FAILED: patch "[PATCH] serial: 8250: of: Fix mapped region size when using" failed to apply to 4.4-stable tree

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From d06b1cf28297e27127d3da54753a3a01a2fa2f28 Mon Sep 17 00:00:00 2001
From: Robert Hancock <[email protected]>
Date: Wed, 12 Jan 2022 13:42:14 -0600
Subject: [PATCH] serial: 8250: of: Fix mapped region size when using
reg-offset property

8250_of supports a reg-offset property which is intended to handle cases where the device registers start at an offset inside the region of memory allocated to the device. The Xilinx 16550 UART, for which this support was initially added, requires this. However, the code did not adjust the overall size of the mapped region accordingly, causing the driver to request an area of memory past the end of the device's allocation. For example, if the UART was allocated an address of 0xb0130000, size of 0x10000 and reg-offset of 0x1000 in the device tree, the region of memory reserved was b0131000-b0140fff, which caused the driver for the region starting at b0140000 to fail to probe.

Fix this by subtracting reg-offset from the mapped region size.

index bce28729dd7b..be8626234627 100644
@@ -83,8 +83,17 @@ static int of_platform_serial_setup(struct platform_device *ofdev,
 		port->mapsize = resource_size(&resource);
 
 		/* Check for shifted address mapping */
-		if (of_property_read_u32(np, "reg-offset", &prop) == 0)
+		if (of_property_read_u32(np, "reg-offset", &prop) == 0) {
+			if (prop >= port->mapsize) {
+				dev_warn(&ofdev->dev, "reg-offset %u exceeds region size %pa\n",
+					 prop, &port->mapsize);
+				ret = -EINVAL;
+				goto err_unprepare;
+			}
+
 			port->mapbase += prop;
+			port->mapsize -= prop;
+		}
 
 		port->iotype = UPIO_MEM;
 		if (of_property_read_u32(np, "reg-io-width", &prop) == 0) {