linux-kernel - Re: [PATCH] drm/panel: simple: ensure Sharp lq123p1jx31 isn't turned off too soon

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Message-ID: <20170206120314.GK27607@ulmo.ba.sec>
Date:   Mon, 6 Feb 2017 13:03:14 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     seanpaul@...omium.org, marcheu@...omium.org,
        briannorris@...omium.org, hoegsberg@...gle.com, airlied@...ux.ie,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/panel: simple: ensure Sharp lq123p1jx31 isn't turned
 off too soon

On Thu, Feb 02, 2017 at 03:38:53PM -0800, Douglas Anderson wrote:
> The Sharp lq123p1jx31 has a requirement that the VDD is on for at
> least 300 ms before being turned off.  At the moment nothing anywhere
> in the kernel is ensuring this.

Looks to me like .delay.prepare would be a better fit. That enables the
regulator and setting it to 300 ms would make sure that the regulator
will always get enabled for at least 300 ms.

Anyway, your commit message says nothing about why this is important.
What are the side-effects if the above isn't true? Does the display hang
in some way?

Thierry

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