linux-kernel - Re: [PATCH] Input: elan_i2c - Wait for initialization after enabling regulator supply

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Message-ID: <ZvvyEux8f2ylRQOn@google.com>
Date: Tue, 1 Oct 2024 05:58:58 -0700
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: Mark Brown <broonie@...nel.org>
Cc: Chen-Yu Tsai <wenst@...omium.org>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mediatek@...ts.infradead.org,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH] Input: elan_i2c - Wait for initialization after enabling
 regulator supply

On Tue, Oct 01, 2024 at 12:07:16PM +0100, Mark Brown wrote:
> On Tue, Oct 01, 2024 at 02:57:10AM -0700, Dmitry Torokhov wrote:
> 
> > This will add an unwanted delay on ACPI systems that handle power
> > sequencing in firmware. However use of "optional" regulators is frowned
> > upon in this case as the supply in reality is not optional.
> 
> > Mark, has there been any developments that would help reconciling
> > difference in behavior between ACPI and DT systems. Ideally we'd need to
> > know when supply was turned on, and adjust the wait accordingly.
> 
> There's not been any changes here, but there's always been an event
> availalbe when a regulator is turned on?  There's also no difference
> between DT and ACPI systems here, both could have the regulator fixed on
> and I'd certainly not want to rely on an ACPI system implementing a
> device specific delay after power on given the sort of stuff they like
> to put into machine specific drivers.

Well with Elan in native mode ACPI FW does do proper power sequencing,
that is why this commit mentions failures observed on Mediatek devices.

Thanks.

-- 
Dmitry