From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C2960C53200 for ; Wed, 29 Jul 2026 17:35:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type: Content-Transfer-Encoding:MIME-Version:References:In-Reply-To:Message-ID:Date :Subject:Cc:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=PpUrkAYPFOVA1pV5Hqor5M/8KfkA4Zbov6foGmLt584=; b=pDdDM2CaXmzPVenI5l9ab7FvGo 9VYmQzSSZsTRZGSKaIWnKjAzb9CGyruIdknVqGhLm3TyXFmXBn+oyiFaTH8+WQA8E0ySD7wpf1OqV 7bWvlkQGoFQSaOX1rjaywjeO2nCPmetv3LvKo0kIG94Z5Y6n7n8EFyQf7T/wcxbfYM80EQYotnHSi pOiCe0q1SaWA2X6ucoe5zXJ6FHBfyFJURlaxOKWQqOqqDc8t26wshbzE4nrwLe7zzZTcyfDwmxp/w UV/Rx9fpTfgGrUvZDEmRUbk7hGRoZZmnCOO0bJ2V6UzsKTOsRBo8Zi+fUIIyiyBlfz23205nvTSqF wGjfy9xQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wp8Bm-00000008iQP-1QR6; Wed, 29 Jul 2026 17:35:30 +0000 Received: from gloria.sntech.de ([185.11.138.130]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wp8Bk-00000008iPm-0RfF; Wed, 29 Jul 2026 17:35:29 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sntech.de; s=gloria202408; h=Content-Type:Content-Transfer-Encoding:MIME-Version: References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From:Reply-To; bh=PpUrkAYPFOVA1pV5Hqor5M/8KfkA4Zbov6foGmLt584=; b=0VN8FIB2IsiVhWK2p21wuwWWqr 1s2Yll/671IrZG4xK0SXvE8kKTBU/U/Fv3UrEqxR74QvYcjemQlGi/1E4a3TWcqmJB6/mM1qaXzcc zZv56SvcjWWgUwXh6KwjztEA3TQhdXMY1vpwbcbOCZ5PEoGjIlwcUvw75Ympun009ppy+aIa7jy5G EfbfxdsNwAyZk9gGi1qvURU0dDfByTiKUvzoZsTVnA2Y6yJ5KI+WF9rFV6gdh7Nl+BDJ2WbLSY4aE xGDRT3R1XlGB0an+5X0wZGPVG0tPftDJHEVSLGxjb+r8mus24Ii9963sc/AzkjILveFkNybI5kacS g+NuHZSg==; From: Heiko =?UTF-8?B?U3TDvGJuZXI=?= To: Alexey Charkov Cc: Rob Herring , Krzysztof Kozlowski , Conor Dooley , devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org, Nicolas Frattaroli Subject: Re: [PATCH] arm64: dts: rockchip: Add DSI LCD display on rk3576-evb1 Date: Wed, 29 Jul 2026 19:35:22 +0200 Message-ID: <12148936.RiKt1P0BV1@diego> In-Reply-To: References: <20250925-rk3576-evb1-dsi-v1-1-c76fc3740abc@gmail.com> <29759328.czjnFlTdjD@diego> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260729_103528_174510_2572F73D X-CRM114-Status: GOOD ( 42.50 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Am Mittwoch, 29. Juli 2026, 18:32:08 Mitteleurop=C3=A4ische Sommerzeit schr= ieb Alexey Charkov: > On Wed, Jul 29, 2026 at 6:46=E2=80=AFPM Heiko St=C3=BCbner wrote: > > > > Am Montag, 20. Oktober 2025, 14:31:12 Mitteleurop=C3=A4ische Sommerzeit= schrieb Heiko Stuebner: > > > Am Montag, 20. Oktober 2025, 10:50:58 Mitteleurop=C3=A4ische Sommerze= it schrieb Alexey Charkov: > > > > > > > > On Mon, Oct 20, 2025 at 12:31=E2=80=AFPM Heiko Stuebner wrote: > > > > > > > > > > Am Montag, 20. Oktober 2025, 10:19:51 Mitteleurop=C3=A4ische Somm= erzeit schrieb Alexey Charkov: > > > > > > On Thu, Sep 25, 2025 at 12:38=E2=80=AFAM Alexey Charkov wrote: > > > > > > > > > > > > > > Add support for the Rockchip W552793DBA-V10 LCD+touchscreen a= ssembly which > > > > > > > comes physically attached to Rockchip RK3576 EVB1 boards. > > > > > > > > > > > > > > The display part is driven by the on-chip MIPI DSI controller= , and the > > > > > > > touchscreen is connected over I2C. > > > > > > > > > > > > > > Signed-off-by: Alexey