Merge "feat(arm): unify Linux kernel as BL33 handling" into integration

manish-pandey-arm · TrustedFirmware Code Review · commit 7924b69fdac0 · 2025-09-03T15:55:01.000Z
diff --git a/Makefile b/Makefile
@@ -898,6 +898,7 @@ $(eval $(call add_defines,\
 	EARLY_CONSOLE \
 	PRESERVE_DSU_PMU_REGS \
 	HOB_LIST \
+	HW_CONFIG_BASE \
 	LFA_SUPPORT \
 )))
 
diff --git a/docs/getting_started/build-options.rst b/docs/getting_started/build-options.rst
@@ -794,6 +794,9 @@ Common build options
    algorithm. It accepts 3 values: ``sha256``, ``sha384`` and ``sha512``.
    The default value of this flag is ``sha256``.
 
+- ``HW_CONFIG_BASE``: This option specifies the location in memory where the DTB
+   should either be loaded by BL2 or can be found by later stages.
+
 -  ``LDFLAGS``: Extra user options appended to the linkers' command line in
    addition to the one set by the build system.
 
diff --git a/docs/plat/arm/arm-build-options.rst b/docs/plat/arm/arm-build-options.rst
@@ -33,12 +33,12 @@ Arm Platform Build Options
 -  ``ARM_LINUX_KERNEL_AS_BL33``: The Linux kernel expects registers x0-x3 to
    have specific values at boot. This boolean option allows the Trusted Firmware
    to have a Linux kernel image as BL33 by preparing the registers to these
-   values before jumping to BL33. This option defaults to 0 (disabled). For
-   AArch64 ``RESET_TO_BL31`` and for AArch32 ``RESET_TO_SP_MIN`` must be 1 when
-   using it. If this option is set to 1, ``ARM_PRELOADED_DTB_BASE`` must be set
-   to the location of a device tree blob (DTB) already loaded in memory. The
-   Linux Image address must be specified using the ``PRELOADED_BL33_BASE``
-   option.
+   values before jumping to BL33. This option defaults to 0 (disabled). When
+   enabled (1), the address of the Linux image must be provided via the
+   ``PRELOADED_BL33_BASE`` option. Additionally, either the ``HW_CONFIG_BASE``
+   or ``ARM_PRELOADED_DTB_BASE`` option must specify the memory location of a
+   preloaded device tree blob (DTB). This option implies
+   ``USE_KERNEL_DT_CONVENTION``.
 
 -  ``ARM_PLAT_MT``: This flag determines whether the Arm platform layer has to
    cater for the multi-threading ``MT`` bit when accessing MPIDR. When this flag
@@ -167,4 +167,4 @@ Arm Neoverse RD Platform Build Options
 
 .. |FIP in a GPT image| image:: ../../resources/diagrams/FIP_in_a_GPT_image.png
 
-*Copyright (c) 2019-2024, Arm Limited. All rights reserved.*
+*Copyright (c) 2019-2025, Arm Limited. All rights reserved.*
diff --git a/docs/plat/arm/fvp/fvp-build-options.rst b/docs/plat/arm/fvp/fvp-build-options.rst
@@ -42,9 +42,6 @@ Arm FVP Platform Specific Build Options
    HW_CONFIG blob instead of the DTS file. This option is useful to override
    the default HW_CONFIG selected by the build system.
 
--  ``FVP_HW_CONFIG_ADDR`` : Specify the memory address in which to load the
-   HW_CONFIG. The default value is ``0x82000000``.
-
 -  ``FVP_GICR_REGION_PROTECTION``: Mark the redistributor pages of
    inactive/fused CPU cores as read-only. The default value of this option
    is ``0``, which means the redistributor pages of all CPU cores are marked
diff --git a/plat/arm/board/fvp/fdts/fvp_fw_config.dts b/plat/arm/board/fvp/fdts/fvp_fw_config.dts
@@ -27,7 +27,7 @@
 			load-address = <0x0 0x07f00000>;
 			max-size = <PLAT_ARM_HW_CONFIG_SIZE>;
 			id = <HW_CONFIG_ID>;
-			secondary-load-address = <0x0 FVP_HW_CONFIG_ADDR>;
+			secondary-load-address = <0x0 HW_CONFIG_BASE>;
 		};
 
