ALSA: hda: add member to store ratio for stripe control

Stripe control programming is governed by following formula, which is
referenced from the HD Audio specification(Revision 1.0a).
  { ((num_channels * bits_per_sample) / number of SDOs) >= 8 }

Currently above is implemented in snd_hdac_get_stream_stripe_ctl().
This patch introduces a structure member to store the default factor
of '8'. If any HW wants to use a different value, this member can be
easily updated.

Signed-off-by: Sameer Pujar <spujar@nvidia.com>
Link: https://lore.kernel.org/r/1588580176-2801-3-git-send-email-spujar@nvidia.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>

include/sound/hdaudio.h

@@ -364,6 +364,9 @@ struct hdac_bus {
 	/* link management */
 	struct list_head hlink_list;
 	bool cmd_dma_state;
+
+	/* factor used to derive STRIPE control value */
+	unsigned int sdo_limit;
 };
 
 int snd_hdac_bus_init(struct hdac_bus *bus, struct device *dev,

sound/hda/hdac_controller.c

@@ -527,6 +527,18 @@ bool snd_hdac_bus_init_chip(struct hdac_bus *bus, bool full_reset)
 	}
 
 	bus->chip_init = true;
+
+	/*
+	 * Default value of '8' is as per the HD audio specification (Rev 1.0a).
+	 * Following relation is used to derive STRIPE control value.
+	 *  For sample rate <= 48K:
+	 *   { ((num_channels * bits_per_sample) / number of SDOs) >= 8 }
+	 *  For sample rate > 48K:
+	 *   { ((num_channels * bits_per_sample * rate/48000) /
+	 *	number of SDOs) >= 8 }
+	 */
+	bus->sdo_limit = 8;
+
 	return true;
 }
 EXPORT_SYMBOL_GPL(snd_hdac_bus_init_chip);

sound/hda/hdac_stream.c

@@ -38,7 +38,7 @@ int snd_hdac_get_stream_stripe_ctl(struct hdac_bus *bus,
 		else
 			value = (channels * bits_per_sample) / sdo_line;
 
-		if (value >= 8)
+		if (value >= bus->sdo_limit)
 			break;
 	}