[PATCH v2 3/9] ALSA: hda: Introduce snd_hdac_stream_wait_drsm()

[Cezary Rojewski]

Allow for waiting for DRSM bit for specified stream to be cleared from
HDAudio library level. Drivers may utilize this optional step during the
stream resume procedure.

Suggested-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
Signed-off-by: Cezary Rojewski <cezary.rojewski at intel.com>
---
 include/sound/hdaudio.h |  1 +
 sound/hda/hdac_stream.c | 21 +++++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/include/sound/hdaudio.h b/include/sound/hdaudio.h
index 78f1809a4ad6..a6872537724d 100644
--- a/include/sound/hdaudio.h
+++ b/include/sound/hdaudio.h
@@ -597,6 +597,7 @@ int snd_hdac_stream_get_spbmaxfifo(struct hdac_bus *bus,
 				   struct hdac_stream *azx_dev);
 void snd_hdac_stream_drsm_enable(struct hdac_bus *bus,
 				 bool enable, int index);
+int snd_hdac_stream_wait_drsm(struct hdac_stream *azx_dev);
 int snd_hdac_stream_set_dpibr(struct hdac_bus *bus,
 			      struct hdac_stream *azx_dev, u32 value);
 int snd_hdac_stream_set_lpib(struct hdac_stream *azx_dev, u32 value);
diff --git a/sound/hda/hdac_stream.c b/sound/hda/hdac_stream.c
index 35fe2bd582ac..59e8bfe4feca 100644
--- a/sound/hda/hdac_stream.c
+++ b/sound/hda/hdac_stream.c
@@ -821,6 +821,27 @@ void snd_hdac_stream_drsm_enable(struct hdac_bus *bus,
 }
 EXPORT_SYMBOL_GPL(snd_hdac_stream_drsm_enable);
 
+/*
+ * snd_hdac_stream_wait_drsm - wait for HW to clear RSM for a stream
+ * @azx_dev: HD-audio core stream to await RSM for
+ *
+ * Returns 0 on success and -ETIMEDOUT upon a timeout.
+ */
+int snd_hdac_stream_wait_drsm(struct hdac_stream *azx_dev)
+{
+	struct hdac_bus *bus = azx_dev->bus;
+	u32 mask, reg;
+	int ret;
+
+	mask = 1 << azx_dev->index;
+
+	ret = readb_poll_timeout(bus->drsmcap + AZX_REG_DRSM_CTL, reg, !(reg & mask), 250, 2000);
+	if (ret)
+		dev_dbg(bus->dev, "polling RSM 0x%08x failed: %d\n", mask, ret);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(snd_hdac_stream_wait_drsm);
+
 /**
  * snd_hdac_stream_set_dpibr - sets the dpibr value of a stream
  * @bus: HD-audio core bus
-- 
2.25.1