In _sdw_prepare_stream(), the restore_params: error path restores state only for the last bus iterated. In multi-link streams, earlier buses' params (and the new bpt_hstop added by PR #5604) are left partially modified after failures from do_bank_switch() or port-prepare — inconsistent state that affects subsequent compute_params() calls.

Changes

• include/linux/soundwire/sdw.h: Add bpt_hstop to sdw_bus — the per-bus column-stop index for the BPT DP0 port referenced by the review comment.

• drivers/soundwire/bus.h: Add saved_params and saved_bpt_hstop to sdw_master_runtime for per-bus backup storage without dynamic allocation.

• drivers/soundwire/stream.c: Restructure _sdw_prepare_stream() error recovery:

  • Add a pre-save pass over stream->master_list before any modifications, snapshotting each bus's params and bpt_hstop into the corresponding m_rt.
  • Rewrite restore_params: to iterate all masters and restore from per-m_rt snapshots, ensuring every bus is rolled back regardless of where the failure occurs.

/* before: only last bus restored */
restore_params:
    memcpy(&bus->params, &params, sizeof(params));
    return ret;

/* after: all buses restored */
restore_params:
    list_for_each_entry(m_rt, &stream->master_list, stream_node) {
        bus = m_rt->bus;
        memcpy(&bus->params, &m_rt->saved_params, sizeof(bus->params));
        bus->bpt_hstop = m_rt->saved_bpt_hstop;
    }
    return ret;