linux-kernel - Re: [PATCH 04/12] riscv: cleanup the default power off implementation

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Date:   Thu, 31 Oct 2019 13:49:47 -0700 (PDT)
From:   Paul Walmsley <paul.walmsley@...ive.com>
To:     Christoph Hellwig <hch@....de>
cc:     Palmer Dabbelt <palmer@...ive.com>,
        Damien Le Moal <damien.lemoal@....com>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Anup Patel <anup@...infault.org>,
        Atish Patra <atish.patra@....com>
Subject: Re: [PATCH 04/12] riscv: cleanup the default power off
 implementation

On Mon, 28 Oct 2019, Christoph Hellwig wrote:

> Move the sbi poweroff to a separate function and file that is only
> compiled if CONFIG_SBI is set.  Provide a new default fallback
> power off that just sits in a wfi loop to save some power.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> Reviewed-by: Anup Patel <anup@...infault.org>
> Reviewed-by: Atish Patra <atish.patra@....com>

Thanks, I've split the WFI optimization out into a separate patch (below) 
and queued it for v5.5-rc1.


- Paul

From: Christoph Hellwig <hch@....de>
Date: Wed, 30 Oct 2019 16:11:47 -0700
Subject: [PATCH] riscv: enter WFI in default_power_off() if SBI does not
 shutdown

Provide a new default fallback power off that just sits in a wfi loop
to save some power.

Signed-off-by: Christoph Hellwig <hch@....de>
Reviewed-by: Anup Patel <anup@...infault.org>
Reviewed-by: Atish Patra <atish.patra@....com>
[paul.walmsley@...ive.com: split the WFI improvement apart from the
 nommu-related default_power_off() changes; wrote commit summary]
Signed-off-by: Paul Walmsley <paul.walmsley@...ive.com>
---
 arch/riscv/kernel/reset.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/reset.c b/arch/riscv/kernel/reset.c
index aa56bb135ec4..485be426d9b1 100644
--- a/arch/riscv/kernel/reset.c
+++ b/arch/riscv/kernel/reset.c
@@ -10,7 +10,8 @@
 static void default_power_off(void)
 {
 	sbi_shutdown();
-	while (1);
+	while (1)
+		wait_for_interrupt();
 }
 
 void (*pm_power_off)(void) = default_power_off;
-- 
2.24.0.rc0