MIPS: perf: Add cpu feature bit for PCI (performance counter interrupt)

The PCI (Program Counter Interrupt) bit in the "cause" register
is mandatory for MIPS32R2 cores, but has also been added to some R1
cores (BMIPS5000). This change adds a cpu feature bit to make it
easier to check for and use this feature.

Signed-off-by: Al Cooper <alcooperx@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/4106/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/cpu-features.h

@@ -252,4 +252,8 @@
 #define cpu_hwrena_impl_bits		0
 #endif
 
+#ifndef cpu_has_perf_cntr_intr_bit
+#define cpu_has_perf_cntr_intr_bit	(cpu_data[0].options & MIPS_CPU_PCI)
+#endif
+
 #endif /* __ASM_CPU_FEATURES_H */

arch/mips/include/asm/cpu.h

@@ -320,7 +320,8 @@ enum cpu_type_enum {
 #define MIPS_CPU_VINT		0x00080000 /* CPU supports MIPSR2 vectored interrupts */
 #define MIPS_CPU_VEIC		0x00100000 /* CPU supports MIPSR2 external interrupt controller mode */
 #define MIPS_CPU_ULRI		0x00200000 /* CPU has ULRI feature */
-#define MIPS_CPU_RIXI		0x00400000 /* CPU has TLB Read/eXec Inhibit */
+#define MIPS_CPU_PCI		0x00400000 /* CPU has Perf Ctr Int indicator */
+#define MIPS_CPU_RIXI		0x00800000 /* CPU has TLB Read/eXec Inhibit */
 
 /*
  * CPU ASE encodings

arch/mips/include/asm/mipsregs.h

@@ -458,6 +458,8 @@
 #define  CAUSEF_IP7		(_ULCAST_(1)   << 15)
 #define  CAUSEB_IV		23
 #define  CAUSEF_IV		(_ULCAST_(1)   << 23)
+#define  CAUSEB_PCI		26
+#define  CAUSEF_PCI		(_ULCAST_(1)   << 26)
 #define  CAUSEB_CE		28
 #define  CAUSEF_CE		(_ULCAST_(3)   << 28)
 #define  CAUSEB_TI		30

arch/mips/kernel/cpu-probe.c

@@ -1194,8 +1194,11 @@ __cpuinit void cpu_probe(void)
 		}
 	}
 
-	if (cpu_has_mips_r2)
+	if (cpu_has_mips_r2) {
 		c->srsets = ((read_c0_srsctl() >> 26) & 0x0f) + 1;
+		/* R2 has Performance Counter Interrupt indicator */
+		c->options |= MIPS_CPU_PCI;
+	}
 	else
 		c->srsets = 1;
 

arch/mips/kernel/perf_event_mipsxx.c

@@ -1158,7 +1158,7 @@ static int mipsxx_pmu_handle_shared_irq(void)
 	int handled = IRQ_NONE;
 	struct pt_regs *regs;
 
-	if (cpu_has_mips_r2 && !(read_c0_cause() & (1 << 26)))
+	if (cpu_has_perf_cntr_intr_bit && !(read_c0_cause() & CAUSEF_PCI))
 		return handled;
 	/*
 	 * First we pause the local counters, so that when we are locked