Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:4 as permitted sender) client-ip=2620:137:e000::3:4;
Date:   Tue, 19 Sep 2023 07:40:58 +1000
From:   John Watts <contact@jookia.org>
To:     Paul Cercueil <paul@crapouillou.net>
Cc:     Jessica Zhang <quic_jesszhan@quicinc.com>,
        dri-devel@lists.freedesktop.org,
        Neil Armstrong <neil.armstrong@linaro.org>,
        Sam Ravnborg <sam@ravnborg.org>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Shawn Guo <shawnguo@kernel.org>,
        Heiko Stuebner <heiko@sntech.de>,
        Chris Morgan <macromorgan@hotmail.com>,
        Jagan Teki <jagan@edgeble.ai>,
        Christophe Branchereau <cbranchereau@gmail.com>,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v2 3/9] drm/panel: nv3052c: Sleep for 150ms after
 reset
Message-ID: <ZQjD6gCEo62gMBX2@titan>
References: <20230918125853.2249187-1-contact@jookia.org>
 <20230918125853.2249187-4-contact@jookia.org>
 <7fc1ca68-ca7c-59b2-0b70-27bc34d83cee@quicinc.com>
 <ZQi4fFZ0VnsUIiXO@titan>
 <4d2079d66249a7052acded0abf30169a4e95d151.camel@crapouillou.net>
 <ZQi8Z45VCqr-GqN6@titan>
 <0d6b0159552b10548391a9bd88449d12c13fdcd6.camel@crapouillou.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <0d6b0159552b10548391a9bd88449d12c13fdcd6.camel@crapouillou.net>
Precedence: bulk

On Mon, Sep 18, 2023 at 11:34:51PM +0200, Paul Cercueil wrote:
> The driver is guaranteed to always reset the panel in sleep-in mode -
> as long as the panel was off when the driver started.
> 
> What I'd suggest if you really need to support a case where the panel
> was enabled by the bootloader, is to read the 0x0a register after
> enabling the regulator to read the mode, and sleep 120ms if it was in
> sleep-out mode.
> 
> But that's only if it's a case that you can test with. I won't accept a
> patch that makes sense on the surface if it addresses a corner case
> that nobody ever tested for.
> 
> For what I know, this patch just adds a huge delay to panel boot-up for
> all existing users for no valid reason.
>
> 
> Cheers,
> -Paul

Thank you very much for this feedback. I am more than happy to throw these
sleep patches in the trash and come back later with a proper solution when
I have an actual hardware setup and use case to test on.

John.