On Tue, Sep 05, 2023 at 10:15:46PM +0300, Cristian Ciocaltea wrote: > On 9/5/23 12:45, Charles Keepax wrote: > > On Sun, Sep 03, 2023 at 12:06:21AM +0300, Cristian Ciocaltea wrote: > >> Simplify runtime PM during probe by converting pm_runtime_enable() to > >> the managed version. > >> > >> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@xxxxxxxxxxxxx> > >> --- > >> @@ -1376,7 +1379,6 @@ void cs35l41_remove(struct cs35l41_private *cs35l41) > >> cancel_work_sync(&cs35l41->mdsync_up_work); > >> > >> pm_runtime_get_sync(cs35l41->dev); > >> - pm_runtime_disable(cs35l41->dev); > >> > >> regmap_write(cs35l41->regmap, CS35L41_IRQ1_MASK1, 0xFFFFFFFF); > >> if (cs35l41->hw_cfg.bst_type == CS35L41_SHD_BOOST_PASS || > > > > Are we sure this is safe? The remove handler appears to be > > written to disable pm_runtime at the start presumably to stop the > > resume/suspend handler running during the remove callback. > > Whereas after this change the pm_runtime isn't disabled until > > after the remove callback has run. Does this open a window were > > we could get an erroneous pm_runtime suspend after the > > pm_runtime_put_noidle? > > I've just made a test adding a 6s sleep before returning from the remove > handler: > > [14444.894316] cs35l41 spi-VLV1776:00: Runtime resume > [14444.894469] cs35l41 spi-VLV1776:00: sleep 6s before return of cs35l41_remove() > [14448.338994] cs35l41 spi-VLV1776:00: Runtime suspend > [14451.079649] cs35l41 spi-VLV1776:00: return from cs35l41_remove() > [14451.080129] cs35l41 spi-VLV1776:00: Runtime resume > [14451.080165] cs35l41 spi-VLV1776:00: ASoC: Unregistered DAI 'cs35l41-pcm' > [14451.080181] cs35l41 spi-VLV1776:00: Runtime suspend > [14451.813639] acp5x_i2s_playcap acp5x_i2s_playcap.0: ASoC: Unregistered DAI 'acp5x_i2s_playcap.0' > > As expected, suspend triggered, but a resume was issued later, before DAI > got unregistered. > > I didn't notice any issues while repeating the test several times, hence > I wonder what would be the reason to prevent getting suspend/resume events > at this point? The enter/exit hibernate code might run, which at the very least might result in a bunch of unexpected and failing bus traffic. Having a bit of a poke through the code, I guess the most dangerous thing would if you actually got as far as an extra runtime resume. This might cause cs35l41_init_boost to run which would undo the work done by the call to cs35l41_safe_reset in remove, which could leave the boost in a dangerous state when we enable reset/power down the supplies, which I think was not considered good. But its just likely simpler/cleaner if we don't have to think about all the possible implications of such things by just not allowing it to happen. Thanks, Charles
