[alsa-devel] [PATCH] tea575x: fix HW seek

[Ondrej Zary]

On Tuesday 21 February 2012, Hans Verkuil wrote:
> On Saturday, February 18, 2012 17:45:45 Ondrej Zary wrote:
> > Fix HW seek in TEA575x to work properly:
> >  - a delay must be present after search start and before first register
> > read or the seek does weird things
> >  - when the search stops, the new frequency is not available immediately,
> > we must wait until it appears in the register (fortunately, we can clear
> > the frequency bits when starting the search as it starts at the frequency
> > currently set, not from the value written)
> >  - sometimes, seek remains on the current frequency (or moves only a
> > little), so repeat it until it moves by at least 50 kHz
> >
> > Signed-off-by: Ondrej Zary <linux at rainbow-software.org>
> >
> > --- a/sound/i2c/other/tea575x-tuner.c
> > +++ b/sound/i2c/other/tea575x-tuner.c
> > @@ -89,7 +89,7 @@ static void snd_tea575x_write(struct snd_tea575x *tea,
> > unsigned int val) tea->ops->set_pins(tea, 0);
> >  }
> >
> > -static unsigned int snd_tea575x_read(struct snd_tea575x *tea)
> > +static u32 snd_tea575x_read(struct snd_tea575x *tea)
> >  {
> >  	u16 l, rdata;
> >  	u32 data = 0;
> > @@ -120,6 +120,27 @@ static unsigned int snd_tea575x_read(struct
> > snd_tea575x *tea) return data;
> >  }
> >
> > +static void snd_tea575x_get_freq(struct snd_tea575x *tea)
> > +{
> > +	u32 freq = snd_tea575x_read(tea) & TEA575X_BIT_FREQ_MASK;
> > +
> > +	if (freq == 0) {
> > +		tea->freq = 0;
>
> Wouldn't it be better to return -EBUSY in this case? VIDIOC_G_FREQUENCY
> should not return frequencies outside the valid frequency range. In this
> case returning -EBUSY seems to make more sense to me.

The device returns zero frequency when the scan fails to find a frequency. 
This is not an error, just an indication that "nothing" is tuned. So maybe we 
can return some bogus frequency in vidioc_g_frequency (like FREQ_LO) in this 
case (don't know if -EBUSY will break anything). But HW seek should get the 
real one (i.e. zero when it's there).

> I'm proposing adding this patch:
>
> diff --git a/sound/i2c/other/tea575x-tuner.c
> b/sound/i2c/other/tea575x-tuner.c index 474bb81..02da22f 100644
> --- a/sound/i2c/other/tea575x-tuner.c
> +++ b/sound/i2c/other/tea575x-tuner.c
> @@ -120,14 +120,12 @@ static u32 snd_tea575x_read(struct snd_tea575x *tea)
>  	return data;
>  }
>
> -static void snd_tea575x_get_freq(struct snd_tea575x *tea)
> +static int snd_tea575x_get_freq(struct snd_tea575x *tea)
>  {
>  	u32 freq = snd_tea575x_read(tea) & TEA575X_BIT_FREQ_MASK;
>
> -	if (freq == 0) {
> -		tea->freq = 0;
> -		return;
> -	}
> +	if (freq == 0)
> +		return -EBUSY;
>
>  	/* freq *= 12.5 */
>  	freq *= 125;
> @@ -139,6 +137,7 @@ static void snd_tea575x_get_freq(struct snd_tea575x
> *tea) freq -= TEA575X_FMIF;
>
>  	tea->freq = clamp(freq * 16, FREQ_LO, FREQ_HI); /* from kHz */
> +	return 0;
>  }
>
>  static void snd_tea575x_set_freq(struct snd_tea575x *tea)
> @@ -220,14 +219,15 @@ static int vidioc_g_frequency(struct file *file, void
> *priv, struct v4l2_frequency *f)
>  {
>  	struct snd_tea575x *tea = video_drvdata(file);
> +	int ret = 0;
>
>  	if (f->tuner != 0)
>  		return -EINVAL;
>  	f->type = V4L2_TUNER_RADIO;
>  	if (!tea->cannot_read_data)
> -		snd_tea575x_get_freq(tea);
> +		ret = snd_tea575x_get_freq(tea);
>  	f->frequency = tea->freq;
> -	return 0;
> +	return ret;
>  }
>
>  static int vidioc_s_frequency(struct file *file, void *priv,
> @@ -250,11 +250,14 @@ static int vidioc_s_hw_freq_seek(struct file *file,
> void *fh, struct snd_tea575x *tea = video_drvdata(file);
>  	int i, old_freq;
>  	unsigned long timeout;
> +	int ret;
>
>  	if (tea->cannot_read_data)
>  		return -ENOTTY;
>
> -	snd_tea575x_get_freq(tea);
> +	ret = snd_tea575x_get_freq(tea);
> +	if (ret)
> +		return ret;
>  	old_freq = tea->freq;
>  	/* clear the frequency, HW will fill it in */
>  	tea->val &= ~TEA575X_BIT_FREQ_MASK;
> @@ -278,8 +281,8 @@ static int vidioc_s_hw_freq_seek(struct file *file,
> void *fh, /* Found a frequency, wait until it can be read */
>  			for (i = 0; i < 100; i++) {
>  				msleep(10);
> -				snd_tea575x_get_freq(tea);
> -				if (tea->freq != 0) /* available */
> +				ret = snd_tea575x_get_freq(tea);
> +				if (ret == 0) /* available */
>  					break;
>  			}
>  			/* if we moved by less than 50 kHz, continue seeking */
>
> If you are OK with this, then I'll put everything together and make a final
> pull request.
>
> Regards,
>
> 	Hans



-- 
Ondrej Zary