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

[Hans Verkuil]

On Wednesday, February 22, 2012 09:35:28 Ondrej Zary wrote:
> 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).

How about the following patch? vidioc_g_frequency just returns the last set
frequency and the hw_seek restores the original frequency if it can't find
another channel.

Also note that the check for < 50 kHz in hw_seek actually checked for < 500 kHz.
I've fixed that, but I can't test it.

Do you also know what happens at the boundaries of the frequency range? Does
it wrap around, or do you get a timeout?

Regards,

	Hans

diff --git a/sound/i2c/other/tea575x-tuner.c b/sound/i2c/other/tea575x-tuner.c
index 474bb81..1bdf1f3 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 u32 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 freq;
 
 	/* freq *= 12.5 */
 	freq *= 125;
@@ -138,7 +136,7 @@ static void snd_tea575x_get_freq(struct snd_tea575x *tea)
 	else
 		freq -= TEA575X_FMIF;
 
-	tea->freq = clamp(freq * 16, FREQ_LO, FREQ_HI); /* from kHz */
+	return clamp(freq * 16, FREQ_LO, FREQ_HI); /* from kHz */
 }
 
 static void snd_tea575x_set_freq(struct snd_tea575x *tea)
@@ -224,8 +222,6 @@ static int vidioc_g_frequency(struct file *file, void *priv,
 	if (f->tuner != 0)
 		return -EINVAL;
 	f->type = V4L2_TUNER_RADIO;
-	if (!tea->cannot_read_data)
-		snd_tea575x_get_freq(tea);
 	f->frequency = tea->freq;
 	return 0;
 }
@@ -248,14 +244,12 @@ static int vidioc_s_hw_freq_seek(struct file *file, void *fh,
 					struct v4l2_hw_freq_seek *a)
 {
 	struct snd_tea575x *tea = video_drvdata(file);
-	int i, old_freq;
 	unsigned long timeout;
+	int i;
 
 	if (tea->cannot_read_data)
 		return -ENOTTY;
 
-	snd_tea575x_get_freq(tea);
-	old_freq = tea->freq;
 	/* clear the frequency, HW will fill it in */
 	tea->val &= ~TEA575X_BIT_FREQ_MASK;
 	tea->val |= TEA575X_BIT_SEARCH;
@@ -271,26 +265,33 @@ static int vidioc_s_hw_freq_seek(struct file *file, void *fh,
 		if (schedule_timeout_interruptible(msecs_to_jiffies(10))) {
 			/* some signal arrived, stop search */
 			tea->val &= ~TEA575X_BIT_SEARCH;
-			snd_tea575x_write(tea, tea->val);
+			snd_tea575x_set_freq(tea);
 			return -ERESTARTSYS;
 		}
 		if (!(snd_tea575x_read(tea) & TEA575X_BIT_SEARCH)) {
+			u32 freq;
+
 			/* 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 */
+				freq = snd_tea575x_get_freq(tea);
+				if (freq) /* available */
 					break;
 			}
+			if (freq == 0) /* shouldn't happen */
+				break;
 			/* if we moved by less than 50 kHz, continue seeking */
-			if (abs(old_freq - tea->freq) < 16 * 500) {
+			if (abs(tea->freq - freq) < 16 * 50) {
 				snd_tea575x_write(tea, tea->val);
 				continue;
 			}
+			tea->freq = freq;
 			tea->val &= ~TEA575X_BIT_SEARCH;
 			return 0;
 		}
 	}
+	tea->val &= ~TEA575X_BIT_SEARCH;
+	snd_tea575x_set_freq(tea);
 	return -ETIMEDOUT;
 }