The Aspeed MDIO controller may return incorrect data when a read operation follows immediately after a write. Due to a controller bug, the subsequent read can latch stale data, causing the polling logic to terminate earlier than expected. To work around this hardware issue, insert a dummy read after each write operation. This ensures that the next actual read returns the correct data and prevents premature polling exit. This workaround has been verified to stabilize MDIO transactions on affected Aspeed platforms. Signed-off-by: Jacky Chou --- drivers/net/mdio/mdio-aspeed.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/net/mdio/mdio-aspeed.c b/drivers/net/mdio/mdio-aspeed.c index e55be6dc9ae7..00e61b922876 100644 --- a/drivers/net/mdio/mdio-aspeed.c +++ b/drivers/net/mdio/mdio-aspeed.c @@ -62,6 +62,12 @@ static int aspeed_mdio_op(struct mii_bus *bus, u8 st, u8 op, u8 phyad, u8 regad, | FIELD_PREP(ASPEED_MDIO_DATA_MIIRDATA, data); iowrite32(ctrl, ctx->base + ASPEED_MDIO_CTRL); + /* Workaround for read-after-write issue. + * The controller may return stale data if a read follows immediately + * after a write. A dummy read forces the hardware to update its + * internal state, ensuring that the next real read returns correct data. + */ + (void)ioread32(ctx->base + ASPEED_MDIO_CTRL); return readl_poll_timeout(ctx->base + ASPEED_MDIO_CTRL, ctrl, !(ctrl & ASPEED_MDIO_CTRL_FIRE), --- base-commit: 8f7aa3d3c7323f4ca2768a9e74ebbe359c4f8f88 change-id: 20251205-aspeed_mdio_add_dummy_read-d58d1e49412d Best regards, -- Jacky Chou