linux-kernel - Re: [PATCH 5/5] ASoC: cs34l45: Hibernation support

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Message-ID: <c7d98128-32ce-9a63-7dae-2f4b735d95e9@opensource.cirrus.com>
Date:   Thu, 2 Mar 2023 14:03:29 -0600
From:   Vlad Karpovich <vkarpovi@...nsource.cirrus.com>
To:     Mark Brown <broonie@...nel.org>
CC:     Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, <alsa-devel@...a-project.org>,
        <patches@...nsource.cirrus.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/5] ASoC: cs34l45: Hibernation support


On 3/2/23 12:08, Mark Brown wrote:
> On Thu, Mar 02, 2023 at 11:59:05AM -0600, Vlad Karpovich wrote:
>> The CS35L45 features a low-power Hibernation State. In this state, all
>> register contents are lost, but the contents of
>> RAM are retained. In the Hibernation State, only always-on digital functions
>> to support wake-up are enabled.
>> Entry to this state is achieved via the register interface (either by an
>> external driver using the control port, or the
>> programmable DSP). Exit from this state is triggered by activity on device
>> GPIO pins, intended SPI transaction, or I2C
>> transaction with intended slave address
> OK, so it's essentially just a faster mechanism for bringing the device
> out of runtime suspend?

I don't think it is a faster way since it requires interaction with DSP 
and restoring all wiped registers.

But it saves a some power comparing a low power state in the current driver

>   I would suggest doing something in the code to
> clarify that this is not the same thing as system level hibernation,
> having references to hibernate in the driver is likely to lead to
> confusion down the line.

The feature is named hibernation in the data sheet.  Renaming it in the 
driver will add confusing for the driver user.

>   I'd also include a bit more description in the
> commit message too.
I will do in next version.
> Please don't top post, reply in line with needed context.  This allows
> readers to readily follow the flow of conversation and understand what
> you are talking about and also helps ensure that everything in the
> discussion is being addressed.
Thanks. I will do.