linux-kernel - Re: [PATCH v2 3/3] Input: ti_am335x_tsc - Prevent system suspend when TSC is in use

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Message-ID: <20180416180148.GD77055@dtor-ws>
Date:   Mon, 16 Apr 2018 11:01:48 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Vignesh R <vigneshr@...com>
Cc:     Grygorii Strashko <grygorii.strashko@...com>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-omap@...r.kernel.org, Tony Lindgren <tony@...mide.com>
Subject: Re: [PATCH v2 3/3] Input: ti_am335x_tsc - Prevent system suspend
 when TSC is in use

On Sat, Apr 14, 2018 at 03:21:53PM +0530, Vignesh R wrote:
> From: Grygorii Strashko <grygorii.strashko@...com>
> 
> Prevent system suspend while user has finger on touch screen,
> because TSC is wakeup source and suspending device while in use will
> result in failure to disable the module.
> This patch uses pm_stay_awake() and pm_relax() APIs to prevent and
> resume system suspend as required.

This looks like common behavior for all touchscreens and many other
input devices, but other systems seem to cope without having to add
pm_stay_awake() and pm_relax(). I wonder why your system requires it and
whether we can generalize this somehow.

> 
> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
> Signed-off-by: Vignesh R <vigneshr@...com>
> ---
> 
> v2: No changes.
> 
>  drivers/input/touchscreen/ti_am335x_tsc.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/input/touchscreen/ti_am335x_tsc.c b/drivers/input/touchscreen/ti_am335x_tsc.c
> index dcd9db768169..43b22e071842 100644
> --- a/drivers/input/touchscreen/ti_am335x_tsc.c
> +++ b/drivers/input/touchscreen/ti_am335x_tsc.c
> @@ -275,6 +275,7 @@ static irqreturn_t titsc_irq(int irq, void *dev)
>  	if (status & IRQENB_HW_PEN) {
>  		ts_dev->pen_down = true;
>  		irqclr |= IRQENB_HW_PEN;
> +		pm_stay_awake(ts_dev->mfd_tscadc->dev);
>  	}
>  
>  	if (status & IRQENB_PENUP) {
> @@ -284,6 +285,7 @@ static irqreturn_t titsc_irq(int irq, void *dev)
>  			input_report_key(input_dev, BTN_TOUCH, 0);
>  			input_report_abs(input_dev, ABS_PRESSURE, 0);
>  			input_sync(input_dev);
> +			pm_relax(ts_dev->mfd_tscadc->dev);
>  		} else {
>  			ts_dev->pen_down = true;
>  		}
> @@ -524,6 +526,7 @@ static int __maybe_unused titsc_resume(struct device *dev)
>  		titsc_writel(ts_dev, REG_IRQWAKEUP,
>  				0x00);
>  		titsc_writel(ts_dev, REG_IRQCLR, IRQENB_HW_PEN);
> +		pm_relax(ts_dev->mfd_tscadc->dev);
>  	}
>  	titsc_step_config(ts_dev);
>  	titsc_writel(ts_dev, REG_FIFO0THR,
> -- 
> 2.17.0
> 

Thanks.

-- 
Dmitry