linux-kernel - [PATCH] powerpc/8xx: use SPRN_EIE and SPRN

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Date:   Thu, 18 Aug 2016 17:56:02 +0200 (CEST)
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Scott Wood <oss@...error.net>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH] powerpc/8xx: use SPRN_EIE and SPRN_EID to enable/disable
 interrupts

The 8xx has two special registers called EID (External Interrupt
Disable) and EIE (External Interrupt Enable) for clearing/setting
EE in MSR. It avoids the three instructions set mfmsr/ori/mtmsr or
mfmsr/rlwinm/mtmsr.

We just have to write something in the register to change MSR EE
bit. So we write r0 into the register, regardless of r0 value.

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
 arch/powerpc/include/asm/hw_irq.h  | 6 ++++++
 arch/powerpc/include/asm/reg.h     | 2 ++
 arch/powerpc/include/asm/reg_8xx.h | 5 +++++
 3 files changed, 13 insertions(+)

diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h
index c7d82ff..7ffb392 100644
--- a/arch/powerpc/include/asm/hw_irq.h
+++ b/arch/powerpc/include/asm/hw_irq.h
@@ -155,6 +155,8 @@ static inline unsigned long arch_local_irq_save(void)
 	unsigned long flags = arch_local_save_flags();
 #ifdef CONFIG_BOOKE
 	asm volatile("wrteei 0" : : : "memory");
+#elif defined(CONFIG_PPC_8xx)
+	wrtspr(SPRN_EID);
 #else
 	SET_MSR_EE(flags & ~MSR_EE);
 #endif
@@ -165,6 +167,8 @@ static inline void arch_local_irq_disable(void)
 {
 #ifdef CONFIG_BOOKE
 	asm volatile("wrteei 0" : : : "memory");
+#elif defined(CONFIG_PPC_8xx)
+	wrtspr(SPRN_EID);
 #else
 	arch_local_irq_save();
 #endif
@@ -174,6 +178,8 @@ static inline void arch_local_irq_enable(void)
 {
 #ifdef CONFIG_BOOKE
 	asm volatile("wrteei 1" : : : "memory");
+#elif defined(CONFIG_PPC_8xx)
+	wrtspr(SPRN_EIE);
 #else
 	unsigned long msr = mfmsr();
 	SET_MSR_EE(msr | MSR_EE);
diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index f69f40f..4bbd9be 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -1246,6 +1246,8 @@ static inline void mtmsr_isync(unsigned long val)
 				     : "r" ((unsigned long)(v)) \
 				     : "memory")
 #endif
+#define wrtspr(rn)	asm volatile("mtspr " __stringify(rn) ",0" : \
+				     : : "memory")
 
 extern void msr_check_and_set(unsigned long bits);
 extern bool strict_msr_control;
diff --git a/arch/powerpc/include/asm/reg_8xx.h b/arch/powerpc/include/asm/reg_8xx.h
index 6dae71f..d4bca3de 100644
--- a/arch/powerpc/include/asm/reg_8xx.h
+++ b/arch/powerpc/include/asm/reg_8xx.h
@@ -6,6 +6,11 @@
 
 #include <asm/mmu.h>
 
+/* Special MSR manipulation registers */
+#define SPRN_EIE	80	/* External interrupt enable (EE=1, RI=1) */
+#define SPRN_EID	81	/* External interrupt disable (EE=0, RI=1) */
+#define SPRN_NRI	81	/* Non Recoverable interrupt (EE=0, RI=0) */
+
 /* Cache control on the MPC8xx is provided through some additional
  * special purpose registers.
  */
-- 
2.1.0