soundwire: Fix bandwidth leak in multi-link aggregation failure by bardliao · Pull Request #5972 · thesofproject/linux

bardliao · 2026-10-13T03:17:44Z

When preparing a multi-link aggregation stream, a failure on a subsequent link during _sdw_prepare_stream() causes the stream preparation to fail. However, the bandwidth allocated on the preceding successful links is never released, causing a cumulative bandwidth leak.
Fix this by restoring the parameters for all buses.

lane_used_bandwidth is used to store the used bandwidth for each lane. When we restore the bus->params, the lane_used_bandwidth value will not be restored in current code. Move it to sdw_bus_params to fix the issue. Fixes: 366fd59 ("soundwire: generic_bandwidth_allocation: add lane in sdw_group_params") Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>

Copilot

🟡 Changes recommended

The rollback path can program the wrong bus and perform invalid or unnecessary bank switches.

1 open finding

Restore post-switch bank selectors before rolling back parameters · New

What changed in this PR

Fixes SoundWire bandwidth leakage when multi-link stream preparation fails.

Changes:

Includes per-lane bandwidth in restorable bus parameters.
Snapshots each master’s parameters before preparation.
Adds multi-link rollback and bank restoration logic.

File	Description
`include/linux/soundwire/sdw.h`	Moves lane bandwidth into bus parameters.
`drivers/soundwire/stream.c`	Adds snapshot and rollback handling.
`drivers/soundwire/generic_bandwidth_allocation.c`	Uses relocated lane bandwidth state.
`drivers/soundwire/bus.h`	Stores parameter snapshots per master runtime.

🧠 Review effort: Balanced

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Copilot

🟡 Changes recommended

The rollback can program or switch incorrect buses and corrupt bank state.

2 open findings

1 resolved since last review

Restore post-switch bank selectors before rolling back parameters

🧠 Review effort: Balanced

Copilot

🟡 Changes recommended

Rollback can program the wrong bus and perform unsafe bank switches on failure paths.

2 open findings

2 resolved since last review

🧠 Review effort: Balanced

+	ret1 = do_bank_switch(stream);
+	if (ret1 < 0)
+		pr_err("%s: do_bank_switch failed: %d after restoring params\n", __func__, ret1);


Copilot

🟡 Changes recommended

Rollback targets the wrong bus and leaves successfully prepared ports configured.

3 open findings

🧠 Review effort: Balanced

 			dev_err(bus->dev, "Prepare port(s) failed ret = %d\n",
 				ret);
-			goto restore_params;
+			goto revert_bank;


Copilot

🟡 Changes recommended

Rollback can program stale per-port configuration against restored bus parameters.

3 open findings

1 resolved since last review

Use the current bus when restoring each link

🧠 Review effort: Balanced

+		m_rt->bus->params = m_rt->params_backup;
+		ret1 = sdw_program_params(m_rt->bus, true);


The bank values are already switched in do_bank_switch(), so we need to switch curr_bank and next_bank back to reflect the actual bank. Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>

Restoring bus->params alone leaves the hardware programmed with the values from the failed stream preparation. Reprogram the restored params and switch banks so software and hardware use the same bus configuration. Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>

When preparing a multi-link aggregation stream, a failure on a subsequent link during _sdw_prepare_stream() causes the stream preparation to fail. However, the bandwidth allocated on the preceding successful links is never released, causing a cumulative bandwidth leak. Fix this by saving a snapshot of each bus's parameters before making any modifications. In case of failure, we iterate through the stream's master list and restore each bus to its original parameter state, ensuring an atomic rollback and preventing any bandwidth leaks. Signed-off-by: David Lin <david.lin@intel.com>

Copilot

🟡 Changes recommended

A rollback programming failure can leave later buses’ bandwidth allocations unrestored.

4 open findings

🧠 Review effort: Balanced

+	list_for_each_entry(m_rt, &stream->master_list, stream_node) {
+		/*
+		 * Revert all masters to their snapshotted original parameters.
+		 * Any master that was not modified will safely revert to its own original state.
+		 */
+		m_rt->bus->params = m_rt->params_backup;
+		ret1 = sdw_program_params(m_rt->bus, true);
+		if (ret1 < 0) {
+			dev_err(m_rt->bus->dev,
+				"Program params failed: %d after restoring params\n",
+				ret1);
+			/* No need to do bank switch and return the original error code */
+			return ret;
+		}
+	}


bardliao requested review from davidlin923, plbossart and ujfalusi and a balanced review from Copilot October 13, 2026 03:17

bardliao requested review from jack-cy-yu, oder-chiou and shumingfan as code owners October 13, 2026 03:17

Copilot started reviewing on behalf of bardliao October 13, 2026 03:18 View session

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Comment thread drivers/soundwire/stream.c Outdated

Copilot AI balanced review requested due to automatic review settings October 13, 2026 03:23

bardliao force-pushed the for-sdw-bandwidth-leak branch from 8f71e3c to 7f32ec1 Compare October 13, 2026 03:23

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Comment thread drivers/soundwire/stream.c Outdated

Comment thread drivers/soundwire/stream.c Outdated

bardliao force-pushed the for-sdw-bandwidth-leak branch from 7f32ec1 to b6fad93 Compare October 13, 2026 03:35

Copilot AI balanced review requested due to automatic review settings October 13, 2026 03:35

Copilot started reviewing on behalf of bardliao October 13, 2026 03:35 View session

bardliao force-pushed the for-sdw-bandwidth-leak branch from b6fad93 to dc95264 Compare October 13, 2026 03:36

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Comment thread drivers/soundwire/stream.c Outdated

Comment thread drivers/soundwire/stream.c

Comment on lines +1579 to +1581

ret1 = do_bank_switch(stream);

if (ret1 < 0)

pr_err("%s: do_bank_switch failed: %d after restoring params\n", __func__, ret1);

Copilot AI balanced review requested due to automatic review settings October 13, 2026 03:39

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Comment thread drivers/soundwire/stream.c

dev_err(bus->dev, "Prepare port(s) failed ret = %d\n",

ret);

goto restore_params;

goto revert_bank;

Copilot AI balanced review requested due to automatic review settings October 13, 2026 03:51

bardliao force-pushed the for-sdw-bandwidth-leak branch from dc95264 to 18d020e Compare October 13, 2026 03:51

Copilot started reviewing on behalf of bardliao October 13, 2026 03:51 View session

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Comment thread drivers/soundwire/stream.c

Comment on lines +1571 to +1572

m_rt->bus->params = m_rt->params_backup;

ret1 = sdw_program_params(m_rt->bus, true);

bardliao added 3 commits October 13, 2026 12:36

soundwire: revert bank if failed after bank switch

915cdac

The bank values are already switched in do_bank_switch(), so we need to switch curr_bank and next_bank back to reflect the actual bank. Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>

bardliao force-pushed the for-sdw-bandwidth-leak branch from 18d020e to a90934b Compare October 13, 2026 04:38

Copilot AI balanced review requested due to automatic review settings October 13, 2026 04:38

Copilot started reviewing on behalf of bardliao October 13, 2026 04:38 View session

Copilot AI reviewed Oct 13, 2026

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bardliao closed this Oct 13, 2026

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soundwire: Fix bandwidth leak in multi-link aggregation failure - #5972

soundwire: Fix bandwidth leak in multi-link aggregation failure#5972
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		m_rt->bus->params = m_rt->params_backup;
		ret1 = sdw_program_params(m_rt->bus, true);

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