linux-kernel - [PATCH] ARM: owl: smp: Drop bogus holding pen

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Date:   Sat,  1 Jul 2017 23:29:30 +0200
From:   Andreas Färber <afaerber@...e.de>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     mp-cs@...ions-semi.com, Thomas Liau <thomas.liau@...ions-semi.com>,
        张东风 <zhangdf@...ions-semi.com>,
        刘炜 <liuwei@...ions-semi.com>,
        张天益 <tyzhang@...ions-semi.com>,
        梅利 <harrymei@...ions-semi.com>,
        support@...aker.org, support@...ietech.com, lee@...ietech.com,
        Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
        Andreas Färber <afaerber@...e.de>,
        Russell King <linux@...linux.org.uk>
Subject: [PATCH] ARM: owl: smp: Drop bogus holding pen

The S500 SoC can start secondary CPUs without busy-looping for pen_release,
so simplify the SMP code compared to the LeMaker kernel tree.

Fixes: 172067e0bc87 ("ARM: owl: Implement CPU enable-method for S500")
Suggested-by: Arnd Bergmann <arnd@...db.de>
Cc: David Liu <liuwei@...ions-semi.com>
Signed-off-by: Andreas Färber <afaerber@...e.de>
---
 arch/arm/mach-actions/headsmp.S | 20 ++------------------
 arch/arm/mach-actions/platsmp.c | 29 +----------------------------
 2 files changed, 3 insertions(+), 46 deletions(-)

diff --git a/arch/arm/mach-actions/headsmp.S b/arch/arm/mach-actions/headsmp.S
index dc4832fc101a..65f53bdb69e7 100644
--- a/arch/arm/mach-actions/headsmp.S
+++ b/arch/arm/mach-actions/headsmp.S
@@ -2,6 +2,8 @@
  * Copyright 2012 Actions Semi Inc.
  * Author: Actions Semi, Inc.
  *
+ * Copyright (c) 2017 Andreas Färber
+ *
  * 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
@@ -46,23 +48,5 @@ ENTRY(owl_v7_invalidate_l1)
 ENDPROC(owl_v7_invalidate_l1)
 
 ENTRY(owl_secondary_startup)
-	mrc	p15, 0, r0, c0, c0, 5
-	and	r0, r0, #0xf
-	adr	r4, 1f
-	ldmia	r4, {r5, r6}
-	sub	r4, r4, r5
-	add	r6, r6, r4
-pen:
-	ldr	r7, [r6]
-	cmp	r7, r0
-	bne	pen
-
-	/*
-	 * we've been released from the holding pen: secondary_stack
-	 * should now contain the SVC stack for this core
-	 */
 	bl	owl_v7_invalidate_l1
 	b	secondary_startup
-
-1:	.long	.
-	.long	pen_release
diff --git a/arch/arm/mach-actions/platsmp.c b/arch/arm/mach-actions/platsmp.c
index b4806ce0e9bb..12a9e331b432 100644
--- a/arch/arm/mach-actions/platsmp.c
+++ b/arch/arm/mach-actions/platsmp.c
@@ -41,26 +41,6 @@ static int ncores;
 
 static DEFINE_SPINLOCK(boot_lock);
 
-static void write_pen_release(int val)
-{
-	pen_release = val;
-	smp_wmb();
-	__cpuc_flush_dcache_area((void *)&pen_release, sizeof(pen_release));
-	outer_clean_range(__pa(&pen_release), __pa(&pen_release + 1));
-}
-
-static void s500_smp_secondary_init(unsigned int cpu)
-{
-	/*
-	 * let the primary processor know we're out of the
-	 * pen, then head off into the C entry point
-	 */
-	write_pen_release(-1);
-
-	spin_lock(&boot_lock);
-	spin_unlock(&boot_lock);
-}
-
 void owl_secondary_startup(void);
 
 static int s500_wakeup_secondary(unsigned int cpu)
@@ -115,12 +95,6 @@ static int s500_smp_boot_secondary(unsigned int cpu, struct task_struct *idle)
 
 	spin_lock(&boot_lock);
 
-	/*
-	 * The secondary processor is waiting to be released from
-	 * the holding pen - release it, then wait for it to flag
-	 * that it has been released by resetting pen_release.
-	 */
-	write_pen_release(cpu_logical_map(cpu));
 	smp_send_reschedule(cpu);
 
 	timeout = jiffies + (1 * HZ);
@@ -134,7 +108,7 @@ static int s500_smp_boot_secondary(unsigned int cpu, struct task_struct *idle)
 
 	spin_unlock(&boot_lock);
 
-	return pen_release != -1 ? -ENOSYS : 0;
+	return 0;
 }
 
 static void __init s500_smp_prepare_cpus(unsigned int max_cpus)
@@ -192,7 +166,6 @@ static void __init s500_smp_prepare_cpus(unsigned int max_cpus)
 
 static const struct smp_operations s500_smp_ops __initconst = {
 	.smp_prepare_cpus = s500_smp_prepare_cpus,
-	.smp_secondary_init = s500_smp_secondary_init,
 	.smp_boot_secondary = s500_smp_boot_secondary,
 };
 CPU_METHOD_OF_DECLARE(s500_smp, "actions,s500-smp", &s500_smp_ops);
-- 
2.12.3