linux-kernel - Re: [RESEND PATCH V13 3/3] Input: new da7280 haptic driver

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Date:   Wed, 24 Jun 2020 18:28:18 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Roy Im <roy.im.opensource@...semi.com>
Cc:     Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Brian Masney <masneyb@...tation.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Lee Jones <lee.jones@...aro.org>, Luca Weiss <luca@...tu.xyz>,
        Maximilian Luz <luzmaximilian@...il.com>,
        Pascal PAILLET-LME <p.paillet@...com>,
        Rob Herring <robh@...nel.org>,
        Samuel Ortiz <sameo@...ux.intel.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Support Opensource <Support.Opensource@...semi.com>,
        "linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>
Subject: Re: [RESEND PATCH V13 3/3] Input: new da7280 haptic driver

Hello,

On Wed, Jun 24, 2020 at 03:39:52PM +0000, Roy Im wrote:
> On Wed, Jun 24, 2020 at 10:37 PM, Uwe Kleine-König wrote:
> > On Wed, Jun 24, 2020 at 12:04:24PM +0900, Roy Im wrote:
> > > 		period2freq = 1000000 / state.period;
> > > 		if (period2freq < DA7280_MIN_PWM_FREQ_KHZ ||
> > > 		    period2freq > DA7280_MAX_PWM_FREQ_KHZ) {
> > > 			dev_err(dev, "Unsupported PWM frequency (%u)\n",
> > > 				period2freq);
> > > 			return -EINVAL;
> > > 		}
> > > If you look ok, let me update this so.
> > 
> > looks fine.
> > 
> > Note that you don't need the division if you check for:
> > 
> > 	if (state.period > 100000 || state.period < 4000) {
> > 		...
> > 
> > (maybe the compiler is already clever enough to get rid of the division for you, but then the check is:
> > 
> > 	if (state.period > 100000 || state.period < 3985) {
> > 
> > because of rounding errors.)
> 
> OK, you are right, that will be better. So let me change that as below
> if you look fine.

I look fine, the code however is wrong. :-)

> 	/* Check PWM period, PWM freq = 1000000 / state.period.
> 	 * The valid PWM freq range: 10k ~ 250kHz.
> 	 */
> 	if (state.period > 100000 || state.period < 3985) {

You want 4000 here ---------------------------------^^^^, don't you?

> 		dev_err(dev, "Unsupported PWM period (%u)\n",
> 			state.period);
> 		return -EINVAL;
> 	}

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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