From: Wolfram Sang <wsa+renesas@sang-engineering.com>
To: Chen-Yu Tsai <wenst@chromium.org>
Cc: Mark Brown <broonie@kernel.org>,
Matthias Brugger <matthias.bgg@gmail.com>,
AngeloGioacchino Del Regno
<angelogioacchino.delregno@collabora.com>,
Dmitry Torokhov <dmitry.torokhov@gmail.com>,
Jiri Kosina <jikos@kernel.org>,
Andi Shyti <andi.shyti@kernel.org>,
Benson Leung <bleung@chromium.org>,
Tzung-Bi Shih <tzungbi@kernel.org>,
linux-mediatek@lists.infradead.org, devicetree@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
chrome-platform@lists.linux.dev, linux-input@vger.kernel.org,
linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v7 4/8] i2c: of-prober: skip post-power-on delay if powered on sufficiently long
Date: Tue, 10 Nov 2026 11:24:24 +0100 [thread overview]
Message-ID: <avLw2AiqcnO9Blun@shikoro> (raw)
In-Reply-To: <20261103043734.2179858-5-wenst@chromium.org>
On Tue, Nov 03, 2026 at 12:37:28PM +0800, Chen-Yu Tsai wrote:
> On some devices the I2C component is powered from an always-on power
> rail, or the power rail has been left on by either POR defaults or
> the bootloader. By the time the prober probes the device, the device
> most certainly has finished initializing and can respond. There is no
> need for the delay.
>
> In such designs, the system integrators tend to work around the delay
> to avoid the boot time penalty by simply omitting it from the device
> tree and the component prober. This is undesired, as the device tree
> is not fully describing the hardware.
>
> Switch to the new regulator_enable_and_wait() function that makes sure
> a certain amount of time has passed since the regulator supply was
> actually enabled.
>
> Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Acked-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
@Andi: Chen-Yu is the maintainer of the of-prober, so I suggest these
changes just go in together with this series.
next prev parent reply other threads:[~2026-11-10 10:24 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-03 4:37 [PATCH v7 0/8] arm64: mediatek: Chromebook trackpad supply fixes Chen-Yu Tsai
2026-11-03 4:37 ` [PATCH v7 1/8] regulator: core: Add "enable and wait" functions Chen-Yu Tsai
2026-11-03 4:37 ` [PATCH v7 2/8] Input: elan_i2c - Wait for initialization after enabling regulator supply Chen-Yu Tsai
2026-11-03 4:37 ` [PATCH v7 3/8] HID: i2c-hid-of: skip post-power-on delay if powered on sufficiently long Chen-Yu Tsai
2026-11-03 4:37 ` [PATCH v7 4/8] i2c: of-prober: " Chen-Yu Tsai
2026-11-10 10:24 ` Wolfram Sang [this message]
2026-11-03 4:37 ` [PATCH v7 5/8] i2c: of-prober: Let cleanup op know if a device was found Chen-Yu Tsai
2026-11-10 10:24 ` Wolfram Sang
2026-11-03 4:37 ` [PATCH v7 6/8] i2c: of-prober: Defer regulator_disable() on successful probe in simple helper Chen-Yu Tsai
2026-11-10 10:24 ` Wolfram Sang
2026-11-03 4:37 ` [PATCH v7 7/8] arm64: dts: mediatek: mt8173-elm-hana: Unmark trackpad supply as always-on Chen-Yu Tsai
2026-11-03 4:37 ` [PATCH v7 8/8] arm64: dts: mediatek: mt8192-asurada-spherion: Add Synaptics trackpad's supply Chen-Yu Tsai
2026-11-07 16:43 ` (subset) [PATCH v7 0/8] arm64: mediatek: Chromebook trackpad supply fixes Mark Brown
2026-11-09 5:41 ` Chen-Yu Tsai
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