add dts config

hc

2023-12-06 08f87f769b595151be1afeff53e144f543faa614

 kernel/arch/arm/plat-versatile/platsmp.c
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@@ -1,12 +1,14 @@
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+// SPDX-License-Identifier: GPL-2.0-only
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 /*
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  *  linux/arch/arm/plat-versatile/platsmp.c
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  *
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  *  Copyright (C) 2002 ARM Ltd.
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  *  All Rights Reserved
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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 version 2 as
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- * published by the Free Software Foundation.
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+ * This code is specific to the hardware found on ARM Realview and
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+ * Versatile Express platforms where the CPUs are unable to be individually
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+ * woken, and where there is no way to hot-unplug CPUs.  Real platforms
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+ * should not copy this code.
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  */
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 #include <linux/init.h>
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 #include <linux/errno.h>
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@@ -21,18 +23,32 @@
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 #include <plat/platsmp.h>
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 /*
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- * Write pen_release in a way that is guaranteed to be visible to all
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- * observers, irrespective of whether they're taking part in coherency
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+ * versatile_cpu_release controls the release of CPUs from the holding
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+ * pen in headsmp.S, which exists because we are not always able to
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+ * control the release of individual CPUs from the board firmware.
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+ * Production platforms do not need this.
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+ */
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+volatile int versatile_cpu_release = -1;
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+
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+/*
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+ * Write versatile_cpu_release in a way that is guaranteed to be visible to
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+ * all observers, irrespective of whether they're taking part in coherency
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  * or not.  This is necessary for the hotplug code to work reliably.
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  */
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-static void write_pen_release(int val)
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+static void versatile_write_cpu_release(int val)
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 {
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-	pen_release = val;
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+	versatile_cpu_release = val;
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 	smp_wmb();
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-	sync_cache_w(&pen_release);
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+	sync_cache_w(&versatile_cpu_release);
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 }
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-static DEFINE_RAW_SPINLOCK(boot_lock);
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+/*
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+ * versatile_lock exists to avoid running the loops_per_jiffy delay loop
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+ * calibrations on the secondary CPU while the requesting CPU is using
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+ * the limited-bandwidth bus - which affects the calibration value.
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+ * Production platforms do not need this.
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+ */
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+static DEFINE_RAW_SPINLOCK(versatile_lock);
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52
 
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 void versatile_secondary_init(unsigned int cpu)
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 {
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@@ -40,13 +56,13 @@
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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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-	write_pen_release(-1);
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+	versatile_write_cpu_release(-1);
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 	/*
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 	 * Synchronise with the boot thread.
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 	 */
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-	raw_spin_lock(&boot_lock);
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-	raw_spin_unlock(&boot_lock);
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+	raw_spin_lock(&versatile_lock);
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+	raw_spin_unlock(&versatile_lock);
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 }
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 int versatile_boot_secondary(unsigned int cpu, struct task_struct *idle)
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@@ -57,7 +73,7 @@
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 	 * Set synchronisation state between this boot processor
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 	 * and the secondary one
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 	 */
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-	raw_spin_lock(&boot_lock);
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+	raw_spin_lock(&versatile_lock);
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 	/*
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 	 * This is really belt and braces; we hold unintended secondary
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@@ -65,7 +81,7 @@
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 	 * since we haven't sent them a soft interrupt, they shouldn't
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 	 * be there.
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 	 */
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-	write_pen_release(cpu_logical_map(cpu));
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+	versatile_write_cpu_release(cpu_logical_map(cpu));
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 	/*
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 	 * Send the secondary CPU a soft interrupt, thereby causing
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@@ -77,7 +93,7 @@
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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 (pen_release == -1)
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+		if (versatile_cpu_release == -1)
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 			break;
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 		udelay(10);
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@@ -87,7 +103,7 @@
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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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-	raw_spin_unlock(&boot_lock);
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+	raw_spin_unlock(&versatile_lock);
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-	return pen_release != -1 ? -ENOSYS : 0;
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+	return versatile_cpu_release != -1 ? -ENOSYS : 0;
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 }