Messages in this thread | | | From | "m.shams" <> | Subject | RE: [PATCH] pwm: removes period check from pwm_apply_state() | Date | Wed, 10 Aug 2022 17:09:30 +0530 |
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Hi Uwe,
> Hello, > > I fixed up the quoting for you in this mail. Please fix your mailer to not break > quotes, this is quite annoying. (Looking at the headers of your mail you're using > Outlook. Then your only viable option is to switch to a saner client.) >
Sorry for the inconvenience. I have fixed my mailer.
> On Mon, Aug 08, 2022 at 07:47:03PM +0530, m.shams wrote: > > On Fri, Aug 05, 2022 at 03:41:25PM +0530, Tamseel Shams wrote: > > > > There may be situation when PWM is exported using sysfs, but at > > > > that point PWM period is not set. At this situation if we issue a > > > > system suspend, it calls pwm_class_suspend which in turn calls > > > > pwm_apply_state, where PWM period value is checked which returns > > > > an invalid argument error casuing Kernel to panic. So, check for > > > > PWM period value is removed so as to fix the kernel panic observed > > > > during suspend. > > > > > > This looks and sounds wrong. One thing I would accept is: > > > > > > diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c index > > > 0e042410f6b9..075bbcdad6c1 100644 > > > --- a/drivers/pwm/core.c > > > +++ b/drivers/pwm/core.c > > > @@ -557,8 +557,8 @@ int pwm_apply_state(struct pwm_device *pwm, > const struct pwm_state *state) > > > */ > > > might_sleep(); > > > > > > - if (!pwm || !state || !state->period || > > > - state->duty_cycle > state->period) > > > + if (!pwm || !state || state->enabled && (!state->period || > > > + state->duty_cycle > state->period)) > > > return -EINVAL; > > > > > > chip = pwm->chip; > > > > > > That is, don't refuse calling pwm_apply_state() for state->period = > > > 0 and even state->duty_cycle > state->period if the > > PWM is not enabled. > > > > By this do you mean doing it following way? > > > > if (!pwm || !state || (pwm && !state->period) || > > (pwm && state->duty_cycle > state->period)) > > return -EINVAL; > > No. Your expression is logically equivalent to what we already have. I > meant: > > if (!pwm || !state || state->enabled && (!state->period || > state->duty_cycle > state->period)) > return -EINVAL; > > Learning to read diffs (maybe Outlook scrambled the view for you, too?) is a > nice capability you should master. > > > > But anyhow, even without that the kernel should not panic. So I ask > > > you to research and provide some more info about > > the problem. > > > (Which hardware does it affect? Where does it panic? ...) > > > > Observing Kernel panic in exynos SoC when we issue system suspend. > > Following is the snippet of error: > > > > # echo mem > /sys/power/state > > [ 29.224784] 010: Kernel panic - not syncing: pwm pwmchip0: > > dpm_run_callback failure > > [ 29.240134] 010: Call trace: > > [ 29.242993] 010: dump_backtrace+0x0/0x1b8 > > [ 29.247067] 010: show_stack+0x24/0x30 > > [ 29.250793] 010: dump_stack+0xb8/0x114 > > [ 29.254606] 010: panic+0x180/0x398 > > [ 29.258073] 010: dpm_run_callback+0x270/0x278 > > [ 29.262493] 010: __device_suspend+0x15c/0x628 > > [ 29.266913] 010: dpm_suspend+0x124/0x3b0 > > [ 29.270899] 010: dpm_suspend_start+0xa0/0xa8 > > [ 29.275233] 010: suspend_devices_and_enter+0x110/0x968 > > [ 29.280433] 010: pm_suspend+0x308/0x3d8 > > [ 29.284333] 010: state_store+0x8c/0x110 > > [ 29.288233] 010: kobj_attr_store+0x14/0x28 > > [ 29.292393] 010: sysfs_kf_write+0x5c/0x78 > > [ 29.296466] 010: kernfs_fop_write+0x10c/0x220 > > [ 29.300886] 010: __vfs_write+0x48/0x90 > > [ 29.304699] 010: vfs_write+0xb8/0x1c0 > > [ 29.308426] 010: ksys_write+0x74/0x100 > > [ 29.312240] 010: __arm64_sys_write+0x24/0x30 > > [ 29.316573] 010: el0_svc_handler+0x110/0x1b8 > > [ 29.320906] 010: el0_svc+0x8/0x1bc > > [ 29.324374] 010: SMP: stopping secondary CPUs > > [ 29.328711] 010: Kernel Offset: disabled > > [ 29.332607] 010: CPU features: 0x0002,00006008 > > [ 29.337026] 010: Memory Limit: none > > [ 29.343949] 010: Rebooting in 1 seconds.. > > [ 30.344539] 010: Disabling non-boot CPUs ... > > Just locking at that and starring at drivers/base/power/main.c for a while > doesn't make this clearer to me. Are you using a mainline kernel? > Which version? >
Looks like I had some local patch which was causing the error to trigger Kernel Panic (sorry about that). On removing those local changes, I do not observe kernel panic, but observe following error and then suspend fails.
[ 63.963063] pwm pwmchip0: PM: dpm_run_callback (): pwm_class_suspend+0x0/0xf8 returns -22 [ 63.963079] pwm pwmchip0: PM: failed to suspend: error -22
So, as to fix this issue I will post a new version of patch containing change suggested by you.
Best Regards, Tamseel Shams
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