linux-kernel - [PATCH 3/3] powernv:idle: Set LPCR

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Date:   Wed, 12 Apr 2017 17:16:22 +0530
From:   "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Michael Neuling <mikey@...ling.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        "Shreyas B. Prabhu" <shreyasbp@...il.com>,
        Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
        Anton Blanchard <anton@...ba.org>,
        Balbir Singh <bsingharora@...il.com>,
        Akshay Adiga <akshay.adiga@...ux.vnet.ibm.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Mahesh J Salgaonkar <mahesh@...ux.vnet.ibm.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
Subject: [PATCH 3/3] powernv:idle: Set LPCR_UPRT on wakeup from deep-stop

From: "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>

On wakeup from a deep-stop used for CPU-Hotplug, we invoke
cur_cpu_spec->cpu_restore() which would set sane default values to
various SPRs including LPCR.

On POWER9, the cpu_restore_power9() call would would restore LPCR to a
sane value that is set at early boot time, thereby clearing LPCR_UPRT.

However, LPCR_UPRT is required to be set if we are running in Radix
mode. If this is not set we will end up with a crash when we enable
IR,DR.

To fix this, after returning from cur_cpu_spec->cpu_restore() in the
idle exit path, set LPCR_UPRT if we are running in Radix mode.

Cc: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
Signed-off-by: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>
---
 arch/powerpc/kernel/idle_book3s.S | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index 6a9bd28..39a9b63 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -804,6 +804,19 @@ no_segments:
 #endif
 	mtctr	r12
 	bctrl
+/*
+ * cur_cpu_spec->cpu_restore would restore LPCR to a
+ * sane value that is set at early boot time,
+ * thereby clearing LPCR_UPRT.
+ * LPCR_UPRT is required if we are running in Radix mode.
+ * Set it here if that be the case.
+ */
+BEGIN_MMU_FTR_SECTION
+	mfspr	r3, SPRN_LPCR
+	LOAD_REG_IMMEDIATE(r4, LPCR_UPRT)
+	or	r3, r3, r4
+	mtspr	SPRN_LPCR, r3
+END_MMU_FTR_SECTION_IFSET(MMU_FTR_TYPE_RADIX)
 
 hypervisor_state_restored:
 
-- 
1.9.4