From af9a1f61ac331c2f910d9186767d02f8e982c38e Mon Sep 17 00:00:00 2001
From: Mikko Perttunen <mperttunen@nvidia.com>
Date: Wed, 9 Jun 2021 18:56:55 +0300
Subject: [PATCH] serial: tegra-tcu: Reorder channel initialization
Git-commit: af9a1f61ac331c2f910d9186767d02f8e982c38e
Patch-mainline: v5.14-rc1
References: git-fixes

Request the RX mailbox only after initializing the UART data
structures. Otherwise it can rarely happen that the receive
callback is called before the UART is ready.

Fixes: 2d908b38d409 ("serial: Add Tegra Combined UART driver")
Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Link: https://lore.kernel.org/r/20210609155655.3567545-1-mperttunen@nvidia.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/tty/serial/tegra-tcu.c | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/drivers/tty/serial/tegra-tcu.c b/drivers/tty/serial/tegra-tcu.c
index 52687c65ad74..4877c54c613d 100644
--- a/drivers/tty/serial/tegra-tcu.c
+++ b/drivers/tty/serial/tegra-tcu.c
@@ -195,13 +195,6 @@ static int tegra_tcu_probe(struct platform_device *pdev)
 		return err;
 	}
 
-	tcu->rx = mbox_request_channel_byname(&tcu->rx_client, "rx");
-	if (IS_ERR(tcu->rx)) {
-		err = PTR_ERR(tcu->rx);
-		dev_err(&pdev->dev, "failed to get rx mailbox: %d\n", err);
-		goto free_tx;
-	}
-
 #if IS_ENABLED(CONFIG_SERIAL_TEGRA_TCU_CONSOLE)
 	/* setup the console */
 	strcpy(tcu->console.name, "ttyTCU");
@@ -226,7 +219,7 @@ static int tegra_tcu_probe(struct platform_device *pdev)
 	if (err) {
 		dev_err(&pdev->dev, "failed to register UART driver: %d\n",
 			err);
-		goto free_rx;
+		goto free_tx;
 	}
 
 	/* setup the port */
@@ -246,6 +239,17 @@ static int tegra_tcu_probe(struct platform_device *pdev)
 		goto unregister_uart;
 	}
 
+	/*
+	 * Request RX channel after creating port to ensure tcu->port
+	 * is ready for any immediate incoming bytes.
+	 */
+	tcu->rx = mbox_request_channel_byname(&tcu->rx_client, "rx");
+	if (IS_ERR(tcu->rx)) {
+		err = PTR_ERR(tcu->rx);
+		dev_err(&pdev->dev, "failed to get rx mailbox: %d\n", err);
+		goto remove_uart_port;
+	}
+
 	platform_set_drvdata(pdev, tcu);
 #if IS_ENABLED(CONFIG_SERIAL_TEGRA_TCU_CONSOLE)
 	register_console(&tcu->console);
@@ -253,10 +257,10 @@ static int tegra_tcu_probe(struct platform_device *pdev)
 
 	return 0;
 
+remove_uart_port:
+	uart_remove_one_port(&tcu->driver, &tcu->port);
 unregister_uart:
 	uart_unregister_driver(&tcu->driver);
-free_rx:
-	mbox_free_channel(tcu->rx);
 free_tx:
 	mbox_free_channel(tcu->tx);
 
@@ -270,9 +274,9 @@ static int tegra_tcu_remove(struct platform_device *pdev)
 #if IS_ENABLED(CONFIG_SERIAL_TEGRA_TCU_CONSOLE)
 	unregister_console(&tcu->console);
 #endif
+	mbox_free_channel(tcu->rx);
 	uart_remove_one_port(&tcu->driver, &tcu->port);
 	uart_unregister_driver(&tcu->driver);
-	mbox_free_channel(tcu->rx);
 	mbox_free_channel(tcu->tx);
 
 	return 0;
-- 
2.26.2