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

[Robin Murphy]

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.

Thanks,
Robin.