Messages in this thread | | | Date | Wed, 26 Jul 2023 18:32:55 +0100 | Subject | Re: [PATCH V6 0/6] coresight: etm4x: Migrate ACPI AMBA devices to platform driver | From | Suzuki K Poulose <> |
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On 26/07/2023 18:03, Steve Clevenger OS wrote: > > Hi Suzuki, > > On 7/26/2023 9:59 AM, Suzuki K Poulose wrote: >> On 10/07/2023 07:24, Anshuman Khandual wrote: >>> CoreSight ETM4x devices could be accessed either via MMIO (handled via >>> amba_driver) or CPU system instructions (handled via platform driver). >>> But >>> this has the following issues : >>> >>> - Each new CPU comes up with its own PID and thus we need to keep on >>> adding the "known" PIDs to get it working with AMBA driver. While >>> the ETM4 architecture (and CoreSight architecture) defines way to >>> identify a device as ETM4. Thus older kernels won't be able to >>> "discover" a newer CPU, unless we add the PIDs. >>> >>> - With ACPI, the ETM4x devices have the same HID to identify the >>> device >>> irrespective of the mode of access. This creates a problem where two >>> different drivers (both AMBA based driver and platform driver) would >>> hook into the "HID" and could conflict. e.g., if AMBA driver gets >>> hold of a non-MMIO device, the probe fails. If we have single driver >>> hooked into the given "HID", we could handle them seamlessly, >>> irrespective of the mode of access. >>> >>> - CoreSight is heavily dependent on the runtime power management. With >>> ACPI, amba_driver doesn't get us anywhere with handling the power >>> and thus one need to always turn the power ON to use them. Moving to >>> platform driver gives us the power management for free. >>> >>> Due to all of the above, we are moving ACPI MMIO based etm4x devices >>> to be >>> supported via tha platform driver. The series makes the existing platform >>> driver generic to handle both type of the access modes. Although existing >>> AMBA driver would still continue to support DT based etm4x MMIO devices. >>> Although some problems still remain, such as manually adding PIDs for all >>> new AMBA DT based devices. >>> >>> The series applies on 6.5-rc1. >>> >>> Changes in V6: >>> >>> - Rebased on 6.5-rc1 >>> >> >> I have queued this version for v6.6, should appear on coresight/next soon. >> >> Suzuki > > Is there anyway to queue this for 6.5? Or has that ship sailed?
Only fixes are allowed for v6.5 at this time.
Suzuki
> > Thanks, > > Steve C.
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