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Date:   Wed, 2 Dec 2020 12:19:56 -0800
From:   Nicolin Chen <nicoleotsuka@gmail.com>
To:     Shengjiu Wang <shengjiu.wang@nxp.com>
Cc:     timur@kernel.org, Xiubo.Lee@gmail.com, festevam@gmail.com,
        broonie@kernel.org, perex@perex.cz, tiwai@suse.com,
        alsa-devel@alsa-project.org, lgirdwood@gmail.com,
        robh+dt@kernel.org, devicetree@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] ASoC: fsl: Add imx-hdmi machine driver
Message-ID: <20201202201955.GB1498@Asurada-Nvidia>
References: <1606455021-18882-1-git-send-email-shengjiu.wang@nxp.com>
 <1606455021-18882-2-git-send-email-shengjiu.wang@nxp.com>
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On Fri, Nov 27, 2020 at 01:30:21PM +0800, Shengjiu Wang wrote:
> The driver is initially designed for sound card using HDMI
> interface on i.MX platform. There is internal HDMI IP or
> external HDMI modules connect with SAI or AUD2HTX interface.
> It supports both transmitter and receiver devices.
> 
> Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
> ---
>  sound/soc/fsl/Kconfig    |  12 ++
>  sound/soc/fsl/Makefile   |   2 +
>  sound/soc/fsl/imx-hdmi.c | 235 +++++++++++++++++++++++++++++++++++++++
>  3 files changed, 249 insertions(+)
>  create mode 100644 sound/soc/fsl/imx-hdmi.c

> diff --git a/sound/soc/fsl/imx-hdmi.c b/sound/soc/fsl/imx-hdmi.c
> new file mode 100644
> index 000000000000..ac164514b1b2
> --- /dev/null
> +++ b/sound/soc/fsl/imx-hdmi.c

> +static int imx_hdmi_hw_params(struct snd_pcm_substream *substream,
> +			      struct snd_pcm_hw_params *params)
> +{
> +	struct snd_soc_pcm_runtime *rtd = substream->private_data;
> +	struct imx_hdmi_data *data = snd_soc_card_get_drvdata(rtd->card);
> +	bool tx = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
> +	struct snd_soc_dai *cpu_dai = asoc_rtd_to_cpu(rtd, 0);
> +	struct snd_soc_card *card = rtd->card;
> +	struct device *dev = card->dev;
> +	int ret;
> +
> +	/* set cpu DAI configuration */
> +	ret = snd_soc_dai_set_sysclk(cpu_dai, data->cpu_priv.sysclk_id[tx],
> +				     8 * data->cpu_priv.slot_width * params_rate(params),

Looks like fixed 2 slots being used, judging by the set_tdm_slot
call below. Then...why "8 *"? Probably need a line of comments?

> +				     tx ? SND_SOC_CLOCK_OUT : SND_SOC_CLOCK_IN);
> +	if (ret && ret != -ENOTSUPP) {
> +		dev_err(dev, "failed to set cpu sysclk: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = snd_soc_dai_set_tdm_slot(cpu_dai, 0, 0, 2, data->cpu_priv.slot_width);

May have a local variable to cache slot_width.

> +static int imx_hdmi_probe(struct platform_device *pdev)

> +	data->dai.name = "i.MX HDMI";
> +	data->dai.stream_name = "i.MX HDMI";
> +	data->dai.cpus->dai_name = dev_name(&cpu_pdev->dev);
> +	data->dai.platforms->of_node = cpu_np;
> +	data->dai.ops = &imx_hdmi_ops;
> +	data->dai.playback_only = true;
> +	data->dai.capture_only = false;
> +	data->dai.init = imx_hdmi_init;
> +
> +
> +	if (of_property_read_bool(np, "hdmi-out")) {
> +		data->dai.playback_only = true;
> +		data->dai.capture_only = false;
> +		data->dai.codecs->dai_name = "i2s-hifi";
> +		data->dai.codecs->name = "hdmi-audio-codec.1";
> +		data->dai.dai_fmt = data->dai_fmt |
> +				    SND_SOC_DAIFMT_NB_NF |
> +				    SND_SOC_DAIFMT_CBS_CFS;
> +	}
> +
> +	if (of_property_read_bool(np, "hdmi-in")) {
> +		data->dai.playback_only = false;
> +		data->dai.capture_only = true;
> +		data->dai.codecs->dai_name = "i2s-hifi";
> +		data->dai.codecs->name = "hdmi-audio-codec.2";
> +		data->dai.dai_fmt = data->dai_fmt |
> +				    SND_SOC_DAIFMT_NB_NF |
> +				    SND_SOC_DAIFMT_CBM_CFM;
> +	}
> +
> +	if ((data->dai.playback_only && data->dai.capture_only) ||
> +	    (!data->dai.playback_only && !data->dai.capture_only)) {
> +		dev_err(&pdev->dev, "Wrongly enable HDMI DAI link\n");
> +		goto fail;
> +	}

Seems that this condition check can never be true, given that:
1. By default: playback_only=true && capture_only=false
2. Conditionally overwritten: playback_only=true && capture_only=false
3. Conditionally overwritten: playback_only=false && capture_only=true

If I understand it correctly, probably should be something like:
	bool hdmi_out = of_property_read_bool(np, "hdmi-out");
	bool hdmi_in = of_property_read_bool(np, "hdmi-in");

	if ((hdmi_out && hdmi_in) || (!hdmi_out || !hdmi_in))
		// "Invalid HDMI DAI link"; goto fail;

	if (hdmi_out) {
		// ...
	} else if (hdmi_in) {
		// ...
	} else // No need of this line if two properties are exclusive

> +	data->card.num_links = 1;
> +	data->card.dai_link = &data->dai;
> +
> +	platform_set_drvdata(pdev, &data->card);

Why pass card pointer?