linux-kernel - [PATCH 2/3] ALSA: hda: add member to store ratio for stripe control

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Date:   Mon, 4 May 2020 13:46:15 +0530
From:   Sameer Pujar <spujar@...dia.com>
To:     <perex@...ex.cz>, <tiwai@...e.com>
CC:     <thierry.reding@...il.com>, <jonathanh@...dia.com>,
        <linux-tegra@...r.kernel.org>, <alsa-devel@...a-project.org>,
        <linux-kernel@...r.kernel.org>, <sharadg@...dia.com>,
        <mkumard@...dia.com>, <viswanathl@...dia.com>,
        <rlokhande@...dia.com>, <dramesh@...dia.com>,
        <atalambedu@...dia.com>, Sameer Pujar <spujar@...dia.com>
Subject: [PATCH 2/3] 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@...dia.com>
---
 include/sound/hdaudio.h     |  3 +++
 sound/hda/hdac_controller.c | 12 ++++++++++++
 sound/hda/hdac_stream.c     |  2 +-
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/include/sound/hdaudio.h b/include/sound/hdaudio.h
index affedc2..d365297 100644
--- a/include/sound/hdaudio.h
+++ b/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,
diff --git a/sound/hda/hdac_controller.c b/sound/hda/hdac_controller.c
index bc4a8b6..ac15aa3 100644
--- a/sound/hda/hdac_controller.c
+++ b/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);
diff --git a/sound/hda/hdac_stream.c b/sound/hda/hdac_stream.c
index a314b03..a38a2af 100644
--- a/sound/hda/hdac_stream.c
+++ b/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;
 	}
 
-- 
2.7.4