bus: mhi: Add memory barrier before ringing doorbell

We need to be sure that MHI data structure configuration such has
transfer ring element and channel context (wp pointer) have been
propagated before ringing the doorbell.

Note: Not necessary if doorbell is MMIO (writeX)

Signed-off-by: Loic Poulain <loic.poulain@linaro.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index 4eb93d8bea1d..e11f716c56e7 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -101,6 +101,10 @@ void mhi_ring_cmd_db(struct mhi_controller *mhi_cntrl, struct mhi_cmd *mhi_cmd)
 
 	db = ring->iommu_base + (ring->wp - ring->base);
 	*ring->ctxt_wp = db;
+
+	/* Ensure MHI data structures update before ringing the doorbell. */
+	dma_wmb();
+
 	mhi_write_db(mhi_cntrl, ring->db_addr, db);
 }
 
@@ -112,6 +116,10 @@ void mhi_ring_chan_db(struct mhi_controller *mhi_cntrl,
 
 	db = ring->iommu_base + (ring->wp - ring->base);
 	*ring->ctxt_wp = db;
+
+	/* Ensure MHI data structures update before ringing the doorbell. */
+	dma_wmb();
+
 	mhi_chan->db_cfg.process_db(mhi_cntrl, &mhi_chan->db_cfg,
 				    ring->db_addr, db);
 }