Patch "serial: 8250_bcm7271: Fix arbitration handling" has been added to the 6.2-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    serial: 8250_bcm7271: Fix arbitration handling

to the 6.2-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     serial-8250_bcm7271-fix-arbitration-handling.patch
and it can be found in the queue-6.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 975898381a400cb641add649ad016b2c9533bc44
Author: Doug Berger <opendmb@xxxxxxxxx>
Date:   Thu Mar 9 11:02:24 2023 -0800

    serial: 8250_bcm7271: Fix arbitration handling
    
    [ Upstream commit 15ac1122fd6d4bf408a03e6f23c7ad4f60b22f9e ]
    
    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@xxxxxxxxx>
    Acked-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
    Link: https://lore.kernel.org/r/20230309190224.687380-1-opendmb@xxxxxxxxx
    Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/tty/serial/8250/8250_bcm7271.c b/drivers/tty/serial/8250/8250_bcm7271.c
index ed5a947476920..f801b1f5b46c0 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;
 }