From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shawn Guo Subject: Re: [PATCH] ARM: dts: imx53: add support for Ka-Ro TX53 modules Date: Fri, 13 Dec 2013 20:16:48 +0800 Message-ID: <20131213121646.GU18380@S2101-09.ap.freescale.net> References: <1386852128-32220-1-git-send-email-LW@KARO-electronics.de> <20131213081744.GR18380@S2101-09.ap.freescale.net> <20131213105417.71a42133@ipc1.ka-ro> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <20131213105417.71a42133-VjFSrY7JcPWvSplVBqRQBQ@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Lothar =?iso-8859-1?Q?Wa=DFmann?= Cc: linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala List-Id: devicetree@vger.kernel.org On Fri, Dec 13, 2013 at 10:54:17AM +0100, Lothar Wa=DFmann wrote: > > > + compatible =3D "pwm-backlight"; > > > + pwms =3D <&pwm2 0 500000>; > > > + power-supply =3D <®_3v3>; > > > + brightness-levels =3D < > > > + 100 99 98 97 96 95 94 93 92 91 > > > + 90 89 88 87 86 85 84 83 82 81 > > > + 80 79 78 77 76 75 74 73 72 71 > > > + 70 69 68 67 66 65 64 63 62 61 > > > + 60 59 58 57 56 55 54 53 52 51 > > > + 50 49 48 47 46 45 44 43 42 41 > > > + 40 39 38 37 36 35 34 33 32 31 > > > + 30 29 28 27 26 25 24 23 22 21 > > > + 20 19 18 17 16 15 14 13 12 11 > > > + 10 9 8 7 6 5 4 3 2 1 > > > + 0 > >=20 > > Why is it so unique to start with 100 and end with 0? Does it even > > work? Here is what I read from bindings doc. > >=20 > Yes, it works. The backlight control of the displays we typically use > is active low. This is a poor man's way to get an inverted PWM output= ! > (And one in which the number written to the sysfs file corresponds to > the actual duty cycle of the PWM output) I think Linux pwm driver should be improved for this case rather than manipulate device tree in a way that violate the defined bindings. Shawn -- To unsubscribe from this list: send the line "unsubscribe devicetree" i= n the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html