[alsa-devel] [PATCH] ASoC: wm8903: disable IRQs during BIAS_OFF
From: Stephen Warren swarren@nvidia.com
If the WM8903 IRQ is triggered after the device is suspended, or before it is resumed, the underlying I2C bus that the WM8903 is attached to may not be available. This may cause the IRQ handler to emit the following error:
wm8903 0-001a: Failed to read IRQ status: -16
... or perhaps even cause a failure inside the I2C driver.
To prevent this, explicitly mask all interrupt sources when entering BIAS_OFF. Also, modify the IRQ handler to immediately return if the device is in BIAS_OFF, so that shared interrupt lines don't cause a similar problem. This requires that WM8903 interrupts be disabled to avoid interrupt storms.
During resume (actually, the transition back to BIAS_STANDBY), restore the desired IRQ mask.
Signed-off-by: Stephen Warren swarren@nvidia.com --- sound/soc/codecs/wm8903.c | 38 ++++++++++++++++++++++++++++---------- 1 file changed, 28 insertions(+), 10 deletions(-)
diff --git a/sound/soc/codecs/wm8903.c b/sound/soc/codecs/wm8903.c index eebcb1d..e847bbe 100644 --- a/sound/soc/codecs/wm8903.c +++ b/sound/soc/codecs/wm8903.c @@ -1091,6 +1091,22 @@ static const struct snd_soc_dapm_route wm8903_intercon[] = { { "Right Line Output PGA", NULL, "Charge Pump" }, };
+static void wm8903_setup_mic_det_irqs(struct snd_soc_codec *codec) +{ + struct wm8903_priv *wm8903 = snd_soc_codec_get_drvdata(codec); + int irq_mask = WM8903_MICDET_EINT | WM8903_MICSHRT_EINT; + + /* Enable interrupts we've got a report configured for */ + if (wm8903->mic_det) + irq_mask &= ~WM8903_MICDET_EINT; + if (wm8903->mic_short) + irq_mask &= ~WM8903_MICSHRT_EINT; + + snd_soc_update_bits(codec, WM8903_INTERRUPT_STATUS_1_MASK, + WM8903_MICDET_EINT | WM8903_MICSHRT_EINT, + irq_mask); +} + static int wm8903_set_bias_level(struct snd_soc_codec *codec, enum snd_soc_bias_level level) { @@ -1169,6 +1185,8 @@ static int wm8903_set_bias_level(struct snd_soc_codec *codec, WM8903_CP_DYN_V, WM8903_CP_DYN_FREQ | WM8903_CP_DYN_V); + + wm8903_setup_mic_det_irqs(codec); }
snd_soc_update_bits(codec, WM8903_VMID_CONTROL_0, @@ -1177,6 +1195,8 @@ static int wm8903_set_bias_level(struct snd_soc_codec *codec, break;
case SND_SOC_BIAS_OFF: + snd_soc_write(codec, WM8903_INTERRUPT_STATUS_1_MASK, 0xffff); + snd_soc_update_bits(codec, WM8903_BIAS_CONTROL_0, WM8903_BIAS_ENA, 0);
@@ -1600,7 +1620,6 @@ int wm8903_mic_detect(struct snd_soc_codec *codec, struct snd_soc_jack *jack, int det, int shrt) { struct wm8903_priv *wm8903 = snd_soc_codec_get_drvdata(codec); - int irq_mask = WM8903_MICDET_EINT | WM8903_MICSHRT_EINT;
dev_dbg(codec->dev, "Enabling microphone detection: %x %x\n", det, shrt); @@ -1610,15 +1629,7 @@ int wm8903_mic_detect(struct snd_soc_codec *codec, struct snd_soc_jack *jack, wm8903->mic_det = det; wm8903->mic_short = shrt;
- /* Enable interrupts we've got a report configured for */ - if (det) - irq_mask &= ~WM8903_MICDET_EINT; - if (shrt) - irq_mask &= ~WM8903_MICSHRT_EINT; - - snd_soc_update_bits(codec, WM8903_INTERRUPT_STATUS_1_MASK, - WM8903_MICDET_EINT | WM8903_MICSHRT_EINT, - irq_mask); + wm8903_setup_mic_det_irqs(codec);
if (det || shrt) { /* Enable mic detection, this may not have been set through @@ -1642,6 +1653,13 @@ static irqreturn_t wm8903_irq(int irq, void *data) int mic_report, ret; unsigned int int_val, mask, int_pol;
+ /* + * During suspend, a shared IRQ may be triggered by some other device. + * If so, just ignore it; WM8903 shouldn't be generating interrupts. + */ + if (wm8903->codec->dapm.bias_level == SND_SOC_BIAS_OFF) + return IRQ_NONE; + ret = regmap_read(wm8903->regmap, WM8903_INTERRUPT_STATUS_1_MASK, &mask); if (ret != 0) {
On Mon, Sep 09, 2013 at 12:44:49PM -0600, Stephen Warren wrote:
