[PATCH 2/3] ARM: uniphier: rework SMP operations to use trampoline code
The complexity of the boot sequence of UniPhier SoC family is a PITA due to the following hardware limitations: [1] No dedicated on-chip SRAM SoCs in general have small SRAM, on which a tiny firmware or a boot loader can run before SDRAM is initialized. As UniPhier SoCs do not have any dedicated SRAM accessible from CPUs, the locked outer cache is used instead. Due to the ARM specification, to have access to the outer cache, the MMU must be enabled. This is done for all CPU cores by the program hard-wired in the boot ROM. The boot ROM code loads a small amount of program (this is usually SPL of U-Boot) from a non-volatile device onto the locked outer cache, and the primary CPU jumps to it. The secondary CPUs stay in the boot ROM until they are kicked by the primary CPU. [2] CPUs can not directly jump to SDRAM address space As mentioned above, the MMU is enable for all the CPUs with the page table hard-wired in the boot ROM. Unfortunately, the page table only has minimal sets of valid sections; all the sections of SDRAM address space are zero-filled. That means all the CPUs, including secondary ones, can not jump directly to SDRAM address space. So, the primary CPU must bring up secondary CPUs to accessible address mapped onto the outer cache, then again kick them to SDRAM address space. Before this commit, this complex task was done with help of a boot loader (U-Boot); U-Boot SPL brings up the secondary CPUs to the entry of U-Boot SPL and they stay there until they are kicked by Linux. This is not nice because a boot loader must put the secondary CPUs into a certain state the kernel expects. It makes difficult to port another boot loader because the boot loader and the kernel must work in sync to wake up the secondary CPUs. This commit reworks the SMP operations without any help of the boot loader; the SMP operations (mach-uniphier/platsmp.c) enables the locked outer cache and puts trampoline code (mach-uniphier/headsmp.S) there. The secondary CPUs jump from the boot ROM to secondary_entry via the trampoline code. The boot loader no longer need to take care of SMP. Signed-off-by: Masahiro Yamada --- arch/arm/mach-uniphier/Makefile | 2 +- arch/arm/mach-uniphier/headsmp.S | 43 + arch/arm/mach-uniphier/platsmp.c | 183 +++--- arch/arm/mach-uniphier/uniphier.c | 2 +- 4 files changed, 197 insertions(+), 33 deletions(-) create mode 100644 arch/arm/mach-uniphier/headsmp.S diff --git a/arch/arm/mach-uniphier/Makefile b/arch/arm/mach-uniphier/Makefile index 60bd226..1233f9b 100644 --- a/arch/arm/mach-uniphier/Makefile +++ b/arch/arm/mach-uniphier/Makefile @@ -1,2 +1,2 @@ obj-y := uniphier.o -obj-$(CONFIG_SMP) += platsmp.o +obj-$(CONFIG_SMP) += platsmp.o headsmp.o diff --git a/arch/arm/mach-uniphier/headsmp.S b/arch/arm/mach-uniphier/headsmp.S new file mode 100644 index 000..c819dff --- /dev/null +++ b/arch/arm/mach-uniphier/headsmp.S @@ -0,0 +1,43 @@ +/* + * Copyright (C) 2015 Masahiro Yamada + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + */ + +#include +#include +#include + +ENTRY(uniphier_smp_trampoline) +ARM_BE8(setend be) @ ensure we are in BE8 mode + mrc p15, 0, r0, c0, c0, 5 @ MPIDR (Multiprocessor Affinity Reg) + and r2, r0, #0x3@ CPU ID + ldr r1, uniphier_smp_trampoline_jump + ldr r3, uniphier_smp_trampoline_poll_addr + mrc p15, 0, r0, c1, c0, 0 @ SCTLR (System Control Register) + orr r0, r0, #CR_I @ Enable ICache + bic r0, r0, #(CR_C | CR_M) @ Disable MMU and Dcache + mcr p15, 0, r0, c1, c0, 0 + b 1f @ cache the following 5 instructions +0: wfe +1: ldr r0, [r3] + cmp r0, r2 + bxeqr1 @ branch to secondary_startup + b 0b + .globl uniphier_smp_trampoline_jump +uniphier_smp_trampoline_jump: + .word 0 @ set virt_to_phys(secondary_startup) + .globl uniphier_smp_trampoline_poll_addr +uniphier_smp_trampoline_poll_addr: + .word 0 @ set CPU ID to be kicked to this reg + .globl uniphier_smp_trampoline_end +uniphier_smp_trampoline_end: +ENDPROC(uniphier_smp_trampoline) diff --git a/arch/arm/mach-uniphier/platsmp.c b/arch/arm/mach-uniphier/platsmp.c index 4b784f7..774dd5f 100644 --- a/arch/arm/mach-uniphier/platsmp.c +++
