[PATCH v2 3/8] thunderbolt: Use 32-bit writes when writing ring producer/consumer

[Mika Westerberg]

The register access should be using 32-bit reads/writes according to the
datasheet. With the previous generation hardware 16-bit writes have been
working but starting with ICL this is not the case anymore so fix
producer/consumer register update to use correct width register address.

Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Reviewed-by: Yehezkel Bernat <YehezkelShB@xxxxxxxxx>
---
 drivers/thunderbolt/nhi.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/drivers/thunderbolt/nhi.c b/drivers/thunderbolt/nhi.c
index 27fbe62c7ddd..9c782706e652 100644
--- a/drivers/thunderbolt/nhi.c
+++ b/drivers/thunderbolt/nhi.c
@@ -143,9 +143,20 @@ static void __iomem *ring_options_base(struct tb_ring *ring)
 	return io;
 }
 
-static void ring_iowrite16desc(struct tb_ring *ring, u32 value, u32 offset)
+static void ring_iowrite_cons(struct tb_ring *ring, u16 cons)
 {
-	iowrite16(value, ring_desc_base(ring) + offset);
+	/*
+	 * The other 16-bits in the register is read-only and writes to it
+	 * are ignored by the hardware so we can save one ioread32() by
+	 * filling the read-only bits with zeroes.
+	 */
+	iowrite32(cons, ring_desc_base(ring) + 8);
+}
+
+static void ring_iowrite_prod(struct tb_ring *ring, u16 prod)
+{
+	/* See ring_iowrite_cons() above for explanation */
+	iowrite32(prod << 16, ring_desc_base(ring) + 8);
 }
 
 static void ring_iowrite32desc(struct tb_ring *ring, u32 value, u32 offset)
@@ -197,7 +208,10 @@ static void ring_write_descriptors(struct tb_ring *ring)
 			descriptor->sof = frame->sof;
 		}
 		ring->head = (ring->head + 1) % ring->size;
-		ring_iowrite16desc(ring, ring->head, ring->is_tx ? 10 : 8);
+		if (ring->is_tx)
+			ring_iowrite_prod(ring, ring->head);
+		else
+			ring_iowrite_cons(ring, ring->head);
 	}
 }
 
@@ -662,7 +676,7 @@ void tb_ring_stop(struct tb_ring *ring)
 
 	ring_iowrite32options(ring, 0, 0);
 	ring_iowrite64desc(ring, 0, 0);
-	ring_iowrite16desc(ring, 0, ring->is_tx ? 10 : 8);
+	ring_iowrite32desc(ring, 0, 8);
 	ring_iowrite32desc(ring, 0, 12);
 	ring->head = 0;
 	ring->tail = 0;
-- 
2.20.1