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

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Date:	Thu, 22 Oct 2015 20:09:38 +0100
From:	Damien Horsley <Damien.Horsley@...tec.com>
To:	Mark Brown <broonie@...nel.org>
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 19/10/15 18:47, Mark Brown wrote:
> 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.
>

Sure. It reduces the number of register accesses this way, but the
difference in execution time is not significant. Would you prefer these
to both do read-modify-writes?

>> +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...
> 

They are also used during hw_params and set_format.

>> +	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 the FIFOs are not flushed, some samples from the previous stream will
be transferred to the user application when the block is started again

>> +	if ((channels < 2) ||
>> +			(channels > (i2s->max_i2s_chan * 2)) ||
>> +			(channels % 2))
>> +		return -EINVAL;
> 
> This indentation is very weird.
> 

Ok. What is the correct indentation for this?

>> +	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.
> 

Ok

>> +	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.
>

Ok


>> +	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).
> 

Ok
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