linux-kernel - Re: [PATCH 1/2] usb: dwc3: support continuous runtime PM with dual role

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Date:   Wed, 18 Mar 2020 13:13:41 +0200
From:   Roger Quadros <rogerq@...com>
To:     Martin Kepplinger <martin.kepplinger@...i.sm>, <balbi@...nel.org>,
        <robh@...nel.org>
CC:     <gregkh@...uxfoundation.org>, <linux-usb@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] usb: dwc3: support continuous runtime PM with dual
 role

Martin,

On 18/03/2020 10:35, Martin Kepplinger wrote:
> The DRD module calls dwc3_set_mode() on role switches, i.e. when a device is
> being pugged in. In order to support continuous runtime power management when
> plugging in / unplugging a cable, we need to call pm_runtime_get() in this path.
> 
> Signed-off-by: Martin Kepplinger <martin.kepplinger@...i.sm>
> ---
>   drivers/usb/dwc3/core.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index edc17155cb2b..7743c4de82e9 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -196,11 +196,16 @@ void dwc3_set_mode(struct dwc3 *dwc, u32 mode)
>   {
>   	unsigned long flags;
>   
> +	pm_runtime_get(dwc->dev);
> +
>   	spin_lock_irqsave(&dwc->lock, flags);
>   	dwc->desired_dr_role = mode;
>   	spin_unlock_irqrestore(&dwc->lock, flags);
>   
>   	queue_work(system_freezable_wq, &dwc->drd_work);

We are not touching any IP registers and just scheduling
the drd_work in this function so it doesn't make sense to do pm_runtime_get here.

How about dong pm_runtime_get/put in __dwc3_set_mode()?

> +
> +	pm_runtime_mark_last_busy(dwc->dev);
> +	pm_runtime_put_autosuspend(dwc->dev);
>   }
>   
>   u32 dwc3_core_fifo_space(struct dwc3_ep *dep, u8 type)
> 

-- 
cheers,
-roger

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