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6213f70e7c
Consolidating the "pen_release" stuff amongst the various SoC implementations gives credence to having a CPU holding pen for secondary CPUs. However, this is far from the truth. Many SoC implementations cargo-cult copied various bits of the pen release implementation from the initial Realview/Versatile Express implementation without understanding what it was or why it existed. The reason it existed is because these are _development_ platforms, and some board firmware is unable to individually control the startup of secondary CPUs. Moreover, they do not have a way to power down or reset secondary CPUs for hot-unplug. Hence, the pen_release implementation was designed for ARM Ltd's development platforms to provide a working implementation, even though it is very far from what is required. It was decided a while back to reduce the duplication by consolidating the "pen_release" variable, but this only made the situation worse - we have ended up with several implementations that read this variable but do not write it - again, showing the cargo-cult mentality at work, lack of proper review of new code, and in some cases a lack of testing. While it would be preferable to remove pen_release entirely from the kernel, this is not possible without help from the SoC maintainers, which seems to be lacking. However, I want to remove pen_release from arch code to remove the credence that having it gives. This patch removes pen_release from the arch code entirely, adding private per-SoC definitions for it instead, and explicitly stating that write_pen_release() is cargo-cult copied and should not be copied any further. Rename write_pen_release() in a similar fashion as well. Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
125 lines
3.0 KiB
C
125 lines
3.0 KiB
C
/*
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* plat smp support for CSR Marco dual-core SMP SoCs
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*
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* Copyright (c) 2012 Cambridge Silicon Radio Limited, a CSR plc group company.
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*
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* Licensed under GPLv2 or later.
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*/
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#include <linux/init.h>
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#include <linux/smp.h>
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#include <linux/delay.h>
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#include <linux/of.h>
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#include <linux/of_address.h>
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#include <asm/page.h>
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#include <asm/mach/map.h>
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#include <asm/smp_plat.h>
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#include <asm/smp_scu.h>
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#include <asm/cacheflush.h>
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#include <asm/cputype.h>
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#include "common.h"
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static void __iomem *clk_base;
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static DEFINE_SPINLOCK(boot_lock);
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/* XXX prima2_pen_release is cargo culted code - DO NOT COPY XXX */
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volatile int prima2_pen_release = -1;
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static void sirfsoc_secondary_init(unsigned int cpu)
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{
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/*
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* let the primary processor know we're out of the
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* pen, then head off into the C entry point
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*/
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prima2_pen_release = -1;
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smp_wmb();
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/*
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* Synchronise with the boot thread.
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*/
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spin_lock(&boot_lock);
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spin_unlock(&boot_lock);
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}
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static const struct of_device_id clk_ids[] = {
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{ .compatible = "sirf,atlas7-clkc" },
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{},
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};
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static int sirfsoc_boot_secondary(unsigned int cpu, struct task_struct *idle)
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{
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unsigned long timeout;
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struct device_node *np;
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np = of_find_matching_node(NULL, clk_ids);
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if (!np)
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return -ENODEV;
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clk_base = of_iomap(np, 0);
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if (!clk_base)
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return -ENOMEM;
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/*
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* write the address of secondary startup into the clkc register
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* at offset 0x2bC, then write the magic number 0x3CAF5D62 to the
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* clkc register at offset 0x2b8, which is what boot rom code is
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* waiting for. This would wake up the secondary core from WFE
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*/
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#define SIRFSOC_CPU1_JUMPADDR_OFFSET 0x2bc
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__raw_writel(__pa_symbol(sirfsoc_secondary_startup),
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clk_base + SIRFSOC_CPU1_JUMPADDR_OFFSET);
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#define SIRFSOC_CPU1_WAKEMAGIC_OFFSET 0x2b8
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__raw_writel(0x3CAF5D62,
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clk_base + SIRFSOC_CPU1_WAKEMAGIC_OFFSET);
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/* make sure write buffer is drained */
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mb();
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spin_lock(&boot_lock);
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/*
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* The secondary processor is waiting to be released from
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* the holding pen - release it, then wait for it to flag
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* that it has been released by resetting prima2_pen_release.
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*
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* Note that "prima2_pen_release" is the hardware CPU ID, whereas
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* "cpu" is Linux's internal ID.
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*/
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prima2_pen_release = cpu_logical_map(cpu);
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sync_cache_w(&prima2_pen_release);
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/*
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* Send the secondary CPU SEV, thereby causing the boot monitor to read
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* the JUMPADDR and WAKEMAGIC, and branch to the address found there.
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*/
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dsb_sev();
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timeout = jiffies + (1 * HZ);
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while (time_before(jiffies, timeout)) {
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smp_rmb();
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if (prima2_pen_release == -1)
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break;
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udelay(10);
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}
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/*
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* now the secondary core is starting up let it run its
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* calibrations, then wait for it to finish
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*/
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spin_unlock(&boot_lock);
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return prima2_pen_release != -1 ? -ENOSYS : 0;
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}
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const struct smp_operations sirfsoc_smp_ops __initconst = {
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.smp_secondary_init = sirfsoc_secondary_init,
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.smp_boot_secondary = sirfsoc_boot_secondary,
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#ifdef CONFIG_HOTPLUG_CPU
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.cpu_die = sirfsoc_cpu_die,
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#endif
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};
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