linux-kernel - Re: [PATCH v2 05/10] media: adv748x: add support for HDMI audio

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Message-ID: <CAMuHMdVRJZ+RLSxeFdXXPntVxCUMd-Ai+=vizFrvN-CHNW=kjA@mail.gmail.com>
Date:   Fri, 20 Mar 2020 12:05:20 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Alex Riesen <alexander.riesen@...itec.com>,
        Kieran Bingham <kieran.bingham@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        driverdevel <devel@...verdev.osuosl.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>
Subject: Re: [PATCH v2 05/10] media: adv748x: add support for HDMI audio

Hi Alex,

On Fri, Mar 20, 2020 at 11:58 AM Alex Riesen
<alexander.riesen@...itec.com> wrote:
> Geert Uytterhoeven, Fri, Mar 20, 2020 09:43:29 +0100:
> > On Thu, Mar 19, 2020 at 6:42 PM Alex Riesen <alexander.riesen@...itec.com> wrote:
> > > This adds an implemention of SoC DAI driver which provides access to the
> > > I2S port of the device.
>
> I just noticed I don't do clk_prepare_enable anywhere.
> Shouldn't the clock master enable its clocks somewhere?

Usually the consumer is responsible for doing that.
Does the rcar-sound driver do that?

But in this case, perhaps the clock should be enabled implicitly in response
to a request from the audio subsystem, like you do below.

Note that you register a fixed-rate clock, which is assumed to be always
enabled. Perhaps a gateable clock type is more appropriate?

> > > diff --git a/drivers/media/i2c/adv748x/adv748x-dai.c b/drivers/media/i2c/adv748x/adv748x-dai.c
> > > new file mode 100644
> > > index 000000000000..4775a0c7ed7f
> > > --- /dev/null
> > > +++ b/drivers/media/i2c/adv748x/adv748x-dai.c
> ...
> > > +static int adv748x_dai_startup(struct snd_pcm_substream *sub, struct snd_soc_dai *dai)
> > > +{
> > > +       struct adv748x_state *state = state_of(dai);
> > > +
> > > +       if (sub->stream != SNDRV_PCM_STREAM_CAPTURE)
> > > +               return -EINVAL;
> > > +       return set_audio_pads_state(state, 1);
> > > +}
>
> For example, here, after activation of the lines succeeded?
>
> > > +static void adv748x_dai_shutdown(struct snd_pcm_substream *sub, struct snd_soc_dai *dai)
> > > +{
> > > +       struct adv748x_state *state = state_of(dai);
> > > +
> > > +       set_audio_pads_state(state, 0);
> > > +}
>
> And clk_disable_unprepare here, before shutting down the pads?
Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds