[PATCH V2 04/16] i3c: mipi-i3c-hci: Wait for DMA ring restart to complete

Adrian Hunter
2026-04-21T17:54:59Z

Although hci_dma_dequeue_xfer() is serialized against itself via
control_mutex, this does not guarantee that a DMA ring restart
triggered by a previous invocation has fully completed.

When the function is called again in rapid succession, the DMA ring may
still be transitioning back to the running state, which may confound or
disrupt further state changes.

Address this by waiting for the DMA ring restart to complete before
continuing.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---

Changes in V2:

None

drivers/i3c/master/mipi-i3c-hci/dma.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/i3c/master/mipi-i3c-hci/dma.c b/drivers/i3c/master/mipi-i3c-hci/dma.c
index 314635e6e190..28614fdbf558 100644
--- a/drivers/i3c/master/mipi-i3c-hci/dma.c
+++ b/drivers/i3c/master/mipi-i3c-hci/dma.c
@@ -617,6 +617,7 @@ static bool hci_dma_dequeue_xfer(struct i3c_hci *hci,
}

/* restart the ring */
+ reinit_completion(&rh->op_done);
mipi_i3c_hci_resume(hci);
rh_reg_write(RING_CONTROL, RING_CTRL_ENABLE);
rh_reg_write(RING_CONTROL, RING_CTRL_ENABLE | RING_CTRL_RUN_STOP);
@@ -625,6 +626,8 @@ static bool hci_dma_dequeue_xfer(struct i3c_hci *hci,

spin_unlock_irq(&hci->lock);

+ wait_for_completion_timeout(&rh->op_done, HZ);
+
return did_unqueue;