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/* SPDX-License-Identifier: GPL-2.0+ */
/*
* Workaround for "PSCI bug" on DragonBoard 410c
* Copyright (C) 2021 Stephan Gerhold <stephan@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:
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