[PATCH v5 04/11] mach-snapdragon: boot0.h: split out msm8916_boot0.h

Tue May 5 02:47:50 CEST 2026

From: Michael Srba <Michael.Srba at seznam.cz>

Prepare for supporting alternative boot0.h per-SoC by splitting out
the existing msm8916-specific code.

There is now a selection mechanism to choose a specific boot0.h
in the Kconfig. BOOT0_MSM8916_PSCI_WORKAROUND is the only option
right now, but more can be added. The toplevel boot0.h additionally
enables conditionally performing the include only in u-boot proper,
or only in SPL.

Signed-off-by: Michael Srba <Michael.Srba at seznam.cz>
---
 arch/arm/mach-snapdragon/Kconfig                   | 16 ++++++
 arch/arm/mach-snapdragon/include/mach/boot0.h      | 58 +++-------------------
 .../mach-snapdragon/include/mach/msm8916_boot0.h   | 54 ++++++++++++++++++++
 configs/dragonboard410c_defconfig                  |  1 +
 4 files changed, 77 insertions(+), 52 deletions(-)

diff --git a/arch/arm/mach-snapdragon/Kconfig b/arch/arm/mach-snapdragon/Kconfig
index d3de8693b5a..f863daf6bb9 100644
--- a/arch/arm/mach-snapdragon/Kconfig
+++ b/arch/arm/mach-snapdragon/Kconfig
@@ -42,4 +42,20 @@ config SYS_CONFIG_NAME
 	  Based on this option include/configs/<CONFIG_SYS_CONFIG_NAME>.h header
 	  will be used for board configuration.
 
