UFS devices have a built-in A/B boot mechanism implemented via the "boot well known logical unit" (boot W-LU). This works by marking two of the provisioned LUs with a flag in their unit configuration descriptor, and setting the active boot LU in the whole device's attributes. The device then exposes a special logical unit 0xb0 (the boot W-LU) which is internally aliased to the currently active boot LU (if one is set). It allows reading and writing directly through the 0xb0 LU, but doesn't expose the LU geometry, so it is not quite a full-fledged block device.
Given that the normal use of this mechanism is for symmetric A/B boot, real world scenarios will usually have both W-LU-A and W-LU-B provisioned with identical geometry, so the geometry for the boot W-LU can be inferred from the active boot LU, while its special 0xb0 LUN can still be used for reads and writes to have the device itself abstract away the actual request routing, even when the active boot LU is changed. This series adds support for loading the U-Boot proper from the boot W-LU, allowing to use the native A/B boot mechanism without the need to hardcode the "real" LUN in the SPL configuration. Two classes of prerequisites are handled by the first half of this series before the enablement itself: 1. The SCSI core needs to learn to repeat inquiry requests when they return with a transitive non-zero status, such as the UNIT ATTENTION condition, which the W-LU returns when it's first talked to and which is not an error (patches 1-2) 2. The scan itself needs to learn to look beyond the normal LUN range when the implementation supports W-LUs, as they are numbered above 0x80, and "borrow" the geometry from the physical LU the W-LU is aliased to (patches 3-5) Patches 6-10 are the enablement itself, split by logical parts. CI passes all green: https://git.u-boot-project.org/u-boot/contributors/alchark/u-boot/-/pipelines/1175 Signed-off-by: Alexey Charkov <[email protected]> --- Alexey Charkov (10): ufs: hand sense data to the SCSI layer scsi: repeat an INQUIRY that a unit attention interrupted scsi: size a well known unit from the unit it stands in for scsi: allow a controller to declare well known logical units scsi: add a lookup by target and LUN part: name the well known logical unit device type ufs: define the well known logical unit ids ufs: report the logical unit the boot W-LU presents ufs: expose the boot logical unit as a block device spl: ufs: allow loading U-Boot from the boot logical unit common/spl/Kconfig | 30 +++++++++++++- common/spl/spl_ufs.c | 18 +++++++-- disk/part.c | 3 ++ drivers/scsi/scsi-uclass.c | 32 +++++++++++++++ drivers/scsi/scsi.c | 98 ++++++++++++++++++++++++++++++++++++++++------ drivers/ufs/ufs-uclass.c | 76 ++++++++++++++++++++++++++++++++++- drivers/ufs/ufs.h | 28 +++++++++++++ include/part.h | 1 + include/scsi.h | 45 +++++++++++++++++++++ include/ufs.h | 8 ++++ 10 files changed, 321 insertions(+), 18 deletions(-) --- base-commit: 1c5004ffc5e3f000eca6cada32af7c83bd925c2b change-id: 20260903-ufs-spl-boot-wlu-10ce2e14bf15 Best regards, -- Alexey Charkov <[email protected]>
