linux-kernel - [RFC PATCH RESEND] ARM: spear: send SGI to trigger secondary CPU start

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Message-Id: <1396996288-32020-1-git-send-email-elder@linaro.org>
Date:	Tue,  8 Apr 2014 17:31:28 -0500
From:	Alex Elder <elder@...aro.org>
To:	viresh.linux@...il.com, shiraz.hashim@...il.com
Cc:	spear-devel@...t.st.com, vk.vipin@...il.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH RESEND] ARM: spear: send SGI to trigger secondary CPU start

The ARM spear machine uses the "holding pen" mechanism for starting
secondary CPUs.  Most implementations indicate it's a secondary
core's time to start by writing its CPU id into a location and
then signaling the core with a software-generated interrupt.

The spear code does not send the signal.  Comments elsewhere
in the code seem to indicate it should:
    The BootMonitor waits until it receives a soft interrupt, and
    then the secondary CPU branches to this address.

I suspect this is an oversight, and this patch proposes a remedy.

  *** I need the attention of a maintainer to verify this
  *** because I am unable to test this proposed change.

Signed-off-by: Alex Elder <elder@...aro.org>
---
 arch/arm/mach-spear/platsmp.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm/mach-spear/platsmp.c b/arch/arm/mach-spear/platsmp.c
index 5c4a198..c9064fe 100644
--- a/arch/arm/mach-spear/platsmp.c
+++ b/arch/arm/mach-spear/platsmp.c
@@ -62,6 +62,8 @@ static int spear13xx_boot_secondary(unsigned int cpu, struct task_struct *idle)
 	flush_cache_all();
 	outer_flush_all();
 
+	arch_send_wakeup_ipi_mask(cpumask_of(cpu));
+
 	timeout = jiffies + (1 * HZ);
 	while (time_before(jiffies, timeout)) {
 		smp_rmb();
-- 
1.7.9.5

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