linux-kernel - Re: [PATCH v6 10/10] clocksource: timer-dm: Check prescaler value

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Date:   Thu, 4 Jan 2018 23:47:13 +0100
From:   Ladislav Michl <ladis@...ux-mips.org>
To:     Keerthy <j-keerthy@...com>
Cc:     daniel.lezcano@...aro.org, tony@...mide.com, aaro.koskinen@....fi,
        thierry.reding@...il.com, grygorii.strashko@...com,
        linux-omap@...r.kernel.org, robh+dt@...nel.org,
        linux-arm-kernel@...ts.infradead.org, linux-pwm@...r.kernel.org,
        sebastian.reichel@...labora.co.uk, linux-kernel@...r.kernel.org,
        t-kristo@...com
Subject: Re: [PATCH v6 10/10] clocksource: timer-dm: Check prescaler value

On Tue, Jan 02, 2018 at 03:39:59PM +0530, Keerthy wrote:
> From: Ladislav Michl <ladis@...ux-mips.org>
> 
> Invalid prescaler value is silently ignored. Fix that
> by returning -EINVAL in such case. As invalid value
> disabled use of the prescaler, use -1 explicitely for
> that purpose.
> 
> Signed-off-by: Ladislav Michl <ladis@...ux-mips.org>
> ---
>  drivers/clocksource/timer-dm.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/clocksource/timer-dm.c b/drivers/clocksource/timer-dm.c
> index 60db173..01a9cb0 100644
> --- a/drivers/clocksource/timer-dm.c
> +++ b/drivers/clocksource/timer-dm.c
> @@ -672,6 +672,9 @@ int omap_dm_timer_set_prescaler(struct omap_dm_timer *timer, int prescaler)
>  	if (prescaler >= 0x00 && prescaler <= 0x07) {
>  		l |= OMAP_TIMER_CTRL_PRE;
>  		l |= prescaler << 2;
> +	} else {
> +		if (prescaler != -1)
> +			return -EINVAL;

Argh... This is actually wrong, as it leaves timer enabled.
I suggest simply dropping this patch and I'll rethink whole
approach a bit later (and better).

>  	}
>  	omap_dm_timer_write_reg(timer, OMAP_TIMER_CTRL_REG, l);
>  

Sorry for the noise,
	ladis