diff options
author | Tzung-Bi Shih <tzungbi@google.com> | 2019-11-22 15:31:14 +0800 |
---|---|---|
committer | Mark Brown <broonie@kernel.org> | 2019-11-27 12:55:36 +0000 |
commit | 45dfbf56975994822cce00b7475732a49f8aefed (patch) | |
tree | deec558ea382e085938d7a7453efe1474272296d /sound/soc/codecs | |
parent | 6f49919d11690a9b5614445ba30fde18083fdd63 (diff) |
ASoC: max98090: fix possible race conditions
max98090_interrupt() and max98090_pll_work() run in 2 different threads.
There are 2 possible races:
Note: M98090_REG_DEVICE_STATUS = 0x01.
Note: ULK == 0, PLL is locked; ULK == 1, PLL is unlocked.
max98090_interrupt max98090_pll_work
----------------------------------------------
schedule max98090_pll_work
restart max98090 codec
receive ULK INT
assert ULK == 0
schedule max98090_pll_work (1).
In the case (1), the PLL is locked but max98090_interrupt unnecessarily
schedules another max98090_pll_work.
max98090_interrupt max98090_pll_work max98090 codec
----------------------------------------------------------------------
ULK = 1
receive ULK INT
read 0x01
ULK = 0 (clear on read)
schedule max98090_pll_work
restart max98090 codec
ULK = 1
receive ULK INT
read 0x01
ULK = 0 (clear on read)
read 0x01
assert ULK == 0 (2).
In the case (2), both max98090_interrupt and max98090_pll_work read
the same clear-on-read register. max98090_pll_work would falsely
thought PLL is locked.
Note: the case (2) race is introduced by the previous commit ("ASoC:
max98090: exit workaround earlier if PLL is locked") to check the status
and exit the loop earlier in max98090_pll_work.
There are 2 possible solution options:
A. turn off ULK interrupt before scheduling max98090_pll_work; and turn
on again before exiting max98090_pll_work.
B. remove the second thread of execution.
Option A cannot fix the case (2) race because it still has 2 threads
access the same clear-on-read register simultaneously. Although we
could suppose the register is volatile and read the status via I2C could
be much slower than the hardware raises the bits.
Option B introduces a maximum 10~12 msec penalty delay in the interrupt
handler. However, it could only punish the jack detection by extra
10~12 msec.
Adopts option B which is the better solution overall.
Signed-off-by: Tzung-Bi Shih <tzungbi@google.com>
Link: https://lore.kernel.org/r/20191122073114.219945-4-tzungbi@google.com
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'sound/soc/codecs')
-rw-r--r-- | sound/soc/codecs/max98090.c | 8 | ||||
-rw-r--r-- | sound/soc/codecs/max98090.h | 1 |
2 files changed, 2 insertions, 7 deletions
diff --git a/sound/soc/codecs/max98090.c b/sound/soc/codecs/max98090.c index f531e5a11bdd..e46b6ada13b1 100644 --- a/sound/soc/codecs/max98090.c +++ b/sound/soc/codecs/max98090.c @@ -2103,10 +2103,8 @@ static void max98090_pll_det_disable_work(struct work_struct *work) M98090_IULK_MASK, 0); } -static void max98090_pll_work(struct work_struct *work) +static void max98090_pll_work(struct max98090_priv *max98090) { - struct max98090_priv *max98090 = - container_of(work, struct max98090_priv, pll_work); struct snd_soc_component *component = max98090->component; unsigned int pll; int i; @@ -2275,7 +2273,7 @@ static irqreturn_t max98090_interrupt(int irq, void *data) if (active & M98090_ULK_MASK) { dev_dbg(component->dev, "M98090_ULK_MASK\n"); - schedule_work(&max98090->pll_work); + max98090_pll_work(max98090); } if (active & M98090_JDET_MASK) { @@ -2438,7 +2436,6 @@ static int max98090_probe(struct snd_soc_component *component) max98090_pll_det_enable_work); INIT_WORK(&max98090->pll_det_disable_work, max98090_pll_det_disable_work); - INIT_WORK(&max98090->pll_work, max98090_pll_work); /* Enable jack detection */ snd_soc_component_write(component, M98090_REG_JACK_DETECT, @@ -2491,7 +2488,6 @@ static void max98090_remove(struct snd_soc_component *component) cancel_delayed_work_sync(&max98090->jack_work); cancel_delayed_work_sync(&max98090->pll_det_enable_work); cancel_work_sync(&max98090->pll_det_disable_work); - cancel_work_sync(&max98090->pll_work); max98090->component = NULL; } diff --git a/sound/soc/codecs/max98090.h b/sound/soc/codecs/max98090.h index 57965cd678b4..a197114b0dad 100644 --- a/sound/soc/codecs/max98090.h +++ b/sound/soc/codecs/max98090.h @@ -1530,7 +1530,6 @@ struct max98090_priv { struct delayed_work jack_work; struct delayed_work pll_det_enable_work; struct work_struct pll_det_disable_work; - struct work_struct pll_work; struct snd_soc_jack *jack; unsigned int dai_fmt; int tdm_slots; |