powerpc/64s: Fix Power9 DD2.0 workarounds by adding DD2.1 feature

Recently we added a CPU feature for Power9 DD2.0, to capture the fact
that some workarounds are required only on Power9 DD1 and DD2.0 but
not DD2.1 or later.

Then in commit 9d2f510a ("powerpc/64s/idle: avoid POWER9 DD1 and
DD2.0 ERAT workaround on DD2.1") and commit e3646330
"powerpc/64s/idle: avoid POWER9 DD1 and DD2.0 PMU workaround on
DD2.1") we changed CPU_FTR_SECTIONs to check for DD1 or DD20, eg:

  BEGIN_FTR_SECTION
          PPC_INVALIDATE_ERAT
  END_FTR_SECTION_IFSET(CPU_FTR_POWER9_DD1 | CPU_FTR_POWER9_DD20)

Unfortunately although this reads as "if set DD1 or DD2.0", the or is
a bitwise or and actually generates a mask of both bits. The code that
does the feature patching then checks that the value of the CPU
features masked with that mask are equal to the mask.

So the end result is we're checking for DD1 and DD20 being set, which
never happens. Yes the API is terrible.

Removing the ERAT workaround on DD2.0 results in random SEGVs, the
system tends to boot, but things randomly die including sometimes
dhclient, udev etc.

To fix the problem and hopefully avoid it in future, we remove the
DD2.0 CPU feature and instead add a DD2.1 (or later) feature. This
allows us to easily express that the workarounds are required if DD2.1
is not set.

At some point we will drop the DD1 workarounds entirely and some of
this can be cleaned up.

Fixes: 9d2f510a ("powerpc/64s/idle: avoid POWER9 DD1 and DD2.0 ERAT workaround on DD2.1")
Fixes: e3646330 ("powerpc/64s/idle: avoid POWER9 DD1 and DD2.0 PMU workaround on DD2.1")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/cputable.h

@@ -215,7 +215,7 @@ enum {
 #define CPU_FTR_DABRX			LONG_ASM_CONST(0x0800000000000000)
 #define CPU_FTR_PMAO_BUG		LONG_ASM_CONST(0x1000000000000000)
 #define CPU_FTR_POWER9_DD1		LONG_ASM_CONST(0x4000000000000000)
-#define CPU_FTR_POWER9_DD20		LONG_ASM_CONST(0x8000000000000000)
+#define CPU_FTR_POWER9_DD2_1		LONG_ASM_CONST(0x8000000000000000)
 
 #ifndef __ASSEMBLY__
 
@@ -478,7 +478,8 @@ enum {
 	    CPU_FTR_ARCH_207S | CPU_FTR_TM_COMP | CPU_FTR_ARCH_300)
 #define CPU_FTRS_POWER9_DD1 ((CPU_FTRS_POWER9 | CPU_FTR_POWER9_DD1) & \
 			     (~CPU_FTR_SAO))
-#define CPU_FTRS_POWER9_DD20 (CPU_FTRS_POWER9 | CPU_FTR_POWER9_DD20)
+#define CPU_FTRS_POWER9_DD2_0 CPU_FTRS_POWER9
+#define CPU_FTRS_POWER9_DD2_1 (CPU_FTRS_POWER9 | CPU_FTR_POWER9_DD2_1)
 #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 | \
@@ -498,7 +499,7 @@ enum {
 	     CPU_FTRS_POWER6 | CPU_FTRS_POWER7 | CPU_FTRS_POWER8E | \
 	     CPU_FTRS_POWER8 | CPU_FTRS_POWER8_DD1 | CPU_FTRS_CELL | \
 	     CPU_FTRS_PA6T | CPU_FTR_VSX | CPU_FTRS_POWER9 | \
-	     CPU_FTRS_POWER9_DD1 | CPU_FTRS_POWER9_DD20)
+	     CPU_FTRS_POWER9_DD1 | CPU_FTRS_POWER9_DD2_1)
 #endif
 #else
 enum {

arch/powerpc/kernel/cputable.c

@@ -551,7 +551,7 @@ static struct cpu_spec __initdata cpu_specs[] = {
 		.pvr_mask		= 0xffffefff,
 		.pvr_value		= 0x004e0200,
 		.cpu_name		= "POWER9 (raw)",
-		.cpu_features		= CPU_FTRS_POWER9_DD20,
+		.cpu_features		= CPU_FTRS_POWER9_DD2_0,
 		.cpu_user_features	= COMMON_USER_POWER9,
 		.cpu_user_features2	= COMMON_USER2_POWER9,
 		.mmu_features		= MMU_FTRS_POWER9,
@@ -567,11 +567,11 @@ static struct cpu_spec __initdata cpu_specs[] = {
 		.machine_check_early	= __machine_check_early_realmode_p9,
 		.platform		= "power9",
 	},
-	{	/* Power9 */
+	{	/* Power9 DD 2.1 or later (see DD2.0 above) */
 		.pvr_mask		= 0xffff0000,
 		.pvr_value		= 0x004e0000,
 		.cpu_name		= "POWER9 (raw)",
-		.cpu_features		= CPU_FTRS_POWER9,
+		.cpu_features		= CPU_FTRS_POWER9_DD2_1,
 		.cpu_user_features	= COMMON_USER_POWER9,
 		.cpu_user_features2	= COMMON_USER2_POWER9,
 		.mmu_features		= MMU_FTRS_POWER9,

arch/powerpc/kernel/dt_cpu_ftrs.c

@@ -736,7 +736,7 @@ static __init void cpufeatures_cpu_quirks(void)
 	if ((version & 0xffffff00) == 0x004e0100)
 		cur_cpu_spec->cpu_features |= CPU_FTR_POWER9_DD1;
 	else if ((version & 0xffffefff) == 0x004e0200)
-		cur_cpu_spec->cpu_features |= CPU_FTR_POWER9_DD20;
+		cur_cpu_spec->cpu_features &= ~CPU_FTR_POWER9_DD2_1;
 }
 
 static void __init cpufeatures_setup_finished(void)

arch/powerpc/kernel/idle_book3s.S

@@ -357,13 +357,13 @@ power_enter_stop:
 .Lhandle_esl_ec_set:
 BEGIN_FTR_SECTION
 	/*
-	 * POWER9 DD2 can incorrectly set PMAO when waking up after a
-	 * state-loss idle. Saving and restoring MMCR0 over idle is a
+	 * POWER9 DD2.0 or earlier can incorrectly set PMAO when waking up after
+	 * a state-loss idle. Saving and restoring MMCR0 over idle is a
 	 * workaround.
 	 */
 	mfspr	r4,SPRN_MMCR0
 	std	r4,_MMCR0(r1)
-END_FTR_SECTION_IFSET(CPU_FTR_POWER9_DD1 | CPU_FTR_POWER9_DD20)
+END_FTR_SECTION_IFCLR(CPU_FTR_POWER9_DD2_1)
 
 /*
  * Check if the requested state is a deep idle state.
@@ -554,7 +554,7 @@ BEGIN_FTR_SECTION
 	ld	r1,PACAR1(r13)
 	ld	r4,_MMCR0(r1)
 	mtspr	SPRN_MMCR0,r4
-END_FTR_SECTION_IFSET(CPU_FTR_POWER9_DD1 | CPU_FTR_POWER9_DD20)
+END_FTR_SECTION_IFCLR(CPU_FTR_POWER9_DD2_1)
 	mfspr	r4,SPRN_MMCRA
 	ori	r4,r4,(1 << (63-60))
 	mtspr	SPRN_MMCRA,r4