+choice
+	prompt "Qualcomm boot0.h workaround"
+	optional
+	help
+	  While U-Boot on Qualcomm platforms doesn't generally need compile-time
+	  adjustments based on the target SoC, workarounds in boot0.h can't
+	  practically detect the SoC at runtime. Enable one of these workarounds
+	  if you know you need it.
+
+config BOOT0_MSM8916_PSCI_WORKAROUND
+	bool "boot0.h workaround for buggy PSCI on the msm8916 SoC"
+	help
+	  Select this if you are building U-Boot proper for an msm8916 board that
+	  uses the buggy PSCI implementation.
+endchoice
+
 endif
diff --git a/arch/arm/mach-snapdragon/include/mach/boot0.h b/arch/arm/mach-snapdragon/include/mach/boot0.h
index 953cccad790..fb67aed7bc8 100644
--- a/arch/arm/mach-snapdragon/include/mach/boot0.h
+++ b/arch/arm/mach-snapdragon/include/mach/boot0.h
@@ -1,54 +1,8 @@
 /* SPDX-License-Identifier: GPL-2.0+ */
-/*
- * Workaround for "PSCI bug" on DragonBoard 410c
- * Copyright (C) 2021 Stephan Gerhold <stephan at gerhold.net>
- *
- * Syscall parameters taken from Qualcomm's LK fork (scm.h):
- * Copyright (c) 2011-2015, The Linux Foundation. All rights reserved.
- *
- * The PSCI implementation in the TrustZone/tz firmware on DragonBoard 410c has
- * a bug that starts all other CPU cores in 32-bit mode unless the TZ syscall
- * that switches from 32-bit to 64-bit mode is executed at least once.
- *
- * Normally this happens inside Qualcomm's LK bootloader which runs in 32-bit
- * mode and uses the TZ syscall to boot a kernel in 64-bit mode. However, if
- * U-Boot is installed to the "aboot" partition (replacing LK) the switch to
- * 64-bit mode never happens since U-Boot is already running in 64-bit mode.
- *
- * A workaround for this "PSCI bug" is to execute the TZ syscall when entering
- * U-Boot. That way PSCI is made aware of the 64-bit switch and starts all other
- * CPU cores in 64-bit mode as well.
- */
-#include <linux/arm-smccc.h>
-
-#define ARM_SMCCC_SIP32_FAST_CALL \
-	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_32, ARM_SMCCC_OWNER_SIP, 0)
-
-	/*
-	 * U-Boot might be started in EL2 or EL3 with custom firmware.
-	 * In that case, we assume that the workaround is not necessary or is
-	 * handled already by the alternative firmware. Using the syscall in EL2
-	 * would demote U-Boot to EL1; in EL3 it would probably just crash.
-	 */
-	mrs	x0, CurrentEL
-	cmp	x0, #(1 << 2)	/* EL1 */
-	bne	reset
-
-	/* Prepare TZ syscall parameters */
-	mov	x0, #ARM_SMCCC_SIP32_FAST_CALL
-	movk	x0, #0x10f	/* SCM_SVC_MILESTONE_CMD_ID */
-	mov	x1, #0x12	/* MAKE_SCM_ARGS(0x2, SMC_PARAM_TYPE_BUFFER_READ) */
-	adr	x2, el1_system_param
-	mov	x3, el1_system_param_end - el1_system_param
-
-	/* Switch PSCI to 64-bit mode. Resets CPU and returns at el1_elr */
-	smc	#0
-
-	/* Something went wrong, perhaps PSCI is already in 64-bit mode? */
+#if defined(CONFIG_SPL_BUILD)
 	b	reset
-
-	.align	3
-el1_system_param:
-	.quad	0, 0, 0, 0, 0, 0, 0, 0, 0	/* el1_x0-x8 */
-	.quad	reset				/* el1_elr */
-el1_system_param_end:
+#else
+#if defined(CONFIG_BOOT0_MSM8916_PSCI_WORKAROUND)
+#include "msm8916_boot0.h"
+#endif
+#endif
diff --git a/arch/arm/mach-snapdragon/include/mach/msm8916_boot0.h b/arch/arm/mach-snapdragon/include/mach/msm8916_boot0.h
new file mode 100644
index 00000000000..953cccad790
--- /dev/null
+++ b/arch/arm/mach-snapdragon/include/mach/msm8916_boot0.h
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Workaround for "PSCI bug" on DragonBoard 410c
+ * Copyright (C) 2021 Stephan Gerhold <stephan at gerhold.net>
+ *
+ * Syscall parameters taken from Qualcomm's LK fork (scm.h):
+ * Copyright (c) 2011-2015, The Linux Foundation. All rights reserved.
+ *
+ * The PSCI implementation in the TrustZone/tz firmware on DragonBoard 410c has
+ * a bug that starts all other CPU cores in 32-bit mode unless the TZ syscall
+ * that switches from 32-bit to 64-bit mode is executed at least once.
+ *
+ * Normally this happens inside Qualcomm's LK bootloader which runs in 32-bit
+ * mode and uses the TZ syscall to boot a kernel in 64-bit mode. However, if
+ * U-Boot is installed to the "aboot" partition (replacing LK) the switch to
+ * 64-bit mode never happens since U-Boot is already running in 64-bit mode.
+ *
+ * A workaround for this "PSCI bug" is to execute the TZ syscall when entering
+ * U-Boot. That way PSCI is made aware of the 64-bit switch and starts all other
+ * CPU cores in 64-bit mode as well.
+ */
+#include <linux/arm-smccc.h>
+
+#define ARM_SMCCC_SIP32_FAST_CALL \
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_32, ARM_SMCCC_OWNER_SIP, 0)
+
+	/*
+	 * U-Boot might be started in EL2 or EL3 with custom firmware.
+	 * In that case, we assume that the workaround is not necessary or is
+	 * handled already by the alternative firmware. Using the syscall in EL2
+	 * would demote U-Boot to EL1; in EL3 it would probably just crash.
+	 */
+	mrs	x0, CurrentEL
+	cmp	x0, #(1 << 2)	/* EL1 */
+	bne	reset
+
+	/* Prepare TZ syscall parameters */
+	mov	x0, #ARM_SMCCC_SIP32_FAST_CALL
+	movk	x0, #0x10f	/* SCM_SVC_MILESTONE_CMD_ID */
+	mov	x1, #0x12	/* MAKE_SCM_ARGS(0x2, SMC_PARAM_TYPE_BUFFER_READ) */
+	adr	x2, el1_system_param
+	mov	x3, el1_system_param_end - el1_system_param
+
+	/* Switch PSCI to 64-bit mode. Resets CPU and returns at el1_elr */
+	smc	#0
+
+	/* Something went wrong, perhaps PSCI is already in 64-bit mode? */
+	b	reset
+
+	.align	3
+el1_system_param:
+	.quad	0, 0, 0, 0, 0, 0, 0, 0, 0	/* el1_x0-x8 */
+	.quad	reset				/* el1_elr */
+el1_system_param_end:
diff --git a/configs/dragonboard410c_defconfig b/configs/dragonboard410c_defconfig
index 51ad265688c..645f0816701 100644
--- a/configs/dragonboard410c_defconfig
+++ b/configs/dragonboard410c_defconfig
@@ -11,6 +11,7 @@ CONFIG_ENV_OFFSET=0x0
 CONFIG_DEFAULT_DEVICE_TREE="qcom/apq8016-sbc"
 CONFIG_OF_LIBFDT_OVERLAY=y
 CONFIG_SYS_LOAD_ADDR=0x80080000
+CONFIG_BOOT0_MSM8916_PSCI_WORKAROUND=y
 CONFIG_IDENT_STRING="\nQualcomm-DragonBoard 410C"
 CONFIG_REMAKE_ELF=y
 CONFIG_BUTTON_CMD=y

-- 
2.53.0

