linux-kernel - [PATCH] openrisc: Allow power off handler overriding

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Date:   Sat, 21 May 2022 10:53:21 +0900
From:   Stafford Horne <shorne@...il.com>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Openrisc <openrisc@...ts.librecores.org>,
        Stafford Horne <shorne@...il.com>,
        "Jason A . Donenfeld" <Jason@...c4.com>,
        Jonas Bonn <jonas@...thpole.se>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Kees Cook <keescook@...omium.org>,
        "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Alexey Dobriyan <adobriyan@...il.com>
Subject: [PATCH] openrisc: Allow power off handler overriding

The OpenRISC platform always defines a default pm_power_off hanlder
which is only useful for simulators.  Having this set also means power
management drivers like syscon-power are not able to wire in their own
pm_power_off handlers.

Fix this by not setting the pm_power_off handler by default and fallback
to the simulator power off handler if no handler is set.

This has been tested with a new OpenRISC virt platform I am working on
for QEMU.

  https://github.com/stffrdhrn/qemu/commits/or1k-virt

Cc: Jason A. Donenfeld <Jason@...c4.com>
Signed-off-by: Stafford Horne <shorne@...il.com>
---
 arch/openrisc/kernel/process.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/arch/openrisc/kernel/process.c b/arch/openrisc/kernel/process.c
index 3c0c91bcdcba..1cca89a3b0c8 100644
--- a/arch/openrisc/kernel/process.c
+++ b/arch/openrisc/kernel/process.c
@@ -60,6 +60,16 @@ void machine_restart(char *cmd)
 	while (1);
 }
 
+/*
+ * This is used if pm_power_off has not been set by a power management
+ * driver, in this case we can assume we are on a simulator.  On
+ * OpenRISC simulators l.nop 1 will trigger the simulator exit.
+ */
+static void default_power_off(void)
+{
+	__asm__("l.nop 1");
+}
+
 /*
  * Similar to machine_power_off, but don't shut off power.  Add code
  * here to freeze the system for e.g. post-mortem debug purpose when
@@ -75,7 +85,10 @@ void machine_halt(void)
 void machine_power_off(void)
 {
 	printk(KERN_INFO "*** MACHINE POWER OFF ***\n");
-	__asm__("l.nop 1");
+	if (pm_power_off != NULL)
+		pm_power_off();
+	else
+		default_power_off();
 }
 
 /*
@@ -89,7 +102,7 @@ void arch_cpu_idle(void)
 		mtspr(SPR_PMR, mfspr(SPR_PMR) | SPR_PMR_DME);
 }
 
-void (*pm_power_off) (void) = machine_power_off;
+void (*pm_power_off)(void) = NULL;
 EXPORT_SYMBOL(pm_power_off);
 
 /*
-- 
2.31.1