Patch "ASoC: meson: axg-fifo: use threaded irq to check periods" has been added to the 6.8-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    ASoC: meson: axg-fifo: use threaded irq to check periods

to the 6.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     asoc-meson-axg-fifo-use-threaded-irq-to-check-period.patch
and it can be found in the queue-6.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 4bbf5177db2f6795301345e90074b5ea5ac19ed4
Author: Jerome Brunet <jbrunet@xxxxxxxxxxxx>
Date:   Fri Apr 26 17:29:38 2024 +0200

    ASoC: meson: axg-fifo: use threaded irq to check periods
    
    [ Upstream commit b11d26660dff8d7430892008616452dc8e5fb0f3 ]
    
    With the AXG audio subsystem, there is a possible random channel shift on
    TDM capture, when the slot number per lane is more than 2, and there is
    more than one lane used.
    
    The problem has been there since the introduction of the axg audio support
    but such scenario is pretty uncommon. This is why there is no loud
    complains about the problem.
    
    Solving the problem require to make the links non-atomic and use the
    trigger() callback to start FEs and BEs in the appropriate order.
    
    This was tried in the past and reverted because it caused the block irq to
    sleep while atomic. However, instead of reverting, the solution is to call
    snd_pcm_period_elapsed() in a non atomic context.
    
    Use the bottom half of a threaded IRQ to do so.
    
    Fixes: 6dc4fa179fb8 ("ASoC: meson: add axg fifo base driver")
    Signed-off-by: Jerome Brunet <jbrunet@xxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20240426152946.3078805-2-jbrunet@xxxxxxxxxxxx
    Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/sound/soc/meson/axg-fifo.c b/sound/soc/meson/axg-fifo.c
index bebee0ca8e388..ecb3eb7a9723d 100644
--- a/sound/soc/meson/axg-fifo.c
+++ b/sound/soc/meson/axg-fifo.c
@@ -204,18 +204,26 @@ static irqreturn_t axg_fifo_pcm_irq_block(int irq, void *dev_id)
 	unsigned int status;
 
 	regmap_read(fifo->map, FIFO_STATUS1, &status);
-
 	status = FIELD_GET(STATUS1_INT_STS, status);
+	axg_fifo_ack_irq(fifo, status);
+
+	/* Use the thread to call period elapsed on nonatomic links */
 	if (status & FIFO_INT_COUNT_REPEAT)
-		snd_pcm_period_elapsed(ss);
-	else
-		dev_dbg(axg_fifo_dev(ss), "unexpected irq - STS 0x%02x\n",
-			status);
+		return IRQ_WAKE_THREAD;
 
-	/* Ack irqs */
-	axg_fifo_ack_irq(fifo, status);
+	dev_dbg(axg_fifo_dev(ss), "unexpected irq - STS 0x%02x\n",
+		status);
+
+	return IRQ_NONE;
+}
+
+static irqreturn_t axg_fifo_pcm_irq_block_thread(int irq, void *dev_id)
+{
+	struct snd_pcm_substream *ss = dev_id;
+
+	snd_pcm_period_elapsed(ss);
 
-	return IRQ_RETVAL(status);
+	return IRQ_HANDLED;
 }
 
 int axg_fifo_pcm_open(struct snd_soc_component *component,
@@ -243,8 +251,9 @@ int axg_fifo_pcm_open(struct snd_soc_component *component,
 	if (ret)
 		return ret;
 
-	ret = request_irq(fifo->irq, axg_fifo_pcm_irq_block, 0,
-			  dev_name(dev), ss);
+	ret = request_threaded_irq(fifo->irq, axg_fifo_pcm_irq_block,
+				   axg_fifo_pcm_irq_block_thread,
+				   IRQF_ONESHOT, dev_name(dev), ss);
 	if (ret)
 		return ret;