From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from galahad.ideasonboard.com ([185.26.127.97]:37326 "EHLO galahad.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753119AbcKUJ7d (ORCPT ); Mon, 21 Nov 2016 04:59:33 -0500 From: Laurent Pinchart To: Geert Uytterhoeven Cc: Laurent Pinchart , DRI Development , Linux-Renesas , Tomi Valkeinen Subject: Re: [PATCH v2 09/13] arm64: dts: r8a7795: salvator-x: Add panel backlight support Date: Mon, 21 Nov 2016 11:59:47 +0200 Message-ID: <2227128.532ZZ8dc1T@avalon> In-Reply-To: References: <1479526093-7014-1-git-send-email-laurent.pinchart+renesas@ideasonboard.com> <1686355.2zT21Pz9pV@avalon> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-renesas-soc-owner@vger.kernel.org List-ID: Hi Geert, On Monday 21 Nov 2016 10:23:46 Geert Uytterhoeven wrote: > On Mon, Nov 21, 2016 at 10:19 AM, Laurent Pinchart wrote: > > On Monday 21 Nov 2016 09:36:22 Geert Uytterhoeven wrote: > >> On Sat, Nov 19, 2016 at 4:28 AM, Laurent Pinchart wrote: > >>> The panel backlight is controlled through a GPIO and a PWM channel. > >>> > >>> --- a/arch/arm64/boot/dts/renesas/r8a7795-salvator-x.dts > >>> +++ b/arch/arm64/boot/dts/renesas/r8a7795-salvator-x.dts > >>> @@ -178,6 +178,16 @@ > >>> }; > >>> }; > >>> }; > >>> + > >>> + backlight: backlight { > >>> + compatible = "pwm-backlight"; > >>> + pwms = <&pwm1 0 50000>; > >>> + > >>> + brightness-levels = <256 128 64 16 8 4 0>; > >> > >> Would it make sense to define more and/or linear levels? > > > > Possibly, this is pretty arbitrary. Linear levels might not be the best > > option given that the human eye doesn't have a linear response to light > > power, but we > > It not only depends on the human eye, but also on the backlight hardware > (is the conversion from voltage (L_VBRT) to light linear?). So we need to specify transfer functions in DT ;-) > > could certainly have more levels. In that case I'd prefer modifying the > > pwm- backlight DT bindings though, and specifying the PWM resolution > > instead of discrete levels. > > > > Note that the LVDS panel backlight PWM control signal is multiplexed with > > the external memory A21 signal on the Salvator-X board, with SW5 > > selecting which how to route the signal. When using backlight control we > > can't access the whole NOR flash anymore, so I'm not sure this patch > > should be merged. > > That NOR flash is also optional, right? > My Ex Memory Connector is not populated. That's correct. The Salvator-X DT file in mainline is just an example anyway, and we should pick the most useful peripherals for that purpose. -- Regards, Laurent Pinchart From mboxrd@z Thu Jan 1 00:00:00 1970 From: Laurent Pinchart Subject: Re: [PATCH v2 09/13] arm64: dts: r8a7795: salvator-x: Add panel backlight support Date: Mon, 21 Nov 2016 11:59:47 +0200 Message-ID: <2227128.532ZZ8dc1T@avalon> References: <1479526093-7014-1-git-send-email-laurent.pinchart+renesas@ideasonboard.com> <1686355.2zT21Pz9pV@avalon> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Received: from galahad.ideasonboard.com (galahad.ideasonboard.com [IPv6:2001:4b98:dc2:45:216:3eff:febb:480d]) by gabe.freedesktop.org (Postfix) with ESMTPS id 459846E3D8 for ; Mon, 21 Nov 2016 09:59:32 +0000 (UTC) In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Geert Uytterhoeven Cc: Linux-Renesas , Tomi Valkeinen , Laurent Pinchart , DRI Development List-Id: dri-devel@lists.freedesktop.org SGkgR2VlcnQsCgpPbiBNb25kYXkgMjEgTm92IDIwMTYgMTA6MjM6NDYgR2VlcnQgVXl0dGVyaG9l dmVuIHdyb3RlOgo+IE9uIE1vbiwgTm92IDIxLCAyMDE2IGF0IDEwOjE5IEFNLCBMYXVyZW50IFBp bmNoYXJ0IHdyb3RlOgo+ID4gT24gTW9uZGF5IDIxIE5vdiAyMDE2IDA5OjM2OjIyIEdlZXJ0IFV5 dHRlcmhvZXZlbiB3cm90ZToKPiA+PiBPbiBTYXQsIE5vdiAxOSwgMjAxNiBhdCA0OjI4IEFNLCBM YXVyZW50IFBpbmNoYXJ0IHdyb3RlOgo+ID4+PiBUaGUgcGFuZWwgYmFja2xpZ2h0IGlzIGNvbnRy b2xsZWQgdGhyb3VnaCBhIEdQSU8gYW5kIGEgUFdNIGNoYW5uZWwuCj4gPj4+IAo+ID4+PiAtLS0g YS9hcmNoL2FybTY0L2Jvb3QvZHRzL3JlbmVzYXMvcjhhNzc5NS1zYWx2YXRvci14LmR0cwo+ID4+ PiArKysgYi9hcmNoL2FybTY0L2Jvb3QvZHRzL3JlbmVzYXMvcjhhNzc5NS1zYWx2YXRvci14LmR0 cwo+ID4+PiBAQCAtMTc4LDYgKzE3OCwxNiBAQAo+ID4+PiAgICAgICAgICAgICAgICAgICAgICAg ICB9Owo+ID4+PiAgICAgICAgICAgICAgICAgfTsKPiA+Pj4gICAgICAgICB9Owo+ID4+PiArCj4g Pj4+ICsgICAgICAgYmFja2xpZ2h0OiBiYWNrbGlnaHQgewo+ID4+PiArICAgICAgICAgICAgICAg Y29tcGF0aWJsZSA9ICJwd20tYmFja2xpZ2h0IjsKPiA+Pj4gKyAgICAgICAgICAgICAgIHB3bXMg PSA8JnB3bTEgMCA1MDAwMD47Cj4gPj4+ICsKPiA+Pj4gKyAgICAgICAgICAgICAgIGJyaWdodG5l c3MtbGV2ZWxzID0gPDI1NiAxMjggNjQgMTYgOCA0IDA+Owo+ID4+IAo+ID4+IFdvdWxkIGl0IG1h a2Ugc2Vuc2UgdG8gZGVmaW5lIG1vcmUgYW5kL29yIGxpbmVhciBsZXZlbHM/Cj4gPiAKPiA+IFBv c3NpYmx5LCB0aGlzIGlzIHByZXR0eSBhcmJpdHJhcnkuIExpbmVhciBsZXZlbHMgbWlnaHQgbm90 IGJlIHRoZSBiZXN0Cj4gPiBvcHRpb24gZ2l2ZW4gdGhhdCB0aGUgaHVtYW4gZXllIGRvZXNuJ3Qg aGF2ZSBhIGxpbmVhciByZXNwb25zZSB0byBsaWdodAo+ID4gcG93ZXIsIGJ1dCB3ZQo+Cj4gSXQg bm90IG9ubHkgZGVwZW5kcyBvbiB0aGUgaHVtYW4gZXllLCBidXQgYWxzbyBvbiB0aGUgYmFja2xp Z2h0IGhhcmR3YXJlCj4gKGlzIHRoZSBjb252ZXJzaW9uIGZyb20gdm9sdGFnZSAoTF9WQlJUKSB0 byBsaWdodCBsaW5lYXI/KS4KClNvIHdlIG5lZWQgdG8gc3BlY2lmeSB0cmFuc2ZlciBmdW5jdGlv bnMgaW4gRFQgOy0pCgo+ID4gY291bGQgY2VydGFpbmx5IGhhdmUgbW9yZSBsZXZlbHMuIEluIHRo YXQgY2FzZSBJJ2QgcHJlZmVyIG1vZGlmeWluZyB0aGUKPiA+IHB3bS0gYmFja2xpZ2h0IERUIGJp bmRpbmdzIHRob3VnaCwgYW5kIHNwZWNpZnlpbmcgdGhlIFBXTSByZXNvbHV0aW9uCj4gPiBpbnN0 ZWFkIG9mIGRpc2NyZXRlIGxldmVscy4KPiA+IAo+ID4gTm90ZSB0aGF0IHRoZSBMVkRTIHBhbmVs IGJhY2tsaWdodCBQV00gY29udHJvbCBzaWduYWwgaXMgbXVsdGlwbGV4ZWQgd2l0aAo+ID4gdGhl IGV4dGVybmFsIG1lbW9yeSBBMjEgc2lnbmFsIG9uIHRoZSBTYWx2YXRvci1YIGJvYXJkLCB3aXRo IFNXNQo+ID4gc2VsZWN0aW5nIHdoaWNoIGhvdyB0byByb3V0ZSB0aGUgc2lnbmFsLiBXaGVuIHVz aW5nIGJhY2tsaWdodCBjb250cm9sIHdlCj4gPiBjYW4ndCBhY2Nlc3MgdGhlIHdob2xlIE5PUiBm bGFzaCBhbnltb3JlLCBzbyBJJ20gbm90IHN1cmUgdGhpcyBwYXRjaAo+ID4gc2hvdWxkIGJlIG1l cmdlZC4KPgo+IFRoYXQgTk9SIGZsYXNoIGlzIGFsc28gb3B0aW9uYWwsIHJpZ2h0Pwo+IE15IEV4 IE1lbW9yeSBDb25uZWN0b3IgaXMgbm90IHBvcHVsYXRlZC4KClRoYXQncyBjb3JyZWN0LiBUaGUg U2FsdmF0b3ItWCBEVCBmaWxlIGluIG1haW5saW5lIGlzIGp1c3QgYW4gZXhhbXBsZSBhbnl3YXks IAphbmQgd2Ugc2hvdWxkIHBpY2sgdGhlIG1vc3QgdXNlZnVsIHBlcmlwaGVyYWxzIGZvciB0aGF0 IHB1cnBvc2UuCgotLSAKUmVnYXJkcywKCkxhdXJlbnQgUGluY2hhcnQKCl9fX19fX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fCmRyaS1kZXZlbCBtYWlsaW5nIGxpc3QK ZHJpLWRldmVsQGxpc3RzLmZyZWVkZXNrdG9wLm9yZwpodHRwczovL2xpc3RzLmZyZWVkZXNrdG9w Lm9yZy9tYWlsbWFuL2xpc3RpbmZvL2RyaS1kZXZlbAo=