linux-kernel - Re: [PATCH v3 05/11] media: adv748x: add support for HDMI audio

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Message-ID: <20200323083610.GB4298@pflmari>
Date:   Mon, 23 Mar 2020 09:36:10 +0100
From:   Alex Riesen <alexander.riesen@...itec.com>
To:     Stephen Boyd <sboyd@...nel.org>
CC:     Kieran Bingham <kieran.bingham@...asonboard.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        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>,
        <devel@...verdev.osuosl.org>, <linux-media@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-renesas-soc@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>
Subject: Re: [PATCH v3 05/11] media: adv748x: add support for HDMI audio

Stephen Boyd, Sat, Mar 21, 2020 02:09:31 +0100:
> Quoting Alex Riesen (2020-03-20 09:12:00)
> > diff --git a/drivers/media/i2c/adv748x/adv748x-dai.c b/drivers/media/i2c/adv748x/adv748x-dai.c
> > new file mode 100644
> > index 000000000000..6fce7d000423
> > --- /dev/null
> > +++ b/drivers/media/i2c/adv748x/adv748x-dai.c
> > @@ -0,0 +1,265 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +/*
> > + * Driver for Analog Devices ADV748X HDMI receiver with AFE
> > + * The implementation of DAI.
> > + */
> > +
> > +#include "adv748x.h"
> > +
> > +#include <linux/clk.h>
> 
> Is this include used? Please try to make a clk provider or a clk
> consumer and not both unless necessary.

Yes, they're both used: I use clk_get_rate to get the frequency of the clock to validate
the master clock frequency configuration.

> > +int adv748x_dai_init(struct adv748x_dai *dai)
> > +{
> > +       int ret;
> > +       struct adv748x_state *state = adv748x_dai_to_state(dai);
> > +
> > +       dai->mclk_name = kasprintf(GFP_KERNEL, "%s.%s-i2s-mclk",
> > +                                  state->dev->driver->name,
> > +                                  dev_name(state->dev));
> > +       if (!dai->mclk_name) {
> > +               ret = -ENOMEM;
> > +               adv_err(state, "No memory for MCLK\n");
> > +               goto fail;
> > +       }
> > +       dai->mclk = clk_register_fixed_rate(state->dev,
> 
> Please register with clk_hw_register_fixed_rate() instead.

Ok, I see the clk_register_fixed_rate isn't even commented...
I shall change it to used clk_hw_register_fixed_rate.

But could you please point me at some documentation, example, or just add a
few words to explain the preference?

BTW, the clock which the driver attempts to provide can actually be switched
on and off (it output pad can be even tristated). As the device is connected
by I2C to the how, I seems to be unable to use the existing gated clock
implementation because of the mmio register it requires. Or am I wrong?

> > +                                           dai->mclk_name,
> > +                                           NULL /* parent_name */,
> > +                                           0 /* flags */,
> > +                                           12288000 /* rate */);
> 
> Not sure these comments are useful.

You're right. Removed.

> > +       dai->drv.name = ADV748X_DAI_NAME;
> > +       dai->drv.ops = &adv748x_dai_ops;
> > +       dai->drv.capture = (struct snd_soc_pcm_stream){
> 
> Can this be const?

It can. Fixed.

> Please drop extra newline at end of file.

Done.

Thanks a lot for the review and commentary!

Regards,
Alex