On Wed, Sep 23, 2015 at 10:49:36PM +0200, Rafael J. Wysocki wrote: > On 9/23/2015 7:17 PM, Daniel Vetter wrote: > >acpi_target_system_state() seems to be almost the thing we're looking > >for, except that it's only valid in the suspend callbacks since it > >gets reset to ACPI_STATE_S0 when resuming. So probably we want > >something else ... > > Right. > > The idea is to add a way for drivers to check if > (a) suspend is going to enter the BIOS > (b) resume has been triggered by the BIOS > and that's really what drivers need to know. > > For suspend-to-idle those two will return false and for S3 they'll return > true. > > Would that help? Not sure that matches exaxtly what we'd need here ... Essentially we need to know whether we've been in S3/S4 (firmware has been eaten) or in one of the higher suspend-to-idle/standby states (firmware still alive, don't disturb it). Additional fun that just crossed my mind is that if the suspend-to-mem is aborted (some other driver failed) then that function should _not_ indicate that we've been in S3. So maybe something like acpi_source_system_state() which usually is S0 and only when acpi successfully went into the suspend state in platform_suspend_ops->enter it gets set to the value of acpi_target_system_state. And then reset once the resume has completed. I think that would be what we'd want here. Anyway I'll pull in Animesh series meanwhile, amended with a FIXME comment. -Daniel > > Thanks, > Rafael > > > >On Wed, Sep 23, 2015 at 6:28 PM, Daniel Vetter <daniel@xxxxxxxx> wrote: > >>Actually add Rafael this time around ... > >>-Daniel > >> > >>On Wed, Sep 23, 2015 at 6:27 PM, Daniel Vetter <daniel@xxxxxxxx> wrote: > >>>On Wed, Sep 23, 2015 at 9:57 AM, Daniel Vetter <daniel@xxxxxxxx> wrote: > >>>>On Thu, Sep 17, 2015 at 12:53:21AM +0530, Animesh Manna wrote: > >>>>> > >>>>>On 9/14/2015 1:16 PM, Daniel Vetter wrote: > >>>>>>On Fri, Sep 11, 2015 at 12:36:24AM +0530, Animesh Manna wrote: > >>>>>>>On 9/10/2015 8:15 PM, Daniel Vetter wrote: > >>>>>>>>On Thu, Sep 10, 2015 at 01:58:54AM +0530, Animesh Manna wrote: > >>>>>>>>>On 9/2/2015 2:24 PM, Daniel Vetter wrote: > >>>>>>>>>>On Wed, Aug 26, 2015 at 07:40:54PM +0530, Animesh Manna wrote: > >>>>>>>>>>>On 8/26/2015 6:40 PM, Daniel Vetter wrote: > >>>>>>>>>>>>On Wed, Aug 26, 2015 at 01:36:05AM +0530, Animesh Manna wrote: > >>>>>>>>>>>>>Dmc will restore the csr program except DC9, cold boot, > >>>>>>>>>>>>>warm reset, PCI function level reset, and hibernate/suspend. > >>>>>>>>>>>>> > >>>>>>>>>>>>>intel_csr_load_program() function is used to load the firmware > >>>>>>>>>>>>>data from kernel memory to csr address space. > >>>>>>>>>>>>> > >>>>>>>>>>>>>All values of csr address space will be zero if it got reset and > >>>>>>>>>>>>>the first byte of csr program is always a non-zero if firmware > >>>>>>>>>>>>>is loaded successfuly. Based on hardware status will load the > >>>>>>>>>>>>>firmware. > >>>>>>>>>>>>> > >>>>>>>>>>>>>Without this condition check if we overwrite the firmware data the > >>>>>>>>>>>>>counters exposed for dc5/dc6 (help for debugging) will be nullified. > >>>>>>>>>>>Bacause of the above reason mentioned just above we need to block firmware loading again. > >>>>>>>>>>>So only WARN_ON will not help. > >>>>>>>>>>> > >>>>>>>>>>> > >>>>>>>>>>>>>v1: Initial version. > >>>>>>>>>>>>> > >>>>>>>>>>>>>v2: Based on review comments from Daniel, > >>>>>>>>>>>>>- Added a check to know hardware status and load the firmware if not loaded. > >>>>>>>>>>>>> > >>>>>>>>>>>>>Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx> > >>>>>>>>>>>>>Cc: Damien Lespiau <damien.lespiau@xxxxxxxxx> > >>>>>>>>>>>>>Cc: Imre Deak <imre.deak@xxxxxxxxx> > >>>>>>>>>>>>>Cc: Sunil Kamath <sunil.kamath@xxxxxxxxx> > >>>>>>>>>>>>>Signed-off-by: Animesh Manna <animesh.manna@xxxxxxxxx> > >>>>>>>>>>>>>Signed-off-by: Vathsala Nagaraju <vathsala.nagaraju@xxxxxxxxx> > >>>>>>>>>>>>>--- > >>>>>>>>>>>>> drivers/gpu/drm/i915/intel_csr.c | 9 +++++++++ > >>>>>>>>>>>>> 1 file changed, 9 insertions(+) > >>>>>>>>>>>>> > >>>>>>>>>>>>>diff --git a/drivers/gpu/drm/i915/intel_csr.c b/drivers/gpu/drm/i915/intel_csr.c > >>>>>>>>>>>>>index ba1ae03..682cc26 100644 > >>>>>>>>>>>>>--- a/drivers/gpu/drm/i915/intel_csr.c > >>>>>>>>>>>>>+++ b/drivers/gpu/drm/i915/intel_csr.c > >>>>>>>>>>>>>@@ -252,6 +252,15 @@ void intel_csr_load_program(struct drm_device *dev) > >>>>>>>>>>>>> return; > >>>>>>>>>>>>> } > >>>>>>>>>>>>>+ /* > >>>>>>>>>>>>>+ * Dmc will restore the csr the program except DC9, cold boot, > >>>>>>>>>>>>>+ * warm reset, PCI function level reset, and