Charkov > > > > > > > --- > > > > > > > Note that backlight support is left out for now, as it depend= s on PWM > > > > > > > support [0] which has not yet been merged. > > > > > > > > > > > > > > A workaround is simply `gpioset -c 0 13=3D1` to set the respe= ctive GPIO > > > > > > > pin high and thus to light up the display unconditionally. > > > > > > > > > > > > > > [0] https://lore.kernel.org/lkml/20250602-rk3576-pwm-v2-0-a64= 34b0ce60c@collabora.com/ > > > > > > > --- > > > > > > > arch/arm64/boot/dts/rockchip/rk3576-evb1-v10.dts | 89 ++++++= ++++++++++++++++++ > > > > > > > 1 file changed, 89 insertions(+) > > > > > > > > > > > > Hi Heiko, > > > > > > > > > > > > Any thoughts about this one? Can we perhaps get it merged for -= next? > > > > > > > > > > Does the gpio-backlight work on that device? > > > > > That would make the gpioset hack unnecessary. > > > > > > > > I've got a local patch using pwm-gpio and pwm-backlight as a stop-g= ap > > > > solution, but I don't think it's worth merging upstream, because the > > > > backlight is supposed to be driven by the hardware PWM on the same = pin > > > > (not bit-banging the GPIO line). After all, Nicolas has been workin= g on > > > > adding a proper hardware PWM driver for RK3576. > > > > > > > > The display itself works without PWM support, and so does the touch= screen. > > > > > > Right now, I don't think we have an actual timeline if/when Nicolas w= ill > > > be able to work on the pwm again. So my idea was if we want to > > > integrate the baclight as you described below, to have an actual usab= le > > > display and then when the new pwm has landed switch over to that one? > > > > With the ELCE around the corner we're nearing the year-mark here ;-) > > (And I'm surprised, I remembered this pending patch) >=20 > I've been hoping that Nicolas' PWM series gets further along in the meant= ime :) >=20 > > So how about integrating your gpio-pwm backlight for the time being? >=20 > Could do that, but I'm worried if it would immediately become set in > stone because DT is ABI, making it hard to switch to a "proper" > hardware-driven PWM once Nicolas' series lands. The backlight subsystem is using dev_name() to name the sysfs node. So if you keep the node name to "backlight", the backlight device stays the same. I guess the question is if you also consider the brightness levels as unchangeable, though I would assume any sane system should just read max_brightness and adjust accordingly. Also this is an eval-board ... so you won't have any actual real-world users :-) . So, personally I don't see the big hickup here, but we'll do what you think best. Heiko > > Or alternatively just going with a gpio-backlight, like the Anbernic Vi= ta did: > > > > /* > > * LEDs and Backlights can be controlled as a PWM, but PWM > > * support is not yet available. > > */ > > gpio_backlight: backlight { > > compatible =3D "gpio-backlight"; > > gpios =3D <&gpio2 RK_PC4 GPIO_ACTIVE_HIGH>; > > pinctrl-0 =3D <&led_backlight_h>; > > pinctrl-names =3D "default"; > > }; >=20 > In the case of RK3576 EVB1 enabling it at full power is eye-burning > bright, so some sort of PWM is definitely warranted. >=20 > Best regards, > Alexey >=20