linux-kernel - [PATCH 3/6] powernv:idle: Restore LPCR on wakeup from deep-stop

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Date:   Tue, 16 May 2017 14:19:45 +0530
From:   "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
To:     Nicholas Piggin <npiggin@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Michael Neuling <mikey@...ling.org>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
        Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>,
        Akshay Adiga <akshay.adiga@...ux.vnet.ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
Subject: [PATCH 3/6] powernv:idle: Restore LPCR on wakeup from deep-stop

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

On wakeup from a deep stop state which is supposed to lose the
hypervisor state, we don't restore the LPCR to the old value but set
it to a "sane" value via cur_cpu_spec->cpu_restore().

The problem is that the "sane" value doesn't include UPRT and the HR
bits which are required to run correctly in Radix mode.

Fix this on POWER9 onwards by restoring the LPCR value whatever it was
before executing the stop instruction.

Signed-off-by: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>
---
 arch/powerpc/kernel/idle_book3s.S | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index afd029f..6c9920d 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -31,6 +31,7 @@
  * registers for winkle support.
  */
 #define _SDR1	GPR3
+#define _PTCR	GPR3
 #define _RPR	GPR4
 #define _SPURR	GPR5
 #define _PURR	GPR6
@@ -39,7 +40,7 @@
 #define _AMOR	GPR9
 #define _WORT	GPR10
 #define _WORC	GPR11
-#define _PTCR	GPR12
+#define _LPCR	GPR12
 
 #define PSSCR_EC_ESL_MASK_SHIFTED          (PSSCR_EC | PSSCR_ESL) >> 16
 
@@ -55,12 +56,14 @@ save_sprs_to_stack:
 	 * here since any thread in the core might wake up first
 	 */
 BEGIN_FTR_SECTION
-	mfspr	r3,SPRN_PTCR
-	std	r3,_PTCR(r1)
 	/*
 	 * Note - SDR1 is dropped in Power ISA v3. Hence not restoring
 	 * SDR1 here
 	 */
+	mfspr	r3,SPRN_PTCR
+	std	r3,_PTCR(r1)
+	mfspr	r3,SPRN_LPCR
+	std	r3,_LPCR(r1)
 FTR_SECTION_ELSE
 	mfspr	r3,SPRN_SDR1
 	std	r3,_SDR1(r1)
@@ -813,6 +816,10 @@ no_segments:
 	mtctr	r12
 	bctrl
 
+BEGIN_FTR_SECTION
+	ld	r4,_LPCR(r1)
+	mtspr	SPRN_LPCR,r4
+END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
 hypervisor_state_restored:
 
 	mtspr	SPRN_SRR1,r16
-- 
1.8.3.1