Re: [PATCH v3 0/7] qcom: Add NVMEM bitfield support and reboot‑mode integration

[Heinrich Schuchardt]

Am 30. März 2026 19:14:12 MESZ schrieb Aswin Murugan <aswin.murugan at oss.qualcomm.com>:
>This patch series introduces bit-level granularity to NVMEM cells and
>adds complete reboot-mode support for Qualcomm platforms that store
>reboot reasons in PMIC registers.
>
>Qualcomm SoCs rely on PMIC-backed reboot reason storage to implement
>features like "reboot bootloader" for entering fastboot mode. However,
>these PMIC registers often pack multiple fields into a single byte,
>requiring fine-grained bit access that the current NVMEM subsystem does
>not support.
>
>In addition, PMIC generations differ in how reboot-related data is
>stored: older PMICs use PON (Power On) registers, while newer ones
>provide SDAM regions. This series introduces a unified, NVMEM-based
>approach that works seamlessly across both architectures.
>
>This version also integrates reboot-mode handling into Qualcomm board
>initialization, enabling automatic fastboot entry when the reboot reason
>indicates bootloader mode.
>
>Signed-off-by: Aswin Murugan <aswin.murugan at oss.qualcomm.com>

It is unclear to me how endianness is handled in bitfields. Do you assume low-endianness or do you consider the system endianness? Please, ensure that the tests are executed on both low- and big-endian systems.

Best regards

Heinrich


>
>---
>Changes in v3:
>1. Simplified bit field handling to maximum u32 size (32 bits).
>2. Enforced strict size matching (size == cell->size) when nbits == 0.
>3. Enhanced test function for NVMEM read & write
>4. Updated NVMEM API documentation
>
>Link to V2:
>https://lore.kernel.org/all/20260213112717.1256823-1-aswin.murugan@oss.qualcomm.com/
>
>Changes in v2:
>1. Replaced custom reboot reason handling with the standard U-Boot
>   reboot-mode subsystem, per review feedback.
>2. Added bit-field support to the NVMEM core using the new "bits"
>   property.
>3. Introduced the Qualcomm SPMI SDAM driver for unified PMIC storage
>   access.
>4. Updated the reboot-mode driver to support variable-sized NVMEM cells.
>5. Added device tree configuration for the QCS615 RIDE board.
>6. Enabled reboot-mode in qcom_defconfig.
>7. Integrated reboot-mode detection into Snapdragon board
>   initialization:
>   - Added qcom_handle_reboot_mode() in board_late_init() to enable
>     automatic fastboot entry on "reboot bootloader".
>
>Link to v1:
>https://lore.kernel.org/all/20260108065533.1143179-1-aswin.murugan@oss.qualcomm.com/
>---
>
>
>Aswin Murugan (7):
>  misc: Add support for bit fields in NVMEM cells
>  misc: qcom: Add Qualcomm SPMI SDAM NVMEM driver
>  mach-snapdragon: Integrate reboot-mode handling
>  dts: qcs615-ride-u-boot.dtsi: Add reboot-mode support
>  qcom_defconfig: Enable reboot-mode support in qcom_defconfig
>  test: dm: add comprehensive tests for NVMEM bit field operations
>  misc: update API documentation for bit field support in NVMEM
>
> arch/arm/dts/qcs615-ride-u-boot.dtsi |  26 ++++
> arch/arm/mach-snapdragon/board.c     |  56 ++++++--
> arch/sandbox/dts/test.dts            |  12 ++
> configs/qcom_defconfig               |   3 +
> drivers/misc/Kconfig                 |   8 ++
> drivers/misc/Makefile                |   1 +
> drivers/misc/nvmem.c                 | 159 ++++++++++++++++++---
> drivers/misc/qcom-spmi-sdam.c        | 200 +++++++++++++++++++++++++++
> include/nvmem.h                      |  28 +++-
> test/dm/reboot-mode.c                | 137 ++++++++++++++++++
> 10 files changed, 595 insertions(+), 35 deletions(-)
> create mode 100644 drivers/misc/qcom-spmi-sdam.c
>