyan <Arthur.Petrosyan@...opsys.com>,
        Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Minas Harutyunyan <Minas.Harutyunyan@...opsys.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     John Youn <John.Youn@...opsys.com>
Subject: Re: [PATCH 13/15] usb: dwc2: Add exit hibernation mode before
 removing drive

On 15.04.2021 8:41, Artur Petrosyan wrote:

> When dwc2 core is in hibernation mode loading
> driver again causes driver fail. Because in
> that mode registers are not accessible.
> 
> In order to exit from hibernation checking
> dwc2 core power saving state in "dwc2_driver_remove()"
> function. If core is in hibernation, then checking the
> operational mode of the driver. To check whether dwc2 core
> is operating in host mode or device mode there is one way
> which is retrieving the backup value of "gotgctl" and compare
> the "CurMod" value. If previously core entered hibernation
> in host mode then the exit is performed for host if not then
> exit is performed for device mode. The introduced checking
> is because in hibernation state all registers are not
> accessible.
> 
> Signed-off-by: Artur Petrosyan <Arthur.Petrosyan@...opsys.com>
> ---
>   drivers/usb/dwc2/platform.c | 16 ++++++++++++++++
>   1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/usb/dwc2/platform.c b/drivers/usb/dwc2/platform.c
> index f8b819cfa80e..2ae4748ed5ec 100644
> --- a/drivers/usb/dwc2/platform.c
> +++ b/drivers/usb/dwc2/platform.c
> @@ -316,8 +316,24 @@ static int dwc2_lowlevel_hw_init(struct dwc2_hsotg *hsotg)
>   static int dwc2_driver_remove(struct platform_device *dev)
>   {
>   	struct dwc2_hsotg *hsotg = platform_get_drvdata(dev);
> +	struct dwc2_gregs_backup *gr;
>   	int ret = 0;
>   
> +	/* Exit Hibernation when driver is removed. */
> +	if (hsotg->hibernated) {
> +		if (gr->gotgctl & GOTGCTL_CURMODE_HOST) {
> +			ret = dwc2_exit_hibernation(hsotg, 0, 0, 1);
> +			if (ret)
> +				dev_err(hsotg->dev,
> +					"exit hibernation failed.\n");
> +		} else {
> +			ret = dwc2_exit_hibernation(hsotg, 0, 0, 0);
> +			if (ret)
> +				dev_err(hsotg->dev,
> +					"exit hibernation failed.\n");

    Again, why duplicate the innermost *if*?

>  +		}
> +	}
> +
>   	/* Exit Partial Power Down when driver is removed. */
>   	if (hsotg->in_ppd) {
>   		ret = dwc2_exit_partial_power_down(hsotg, 0, true);

MBR, Sergei