![Masahiro Yamada](/assets/img/avatar_default.png)
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 expected by the kernel. 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 so that they do not rely on particular boot loader implementation; the SMP operations (platsmp.c) put trampoline code (headsmp.S) on a locked way of the outer cache. The secondary CPUs jump from the boot ROM to secondary_entry via the trampoline code. The boot loader no longer needs to take care of SMP. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Signed-off-by: Olof Johansson <olof@lixom.net>
210 lines
5.4 KiB
C
210 lines
5.4 KiB
C
/*
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* Copyright (C) 2015 Masahiro Yamada <yamada.masahiro@socionext.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#define pr_fmt(fmt) "uniphier: " fmt
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#include <linux/init.h>
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#include <linux/io.h>
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#include <linux/ioport.h>
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#include <linux/of.h>
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#include <linux/of_address.h>
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#include <linux/sizes.h>
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#include <asm/cacheflush.h>
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#include <asm/hardware/cache-uniphier.h>
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#include <asm/pgtable.h>
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#include <asm/smp.h>
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#include <asm/smp_scu.h>
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/*
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* The secondary CPUs check this register from the boot ROM for the jump
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* destination. After that, it can be reused as a scratch register.
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*/
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#define UNIPHIER_SBC_ROM_BOOT_RSV2 0x1208
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static void __iomem *uniphier_smp_rom_boot_rsv2;
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static unsigned int uniphier_smp_max_cpus;
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extern char uniphier_smp_trampoline;
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extern char uniphier_smp_trampoline_jump;
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extern char uniphier_smp_trampoline_poll_addr;
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extern char uniphier_smp_trampoline_end;
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/*
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* Copy trampoline code to the tail of the 1st section of the page table used
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* in the boot ROM. This area is directly accessible by the secondary CPUs
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* for all the UniPhier SoCs.
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*/
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static const phys_addr_t uniphier_smp_trampoline_dest_end = SECTION_SIZE;
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static phys_addr_t uniphier_smp_trampoline_dest;
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static int __init uniphier_smp_copy_trampoline(phys_addr_t poll_addr)
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{
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size_t trmp_size;
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static void __iomem *trmp_base;
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if (!uniphier_cache_l2_is_enabled()) {
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pr_warn("outer cache is needed for SMP, but not enabled\n");
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return -ENODEV;
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}
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uniphier_cache_l2_set_locked_ways(1);
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outer_flush_all();
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trmp_size = &uniphier_smp_trampoline_end - &uniphier_smp_trampoline;
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uniphier_smp_trampoline_dest = uniphier_smp_trampoline_dest_end -
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trmp_size;
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uniphier_cache_l2_touch_range(uniphier_smp_trampoline_dest,
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uniphier_smp_trampoline_dest_end);
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trmp_base = ioremap_cache(uniphier_smp_trampoline_dest, trmp_size);
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if (!trmp_base) {
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pr_err("failed to map trampoline destination area\n");
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return -ENOMEM;
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}
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memcpy(trmp_base, &uniphier_smp_trampoline, trmp_size);
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writel(virt_to_phys(secondary_startup),
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trmp_base + (&uniphier_smp_trampoline_jump -
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&uniphier_smp_trampoline));
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writel(poll_addr, trmp_base + (&uniphier_smp_trampoline_poll_addr -
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&uniphier_smp_trampoline));
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flush_cache_all(); /* flush out trampoline code to outer cache */
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iounmap(trmp_base);
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return 0;
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}
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static int __init uniphier_smp_prepare_trampoline(unsigned int max_cpus)
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{
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struct device_node *np;
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struct resource res;
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phys_addr_t rom_rsv2_phys;
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int ret;
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np = of_find_compatible_node(NULL, NULL,
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"socionext,uniphier-system-bus-controller");
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ret = of_address_to_resource(np, 1, &res);
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if (ret) {
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pr_err("failed to get resource of system-bus-controller\n");
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return ret;
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}
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rom_rsv2_phys = res.start + UNIPHIER_SBC_ROM_BOOT_RSV2;
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ret = uniphier_smp_copy_trampoline(rom_rsv2_phys);
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if (ret)
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return ret;
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uniphier_smp_rom_boot_rsv2 = ioremap(rom_rsv2_phys, sizeof(SZ_4));
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if (!uniphier_smp_rom_boot_rsv2) {
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pr_err("failed to map ROM_BOOT_RSV2 register\n");
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return -ENOMEM;
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}
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writel(uniphier_smp_trampoline_dest, uniphier_smp_rom_boot_rsv2);
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asm("sev"); /* Bring up all secondary CPUs to the trampoline code */
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uniphier_smp_max_cpus = max_cpus; /* save for later use */
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return 0;
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}
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static void __init uniphier_smp_unprepare_trampoline(void)
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{
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iounmap(uniphier_smp_rom_boot_rsv2);
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if (uniphier_smp_trampoline_dest)
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outer_inv_range(uniphier_smp_trampoline_dest,
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uniphier_smp_trampoline_dest_end);
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uniphier_cache_l2_set_locked_ways(0);
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}
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static int __init uniphier_smp_enable_scu(void)
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{
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unsigned long scu_base_phys = 0;
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void __iomem *scu_base;
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if (scu_a9_has_base())
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scu_base_phys = scu_a9_get_base();
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if (!scu_base_phys) {
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pr_err("failed to get scu base\n");
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return -ENODEV;
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}
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scu_base = ioremap(scu_base_phys, SZ_128);
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if (!scu_base) {
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pr_err("failed to map scu base\n");
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return -ENOMEM;
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}
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scu_enable(scu_base);
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iounmap(scu_base);
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return 0;
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}
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static void __init uniphier_smp_prepare_cpus(unsigned int max_cpus)
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{
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static cpumask_t only_cpu_0 = { CPU_BITS_CPU0 };
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int ret;
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ret = uniphier_smp_prepare_trampoline(max_cpus);
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if (ret)
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goto err;
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ret = uniphier_smp_enable_scu();
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if (ret)
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goto err;
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return;
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err:
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pr_warn("disabling SMP\n");
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init_cpu_present(&only_cpu_0);
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uniphier_smp_unprepare_trampoline();
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}
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static int __init uniphier_smp_boot_secondary(unsigned int cpu,
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struct task_struct *idle)
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{
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if (WARN_ON_ONCE(!uniphier_smp_rom_boot_rsv2))
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return -EFAULT;
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writel(cpu, uniphier_smp_rom_boot_rsv2);
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readl(uniphier_smp_rom_boot_rsv2); /* relax */
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asm("sev"); /* wake up secondary CPUs sleeping in the trampoline */
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if (cpu == uniphier_smp_max_cpus - 1) {
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/* clean up resources if this is the last CPU */
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uniphier_smp_unprepare_trampoline();
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}
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return 0;
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}
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static struct smp_operations uniphier_smp_ops __initdata = {
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.smp_prepare_cpus = uniphier_smp_prepare_cpus,
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.smp_boot_secondary = uniphier_smp_boot_secondary,
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};
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CPU_METHOD_OF_DECLARE(uniphier_smp, "socionext,uniphier-smp",
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&uniphier_smp_ops);
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