| /* 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: |
