ASoC: nau8825: improve semaphore control

After reviewing the crosstalk protection, there are two flaws at
semaphore control. The first one is that the semaphore releases are
not enough; and the other is that down_interruptible has an risk to
make the ISR sleep.
Therefore, the driver add more releases before the funcitons return.
Take down_trylock to replace down_interruptible. The ISR can control
the protection as well and never sleep by semaphore.

Signed-off-by: John Hsu <KCHSU0@nuvoton.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 23 insertions, 15 deletions

diff --git a/sound/soc/codecs/nau8825.c b/sound/soc/codecs/nau8825.c
index 603cd72c2a25..5778eadbf9e6 100644
--- a/sound/soc/codecs/nau8825.c
+++ b/sound/soc/codecs/nau8825.c
@@ -245,13 +245,14 @@ static const unsigned short logtable[256] = {
  * tasks are allowed to acquire the semaphore, calling this function will
  * put the task to sleep. If the semaphore is not released within the
  * specified number of jiffies, this function returns.
- * Acquires the semaphore without jiffies. If no more tasks are allowed
- * to acquire the semaphore, calling this function will put the task to
- * sleep until the semaphore is released.
  * If the semaphore is not released within the specified number of jiffies,
- * this function returns -ETIME.
- * If the sleep is interrupted by a signal, this function will return -EINTR.
- * It returns 0 if the semaphore was acquired successfully.
+ * this function returns -ETIME. If the sleep is interrupted by a signal,
+ * this function will return -EINTR. It returns 0 if the semaphore was
+ * acquired successfully.
+ *
+ * Acquires the semaphore without jiffies. Try to acquire the semaphore
+ * atomically. Returns 0 if the semaphore has been acquired successfully
+ * or 1 if it it cannot be acquired.
  */
 static int nau8825_sema_acquire(struct nau8825 *nau8825, long timeout)
 {
@@ -262,8 +263,8 @@ static int nau8825_sema_acquire(struct nau8825 *nau8825, long timeout)
                 if (ret < 0)
                         dev_warn(nau8825->dev, "Acquire semaphore timeout\n");
         } else {
-                ret = down_interruptible(&nau8825->xtalk_sem);
-                if (ret < 0)
+                ret = down_trylock(&nau8825->xtalk_sem);
+                if (ret)
                         dev_warn(nau8825->dev, "Acquire semaphore fail\n");
         }
 
@@ -1246,8 +1247,10 @@ static int nau8825_hw_params(struct snd_pcm_substream *substream,
                 regmap_read(nau8825->regmap, NAU8825_REG_DAC_CTRL1, &osr);
                 osr &= NAU8825_DAC_OVERSAMPLE_MASK;
                 if (nau8825_clock_check(nau8825, substream->stream,
-                        params_rate(params), osr))
+                        params_rate(params), osr)) {
+                        nau8825_sema_release(nau8825);
                         return -EINVAL;
+                }
                 regmap_update_bits(nau8825->regmap, NAU8825_REG_CLK_DIVIDER,
                         NAU8825_CLK_DAC_SRC_MASK,
                         osr_dac_sel[osr].clk_src << NAU8825_CLK_DAC_SRC_SFT);
@@ -1255,8 +1258,10 @@ static int nau8825_hw_params(struct snd_pcm_substream *substream,
                 regmap_read(nau8825->regmap, NAU8825_REG_ADC_RATE, &osr);
                 osr &= NAU8825_ADC_SYNC_DOWN_MASK;
                 if (nau8825_clock_check(nau8825, substream->stream,
-                        params_rate(params), osr))
+                        params_rate(params), osr)) {
+                        nau8825_sema_release(nau8825);
                         return -EINVAL;
+                }
                 regmap_update_bits(nau8825->regmap, NAU8825_REG_CLK_DIVIDER,
                         NAU8825_CLK_ADC_SRC_MASK,
                         osr_adc_sel[osr].clk_src << NAU8825_CLK_ADC_SRC_SFT);
@@ -1273,8 +1278,10 @@ static int nau8825_hw_params(struct snd_pcm_substream *substream,
                         bclk_div = 1;
                 else if (bclk_fs <= 128)
                         bclk_div = 0;
-                else
+                else {
+                        nau8825_sema_release(nau8825);
                         return -EINVAL;
+                }
                 regmap_update_bits(nau8825->regmap, NAU8825_REG_I2S_PCM_CTRL2,
                         NAU8825_I2S_LRC_DIV_MASK | NAU8825_I2S_BLK_DIV_MASK,
                         ((bclk_div + 1) << NAU8825_I2S_LRC_DIV_SFT) | bclk_div);
@@ -1294,6 +1301,7 @@ static int nau8825_hw_params(struct snd_pcm_substream *substream,
                 val_len |= NAU8825_I2S_DL_32;
                 break;
         default:
+                nau8825_sema_release(nau8825);
                 return -EINVAL;
         }
 
@@ -1312,8 +1320,6 @@ static int nau8825_set_dai_fmt(struct snd_soc_dai *codec_dai, unsigned int fmt)
         struct nau8825 *nau8825 = snd_soc_codec_get_drvdata(codec);
         unsigned int ctrl1_val = 0, ctrl2_val = 0;
 
-        nau8825_sema_acquire(nau8825, 3 * HZ);
-
         switch (fmt & SND_SOC_DAIFMT_MASTER_MASK) {
         case SND_SOC_DAIFMT_CBM_CFM:
                 ctrl2_val |= NAU8825_I2S_MS_MASTER;
@@ -1355,6 +1361,8 @@ static int nau8825_set_dai_fmt(struct snd_soc_dai *codec_dai, unsigned int fmt)
                 return -EINVAL;
         }
 
+        nau8825_sema_acquire(nau8825, 3 * HZ);
+
         regmap_update_bits(nau8825->regmap, NAU8825_REG_I2S_PCM_CTRL1,
                 NAU8825_I2S_DL_MASK | NAU8825_I2S_DF_MASK |
                 NAU8825_I2S_BP_MASK | NAU8825_I2S_PCMB_MASK,
@@ -1701,7 +1709,7 @@ static irqreturn_t nau8825_interrupt(int irq, void *data)
                                         int ret;
                                         nau8825->xtalk_protect = true;
                                         ret = nau8825_sema_acquire(nau8825, 0);
-                                        if (ret < 0)
+                                        if (ret)
                                                 nau8825->xtalk_protect = false;
                                 }
                                 /* Startup cross talk detection process */
@@ -2383,7 +2391,7 @@ static int __maybe_unused nau8825_resume(struct snd_soc_codec *codec)
         regcache_sync(nau8825->regmap);
         nau8825->xtalk_protect = true;
         ret = nau8825_sema_acquire(nau8825, 0);
-        if (ret < 0)
+        if (ret)
                 nau8825->xtalk_protect = false;
         enable_irq(nau8825->irq);