 		/*
diff --git a/plat/arm/board/fvp/platform.mk b/plat/arm/board/fvp/platform.mk
@@ -377,9 +377,7 @@ FDT_SOURCES		+=	${FVP_HW_CONFIG_DTS}
 $(eval FVP_HW_CONFIG	:=	${BUILD_PLAT}/$(patsubst %.dts,%.dtb,$(FVP_HW_CONFIG_DTS)))
 HW_CONFIG		:=	${FVP_HW_CONFIG}
 
-# Allow hw_config's secondary-load-address in the DT to be changed
-FVP_HW_CONFIG_ADDR	?=	0x82000000
-DTC_CPPFLAGS		+=	-DFVP_HW_CONFIG_ADDR=$(FVP_HW_CONFIG_ADDR)
+HW_CONFIG_BASE		?=	0x82000000
 
 # Set default initrd base 128MiB offset of the default kernel address in FVP
 INITRD_BASE		?=	0x90000000
diff --git a/plat/arm/common/arm_bl31_setup.c b/plat/arm/common/arm_bl31_setup.c
@@ -254,14 +254,6 @@ void __init arm_bl31_early_platform_setup(u_register_t arg0, u_register_t arg1,
 	 * is located and the entry state information
 	 */
 	bl33_image_ep_info.pc = plat_get_ns_image_entrypoint();
-
-#if ARM_LINUX_KERNEL_AS_BL33
-	bl33_image_ep_info.args.arg0 = ARM_PRELOADED_DTB_BASE;
-	bl33_image_ep_info.args.arg1 = 0U;
-	bl33_image_ep_info.args.arg2 = 0U;
-	bl33_image_ep_info.args.arg3 = 0U;
-#endif /* ARM_LINUX_KERNEL_AS_BL33 */
-
 	bl33_image_ep_info.spsr = arm_get_spsr(BL33_IMAGE_ID);
 	SET_SECURITY_STATE(bl33_image_ep_info.h.attr, NON_SECURE);
 
@@ -337,6 +329,24 @@ void __init arm_bl31_early_platform_setup(u_register_t arg0, u_register_t arg1,
 		panic();
 #endif
 #endif /* RESET_TO_BL31 */
+
+#if USE_KERNEL_DT_CONVENTION
+	/*
+	 * Only use the default DT base address if TF-A has not supplied one.
+	 * This can occur when the DT is side-loaded and its memory location
+	 * is unknown (e.g., RESET_TO_BL31).
+	 */
+
+	if (bl33_image_ep_info.args.arg0 == 0U) {
+		bl33_image_ep_info.args.arg0 = HW_CONFIG_BASE;
+	}
+
+#if ARM_LINUX_KERNEL_AS_BL33
+	bl33_image_ep_info.args.arg1 = 0U;
+	bl33_image_ep_info.args.arg2 = 0U;
+	bl33_image_ep_info.args.arg3 = 0U;
+#endif
+#endif
 #endif /* TRANSFER_LIST */
 }
 
diff --git a/plat/arm/common/arm_common.mk b/plat/arm/common/arm_common.mk
@@ -112,15 +112,20 @@ $(eval $(call assert_boolean,ARM_LINUX_KERNEL_AS_BL33))
 $(eval $(call add_define,ARM_LINUX_KERNEL_AS_BL33))
 
 ifeq (${ARM_LINUX_KERNEL_AS_BL33},1)
+  USE_KERNEL_DT_CONVENTION  := 1
+
   ifneq (${ARCH},aarch64)
     ifneq (${RESET_TO_SP_MIN},1)
       $(error ARM_LINUX_KERNEL_AS_BL33 is only available if RESET_TO_SP_MIN=1.)
     endif
   endif
-  ifeq (${RESET_TO_BL31},1)
+  ifndef HW_CONFIG_BASE
     ifndef ARM_PRELOADED_DTB_BASE
-      $(error ARM_PRELOADED_DTB_BASE must be set if ARM_LINUX_KERNEL_AS_BL33 is used with RESET_TO_BL31.)
+      $(error If ARM_LINUX_KERNEL_AS_BL33 is used, either HW_CONFIG_BASE or \
+          ARM_PRELOADED_DTB_BASE must be set. )
     endif
+
+    HW_CONFIG_BASE := ${ARM_PRELOADED_DTB_BASE}
     $(eval $(call add_define,ARM_PRELOADED_DTB_BASE))
   endif
 endif
