linux-kernel - RE: [PATCHv2 6/6] ASoC: da7213: Add default clock handling

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Message-ID: <AM5PR1001MB0994D842A2D7051F81A7765B80440@AM5PR1001MB0994.EURPRD10.PROD.OUTLOOK.COM>
Date:   Wed, 27 Nov 2019 13:42:54 +0000
From:   Adam Thomson <Adam.Thomson.Opensource@...semi.com>
To:     Mark Brown <broonie@...nel.org>,
        Adam Thomson <Adam.Thomson.Opensource@...semi.com>
CC:     Sebastian Reichel <sebastian.reichel@...labora.com>,
        Support Opensource <Support.Opensource@...semi.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kernel@...labora.com" <kernel@...labora.com>
Subject: RE: [PATCHv2 6/6] ASoC: da7213: Add default clock handling

On 27 November 2019 12:33, Mark Brown wrote:

> On Wed, Nov 27, 2019 at 11:32:54AM +0000, Adam Thomson wrote:
> 
> > As I said it's a small thing and requires a specific use-case to occur, but
> > having the PLL configured twice for the very first stream in that scenario
> > seems messy. Regarding the SYSCLK approach you mention, I'm not clear how
> that
> > would work so I'm obviously missing something. If we had some init stage
> > indication though that auto PLL was required then we're golden.
> 
> There's a bunch of other drivers using the SYSCLK thing, when you call
> set_sysclk() they provide a different SYSCLK number if they want to use
> manual mode.  If there's a concern about drivers doing stuff on init you
> could always ask them to set the PLL during init, even if only briefly.

Yeah OK I see what you mean; using the sysclk id. Still doesn't feel like the
nicest solution here though. I guess we're stuck with people having to manually
configure the PLL for bypass when a non-generic machine driver inits, to avoid
the initial double config, as I don't see other options unless you have
something to specify at init that it's auto or manual, and this doesn't feel
like a DT device specific property thing as it's more software than hardware.
At least Sebastian's patch has a good comment block to highlight this.