[PATCH v5 25/25] soundwire: amd: fix shared-register RMW race in amd_sdw_host_wake_enable()

[Vijendar Mukunda]

ACP_EXTERNAL_INTR_CNTL(ACP_SDW1) holds host-wake interrupt bits for
both instances (BIT(22) for SDW0, BIT(23) for SDW1).
amd_sdw_host_wake_enable() performed a read-modify-write sequence on
this shared register without holding acp_sdw_lock, leaving it open to
a lost-update race when SDW0 and SDW1 execute concurrent PM transitions.

Acquire acp_sdw_lock around the read-modify-write sequence.

Fixes: 3df75289ddc2 ("soundwire: amd: add soundwire host wake interrupt enable/disable sequence")
Signed-off-by: Vijendar Mukunda <Vijendar.Mukunda@xxxxxxx>
---
 drivers/soundwire/amd_manager.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/soundwire/amd_manager.c b/drivers/soundwire/amd_manager.c
index 495f0607bb0b..2c52fd181e3c 100644
--- a/drivers/soundwire/amd_manager.c
+++ b/drivers/soundwire/amd_manager.c
@@ -320,12 +320,14 @@ static int amd_sdw_host_wake_enable(struct amd_sdw_manager *amd_manager, bool en
 		return -EINVAL;
 	}
 
+	mutex_lock(amd_manager->acp_sdw_lock);
 	intr_cntl1 = readl(amd_manager->acp_mmio + ACP_EXTERNAL_INTR_CNTL(ACP_SDW1));
 	if (enable)
 		intr_cntl1 |= sdw_host_wake_irq_mask;
 	else
 		intr_cntl1 &= ~sdw_host_wake_irq_mask;
 	writel(intr_cntl1, amd_manager->acp_mmio + ACP_EXTERNAL_INTR_CNTL(ACP_SDW1));
+	mutex_unlock(amd_manager->acp_sdw_lock);
 	return 0;
 }
 
-- 
2.53.0