clear-pkgs-linux-iot-lts2018/0388-ALSA-hda-Make-sure-DMA-is-started-by-reading-back-th.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Pardha Saradhi K <pardha.saradhi.kesapragada@intel.com>
Date: Fri, 21 Jul 2017 02:08:12 +0530
Subject: [PATCH] ALSA: hda: Make sure DMA is started by reading back the RUN
 bit

As per HW recommendation, after setting the RUN bit,
software must read a 1 from the RUN bit, before modifying
related control registers/re-starting the DMA engine.

Change-Id: I5e81791a3d210a579f61d2345c4d3a29cd4c7b08
Signed-off-by: Pardha Saradhi K <pardha.saradhi.kesapragada@intel.com>
Reviewed-on:
Reviewed-by: Prakash, Divya1
Reviewed-by: Koul, Vinod <vinod.koul@intel.com>
Tested-by: Sm, Bhadur A <bhadur.a.sm@intel.com>
---
 sound/hda/hdac_stream.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/sound/hda/hdac_stream.c b/sound/hda/hdac_stream.c
index 2ddda76ba91d..00954efaa483 100644
--- a/sound/hda/hdac_stream.c
+++ b/sound/hda/hdac_stream.c
@@ -49,6 +49,8 @@ EXPORT_SYMBOL_GPL(snd_hdac_stream_init);
 void snd_hdac_stream_start(struct hdac_stream *azx_dev, bool fresh_start)
 {
 	struct hdac_bus *bus = azx_dev->bus;
+	int timeout;
+	unsigned char val;
 
 	trace_snd_hdac_stream_start(bus, azx_dev);
 
@@ -61,6 +63,21 @@ void snd_hdac_stream_start(struct hdac_stream *azx_dev, bool fresh_start)
 	/* set DMA start and interrupt mask */
 	snd_hdac_stream_updateb(azx_dev, SD_CTL,
 				0, SD_CTL_DMA_START | SD_INT_MASK);
+
+	timeout = 300;
+	do {
+		udelay(3);
+		val = snd_hdac_stream_readb(azx_dev, SD_CTL) & SD_CTL_DMA_START;
+		if (val)
+			break;
+	} while(--timeout);
+
+	if (!timeout) {
+		dev_err(azx_dev->bus->dev, "unable to start the stream\n");
+		azx_dev->running = false;
+		return;
+	}
+
 	azx_dev->running = true;
 }
 EXPORT_SYMBOL_GPL(snd_hdac_stream_start);
-- 
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