From: Stephen Warren swarren@nvidia.com
If the WM8903 IRQ is triggered after the device is suspended, or before it is resumed, the underlying I2C bus that the WM8903 is attached to may not be available. This may cause the IRQ handler to emit the following error:
wm8903 0-001a: Failed to read IRQ status: -16... or perhaps even cause a failure inside the I2C driver.
To prevent this, explicitly mask all interrupt sources when entering BIAS_OFF. Also, modify the IRQ handler to immediately return if the device is in BIAS_OFF, so that shared interrupt lines don't cause a similar problem. This requires that WM8903 interrupts be disabled to avoid interrupt storms.
During resume (actually, the transition back to BIAS_STANDBY), restore the desired IRQ mask.
This should be being handled in at a framework level, there's a generic problem here that affects essentially every device out there which might need interrupts over suspend (and causes relatively frequent problems). Your fix also won't help if someone has arranged for the wm8903 mic detect to be a wake source which you normally want in phone or tablet type applications but is where this sort of issue most frequently bites since we'll never turn the device off the interrupt does need to be asserted to kick off the wake.
Drivers usually work around this by disabling their interrupt with disable_irq() between suspend() and suspend_late(), then doing the same thing again between resume_noirq() and resume() covering both the windows where this can happen. This preserves the ability to wake from the interrupt but it's not awesome; ideally genirq would be able to understand that it can't deliver interrupts to a suspended device but then of course at the minute genirq has no idea that a device is even associated with the interrupt.
On 09/09/2013 02:27 PM, Mark Brown wrote:
On Mon, Sep 09, 2013 at 12:44:49PM -0600, Stephen Warren wrote:
From: Stephen Warren swarren@nvidia.com
If the WM8903 IRQ is triggered after the device is suspended, or before it is resumed, the underlying I2C bus that the WM8903 is attached to may not be available. This may cause the IRQ handler to emit the following error:
wm8903 0-001a: Failed to read IRQ status: -16
... or perhaps even cause a failure inside the I2C driver.
To prevent this, explicitly mask all interrupt sources when entering BIAS_OFF. Also, modify the IRQ handler to immediately return if the device is in BIAS_OFF, so that shared interrupt lines don't cause a similar problem. This requires that WM8903 interrupts be disabled to avoid interrupt storms.
During resume (actually, the transition back to BIAS_STANDBY), restore the desired IRQ mask.
This should be being handled in at a framework level, there's a generic problem here that affects essentially every device out there which might need interrupts over suspend (and causes relatively frequent problems). Your fix also won't help if someone has arranged for the wm8903 mic detect to be a wake source which you normally want in phone or tablet type applications but is where this sort of issue most frequently bites since we'll never turn the device off the interrupt does need to be asserted to kick off the wake.
Drivers usually work around this by disabling their interrupt with disable_irq() between suspend() and suspend_late(), then doing the same thing again between resume_noirq() and resume() covering both the windows where this can happen. This preserves the ability to wake from the interrupt but it's not awesome; ideally genirq would be able to understand that it can't deliver interrupts to a suspended device but then of course at the minute genirq has no idea that a device is even associated with the interrupt.
