[PATCH] powerpc/dt_cpu_ftrs: Add MMA feature

[Alistair Popple]

MMA (matrix multiply accumulate) instructions are only permitted to
execute when enabled via a PCR bit. Enable this bit when support is
advertised by a CPU device tree feature.

Signed-off-by: Alistair Popple <alistair at popple.id.au>
---
 arch/powerpc/include/asm/reg.h    |  1 +
 arch/powerpc/kernel/dt_cpu_ftrs.c | 17 ++++++++++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index da5cab038e25..6366f0223c80 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -476,6 +476,7 @@
 #define   PCR_VEC_DIS	(__MASK(63-0))	/* Vec. disable (bit NA since POWER8) */
 #define   PCR_VSX_DIS	(__MASK(63-1))	/* VSX disable (bit NA since POWER8) */
 #define   PCR_TM_DIS	(__MASK(63-2))	/* Trans. memory disable (POWER8) */
+#define   PCR_MMA_DIS	(__MASK(63-3)) /* Matrix-Multiply Accelerator */
 #define   PCR_HIGH_BITS	(PCR_VEC_DIS | PCR_VSX_DIS | PCR_TM_DIS)
 /*
  * These bits are used in the function kvmppc_set_arch_compat() to specify and
diff --git a/arch/powerpc/kernel/dt_cpu_ftrs.c b/arch/powerpc/kernel/dt_cpu_ftrs.c
index 36bc0d5c4f3a..26e811ab94c1 100644
--- a/arch/powerpc/kernel/dt_cpu_ftrs.c
+++ b/arch/powerpc/kernel/dt_cpu_ftrs.c
@@ -74,6 +74,7 @@ static struct {
 	u64	lpcr_clear;
 	u64	hfscr;
 	u64	fscr;
+	u64	pcr;
 } system_registers;
 
 static void (*init_pmu_registers)(void);
@@ -101,7 +102,7 @@ static void __restore_cpu_cpufeatures(void)
 	if (hv_mode) {
 		mtspr(SPRN_LPID, 0);
 		mtspr(SPRN_HFSCR, system_registers.hfscr);
-		mtspr(SPRN_PCR, PCR_MASK);
+		mtspr(SPRN_PCR, system_registers.pcr);
 	}
 	mtspr(SPRN_FSCR, system_registers.fscr);
 
@@ -552,6 +553,18 @@ static int __init feat_enable_large_ci(struct dt_cpu_feature *f)
 	return 1;
 }
 
+static int __init feat_enable_mma(struct dt_cpu_feature *f)
+{
+	u64 pcr;
+
+	feat_enable(f);
+	pcr = mfspr(SPRN_PCR);
+	pcr &= ~PCR_MMA_DIS;
+	mtspr(SPRN_PCR, pcr);
+
+	return 1;
+}
+
 struct dt_cpu_feature_match {
 	const char *name;
 	int (*enable)(struct dt_cpu_feature *f);
@@ -625,6 +638,7 @@ static struct dt_cpu_feature_match __initdata
 	{"vector-binary128", feat_enable, 0},
 	{"vector-binary16", feat_enable, 0},
 	{"wait-v3", feat_enable, 0},
+	{"matrix-multiply-accumulate", feat_enable_mma, 0},
 };
 
 static bool __initdata using_dt_cpu_ftrs;
@@ -770,6 +784,7 @@ static void __init cpufeatures_setup_finished(void)
 	system_registers.lpcr = mfspr(SPRN_LPCR);
 	system_registers.hfscr = mfspr(SPRN_HFSCR);
 	system_registers.fscr = mfspr(SPRN_FSCR);
+	system_registers.pcr = mfspr(SPRN_PCR);
 
 	pr_info("final cpu/mmu features = 0x%016lx 0x%08x\n",
 		cur_cpu_spec->cpu_features, cur_cpu_spec->mmu_features);
-- 
2.20.1