| Message ID | 20230523044553.1525048-1-anshuman.khandual@arm.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | coresight: etm4x: Migrate ACPI AMBA devices to platform driver | expand |
On Tue, May 23, 2023 at 10:15:47AM +0530, 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 6.4-rc3. > Tested on Juno with some hacked up UEFI f/w. Tested-by: Sudeep Holla <sudeep.holla@arm.com>
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-rc3. 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: https://lore.kernel.org/all/20230519052149.1367814-1-anshuman.khandual@arm.com/ - Returned from etm4_check_arch_features() for non iomem devices - Renamed ETM_DEVTYPE_ETMv4x_ARCH as CS_DEVTYPE_PE_TRACE - Renamed is_etm4x_devtype() as is_devtype_cpu_trace() - Added a patch to ignore the absence of graph connections Changes in V2: https://lore.kernel.org/all/20230327050537.30861-1-anshuman.khandual@arm.com/ - 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: https://lore.kernel.org/all/20230317030501.1811905-1-anshuman.khandual@arm.com/ Cc: Ganapatrao Kulkarni <gankulkarni@os.amperecomputing.com> Cc: Steve Clevenger <scclevenger@os.amperecomputing.com> Cc: Rob Herring <robh+dt@kernel.org> Cc: Frank Rowand <frowand.list@gmail.com> Cc: Russell King (Oracle) <linux@armlinux.org.uk> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: "Rafael J. Wysocki" <rafael@kernel.org> Cc: Len Brown <lenb@kernel.org> Cc: Sudeep Holla <sudeep.holla@arm.com> Cc: Lorenzo Pieralisi <lpieralisi@kernel.org> Cc: Mathieu Poirier <mathieu.poirier@linaro.org> Cc: Suzuki K Poulose <suzuki.poulose@arm.com> Cc: Mike Leach <mike.leach@linaro.org> Cc: Leo Yan <leo.yan@linaro.org> Cc: devicetree@vger.kernel.org Cc: linux-acpi@vger.kernel.org Cc: coresight@lists.linaro.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org 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(-)