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

hi Charles,

On 18 February 2016 at 21:17, Charles Keepax ckeepax@opensource.wolfsonmicro.com wrote:

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@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

Thanks for fixing this bug. Tested on Odroid U3. Tested-by: Anand Moon linux.amoon@gmail.com

-Anand Moon

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