From 15ac1122fd6d4bf408a03e6f23c7ad4f60b22f9e Mon Sep 17 00:00:00 2001
From: Doug Berger <opendmb@gmail.com>
Date: Thu, 9 Mar 2023 11:02:24 -0800
Subject: [PATCH] serial: 8250_bcm7271: Fix arbitration handling
Git-commit: 15ac1122fd6d4bf408a03e6f23c7ad4f60b22f9e
Patch-mainline: v6.4-rc1
References: git-fixes

The arbitration of the UART DMA is mishandled for a few
exceptional cases when probing and releasing the driver.

It is possible that the DMA register spaces are not defined in
device tree for an instance of the driver, so attempts to access
the registers in brcmuart_arbitration() would use NULL pointers.

It is also possible for the probe function to return an error
while still holding the UART DMA. This would prevent the UART
DMA from being claimed by an instance that could use it.

These errors are addressed by only releasing the UART DMA if it
is held by this instance (i.e. priv->dma_enabled == 1) and
directing early error paths in probe to this common release_dma
handling.

Fixes: 41a469482de2 ("serial: 8250: Add new 8250-core based Broadcom STB driver")
Signed-off-by: Doug Berger <opendmb@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20230309190224.687380-1-opendmb@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/tty/serial/8250/8250_bcm7271.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_bcm7271.c b/drivers/tty/serial/8250/8250_bcm7271.c
index ed5a94747692..f801b1f5b46c 100644
--- a/drivers/tty/serial/8250/8250_bcm7271.c
+++ b/drivers/tty/serial/8250/8250_bcm7271.c
@@ -1014,14 +1014,16 @@ static int brcmuart_probe(struct platform_device *pdev)
 	/* See if a Baud clock has been specified */
 	baud_mux_clk = of_clk_get_by_name(np, "sw_baud");
 	if (IS_ERR(baud_mux_clk)) {
-		if (PTR_ERR(baud_mux_clk) == -EPROBE_DEFER)
-			return -EPROBE_DEFER;
+		if (PTR_ERR(baud_mux_clk) == -EPROBE_DEFER) {
+			ret = -EPROBE_DEFER;
+			goto release_dma;
+		}
 		dev_dbg(dev, "BAUD MUX clock not specified\n");
 	} else {
 		dev_dbg(dev, "BAUD MUX clock found\n");
 		ret = clk_prepare_enable(baud_mux_clk);
 		if (ret)
-			return ret;
+			goto release_dma;
 		priv->baud_mux_clk = baud_mux_clk;
 		init_real_clk_rates(dev, priv);
 		clk_rate = priv->default_mux_rate;
@@ -1029,7 +1031,8 @@ static int brcmuart_probe(struct platform_device *pdev)
 
 	if (clk_rate == 0) {
 		dev_err(dev, "clock-frequency or clk not defined\n");
-		return -EINVAL;
+		ret = -EINVAL;
+		goto release_dma;
 	}
 
 	dev_dbg(dev, "DMA is %senabled\n", priv->dma_enabled ? "" : "not ");
@@ -1116,7 +1119,9 @@ static int brcmuart_probe(struct platform_device *pdev)
 	serial8250_unregister_port(priv->line);
 err:
 	brcmuart_free_bufs(dev, priv);
-	brcmuart_arbitration(priv, 0);
+release_dma:
+	if (priv->dma_enabled)
+		brcmuart_arbitration(priv, 0);
 	return ret;
 }
 
@@ -1128,7 +1133,8 @@ static int brcmuart_remove(struct platform_device *pdev)
 	hrtimer_cancel(&priv->hrt);
 	serial8250_unregister_port(priv->line);
 	brcmuart_free_bufs(&pdev->dev, priv);
-	brcmuart_arbitration(priv, 0);
+	if (priv->dma_enabled)
+		brcmuart_arbitration(priv, 0);
 	return 0;
 }
 
-- 
2.35.3