So I suppose request_irq() could be enhanced to associate IRQs with devices, which would at least give genirq the knowledge it needs to mask interrupts before devices were resumed.
However, I'm not sure it's possible for genirq to handle this transparently in all situations.
When would the IRQ be re-enabled again?
If it the IRQ is enabled immediately before the device's resume() is called, then IRQs can still fire while the device is suspended. That would solve the issue at hand here; that the I2C device used for register IO wasn't resumed when the IRQ fired, but could presumably still be problematic for the device itself, in general if not in this case. Perhaps drivers just need to support this?
If the IRQ is enabled immediately after the device's resume() is called, then a device wouldn't be able to receive IRQs during the execution of resume(), which I assume would completely break some drivers?
This gets more complicated with shared IRQ lines, since it wouldn't be possible to enable the IRQ immediately before/after *a* device's resume() was called, but rather, this could only happen immediately before/after the resume() for *all* devices using that IRQ were called.
It seems like the only way a driver can really manage IRQ handling in the general case is to mask interrupts at the source, like this patch does, rather than mask them at the interrupt controller, where the IRQ may already be shared.
I guess that means that for wakeup interrupts, the driver does indeed need to disable the interrupt at the source between resume_noirq() and resume(), although I have no idea how that could possibly work, if the register IO is over an I2C device that itself uses its own interrupts...
On Wed, Sep 11, 2013 at 10:16:56AM -0600, Stephen Warren wrote:
On 09/09/2013 02:27 PM, Mark Brown wrote:
Drivers usually work around this by disabling their interrupt with disable_irq() between suspend() and suspend_late(), then doing the same thing again between resume_noirq() and resume() covering both the windows where this can happen. This preserves the ability to
However, I'm not sure it's possible for genirq to handle this transparently in all situations.
When would the IRQ be re-enabled again?
See above - during the period between the device being suspended and interrupts being globally disabled, and then during the period between interrupts being reenabled and the device resumed.
If it the IRQ is enabled immediately before the device's resume() is called, then IRQs can still fire while the device is suspended. That would solve the issue at hand here; that the I2C device used for register IO wasn't resumed when the IRQ fired, but could presumably still be problematic for the device itself, in general if not in this case. Perhaps drivers just need to support this?
Yes, that's a problem if it's an issue in the driver/device itself - in that case it seems reasonable for the device to be responsible for quiescing itself (as they mostly do already).
If the IRQ is enabled immediately after the device's resume() is called, then a device wouldn't be able to receive IRQs during the execution of resume(), which I assume would completely break some drivers?
I think you're right there.
This gets more complicated with shared IRQ lines, since it wouldn't be possible to enable the IRQ immediately before/after *a* device's resume() was called, but rather, this could only happen immediately before/after the resume() for *all* devices using that IRQ were called.
Yeah. Fortunately I've only ever run into this with threaded interrupts so they can't be shared in the first place (which to be fair tends to come along with the buses that cause issues here).
It seems like the only way a driver can really manage IRQ handling in the general case is to mask interrupts at the source, like this patch does, rather than mask them at the interrupt controller, where the IRQ may already be shared.
The problem is that this doesn't actually fix the problem in some quite common cases, you can still trigger it so long as the device is still supposed to act as a wake source (and hence won't actually be suspended) - masking the interrupts at the source would actively break those systems since they do want to be woken by the device. To make matters worse if the device is the wake source then the interrupt will be asserted during resume making it more likely that the resume side of the issue will be triggered.
I guess that means that for wakeup interrupts, the driver does indeed need to disable the interrupt at the source between resume_noirq() and resume(), although I have no idea how that could possibly work, if the register IO is over an I2C device that itself uses its own interrupts...
The disable needs to be done with disable_irq() rather than by interacting with the device, just stop the interrupts being delivered until the device is capable of handling them rather than stopping the hardware asserting them. Fortunately since genirq doesn't allow threaded interrupts to be shared I2C devices won't normally have to worry about how rude this is for shared interrupts and generally the buses affected by this will be threaded.
participants (2)
-
Mark Brown -
Stephen Warren