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37 lines
1.3 KiB
37 lines
1.3 KiB
6 years ago
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From 6b8b69ff7c4c25f01535cbe49a80516df6dbcfe8 Mon Sep 17 00:00:00 2001
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From: Phil Elwell <phil@raspberrypi.org>
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Date: Mon, 8 May 2017 16:43:40 +0100
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Subject: [PATCH 010/454] irq_bcm2836: Send event when onlining sleeping cores
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In order to reduce power consumption and bus traffic, it is sensible
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for secondary cores to enter a low-power idle state when waiting to
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be started. The wfe instruction causes a core to wait until an event
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or interrupt arrives before continuing to the next instruction.
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The sev instruction sends a wakeup event to the other cores, so call
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it from bcm2836_smp_boot_secondary, the function that wakes up the
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waiting cores during booting.
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It is harmless to use this patch without the corresponding change
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adding wfe to the ARMv7/ARMv8-32 stubs, but if the stubs are updated
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and this patch is not applied then the other cores will sleep forever.
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See: https://github.com/raspberrypi/linux/issues/1989
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Signed-off-by: Phil Elwell <phil@raspberrypi.org>
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---
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drivers/irqchip/irq-bcm2836.c | 3 +++
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1 file changed, 3 insertions(+)
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--- a/drivers/irqchip/irq-bcm2836.c
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+++ b/drivers/irqchip/irq-bcm2836.c
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@@ -227,6 +227,9 @@ static int __init bcm2836_smp_boot_secon
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writel(secondary_startup_phys,
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intc.base + LOCAL_MAILBOX3_SET0 + 16 * cpu);
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+ dsb(sy); /* Ensure write has completed before waking the other CPUs */
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+ sev();
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+
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return 0;
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}
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