Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751499AbdIJGu7 (ORCPT ); Sun, 10 Sep 2017 02:50:59 -0400 Received: from mail-pf0-f196.google.com ([209.85.192.196]:36949 "EHLO mail-pf0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750965AbdIJGuz (ORCPT ); Sun, 10 Sep 2017 02:50:55 -0400 X-Google-Smtp-Source: ADKCNb6Io3FB0v8phpVL4oG6YKEYtCIluyZFoYbiw68SvikRwnaaNx0uGEme+emHgGj6GkWrcJvokw== From: Stafford Horne To: LKML Cc: Openrisc , Stafford Horne , Jonas Bonn , Stefan Kristiansson , Andrew Morton , Masahiro Yamada , Jan Henrik Weinstock Subject: [PATCH v2 09/14] openrisc: sleep instead of spin on secondary wait Date: Sun, 10 Sep 2017 15:49:21 +0900 Message-Id: <20170910064926.5874-10-shorne@gmail.com> X-Mailer: git-send-email 2.13.5 In-Reply-To: <20170910064926.5874-1-shorne@gmail.com> References: <20170910064926.5874-1-shorne@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3449 Lines: 125 Currently we do a spin on secondary cpus when waiting to boot. This theoretically causes issues with power consumption and does cause issues with qemu cycle burning (it starves cpu 0 from actually being able to boot.) This change puts each secondary cpu to sleep if they have a power management unit, then signals them to wake via IPI when its time to boot. If the cpus have no power management unit they will loop as before. Note: The wakeup IPI requires a special interrupt handler as on secondary cpu's the interrupt infrastructure is not yet established. This interrupt handler is set and reset by updating SPR_EVBAR. Signed-off-by: Stafford Horne --- Changes since v1 - Check if power management exists before sleeping arch/openrisc/kernel/head.S | 51 +++++++++++++++++++++++++++++++++++++++++++-- arch/openrisc/kernel/smp.c | 5 +++++ 2 files changed, 54 insertions(+), 2 deletions(-) diff --git a/arch/openrisc/kernel/head.S b/arch/openrisc/kernel/head.S index a9972dc103f8..fb02b2a1d6f2 100644 --- a/arch/openrisc/kernel/head.S +++ b/arch/openrisc/kernel/head.S @@ -712,9 +712,45 @@ _flush_tlb: #ifdef CONFIG_SMP secondary_wait: + /* Doze the cpu until we are asked to run */ + /* If we dont have power management skip doze */ + l.mfspr r25,r0,SPR_UPR + l.andi r25,r25,SPR_UPR_PMP + l.sfeq r25,r0 + l.bf secondary_check_release + l.nop + + /* Setup special secondary exception handler */ + LOAD_SYMBOL_2_GPR(r3, _secondary_evbar) + tophys(r25,r3) + l.mtspr r0,r25,SPR_EVBAR + + /* Enable Interrupts */ + l.mfspr r25,r0,SPR_SR + l.ori r25,r25,SPR_SR_IEE + l.mtspr r0,r25,SPR_SR + + /* Unmask interrupts interrupts */ + l.mfspr r25,r0,SPR_PICMR + l.ori r25,r25,0xffff + l.mtspr r0,r25,SPR_PICMR + + /* Doze */ + l.mfspr r25,r0,SPR_PMR + LOAD_SYMBOL_2_GPR(r3, SPR_PMR_DME) + l.or r25,r25,r3 + l.mtspr r0,r25,SPR_PMR + + /* Wakeup - Restore exception handler */ + l.mtspr r0,r0,SPR_EVBAR + +secondary_check_release: + /* + * Check if we actually got the release signal, if not go-back to + * sleep. + */ l.mfspr r25,r0,SPR_COREID - l.movhi r3,hi(secondary_release) - l.ori r3,r3,lo(secondary_release) + LOAD_SYMBOL_2_GPR(r3, secondary_release) tophys(r4, r3) l.lwz r3,0(r4) l.sfeq r25,r3 @@ -1663,6 +1699,17 @@ ENTRY(_early_uart_init) l.jr r9 l.nop + .align 0x1000 + .global _secondary_evbar +_secondary_evbar: + + .space 0x800 + /* Just disable interrupts and Return */ + l.ori r3,r0,SPR_SR_SM + l.mtspr r0,r3,SPR_ESR_BASE + l.rfe + + .section .rodata _string_unhandled_exception: .string "\n\rRunarunaround: Unhandled exception 0x\0" diff --git a/arch/openrisc/kernel/smp.c b/arch/openrisc/kernel/smp.c index 154c94a0cfbc..685b4934fa39 100644 --- a/arch/openrisc/kernel/smp.c +++ b/arch/openrisc/kernel/smp.c @@ -26,6 +26,7 @@ unsigned long secondary_release = -1; struct thread_info *secondary_thread_info; enum ipi_msg_type { + IPI_WAKEUP, IPI_RESCHEDULE, IPI_CALL_FUNC, IPI_CALL_FUNC_SINGLE, @@ -42,6 +43,7 @@ static void boot_secondary(unsigned int cpu, struct task_struct *idle) spin_lock(&boot_lock); secondary_release = cpu; + smp_cross_call(cpumask_of(cpu), IPI_WAKEUP); /* * now the secondary core is starting up let it run its @@ -140,6 +142,9 @@ void handle_IPI(unsigned int ipi_msg) unsigned int cpu = smp_processor_id(); switch (ipi_msg) { + case IPI_WAKEUP: + break; + case IPI_RESCHEDULE: scheduler_ipi(); break; -- 2.13.5