hibernate/suspend. > >>>>>>>>>>>>>+ * This condition will help to check if csr address space is reset/ > >>>>>>>>>>>>>+ * not loaded. > >>>>>>>>>>>>>+ */ > >>>>>>>>>>>>Atm we call this from driver load and resume, which doesn seem to cover > >>>>>>>>>>>>all the cases you mention in the comment. Should this be a WARN_ON > >>>>>>>>>>>>instead? Or do we have troubles in our init sequence where we load too > >>>>>>>>>>>>many times? > >>>>>>>>>>>Yes, the above statement taken from bspec to describe about the special cases dmc will not restore the firmware. > >>>>>>>>>>>Agree, In our cases cold boot and hibernate/suspend mainly we need to load the firmware again, so in my > >>>>>>>>>>>second sentence I wanted to comment mainly regarding this condition check added for suspend-hibernate(reset) > >>>>>>>>>>>and cold boot(not loaded). > >>>>>>>>>>> > >>>>>>>>>>>Anyways the same api later can be used to load the firmware from anywhere, so my intention to check firmware loaded or not. > >>>>>>>>>>>If already loaded then not to overwrite the csr address space to maintain the dc5/dc6 counter value. > >>>>>>>>>>> > >>>>>>>>>>>Can the below comment more clear to you. > >>>>>>>>>>> > >>>>>>>>>>> /* > >>>>>>>>>>> * Dmc will restore the csr the program except DC9, cold boot, > >>>>>>>>>>> * warm reset, PCI function level reset, and hibernate/suspend. > >>>>>>>>>>> * If firmware is restored by dmc then no need to load again which > >>>>>>>>>>> * will keep the dc5/dc6 counter exposed by firmware. > >>>>>>>>>>> */ > >>>>>>>>>>> > >>>>>>>>>>>No issue in init sequence. > >>>>>>>>>>That seems to still cover all the callers of the function afaics - we do > >>>>>>>>>>pci resets over suspend resume unconditionally. So I still don't > >>>>>>>>>>understand where exactly we try to load the dmc firmware in i915.ko when > >>>>>>>>>>it's already loaded. > >>>>>>>>>During resume intel_csr_load_program() will be called from > >>>>>>>>>intel_runtime_resume(). > >>>>>>>>> > >>>>>>>>>intel_runtime_resume()-> skl_resume_prepare()-> intel_csr_load_program() > >>>>>>>>> > >>>>>>>>>During Pc10 entry testing I can see dmc is restoring back the firmware always, > >>>>>>>>>but as you mentioned pci-reset can happen unconditionally, but still then > >>>>>>>>>also during resume intel_runtime_resume() will be called and based on > >>>>>>>>>register read of csr-base-address firmware loading will happen. > >>>>>>>>But in your comment you're saying it won't get restored in case of dc9 and > >>>>>>>>suspend. So that seems to mismatch what you're saying here (and what the > >>>>>>>>commit message says) and what the code does. And this function here is > >>>>>>>>called for resume after suspend/hibernate only. > >>>>>>>pc10 entry explanation I told is for skylake. dc9 in skylake is not possible. > >>>>>>>I think you are confusing between dc6 and dc9. Pc10 can be achieved by > >>>>>>>entering into dc6 (not dc9) for skylake. dc9 is the lowest possible state > >>>>>>>for broxton which is not present for skylake. > >>>>>>I have no idea at all about different pc levels on skl. What I'm talking > >>>>>>about is system suspend/resume and driver load, which are the places this > >>>>>>function gets called. At least afaics. > >>>>>> > >>>>>>>Here intel_csr_load_program() will be used for both skylake and broxton, and instruction > >>>>>>>execution flow will be different in case of suspend/resume which I think is confusing > >>>>>>>you. > >>>>>>That seems like really important information. What's different on bxt? > >>>>>>These are the kind of details you should explain in the commit message ... > >>>>>> > >>>>>>>I am ready explain you in detail. It will be good if we discuss specific use-case scenario > >>>>>>>and itz software design for specific platform. Another point - as dmc related code for > >>>>>>>broxton is not merged better first we close design for skylake. Now, I have added dc9 > >>>>>>>description in comment thinking of future. If you want I can remove for now and later > >>>>>>>can add in bxt patch series for enabling dmc. Will wait for your reply. > >>>>>>This question here isn't about the overall design and how to handle power > >>>>>>wells in skl/bxt. That's a separate discussion and tracked somewhere else. > >>>>>>I'm really just confused about when exactly we need to reload to firmware, > >>>>>>and why we need a runtime check for that. Normally we should know when to > >>>>>>reload the firmware and just either reload or not, without checking hw > >>>>>>state. And I don't like checking for hw state since at least in the past > >>>>>>that kind