[PATCH v2 0/2] Add dynamic CSU register sysfs interface

[Michal Simek]

On 5/20/26 11:36, Ronak Jain wrote:
> This patch series adds support for exposing CSU registers through a
> sysfs interface. The implementation uses dynamic discovery via the
> PM_QUERY_DATA firmware API to determine available registers at
> runtime, making the interface flexible and maintainable without
> requiring kernel changes when firmware capabilities evolve.
> 
> Background:
> 
> The ZynqMP platform has several CSU registers that are useful for
> system configuration and debugging. Previously, accessing these
> registers required direct memory access or custom tools. This series
> provides a standardized sysfs interface that leverages existing
> firmware APIs for secure access.
> 
> Key Features:
> 
> - Dynamic register discovery using PM_QUERY_DATA API
>    * PM_QID_GET_NODE_COUNT: Query number of available registers
>    * PM_QID_GET_NODE_NAME: Query register names by index
> - Automatic sysfs attribute creation under csu_registers/ group
> - Read operations via existing IOCTL_READ_REG firmware API
> - Write operations via existing IOCTL_MASK_WRITE_REG firmware API
> - Firmware-enforced access control for read-only registers
> 
> Currently Supported Registers:
> 
> - multiboot (CSU_MULTI_BOOT): Boot mode configuration
> - idcode (CSU_IDCODE): Device identification (read-only)
> - pcap-status (CSU_PCAP_STATUS): PCAP status (read-only)
> 
> The sysfs interface is available at:
>    /sys/devices/platform/firmware:zynqmp-firmware/csu_registers/
> 
> Usage Examples:
> 
> Reading a register:
>    # cat /sys/devices/platform/firmware:zynqmp-firmware/csu_registers/idcode
> 
> Writing a register (mask and value in hex):
>    # echo "0xFFFFFFFF 0x0" > /sys/devices/platform/firmware:zynqmp-firmware/csu_registers/multiboot
> 
> 
> Testing:
> 
> - Verified register read operations return correct values
> - Verified write operations update registers correctly
> - Verified read-only registers reject write attempts
> - Verified dynamic discovery works with different firmware versions
> 
> Changes in v2:
> Patch #1
> - Update date
> 
> Patch #2:
> - Removed unused csu_reg_count field from struct zynqmp_csu_data and
>    its kernel-doc entry.
> - Added explicit devm_kfree() on the csu_regs and attrs allocation
>    failure paths, plus on devm_device_add_group() failure — keeps the
>    footprint minimal when CSU is optional.
> - Expanded the 0644 sysfs-mode inline comment into a block comment
>    explaining the firmware-enforced access-control limitation.Also,
>    update the commit message accordingly.
> - Added zynqmp_pm_is_function_supported check for PM_QID_GET_NODE_NAME
>    ID to mirror the PM_QID_GET_NODE_COUNT verification.
> 
> Ronak Jain (2):
>    Documentation: ABI: add sysfs interface for ZynqMP CSU registers
>    firmware: zynqmp: Add dynamic CSU register discovery and sysfs
>      interface
> 
>   .../ABI/stable/sysfs-driver-firmware-zynqmp   |  33 +++
>   MAINTAINERS                                   |  10 +
>   drivers/firmware/xilinx/Makefile              |   2 +-
>   drivers/firmware/xilinx/zynqmp-csu-reg.c      | 258 ++++++++++++++++++
>   drivers/firmware/xilinx/zynqmp-csu-reg.h      |  18 ++
>   drivers/firmware/xilinx/zynqmp.c              |   6 +
>   include/linux/firmware/xlnx-zynqmp.h          |   4 +-
>   7 files changed, 329 insertions(+), 2 deletions(-)
>   create mode 100644 drivers/firmware/xilinx/zynqmp-csu-reg.c
>   create mode 100644 drivers/firmware/xilinx/zynqmp-csu-reg.h
> 

Applied with kernel version changed to 7.2.

Thanks,
Michal