linux-kernel - Re: [PATCH v4 3/6] ASoC: audio-graph-card: Support setting component plls and sysclks

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Date:   12 Jan 2021 10:35:38 +0900
From:   Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
To:     Richard Fitzgerald <rf@...nsource.cirrus.com>
Cc:     <broonie@...nel.org>, <robh+dt@...nel.org>,
        <nsaenzjulienne@...e.de>, <f.fainelli@...il.com>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <alsa-devel@...a-project.org>, <patches@...nsource.cirrus.com>,
        <bcm-kernel-feedback-list@...adcom.com>,
        <linux-rpi-kernel@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 3/6] ASoC: audio-graph-card: Support setting component plls and sysclks


Hi Richard

> Some codecs need plls and/or sysclks to be configured using the
> snd_soc_component_set_[sysclk|pll] functions. These drivers cannot
> necessarily be converted to use the clock framework. If the codec is on
> a I2C/SPI bus, a nested clk_get would be needed to enable the bus clock.
> But the clock framework does not support nested operations and this would
> deadlock.
> 
> This patch adds new dt properties that list phandles of components with
> the pll/sysclk settings to be applied. Multiple settings can be given for
> the same phandle to allow for components with multiple clocks and plls.
> The plls and sysclks are enabled when the card bias level moves to STANDBY
> and disabled when it moves to OFF.
> 
> The implementation does not attempt to handle specifying complex clock
> ordering interdependencies between components. The plls and sysclks are
> applied to a component as it is passed to the card set_bias_level/
> set_bias_level_post callbacks. It follows from this that the order
> components are configured is the order that they are passed to those
> callbacks.
> 
> Signed-off-by: Richard Fitzgerald <rf@...nsource.cirrus.com>
> ---

As I mentioned in v3, adding *general* pll to common card driver is
maybe difficult.
Using your own customized audio-graph-card driver is better idea,
instead of adding code to common driver.

I think Sameer's Tegra driver (= [3/6]) is good sample for you ?

	https://lore.kernel.org/r/1606413823-19885-1-git-send-email-spujar@nvidia.com

Thank you for your help !!

Best regards
---
Kuninori Morimoto