[PATCH 2/3] ARM: uniphier: rework SMP operations to use trampoline code
The complexity of the boot sequence of UniPhier SoC family is a PITA due to the following hardware limitations: [1] No dedicated on-chip SRAM SoCs in general have small SRAM, on which a tiny firmware or a boot loader can run before SDRAM is initialized. As UniPhier SoCs do not have any dedicated SRAM accessible from CPUs, the locked outer cache is used instead. Due to the ARM specification, to have access to the outer cache, the MMU must be enabled. This is done for all CPU cores by the program hard-wired in the boot ROM. The boot ROM code loads a small amount of program (this is usually SPL of U-Boot) from a non-volatile device onto the locked outer cache, and the primary CPU jumps to it. The secondary CPUs stay in the boot ROM until they are kicked by the primary CPU. [2] CPUs can not directly jump to SDRAM address space As mentioned above, the MMU is enable for all the CPUs with the page table hard-wired in the boot ROM. Unfortunately, the page table only has minimal sets of valid sections; all the sections of SDRAM address space are zero-filled. That means all the CPUs, including secondary ones, can not jump directly to SDRAM address space. So, the primary CPU must bring up secondary CPUs to accessible address mapped onto the outer cache, then again kick them to SDRAM address space. Before this commit, this complex task was done with help of a boot loader (U-Boot); U-Boot SPL brings up the secondary CPUs to the entry of U-Boot SPL and they stay there until they are kicked by Linux. This is not nice because a boot loader must put the secondary CPUs into a certain state the kernel expects. It makes difficult to port another boot loader because the boot loader and the kernel must work in sync to wake up the secondary CPUs. This commit reworks the SMP operations without any help of the boot loader; the SMP operations (mach-uniphier/platsmp.c) enables the locked outer cache and puts trampoline code (mach-uniphier/headsmp.S) there. The secondary CPUs jump from the boot ROM to secondary_entry via the trampoline code. The boot loader no longer need to take care of SMP. Signed-off-by: Masahiro Yamada yamada.masah...@socionext.com --- arch/arm/mach-uniphier/Makefile | 2 +- arch/arm/mach-uniphier/headsmp.S | 43 + arch/arm/mach-uniphier/platsmp.c | 183 +++--- arch/arm/mach-uniphier/uniphier.c | 2 +- 4 files changed, 197 insertions(+), 33 deletions(-) create mode 100644 arch/arm/mach-uniphier/headsmp.S diff --git a/arch/arm/mach-uniphier/Makefile b/arch/arm/mach-uniphier/Makefile index 60bd226..1233f9b 100644 --- a/arch/arm/mach-uniphier/Makefile +++ b/arch/arm/mach-uniphier/Makefile @@ -1,2 +1,2 @@ obj-y := uniphier.o -obj-$(CONFIG_SMP) += platsmp.o +obj-$(CONFIG_SMP) += platsmp.o headsmp.o diff --git a/arch/arm/mach-uniphier/headsmp.S b/arch/arm/mach-uniphier/headsmp.S new file mode 100644 index 000..c819dff --- /dev/null +++ b/arch/arm/mach-uniphier/headsmp.S @@ -0,0 +1,43 @@ +/* + * Copyright (C) 2015 Masahiro Yamada yamada.masah...@socionext.com + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + */ + +#include linux/linkage.h +#include asm/assembler.h +#include asm/cp15.h + +ENTRY(uniphier_smp_trampoline) +ARM_BE8(setend be) @ ensure we are in BE8 mode + mrc p15, 0, r0, c0, c0, 5 @ MPIDR (Multiprocessor Affinity Reg) + and r2, r0, #0x3@ CPU ID + ldr r1, uniphier_smp_trampoline_jump + ldr r3, uniphier_smp_trampoline_poll_addr + mrc p15, 0, r0, c1, c0, 0 @ SCTLR (System Control Register) + orr r0, r0, #CR_I @ Enable ICache + bic r0, r0, #(CR_C | CR_M) @ Disable MMU and Dcache + mcr p15, 0, r0, c1, c0, 0 + b 1f @ cache the following 5 instructions +0: wfe +1: ldr r0, [r3] + cmp r0, r2 + bxeqr1 @ branch to secondary_startup + b 0b + .globl uniphier_smp_trampoline_jump +uniphier_smp_trampoline_jump: + .word 0 @ set virt_to_phys(secondary_startup) + .globl uniphier_smp_trampoline_poll_addr +uniphier_smp_trampoline_poll_addr: + .word 0 @ set CPU ID to be kicked to this reg + .globl uniphier_smp_trampoline_end +uniphier_smp_trampoline_end: +ENDPROC(uniphier_smp_trampoline) diff --git a/arch/arm/mach-uniphier/platsmp.c b/arch/arm/mach-uniphier/platsmp.c index
