[PATCH 2/6] powerpc: Add enable_ppr kernel parameter to enable PPR save/restore

[Haren Myneni <haren@linux.vnet.ibm.com>]

enable_ppr kernel parameter is used to enable PPR save and restore.
Supported on Power7 and later processors.

By default, CPU_FTR_HAS_PPR is set for POWER7. If this parameter is not
passed, disable CPU_FTR_HAS_PPR.

Signed-off-by: Haren Myneni <haren@us.ibm.com>

---
 Documentation/kernel-parameters.txt |    4 ++++
 arch/powerpc/include/asm/cputable.h |    6 ++++--
 arch/powerpc/kernel/setup_64.c      |   14 ++++++++++++++
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index ad7e2e5..2881e5f 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -809,6 +809,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			to discrete, to make X server driver able to add WB
 			entry later. This parameter enables that.
 
+	enable_ppr	[PPC/PSERIES]
+			Saves user defined PPR when process enters to kernel 
+			and restores PPR at exit. But it impacts performance.
+
 	enable_timer_pin_1 [X86]
 			Enable PIN 1 of APIC timer
 			Can be useful to work around chipset bugs
diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h
index b3c083d..880c469 100644
--- a/arch/powerpc/include/asm/cputable.h
+++ b/arch/powerpc/include/asm/cputable.h
@@ -203,6 +203,7 @@ extern const char *powerpc_base_platform;
 #define CPU_FTR_POPCNTD			LONG_ASM_CONST(0x0800000000000000)
 #define CPU_FTR_ICSWX			LONG_ASM_CONST(0x1000000000000000)
 #define CPU_FTR_VMX_COPY		LONG_ASM_CONST(0x2000000000000000)
+#define CPU_FTR_HAS_PPR			LONG_ASM_CONST(0x4000000000000000)
 
 #ifndef __ASSEMBLY__
 
@@ -432,7 +433,8 @@ extern const char *powerpc_base_platform;
 	    CPU_FTR_PURR | CPU_FTR_SPURR | CPU_FTR_REAL_LE | \
 	    CPU_FTR_DSCR | CPU_FTR_SAO  | CPU_FTR_ASYM_SMT | \
 	    CPU_FTR_STCX_CHECKS_ADDRESS | CPU_FTR_POPCNTB | CPU_FTR_POPCNTD | \
-	    CPU_FTR_ICSWX | CPU_FTR_CFAR | CPU_FTR_HVMODE | CPU_FTR_VMX_COPY)
+	    CPU_FTR_ICSWX | CPU_FTR_CFAR | CPU_FTR_HVMODE | \
+	    CPU_FTR_VMX_COPY | CPU_FTR_HAS_PPR)
 #define CPU_FTRS_CELL	(CPU_FTR_USE_TB | CPU_FTR_LWSYNC | \
 	    CPU_FTR_PPCAS_ARCH_V2 | CPU_FTR_CTRL | \
 	    CPU_FTR_ALTIVEC_COMP | CPU_FTR_MMCRA | CPU_FTR_SMT | \
@@ -454,7 +456,7 @@ extern const char *powerpc_base_platform;
 	    (CPU_FTRS_POWER3 | CPU_FTRS_RS64 | CPU_FTRS_POWER4 |	\
 	    CPU_FTRS_PPC970 | CPU_FTRS_POWER5 | CPU_FTRS_POWER6 |	\
 	    CPU_FTRS_POWER7 | CPU_FTRS_CELL | CPU_FTRS_PA6T |		\
-	    CPU_FTR_VSX)
+	    CPU_FTR_VSX | CPU_FTR_HAS_PPR)
 #endif
 #else
 enum {
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 389bd4f..e4c1945 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -98,6 +98,8 @@ int dcache_bsize;
 int icache_bsize;
 int ucache_bsize;
 
+static u32 enable_ppr = 0;
+
 #ifdef CONFIG_SMP
 
 static char *smt_enabled_cmdline;
@@ -357,6 +359,9 @@ void __init setup_system(void)
 {
 	DBG(" -> setup_system()\n");
 
+	if (cpu_has_feature(CPU_FTR_HAS_PPR) && !enable_ppr)
+		cur_cpu_spec->cpu_features &= ~CPU_FTR_HAS_PPR;
+
 	/* Apply the CPUs-specific and firmware specific fixups to kernel
 	 * text (nop out sections not relevant to this CPU or this firmware)
 	 */
@@ -683,6 +688,15 @@ void __init setup_per_cpu_areas(void)
 }
 #endif
 
+/* early_ppr kernel parameter to save/restore PPR register */
+static int __init early_ppr_enabled(char *str)
+{
+	enable_ppr = 1;
+
+	return 0;
+}
+
+early_param("enable_ppr", early_ppr_enabled);
 
 #ifdef CONFIG_PPC_INDIRECT_IO
 struct ppc_pci_io ppc_pci_io;
-- 
1.7.10.4