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

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Message-ID: <DB8PR10MB3356FB869A14EA88AFB40F4885950@DB8PR10MB3356.EURPRD10.PROD.OUTLOOK.COM>
Date:   Wed, 24 Jun 2020 16:56:31 +0000
From:   Roy Im <roy.im.opensource@...semi.com>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        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

On Thu, June 25, 2020 1:28 AM, Uwe Kleine-König
> 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?

Yes, it is now based on period, not frequency. You are right.
4000 is correct now. Thanks.

> 
> > 		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/ |