linux-kernel - [PATCH net v2] net: mdio: aspeed: Add dummy read for fire control

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Message-ID: <20241119095141.1236414-1-jacky_chou@aspeedtech.com>
Date: Tue, 19 Nov 2024 17:51:41 +0800
From: Jacky Chou <jacky_chou@...eedtech.com>
To: <andrew@...n.ch>, <hkallweit1@...il.com>, <linux@...linux.org.uk>,
	<davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
	<pabeni@...hat.com>, <joel@....id.au>, <andrew@...econstruct.com.au>,
	<f.fainelli@...il.com>, <netdev@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-aspeed@...ts.ozlabs.org>,
	<linux-kernel@...r.kernel.org>
CC: <jacky_chou@...eedtech.com>
Subject: [PATCH net v2] net: mdio: aspeed: Add dummy read for fire control

When the command bus is sometimes busy, it may cause the command is not
arrived to MDIO controller immediately. On software, the driver issues a
write command to the command bus does not wait for command complete and
it returned back to code immediately. But a read command will wait for
the data back, once a read command was back indicates the previous write
command had arrived to controller.
Add a dummy read to ensure triggering mdio controller before starting
polling the status of mdio controller to avoid polling unexpected timeout.

Fixes: a9770eac511a ("net: mdio: Move MDIO drivers into a new subdirectory")
Signed-off-by: Jacky Chou <jacky_chou@...eedtech.com>
---
 drivers/net/mdio/mdio-aspeed.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/mdio/mdio-aspeed.c b/drivers/net/mdio/mdio-aspeed.c
index c2170650415c..373902d33b96 100644
--- a/drivers/net/mdio/mdio-aspeed.c
+++ b/drivers/net/mdio/mdio-aspeed.c
@@ -62,6 +62,8 @@ 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);
+	/* Add dummy read to ensure triggering mdio controller */
+	(void)ioread32(ctx->base + ASPEED_MDIO_CTRL);
 
 	return readl_poll_timeout(ctx->base + ASPEED_MDIO_CTRL, ctrl,
 				!(ctrl & ASPEED_MDIO_CTRL_FIRE),
-- 
2.25.1