From: Tzung-Bi Shih tzungbi@google.com

[ Upstream commit 45dfbf56975994822cce00b7475732a49f8aefed ]

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 Signed-off-by: Sasha Levin sashal@kernel.org --- sound/soc/codecs/max98090.c | 8 ++------ 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 172a48d42479..f8cbed6cd0bf 100644 --- a/sound/soc/codecs/max98090.c +++ b/sound/soc/codecs/max98090.c @@ -2121,10 +2121,8 @@ 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; @@ -2293,7 +2291,7 @@ 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) { @@ -2456,7 +2454,6 @@ 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, @@ -2509,7 +2506,6 @@ 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 b1572a2d19da..388d2f74674b 100644 --- a/sound/soc/codecs/max98090.h +++ b/sound/soc/codecs/max98090.h @@ -1533,7 +1533,6 @@ 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;