ipq40xx: Add cmdline override support for kernel 5.4 (#8180)

target/linux/ipq40xx/config-5.4

@@ -52,6 +52,7 @@ CONFIG_BOUNCE=y
 CONFIG_CLKDEV_LOOKUP=y
 CONFIG_CLKSRC_QCOM=y
 CONFIG_CLONE_BACKWARDS=y
+CONFIG_CMDLINE_OVERRIDE=y
 CONFIG_COMMON_CLK=y
 CONFIG_COMMON_CLK_QCOM=y
 CONFIG_COMPAT_32BIT_TIME=y

target/linux/ipq40xx/patches-5.4/900-arm-add-cmdline-override.patch

@@ -0,0 +1,37 @@
+--- a/arch/arm/Kconfig
++++ b/arch/arm/Kconfig
+@@ -1794,6 +1794,14 @@ config ARM_ATAG_DTB_COMPAT_CMDLINE_MANGL
+ 
+ endchoice
+ 
++config CMDLINE_OVERRIDE
++	bool "Use alternative cmdline from device tree"
++	help
++	  Some bootloaders may have uneditable bootargs. While CMDLINE_FORCE can
++	  be used, this is not a good option for kernels that are shared across
++	  devices. This setting enables using "chosen/cmdline-override" as the
++	  cmdline if it exists in the device tree.
++
+ config CMDLINE
+ 	string "Default kernel command string"
+ 	default ""
+--- a/drivers/of/fdt.c
++++ b/drivers/of/fdt.c
+@@ -1056,6 +1056,17 @@ int __init early_init_dt_scan_chosen(uns
+ 	if (p != NULL && l > 0)
+ 		strlcpy(data, p, min(l, COMMAND_LINE_SIZE));
+ 
++    /* CONFIG_CMDLINE_OVERRIDE is used to fallback to a different
++     * device tree option of chosen/bootargs-override. This is
++     * helpful on boards where u-boot sets bootargs, and is unable
++     * to be modified.
++     */
++#ifdef CONFIG_CMDLINE_OVERRIDE
++	p = of_get_flat_dt_prop(node, "bootargs-override", &l);
++	if (p != NULL && l > 0)
++		strlcpy(data, p, min((int)l, COMMAND_LINE_SIZE));
++#endif
++
+ 	/*
+ 	 * CONFIG_CMDLINE is meant to be a default in case nothing else
+ 	 * managed to set the command line, unless CONFIG_CMDLINE_FORCE