[PATCH v4 0/7] qcom: Add NVMEM bitfield support and reboot‑mode integration

[Aswin Murugan]

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>

---
Changes in v4:
1. NVMEM Core (drivers/misc/nvmem.c, include/nvmem.h):

- Explicitly interpret hardware bytes as little-endian for bitfield operations
  to ensure consistent behavior across architectures
- Removed const pointer write violation in nvmem_cell_write()
- Replaced unsafe bit shift expressions with GENMASK() macro to avoid undefined
  behavior when nbits == 32
- Consolidated size validation logic for clarity
- Enhanced documentation with explicit @cell parameters (offset, size, nbits, bit_offset)
- Changed magic number 4 to sizeof(u32) for consistency

2. QCOM SPMI SDAM Driver (drivers/misc/qcom-spmi-sdam.c):

- Fixed address type mismatch using local fdt_addr_t variable to prevent silent
  comparison failure on 64-bit platforms
- Removed non-standard qcom,sdam-size property and hardcoded SDAM size to 0x100
  bytes per hardware specification
- Changed dev_info() to dev_dbg() to reduce boot log verbosity

3. Board Integration (arch/arm/mach-snapdragon/board.c):

- Simplified conditional compilation with runtime check instead of #ifdef wrapper
- Adopted logging subsystem (log_info/log_warning) consistent with rest of file
- Added error handling for fastboot command failures

4. Device Tree (arch/arm/dts/qcs615-ride-u-boot.dtsi):

- Changed bits property to decimal format (bits = <1 7>) for consistency with
  upstream conventions

5. Test Coverage (test/dm/nvmem.c):

- Created separate test file for NVMEM bitfield tests
- Fixed test to use correct I2C EEPROM functions
- Corrected test expectation bug for 4-byte cell with 12-bit field spanning byte boundary
- Added comprehensive error validation tests

Link to v3:
https://lore.kernel.org/u-boot/20260330171419.1117817-1-aswin.murugan@oss.qualcomm.com/

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     |  59 ++++++--
 arch/sandbox/dts/test.dts            |  12 ++
 configs/qcom_defconfig               |   3 +
 drivers/misc/Kconfig                 |   8 ++
 drivers/misc/Makefile                |   1 +
 drivers/misc/nvmem.c                 | 166 +++++++++++++++++++---
 drivers/misc/qcom-spmi-sdam.c        | 202 +++++++++++++++++++++++++++
 include/nvmem.h                      |  40 +++++-
 test/dm/Makefile                     |   1 +
 test/dm/nvmem.c                      | 160 +++++++++++++++++++++
 11 files changed, 641 insertions(+), 37 deletions(-)
 create mode 100644 drivers/misc/qcom-spmi-sdam.c
 create mode 100644 test/dm/nvmem.c

-- 
2.34.1