[PATCH 3/3] drm/panthor: Fix undefined panthor_device_suspend/resume symbol issue

[Boris Brezillon]

On Mon, 11 Mar 2024 13:46:23 +0000
Steven Price <steven.price at arm.com> wrote:

> On 11/03/2024 13:36, Robin Murphy wrote:
> > On 2024-03-11 1:22 pm, Boris Brezillon wrote:  
> >> On Mon, 11 Mar 2024 13:11:28 +0000
> >> Robin Murphy <robin.murphy at arm.com> wrote:
> >>  
> >>> On 2024-03-11 11:52 am, Boris Brezillon wrote:  
> >>>> On Mon, 11 Mar 2024 13:49:56 +0200
> >>>> Jani Nikula <jani.nikula at linux.intel.com> wrote:
> >>>>     
> >>>>> On Mon, 11 Mar 2024, Boris Brezillon
> >>>>> <boris.brezillon at collabora.com> wrote:  
> >>>>>> On Mon, 11 Mar 2024 13:05:01 +0200
> >>>>>> Jani Nikula <jani.nikula at linux.intel.com> wrote:
> >>>>>>       
> >>>>>>> This breaks the config for me:
> >>>>>>>
> >>>>>>>     SYNC    include/config/auto.conf.cmd
> >>>>>>>     GEN     Makefile
> >>>>>>> drivers/iommu/Kconfig:14:error: recursive dependency detected!
> >>>>>>> drivers/iommu/Kconfig:14:    symbol IOMMU_SUPPORT is selected by
> >>>>>>> DRM_PANTHOR
> >>>>>>> drivers/gpu/drm/panthor/Kconfig:3:    symbol DRM_PANTHOR depends
> >>>>>>> on PM
> >>>>>>> kernel/power/Kconfig:183:    symbol PM is selected by PM_SLEEP
> >>>>>>> kernel/power/Kconfig:117:    symbol PM_SLEEP depends on
> >>>>>>> HIBERNATE_CALLBACKS
> >>>>>>> kernel/power/Kconfig:35:    symbol HIBERNATE_CALLBACKS is
> >>>>>>> selected by XEN_SAVE_RESTORE
> >>>>>>> arch/x86/xen/Kconfig:67:    symbol XEN_SAVE_RESTORE depends on XEN
> >>>>>>> arch/x86/xen/Kconfig:6:    symbol XEN depends on PARAVIRT
> >>>>>>> arch/x86/Kconfig:781:    symbol PARAVIRT is selected by HYPERV
> >>>>>>> drivers/hv/Kconfig:5:    symbol HYPERV depends on X86_LOCAL_APIC
> >>>>>>> arch/x86/Kconfig:1106:    symbol X86_LOCAL_APIC depends on
> >>>>>>> X86_UP_APIC
> >>>>>>> arch/x86/Kconfig:1081:    symbol X86_UP_APIC prompt is visible
> >>>>>>> depending on PCI_MSI
> >>>>>>> drivers/pci/Kconfig:39:    symbol PCI_MSI is selected by AMD_IOMMU
> >>>>>>> drivers/iommu/amd/Kconfig:3:    symbol AMD_IOMMU depends on
> >>>>>>> IOMMU_SUPPORT  
> >>>>>>
> >>>>>> Uh, I guess we want a "depends on IOMMU_SUPPORT" instead of "select
> >>>>>> IOMMU_SUPPORT" in panthor then.  
> >>>>>
> >>>>> That works for me.  
> >>>>
> >>>> Let's revert the faulty commit first. We'll see if Steve has a
> >>>> different solution for the original issue.  
> >>>
> >>> FWIW, the reasoning in the offending commit seems incredibly tenuous.
> >>> There are far more practical reasons for building an arm/arm64 kernel
> >>> without PM - for debugging or whatever, and where one may even still
> >>> want a usable GPU, let alone just a non-broken build - than there are
> >>> for building this driver for x86. Using pm_ptr() is trivial, and if you
> >>> want to support COMPILE_TEST then there's really no justifiable excuse
> >>> not to.  
> >>
> >> The problem is not just about using pm_ptr(), but also making sure
> >> panthor_device_resume/suspend() are called called in the init/unplug
> >> path when !PM, as I don't think the PM helpers automate that for us. I
> >> was just aiming for a simple fix that wouldn't force me to test the !PM
> >> case...  
> > Fair enough, at worst we could always have a runtime check and refuse to
> > probe in conditions we don't think are worth the bother of implementing
> > fully-functional support for. However if we want to make an argument for
> > only supporting "realistic" configs at build time then that is an
> > argument for dropping COMPILE_TEST as well.  
> 
> Can we just replace the "depends on PM" with "select PM"? In my
> (admittedly very limited) testing this works. Otherwise I think we need
> to bite the bullet and support !PM in some way (maybe just as Robin
> suggests with a runtime bail out).

I won't have time to test it this week, but if someone is interested,
here's a diff implementing manual resume/suspend in the init/unplug
path:

--->8---