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

[Steven Price]

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).

Steve