Hi guys, so what happens here is: 1/ we put display-subsystem dt node before spi node, which cause rockchip drm driver probed before spi(also before edp driver/vop driver...) 2/ rockchip drm driver bound after spi/edp/vop... drivers probed 3/ in rockchip drm driver's resume callback, it would try to enable edp panel backlight(through spi), but spi master is still suspended, then we got these errors: 1970-01-01T08:02:59.607315+08:00 ERR kernel: [ 178.754005] cros-ec-spi spi2.0: spi transfer failed: -108 1970-01-01T08:02:59.607320+08:00 ERR kernel: [ 178.760102] cros-ec-spi spi2.0: cs- deassert spi transfer failed: -108 1970-01-01T08:02:59.607325+08:00 ERR kernel: [ 178.767380] cros-ec-spi spi2.0: Com mand xfer error (err:-108) 1970-01-01T08:02:59.607331+08:00 ERR kernel: [ 178.773963] cros-ec-spi spi2.0: spi transfer failed: -108 1970-01-01T08:02:59.607336+08:00 ERR kernel: [ 178.780066] cros-ec-spi spi2.0: cs- deassert spi transfer failed: -108 1970-01-01T08:02:59.607341+08:00 ERR kernel: [ 178.787359] cros-ec-spi spi2.0: Com mand xfer error (err:-108) so other than move spi master suspend to late suspend, maybe we could defer rockchip drm driver probe after it's component drivers somehow? On 10/14/2017 02:44 AM, jeffy wrote: > Hi Dmitry, > > On 10/14/2017 02:30 AM, Dmitry Torokhov wrote: >> On Sat, Oct 14, 2017 at 02:19:28AM +0800, jeffy wrote: >>> Hi guys, >>> >>> it looks like the suspend sequence depends on the dt node sequence, >>> and we >>> are putting display-subsystem dt node above spi dt node, so it would be >>> earlier in the device list, then got suspended later than spi device. >> >> Would it not get a deferral when trying to get resource reference, which >> would cause it bumped down to the end of dpm list? > hmm, right, check again, the rockchip drm would not depend on spi, but > the edp driver does. > > so the drm driver(display-subsystem) would probed before spi, but try to > control the backlight in the suspend/resume... > > so i was wrong in the commit message, will fix it in next version. >> >>> >>> the pwm backlight and cros_ec_spi pwm are very interesting, not only >>> about >>> suspend dependency... if we unbind cros_ec_spi pwm, the pwm backlight >>> would >>> still hold a reference to it, and crash the kernel later. >> >> That would be a bug in PWM/cors_ec and it should keep the PWM object >> until last reference drops and simply error out on all requests. > right, and maybe try to refresh the pwm reference when we bind it again >> >>> >>> On 10/14/2017 12:42 AM, Mark Brown wrote: >>>> On Fri, Oct 13, 2017 at 08:51:21AM -0700, Brian Norris wrote: >>>> >>>>> Yes, this does seem odd to me too. This looks like an arms race hack >>>>> that should be avoided unless we know a legit root cause. Also, >>>>> "probe order implies suspend order" doesn't quite work for async >>>>> suspend >>>>> anyway, so we'd probably want to express the dependency properly >>>>> anyway. >>>> >>>> Yeah, it's the same stuff as we get with initcall ordering. This sort >>>> of thing does happen with things like PMICs which tend to have hardware >>>> that the system wants to manipulate in the IRQs off part of suspend. >>>> Ideally the dependency annotation stuff would figure things out though >>>> I'm not sure what the status of that is. >> >> I'd say non-existent for resources such as regulators, pwms, clocks, >> etc. I do not think many places call device_link_add()... I think adding >> this to devm_* APIs might be easiest to get the ball going as they >> naturally have consumer device and can easily figure out the supplier >> side. >> >>>> >>>>> Any chance this is related? Seems like that might break the >>>>> parent/child >>>>> relationship for master/slave: >>>> >>>>> commit d7e2ee257038baeb03baef602500368a51ee9eef >>>>> Author: Linus Walleij <linus.walleij at linaro.org> >>>>> Date: Mon Apr 11 13:51:03 2016 +0200 >>>> >>>>> spi: let SPI masters ignore their children for PM >>>> >>>> That's for runtime PM, I'd not expect it to affect system suspend. >>>> >>> >>> >> >> Thanks. >> >
