[PATCH v3 04/10] ASoC: renesas: fsi: Fix register access from in-flight IRQ after shutdown

[phucduc.bui@gmail.com]

From: bui duc phuc <phucduc.bui@gmail.com>

Ensure that in-flight IRQ handlers do not access hardware registers
after SNDRV_PCM_TRIGGER_STOP and fsi_hw_shutdown().

An IRQ handler may still be running when the SPU clock is disabled,
leading to register access after clock shutdown and causing system
hangs.

Prevent register access in the IRQ path once the hardware has been
shut down.

Signed-off-by: bui duc phuc <phucduc.bui@gmail.com>
---
 sound/soc/renesas/fsi.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/sound/soc/renesas/fsi.c b/sound/soc/renesas/fsi.c
index 94ab2e490810..fc8428cb1ba7 100644
--- a/sound/soc/renesas/fsi.c
+++ b/sound/soc/renesas/fsi.c
@@ -211,6 +211,7 @@ struct fsi_stream {
 	int sample_width;	/* sample width */
 	int uerr_num;
 	int oerr_num;
+	bool running;
 
 	/*
 	 * bus options
@@ -255,6 +256,8 @@ struct fsi_priv {
 
 	u32 fmt;
 
+	int running_streams;
+
 	int chan_num:16;
 	unsigned int clk_master:1;
 	unsigned int clk_cpg:1;
@@ -460,6 +463,9 @@ static int fsi_get_current_fifo_samples(struct fsi_priv *fsi,
 
 static void fsi_count_fifo_err(struct fsi_priv *fsi)
 {
+	if (fsi->running_streams == 0)
+		return;
+
 	u32 ostatus = fsi_reg_read(fsi, DOFF_ST);
 	u32 istatus = fsi_reg_read(fsi, DIFF_ST);
 
@@ -681,6 +687,9 @@ static void fsi_irq_clear_status(struct fsi_priv *fsi)
 	u32 data = 0;
 	struct fsi_master *master = fsi_get_master(fsi);
 
+	if (fsi->running_streams == 0)
+		return;
+
 	data |= AB_IO(1, fsi_get_port_shift(fsi, &fsi->playback));
 	data |= AB_IO(1, fsi_get_port_shift(fsi, &fsi->capture));
 
@@ -1573,10 +1582,17 @@ static int fsi_dai_trigger(struct snd_pcm_substream *substream, int cmd,
 {
 	struct fsi_priv *fsi = fsi_get_priv(substream);
 	struct fsi_stream *io = fsi_stream_get(fsi, substream);
+	bool need_shutdown = false;
 	int ret = 0;
 
 	switch (cmd) {
 	case SNDRV_PCM_TRIGGER_START:
+		scoped_guard(spinlock_irqsave, &fsi->master->lock) {
+			if (!io->running) {
+				io->running = true;
+				fsi->running_streams++;
+			}
+		}
 		fsi_stream_init(fsi, io, substream);
 		if (!ret)
 			ret = fsi_hw_startup(fsi, io, dai->dev);
@@ -1586,8 +1602,15 @@ static int fsi_dai_trigger(struct snd_pcm_substream *substream, int cmd,
 			ret = fsi_stream_transfer(io);
 		break;
 	case SNDRV_PCM_TRIGGER_STOP:
+		scoped_guard(spinlock_irqsave, &fsi->master->lock) {
+			if (io->running) {
+				io->running = false;
+				if (--fsi->running_streams == 0)
+					need_shutdown = true;
+			}
+		}
 		fsi_stream_stop(fsi, io);
-		if (!ret)
+		if (!ret && need_shutdown)
 			ret = fsi_hw_shutdown(fsi, dai->dev);
 		fsi_stream_quit(fsi, io);
 		break;
@@ -1968,6 +1991,7 @@ static int fsi_probe(struct platform_device *pdev)
 	fsi->base	= master->base;
 	fsi->phys	= res->start;
 	fsi->master	= master;
+	fsi->running_streams = 0;
 	fsi_port_info_init(fsi, &info.port_a);
 	fsi_handler_init(fsi, &info.port_a);
 	ret = fsi_stream_probe(fsi, &pdev->dev);
@@ -1981,6 +2005,7 @@ static int fsi_probe(struct platform_device *pdev)
 	fsi->base	= master->base + 0x40;
 	fsi->phys	= res->start + 0x40;
 	fsi->master	= master;
+	fsi->running_streams = 0;
 	fsi_port_info_init(fsi, &info.port_b);
 	fsi_handler_init(fsi, &info.port_b);
 	ret = fsi_stream_probe(fsi, &pdev->dev);
-- 
2.43.0