Messages in this thread |  | | From | Kishore Batta <> | | Subject | [PATCH v3 0/9] Qualcomm Sahara protocol enhancements. | | Date | Tue, 10 Mar 2026 12:51:57 +0530 |
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Hi All,
This series reworks the Sahara protocol driver to make it reusable for multiple MHI based devices and adds support for capturing, restoring and exposing DDR training data using the Sahara command mode.
The Sahara protocol is transported over the MHI bus and is used by multiple flashless devices to transfer firmware images, retrieve memory dumps and exchange command mode data during early boot. However, the current implementation lives under the QAIC accelerator driver and contains device-specific assumptions that limit reuse.
Some MHI devices (for example, QDU100) expose the sahara protocol directly on a "SAHARA" MHI channel and rely on command mode to exchange DDR training data with the host. The existing driver does not bind to such devices and ignores Sahara command mode packets, causing training data to be dropped.
This series addresses these issues by relocating the Sahara driver to the MHI subsystem, centralizing device specific configuration and adding command mode handling for DDR training data.
Overview of the changes in this series - 1. Move Sahara under the MHI subsystem: a. Relocate the sahara protocol driver from QAIC accelerator tree to drivers/bus/mhi. b. Register Sahara as an independent MHI protocol driver.
2. Generalize device matching and configuration a. Allow the driver to bind to devices exposing the protocol on a SAHARA MHI channel. b. Centralize firmware image table selection at probe time using a variant table, instead of scattered conditionals. c. Preserve existing behavior on AIC devices.
3. Add QDU100 firmware image table support a. Add a QDU100 image table and select it based on the matched MHI channel. b. No separate client driver or registration mechanism is required.
4. Add Sahara command mode support for DDR training. a. Handle command mode packets(CMD_READY, EXECUTE, EXECUTE_DATA). b. Query supported commands and retrieve DDR training data from the device. c. Allocate receive buffers based on the reported payload size and copy raw data from the MHI DL. d. Store training data in controller-scoped memory using devres so it survives sahara channel teardown.
5. Expose DDR training data to userspace a. Add a read-only binary sysfs attribute under the MHI controller device. b. The attribute reads directly from controller-scoped storage and remains available after the Sahara channel device is removed. c. Cleanup is handled automatically via device-managed resources.
6. Document the sysfs ABI a. Add ABI documentation describing the DDR training data sysfs node.
Signed-off-by: Kishore Batta <kishore.batta@oss.qualcomm.com> --- Changes in v3: - Dropped the explicit image table entry for the boot critical image ID and added a generic image ID based firmware lookup fallback. - Link to v2: https://lore.kernel.org/r/20260307-sahara_protocol_new_v2-v2-0-29dc748b5e9c@oss.qualcomm.com
Changes in v2: - Rebased onto latest linux-next tip. - Reworked commit messages to clearly start with the problem being solved and end with a technical description of the change. - Moved the Sahara driver to drivers/bus/mhi instead of drivers/soc/qcom, reflecting that its an MHI protocol driver rather than a SoC specific driver. - Removed client side image table registration and consolidated firmware selection directly in the sahara driver using a probe-time variant mechanism. - Ensured each patch is self-contained and does not break the build or runtime behavior at any intermediate point. - Simplified state handling and lifetime management to avoid duplicated state tracking and ad-hoc cleanup. - Updated sysfs handling to use controller-scoped devres and avoid one-shot reads or manual teardown. - Link to v1: https://lore.kernel.org/r/20250825101926.2160554-1-kishore.batta@oss.qualcomm.com
--- Kishore Batta (9): Add documentation for Sahara protocol. bus: mhi: Move sahara protocol driver under drivers/bus/mhi bus: mhi: Match devices exposing the protocol on the SAHARA channel bus: mhi: Centralize firmware image table selection at probe time bus: mhi: Add QDU100 variant and image_id firmware fallback bus: mhi: Load DDR training data using per-device serial number bus: mhi: Capture DDR training data using command mode bus: mhi: Expose DDR training data via controller sysfs Documentation: ABI: Add sysfs ABI documentation for DDR training data
.../ABI/testing/sysfs-bus-mhi-ddr_training_data | 19 + Documentation/sahara/index.rst | 14 + Documentation/sahara/sahara_protocol.rst | 1241 ++++++++++++++++++++ drivers/accel/qaic/Kconfig | 1 + drivers/accel/qaic/Makefile | 3 +- drivers/accel/qaic/qaic_drv.c | 11 +- drivers/bus/mhi/Kconfig | 1 + drivers/bus/mhi/Makefile | 3 + drivers/bus/mhi/sahara/Kconfig | 18 + drivers/bus/mhi/sahara/Makefile | 2 + drivers/{accel/qaic => bus/mhi/sahara}/sahara.c | 601 +++++++++- {drivers/accel/qaic => include/linux}/sahara.h | 0 12 files changed, 1869 insertions(+), 45 deletions(-) --- base-commit: a0ae2a256046c0c5d3778d1a194ff2e171f16e5f change-id: 20260307-sahara_protocol_new_v2-662854773cf7
Best regards, -- Kishore Batta <kishore.batta@oss.qualcomm.com>
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