[alsa-devel] [PATCH] ASoC: samsung: Use IRQ safe spin lock calls

[Charles Keepax]

Lockdep warns of a potential lock inversion, i2s->lock is held numerous
times whilst we are under the substream lock (snd_pcm_stream_lock). If
we use the IRQ unsafe spin lock calls, you can also end up locking
snd_pcm_stream_lock whilst under i2s->lock (if an IRQ happens whilst we
are holding i2s->lock). This could result in deadlock.

[   18.147001]        CPU0                    CPU1
[   18.151509]        ----                    ----
[   18.156022]   lock(&(&pri_dai->spinlock)->rlock);
[   18.160701]                                local_irq_disable();
[   18.166622]                                lock(&(&substream->self_group.lock)->rlock);
[   18.174595]                                lock(&(&pri_dai->spinlock)->rlock);
[   18.181806]   <Interrupt>
[   18.184408]     lock(&(&substream->self_group.lock)->rlock);
[   18.190045]
[   18.190045]  *** DEADLOCK ***

This patch changes to using the irq safe spinlock calls, to avoid this
issue.

Fixes: ce8bcdbb61d9 ("ASoC: samsung: i2s: Protect more registers with a spinlock")
Signed-off-by: Charles Keepax <ckeepax at opensource.wolfsonmicro.com>
---
 sound/soc/samsung/i2s.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/sound/soc/samsung/i2s.c b/sound/soc/samsung/i2s.c
index 84d9e77..70a2559 100644
--- a/sound/soc/samsung/i2s.c
+++ b/sound/soc/samsung/i2s.c
@@ -481,10 +481,11 @@ static int i2s_set_sysclk(struct snd_soc_dai *dai,
 	unsigned int cdcon_mask = 1 << i2s_regs->cdclkcon_off;
 	unsigned int rsrc_mask = 1 << i2s_regs->rclksrc_off;
 	u32 mod, mask, val = 0;
+	unsigned long flags;
 
-	spin_lock(i2s->lock);
+	spin_lock_irqsave(i2s->lock, flags);
 	mod = readl(i2s->addr + I2SMOD);
-	spin_unlock(i2s->lock);
+	spin_unlock_irqrestore(i2s->lock, flags);
 
 	switch (clk_id) {
 	case SAMSUNG_I2S_OPCLK:
@@ -575,11 +576,11 @@ static int i2s_set_sysclk(struct snd_soc_dai *dai,
 		return -EINVAL;
 	}
 
-	spin_lock(i2s->lock);
+	spin_lock_irqsave(i2s->lock, flags);
 	mod = readl(i2s->addr + I2SMOD);
 	mod = (mod & ~mask) | val;
 	writel(mod, i2s->addr + I2SMOD);
-	spin_unlock(i2s->lock);
+	spin_unlock_irqrestore(i2s->lock, flags);
 
 	return 0;
 }
@@ -590,6 +591,7 @@ static int i2s_set_fmt(struct snd_soc_dai *dai,
 	struct i2s_dai *i2s = to_info(dai);
 	int lrp_shift, sdf_shift, sdf_mask, lrp_rlow, mod_slave;
 	u32 mod, tmp = 0;
+	unsigned long flags;
 
 	lrp_shift = i2s->variant_regs->lrp_off;
 	sdf_shift = i2s->variant_regs->sdf_off;
@@ -649,7 +651,7 @@ static int i2s_set_fmt(struct snd_soc_dai *dai,
 		return -EINVAL;
 	}
 
-	spin_lock(i2s->lock);
+	spin_lock_irqsave(i2s->lock, flags);
 	mod = readl(i2s->addr + I2SMOD);
 	/*
 	 * Don't change the I2S mode if any controller is active on this
@@ -657,7 +659,7 @@ static int i2s_set_fmt(struct snd_soc_dai *dai,
 	 */
 	if (any_active(i2s) &&
 		((mod & (sdf_mask | lrp_rlow | mod_slave)) != tmp)) {
-		spin_unlock(i2s->lock);
+		spin_unlock_irqrestore(i2s->lock, flags);
 		dev_err(&i2s->pdev->dev,
 				"%s:%d Other DAI busy\n", __func__, __LINE__);
 		return -EAGAIN;
@@ -666,7 +668,7 @@ static int i2s_set_fmt(struct snd_soc_dai *dai,
 	mod &= ~(sdf_mask | lrp_rlow | mod_slave);
 	mod |= tmp;
 	writel(mod, i2s->addr + I2SMOD);
-	spin_unlock(i2s->lock);
+	spin_unlock_irqrestore(i2s->lock, flags);
 
 	return 0;
 }
@@ -676,6 +678,7 @@ static int i2s_hw_params(struct snd_pcm_substream *substream,
 {
 	struct i2s_dai *i2s = to_info(dai);
 	u32 mod, mask = 0, val = 0;
+	unsigned long flags;
 
 	if (!is_secondary(i2s))
 		mask |= (MOD_DC2_EN | MOD_DC1_EN);
@@ -744,11 +747,11 @@ static int i2s_hw_params(struct snd_pcm_substream *substream,
 		return -EINVAL;
 	}
 
-	spin_lock(i2s->lock);
+	spin_lock_irqsave(i2s->lock, flags);
 	mod = readl(i2s->addr + I2SMOD);
 	mod = (mod & ~mask) | val;
 	writel(mod, i2s->addr + I2SMOD);
-	spin_unlock(i2s->lock);
+	spin_unlock_irqrestore(i2s->lock, flags);
 
 	samsung_asoc_init_dma_data(dai, &i2s->dma_playback, &i2s->dma_capture);
 
-- 
2.1.4