[PATCH V5 0/6] coresight: etm4x: Migrate ACPI AMBA devices to platform driver

From: Anshuman Khandual
Date: Mon May 29 2023 - 02:26:59 EST

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 6.4-rc4.

Changes in V5:

- Updated the comment for apb clock in drvdata structure
- Updated conditional check in etm4_runtime_suspend/resume()
- Asserted that the APB clock is present and also enabled

Changes in V4:


- Changed in-code comment in etm4_check_arch_features()
- Re-ordered pm_runtime_disable() in etm4_remove_platform_dev()
- Renamed back etm4_match as etm4_sysreg_match
- Moved back [PATCH 6/6] as [PATCH 5/6]

Changes in V3:


- Returned from etm4_check_arch_features() for non iomem devices
- Renamed is_etm4x_devtype() as is_devtype_cpu_trace()
- Added a patch to ignore the absence of graph connections

Changes in V2:


- Enables ACPI etm4x device support in the existing platform driver
- Dropped last two patches from the series
- Dropped redundant 'devarch' checking from is_etm4x_device()
- Renamed updated is_etm4x_device() as is_etm4x_devtype()
- Fixed arguments in fallback stub for etm4_check_arch_features()
- Tagged etm4_dev_pm_ops with etm4_platform_driver
- Updated the comment for coresight_get_enable_apb_pclk() helper
- Updated the comment for new 'pclk' element in struct etm4_drvdata
- Dropped the clock when devm_ioremap_resource() fails
- Convert IS_ERR() into a direct pointer check in etm4_remove_platform_dev()
- Dropped "arm,coresight-etm4x" compatible property from etm4_match[]

Changes in V1:


Cc: Ganapatrao Kulkarni <gankulkarni@xxxxxxxxxxxxxxxxxxxxxx>
Cc: Steve Clevenger <scclevenger@xxxxxxxxxxxxxxxxxxxxxx>
Cc: Rob Herring <robh+dt@xxxxxxxxxx>
Cc: Frank Rowand <frowand.list@xxxxxxxxx>
Cc: Russell King (Oracle) <linux@xxxxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
Cc: Len Brown <lenb@xxxxxxxxxx>
Cc: Sudeep Holla <sudeep.holla@xxxxxxx>
Cc: Lorenzo Pieralisi <lpieralisi@xxxxxxxxxx>
Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Cc: Mike Leach <mike.leach@xxxxxxxxxx>
Cc: Leo Yan <leo.yan@xxxxxxxxxx>
Cc: devicetree@xxxxxxxxxxxxxxx
Cc: linux-acpi@xxxxxxxxxxxxxxx
Cc: coresight@xxxxxxxxxxxxxxxx
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx

Anshuman Khandual (4):
coresight: etm4x: Allocate and device assign 'struct etmv4_drvdata' earlier
coresight: etm4x: Drop iomem 'base' argument from etm4_probe()
coresight: etm4x: Drop pid argument from etm4_probe()
coresight: etm4x: Change etm4_platform_driver driver for MMIO devices

Suzuki K Poulose (2):
coresight: platform: acpi: Ignore the absence of graph
coresight: etm4x: Add ACPI support in platform driver

drivers/acpi/acpi_amba.c | 1 -
.../coresight/coresight-etm4x-core.c | 117 ++++++++++++++----
drivers/hwtracing/coresight/coresight-etm4x.h | 4 +
.../hwtracing/coresight/coresight-platform.c | 6 +-
include/linux/coresight.h | 59 +++++++++
5 files changed, 163 insertions(+), 24 deletions(-)