ALSA: hdspm - Work around broken DDS value on PCI RME MADI

On PCI RME MADI cards, the PLL register does not contain the proper
value, so the calculated system_sample_rate is wrong. In this case, we
simply return the cached rate from struct hdspm.

Signed-off-by: Adrian Knoth <adi@drcomp.erfurt.thur.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/rme9652/hdspm.c

@@ -1988,6 +1988,13 @@ static int hdspm_get_system_sample_rate(struct hdspm *hdspm)
 	period = hdspm_read(hdspm, HDSPM_RD_PLL_FREQ);
 	rate = hdspm_calc_dds_value(hdspm, period);
 
+	if (rate > 207000) {
+		/* Unreasonable high sample rate as seen on PCI MADI cards.
+		 * Use the cached value instead.
+		 */
+		rate = hdspm->system_sample_rate;
+	}
+
 	return rate;
 }