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From: Sam Ravnborg <sam@ravnborg.org>
To: "Alex G." <mr.nuke.me@gmail.com>
Cc: dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org,
	Jernej Skrabec <jernej.skrabec@siol.net>,
	Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
	Neil Armstrong <narmstrong@baylibre.com>,
	David Airlie <airlied@linux.ie>, Mark Brown <broonie@kernel.org>,
	Jonas Karlman <jonas@kwiboo.se>,
	linux-kernel@vger.kernel.org, Andrzej Hajda <a.hajda@samsung.com>,
	Rob Herring <robh+dt@kernel.org>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
Subject: Re: [PATCH 1/2] drm/bridge: sii902x: Enable I/O and core VCC supplies if present
Date: Mon, 28 Sep 2020 21:03:41 +0200	[thread overview]
Message-ID: <20200928190341.GA673726@ravnborg.org> (raw)
In-Reply-To: <9c3ce766-743c-705f-7926-21e753c2d02d@gmail.com>

Hi Alex.

On Mon, Sep 28, 2020 at 12:35:01PM -0500, Alex G. wrote:
> On 9/26/20 1:49 PM, Sam Ravnborg wrote:
> > Hi Alexandru
> > 
> > On Thu, Sep 24, 2020 at 03:05:05PM -0500, Alexandru Gagniuc wrote:
> > > On the SII9022, the IOVCC and CVCC12 supplies must reach the correct
> > > voltage before the reset sequence is initiated. On most boards, this
> > > assumption is true at boot-up, so initialization succeeds.
> > > 
> > > However, when we try to initialize the chip with incorrect supply
> > > voltages, it will not respond to I2C requests. sii902x_probe() fails
> > > with -ENXIO.
> > > 
> > > To resolve this, look for the "iovcc" and "cvcc12" regulators, and
> > > make sure they are enabled before starting the reset sequence. If
> > > these supplies are not available in devicetree, then they will default
> > > to dummy-regulator. In that case everything will work like before.
> > > 
> > > This was observed on a STM32MP157C-DK2 booting in u-boot falcon mode.
> > > On this board, the supplies would be set by the second stage
> > > bootloader, which does not run in falcon mode.
> > > 
> > > Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
> > 
> > One nitpick here. The binding should be present in the tree before
> > you start using it. So this patch should be applied after the binding.
> 
> It is :)
>   * arch/arm/boot/dts/stm32mp15xx-dkx.dtsi

This is the device tree. So essentially there is part of the device
tree that is not yet documented - so in a perfect world all parts of the
device tree is documented in bindings
(Documentation/devicetree/bindings/* ) before the device tree is
committed.

	Sam

  reply	other threads:[~2020-09-28 19:03 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-24 20:05 [PATCH 1/2] drm/bridge: sii902x: Enable I/O and core VCC supplies if present Alexandru Gagniuc
2020-09-24 20:05 ` [PATCH 2/2] dt-bindings: display: sii902x: Add supply bindings Alexandru Gagniuc
2020-09-26 18:42   ` Sam Ravnborg
2020-09-24 20:22 ` [PATCH 1/2] drm/bridge: sii902x: Enable I/O and core VCC supplies if present Fabio Estevam
2020-09-24 20:34   ` Alex G.
2020-09-26 18:49 ` Sam Ravnborg
2020-09-28 17:35   ` Alex G.
2020-09-28 19:03     ` Sam Ravnborg [this message]
2020-09-28 17:30 ` [PATCH v2 " Alexandru Gagniuc
2020-09-28 17:30   ` [PATCH v2 2/2] dt-bindings: display: sii902x: Add supply bindings Alexandru Gagniuc
2020-09-29 20:17     ` Rob Herring
2020-10-20  1:24   ` [PATCH v2 1/2] drm/bridge: sii902x: Enable I/O and core VCC supplies if present Alex G.
2020-10-20  7:16     ` Sam Ravnborg
2020-10-20 14:01       ` Alex G.
2020-10-20 15:08         ` Sam Ravnborg
2020-10-20 22:14   ` [PATCH v3 1/3] drm/bridge: sii902x: Refactor init code into separate function Alexandru Gagniuc
2020-10-20 22:14   ` [PATCH v3 2/3] drm/bridge: sii902x: Enable I/O and core VCC supplies if present Alexandru Gagniuc
2020-11-08 10:55     ` Sam Ravnborg
2020-10-20 22:14   ` [PATCH v3 3/3] dt-bindings: display: sii902x: Add supply bindings Alexandru Gagniuc

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