1 /* SPDX-License-Identifier: GPL-2.0+ */ 2 /* 3 * Workaround for "PSCI bug" on DragonBoard 410c 4 * Copyright (C) 2021 Stephan Gerhold <stephan@gerhold.net> 5 * 6 * Syscall parameters taken from Qualcomm's LK fork (scm.h): 7 * Copyright (c) 2011-2015, The Linux Foundation. All rights reserved. 8 * 9 * The PSCI implementation in the TrustZone/tz firmware on DragonBoard 410c has 10 * a bug that starts all other CPU cores in 32-bit mode unless the TZ syscall 11 * that switches from 32-bit to 64-bit mode is executed at least once. 12 * 13 * Normally this happens inside Qualcomm's LK bootloader which runs in 32-bit 14 * mode and uses the TZ syscall to boot a kernel in 64-bit mode. However, if 15 * U-Boot is installed to the "aboot" partition (replacing LK) the switch to 16 * 64-bit mode never happens since U-Boot is already running in 64-bit mode. 17 * 18 * A workaround for this "PSCI bug" is to execute the TZ syscall when entering 19 * U-Boot. That way PSCI is made aware of the 64-bit switch and starts all other 20 * CPU cores in 64-bit mode as well. 21 */ 22 #include <linux/arm-smccc.h> 23 24 #define ARM_SMCCC_SIP32_FAST_CALL \ 25 ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_32, ARM_SMCCC_OWNER_SIP, 0) 26 27 /* 28 * U-Boot might be started in EL2 or EL3 with custom firmware. 29 * In that case, we assume that the workaround is not necessary or is 30 * handled already by the alternative firmware. Using the syscall in EL2 31 * would demote U-Boot to EL1; in EL3 it would probably just crash. 32 */ 33 mrs x0, CurrentEL 34 cmp x0, #(1 << 2) /* EL1 */ 35 bne reset 36 37 /* Prepare TZ syscall parameters */ 38 mov x0, #ARM_SMCCC_SIP32_FAST_CALL 39 movk x0, #0x10f /* SCM_SVC_MILESTONE_CMD_ID */ 40 mov x1, #0x12 /* MAKE_SCM_ARGS(0x2, SMC_PARAM_TYPE_BUFFER_READ) */ 41 adr x2, el1_system_param 42 mov x3, el1_system_param_end - el1_system_param 43 44 /* Switch PSCI to 64-bit mode. Resets CPU and returns at el1_elr */ 45 smc #0 46 47 /* Something went wrong, perhaps PSCI is already in 64-bit mode? */ 48 b reset 49 50 .align 3 51 el1_system_param: 52 .quad 0, 0, 0, 0, 0, 0, 0, 0, 0 /* el1_x0-x8 */ 53 .quad reset /* el1_elr */ 54 el1_system_param_end: 55