ALSA: hda - fix beep tone calculation for IDT/STAC codecs

In the beep tone calculation for IDT/STAC codecs, lower numbers correspond
to higher frequencies and vice versa.  The current code has this backwards,
resulting in beep frequencies which are way too high (and sound bad on
tinny laptop speakers, resulting in complaints).

[Also added hz <= 0 check by tiwai]
Signed-off-by: Paul Vojta <vojta@math.berkeley.edu>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/hda/hda_beep.c

@@ -50,19 +50,22 @@ static void snd_hda_generate_beep(struct work_struct *work)
  * The tone frequency of beep generator on IDT/STAC codecs is
  * defined from the 8bit tone parameter, in Hz,
  *    freq = 48000 * (257 - tone) / 1024
- * that is from 12kHz to 93.75kHz in step of 46.875 hz
+ * that is from 12kHz to 93.75Hz in steps of 46.875 Hz
  */
 static int beep_linear_tone(struct hda_beep *beep, int hz)
 {
+	if (hz <= 0)
+		return 0;
 	hz *= 1000; /* fixed point */
-	hz = hz - DIGBEEP_HZ_MIN;
+	hz = hz - DIGBEEP_HZ_MIN
+		+ DIGBEEP_HZ_STEP / 2; /* round to nearest step */
 	if (hz < 0)
 		hz = 0; /* turn off PC beep*/
 	else if (hz >= (DIGBEEP_HZ_MAX - DIGBEEP_HZ_MIN))
-		hz = 0xff;
+		hz = 1; /* max frequency */
 	else {
 		hz /= DIGBEEP_HZ_STEP;
-		hz++;
+		hz = 255 - hz;
 	}
 	return hz;
 }