of code ended up being fragile - it's an illusion that it does > >>>>>>the right thing no matter what, since often there's other tricky ordering > >>>>>>constraints. And if you have automatic duct-tape like then no one will > >>>>>>ever spot those other, harder to spot issues, until an expensive customer > >>>>>>escalation happens. > >>>>>> > >>>>>>So what I want to know here is: > >>>>>>- When exactly do we need to reload dmc firmware. > >>>>>In skl, during driver load first time we load the firmware, during normal > >>>>>suspend-resume (dc6 entry/exit) > >>>>>no need to reload the firmware again as dmc will take care of it. But during > >>>>>suspend/hibernation > >>>>>dmc will not restore the firmware. In that case driver need to reload it > >>>>>again. I do not know > >>>>>how to differentiate pm-suspend and suspend-hibernation and thought both the > >>>>>cases > >>>>>intel_runtime_resume() will be called where we can check the h/w state and > >>>>>reload the > >>>>>firmware if dmc is not restored. > >>>>> > >>>>>In bxt, during driver load first time we load the firmware, during normal > >>>>>suspend-resume > >>>>>display engine will enter into dc9 and dmc will not restore the firmware. So > >>>>>every > >>>>>suspend-resume we need to reload the firmware. > >>>>>>- What exactly is the reason why we can't make that decision statically in > >>>>>> the code (by calling csr_load at the right spots). > >>>>>As I mentioned before in case of skylake can we differentiate between > >>>>>"resume from pm-suspend" with "resume from suspend-hibernation" inside > >>>>>driver? > >>>>> > >>>>>In case of broxton, every time we need to reload, so we can decide > >>>>>statically. > >>>>Of course we can differentiate between all the different resume paths, and > >>>>we also have a per-platform split to take care of bxt vs. skl. And there > >>>>are actually 3 different resume paths: > >>>> > >>>>- runtime PM resume. This calls the runtime_resume hook. It sounds like on > >>>> skl we should _not_ load the csr firmware, but on bxt we should load it. > >>>> This can be fixed by removing the intel_csr_load_program call from > >>>> skl_resume_prepare. > >>>>- resume from hibernate-to-disk (i.e. system completely off, state stored > >>>> on the swap partition) is done by calling the thaw callbacks. > >>>>- resume from suspend-to-mem (i.e. system in low-power with only memory > >>>> in self-refresh, all state stored in memory) is done by calling the > >>>> resume callbacks. > >>>> > >>>>For i915 we use unified handlers in our dev_pm_ops for both thaw and > >>>>resume, but it sounds like that won't be a problem for skl/bxt since we > >>>>need to reload the csr firmware in all cases. Although I'm not perfectly > >>>>sure since you don't explain what kind of resume you mean exactly (since > >>>>you don't use the linux names for them). > >>>> > >>>>Anyway it sounds like we can replace this patch by one where we remove > >>>>that errornous csr load call from skl runtime pm resume and that's all. > >>>>But I suggest to make sure we get this right we keep the check you're > >>>>adding here, but wrap it in a WARN_ON. Then we'll get a backtrace when > >>>>this is going wrong again. Like this: > >>>> > >>>> if (WARN_ON(csr_loaded_already())) > >>>> return; > >>>> > >>>>Also when redoing the commits please explain in detail what exactly are > >>>>the requirements like you've done above, but please use the standard linux > >>>>names, i.e. "runtime PM" and "hibernate-to-disk" and "suspend-to-mem". > >>>Ok hooray there's more suspend-to-something things I've totally missed: > >>>- suspend-to-idle (done by cat freeze > /sys/power/state) and > >>>- suspend (done by cat suspend > /sys/power/state) > >>> > >>>And apparently there's really no way to drivers to tell them apart. > >>>Rafael, is there really no way for drivers to take different paths for > >>>these 3 suspend cases? I tried grepping for PM_SUSPEND_ON/STANDY/MEM > >>>and didn't spot anything. > >>> > >>>Also we're completely missing test coverage for that in igt. That is > >>>something that needs to be fixed asap (yet another case of > >>>combinatorial explosion in igt tests, yay). And at least one of those > >>>suspend-to-idle testcase better be in the BAT. > >>>-Daniel > >>>-- > >>>Daniel Vetter > >>>Software Engineer, Intel Corporation > >>>+41 (0) 79 365 57 48 - http://blog.ffwll.ch > >> > >> > >>-- > >>Daniel Vetter > >>Software Engineer, Intel Corporation > >>+41 (0) 79 365 57 48 - http://blog.ffwll.ch > > > > > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
