linux-kernel - Re: [alsa-devel] [PATCH V2 02/10] ASoC: img: Add driver for I2S input controller

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Date:	Mon, 19 Oct 2015 18:47:32 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Damien Horsley <Damien.Horsley@...tec.com>
Cc:	alsa-devel@...a-project.org,
	James Hartley <James.Hartley@...tec.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Jaroslav Kysela <perex@...ex.cz>,
	Takashi Iwai <tiwai@...e.com>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [alsa-devel] [PATCH V2 02/10] ASoC: img: Add driver for I2S
 input controller

On Mon, Oct 12, 2015 at 01:40:29PM +0100, Damien Horsley wrote:

> +static inline u32 img_i2s_in_ch_disable(struct img_i2s_in *i2s, u32 chan)
> +{
> +	u32 reg;
> +
> +	reg = img_i2s_in_ch_readl(i2s, chan, IMG_I2S_IN_CH_CTL);
> +	reg &= ~IMG_I2S_IN_CH_CTL_ME_MASK;
> +	img_i2s_in_ch_writel(i2s, chan, reg, IMG_I2S_IN_CH_CTL);
> +
> +	return reg;
> +}
> +
> +static inline void img_i2s_in_ch_enable(struct img_i2s_in *i2s, u32 chan,
> +					u32 reg)
> +{
> +	reg |= IMG_I2S_IN_CH_CTL_ME_MASK;
> +	img_i2s_in_ch_writel(i2s, chan, reg, IMG_I2S_IN_CH_CTL);
> +}

The APIs here all seem a bit odd - for example the enable API taking a
register value as an argument (normally reg is a register address BTW)
and returning a value but the disable API doing a read/modify/write
cycle.

> +static inline void img_i2s_in_flush(struct img_i2s_in *i2s)
> +{
> +	int i;
> +	u32 reg;
> +
> +	for (i = 0; i < i2s->active_channels; i++) {
> +		reg = img_i2s_in_ch_disable(i2s, i);
> +		reg |= IMG_I2S_IN_CH_CTL_FIFO_FLUSH_MASK;
> +		img_i2s_in_ch_writel(i2s, i, reg, IMG_I2S_IN_CH_CTL);
> +		reg &= ~IMG_I2S_IN_CH_CTL_FIFO_FLUSH_MASK;
> +		img_i2s_in_ch_writel(i2s, i, reg, IMG_I2S_IN_CH_CTL);
> +		img_i2s_in_ch_enable(i2s, i, reg);
> +	}
> +}

This all seems to be connected to this, which is itself slightly funky
especially in the context of the only user...

> +	case SNDRV_PCM_TRIGGER_STOP:
> +	case SNDRV_PCM_TRIGGER_SUSPEND:
> +	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
> +		reg = img_i2s_in_readl(i2s, IMG_I2S_IN_CTL);
> +		reg &= ~IMG_I2S_IN_CTL_ME_MASK;
> +		img_i2s_in_writel(i2s, reg, IMG_I2S_IN_CTL);
> +		img_i2s_in_flush(i2s);
> +		break;

...which looks like it'll enable everything, then disable and reenable.
Plus needing to do a flush on trigger seems weird.

> +	if ((channels < 2) ||
> +			(channels > (i2s->max_i2s_chan * 2)) ||
> +			(channels % 2))
> +		return -EINVAL;

This indentation is very weird.

> +	control_mask = (u32)(~IMG_I2S_IN_CTL_16PACK_MASK &
> +			~IMG_I2S_IN_CTL_ACTIVE_CHAN_MASK);

> +	chan_control_mask = (u32)(~IMG_I2S_IN_CH_CTL_16PACK_MASK &
> +			~IMG_I2S_IN_CH_CTL_FEN_MASK &
> +			~IMG_I2S_IN_CH_CTL_FMODE_MASK &
> +			~IMG_I2S_IN_CH_CTL_SW_MASK &
> +			~IMG_I2S_IN_CH_CTL_FW_MASK &
> +			~IMG_I2S_IN_CH_CTL_PACKH_MASK);

This also looks very odd.  Normally we'd write masks as being the valid
bits and or them together.

> +	i2s->clk_sys = devm_clk_get(dev, "sys");
> +	if (IS_ERR(i2s->clk_sys))
> +		return PTR_ERR(i2s->clk_sys);

Please print an error message so people can tell why things failed.

> +	rst = devm_reset_control_get(dev, "rst");
> +	if (IS_ERR(rst)) {
> +		dev_dbg(dev, "No top level reset found\n");

You should check for -EPROBE_DEFER here and just return the error here
if you get it (on the basis that the reset framework ought to be using a
different error if there's nothing bound in DT).

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