powerpc/64s: Support new device tree binding for discovering CPU features

The ibm,powerpc-cpu-features device tree binding describes CPU features with
ASCII names and extensible compatibility, privilege, and enablement metadata
that allows improved flexibility and compatibility with new hardware.

The interface is described in detail in ibm,powerpc-cpu-features.txt in this
patch.

Currently this code is not enabled by default, and there are no released
firmwares that provide the binding.

Signed-off-by: Nicholas Piggin <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>

arch/powerpc/Kconfig

@@ -380,6 +380,22 @@ source "arch/powerpc/platforms/Kconfig"
 
 menu "Kernel options"
 
+config PPC_DT_CPU_FTRS
+	bool "Device-tree based CPU feature discovery & setup"
+	depends on PPC_BOOK3S_64
+	default n
+	help
+	  This enables code to use a new device tree binding for describing CPU
+	  compatibility and features. Saying Y here will attempt to use the new
+	  binding if the firmware provides it. Currently only the skiboot
+	  firmware provides this binding.
+	  If you're not sure say Y.
+
+config PPC_CPUFEATURES_ENABLE_UNKNOWN
+	bool "cpufeatures pass through unknown features to guest/userspace"
+	depends on PPC_DT_CPU_FTRS
+	default y
+
 config HIGHMEM
 	bool "High memory support"
 	depends on PPC32

arch/powerpc/include/asm/cpu_has_feature.h

@@ -1,5 +1,5 @@
-#ifndef __ASM_POWERPC_CPUFEATURES_H
-#define __ASM_POWERPC_CPUFEATURES_H
+#ifndef __ASM_POWERPC_CPU_HAS_FEATURE_H
+#define __ASM_POWERPC_CPU_HAS_FEATURE_H
 
 #ifndef __ASSEMBLY__
 
@@ -52,4 +52,4 @@ static inline bool cpu_has_feature(unsigned long feature)
 #endif
 
 #endif /* __ASSEMBLY__ */
-#endif /* __ASM_POWERPC_CPUFEATURE_H */
+#endif /* __ASM_POWERPC_CPU_HAS_FEATURE_H */

arch/powerpc/include/asm/cputable.h

@@ -118,7 +118,9 @@ extern struct cpu_spec		*cur_cpu_spec;
 
 extern unsigned int __start___ftr_fixup, __stop___ftr_fixup;
 
+extern void set_cur_cpu_spec(struct cpu_spec *s);
 extern struct cpu_spec *identify_cpu(unsigned long offset, unsigned int pvr);
+extern void identify_cpu_name(unsigned int pvr);
 extern void do_feature_fixups(unsigned long value, void *fixup_start,
 			      void *fixup_end);
 

arch/powerpc/include/asm/dt_cpu_ftrs.h

@@ -0,0 +1,26 @@
+#ifndef __ASM_POWERPC_DT_CPU_FTRS_H
+#define __ASM_POWERPC_DT_CPU_FTRS_H
+
+/*
+ *  Copyright 2017, IBM Corporation
+ *  cpufeatures is the new way to discover CPU features with /cpus/features
+ *  devicetree. This supersedes PVR based discovery ("cputable"), and older
+ *  device tree feature advertisement.
+ */
+
+#include <linux/types.h>
+#include <asm/asm-compat.h>
+#include <asm/feature-fixups.h>
+#include <uapi/asm/cputable.h>
+
+#ifdef CONFIG_PPC_DT_CPU_FTRS
+bool dt_cpu_ftrs_init(void *fdt);
+void dt_cpu_ftrs_scan(void);
+bool dt_cpu_ftrs_in_use(void);
+#else
+static inline bool dt_cpu_ftrs_init(void *fdt) { return false; }
+static inline void dt_cpu_ftrs_scan(void) { }
+static inline bool dt_cpu_ftrs_in_use(void) { return false; }
+#endif
+
+#endif /* __ASM_POWERPC_DT_CPU_FTRS_H */

arch/powerpc/include/asm/reg.h

@@ -1229,6 +1229,7 @@
 #define PVR_POWER8E	0x004B
 #define PVR_POWER8NVL	0x004C
 #define PVR_POWER8	0x004D
+#define PVR_POWER9	0x004E
 #define PVR_BE		0x0070
 #define PVR_PA6T	0x0090
 

arch/powerpc/include/uapi/asm/cputable.h

@@ -47,4 +47,11 @@
 #define PPC_FEATURE2_ARCH_3_00		0x00800000 /* ISA 3.00 */
 #define PPC_FEATURE2_HAS_IEEE128	0x00400000 /* VSX IEEE Binary Float 128-bit */
 
+/*
+ * IMPORTANT!
+ * All future PPC_FEATURE definitions should be allocated in cooperation with
+ * OPAL / skiboot firmware, in accordance with the ibm,powerpc-cpu-features
+ * device tree binding.
+ */
+
 #endif /* _UAPI__ASM_POWERPC_CPUTABLE_H */

arch/powerpc/kernel/Makefile

@@ -56,6 +56,7 @@ obj-$(CONFIG_PPC_RTAS)		+= rtas.o rtas-rtc.o $(rtaspci-y-y)
 obj-$(CONFIG_PPC_RTAS_DAEMON)	+= rtasd.o
 obj-$(CONFIG_RTAS_FLASH)	+= rtas_flash.o
 obj-$(CONFIG_RTAS_PROC)		+= rtas-proc.o
+obj-$(CONFIG_PPC_DT_CPU_FTRS)	+= dt_cpu_ftrs.o
 obj-$(CONFIG_EEH)              += eeh.o eeh_pe.o eeh_dev.o eeh_cache.o \
 				  eeh_driver.o eeh_event.o eeh_sysfs.o
 obj-$(CONFIG_GENERIC_TBSYNC)	+= smp-tbsync.o

arch/powerpc/kernel/cputable.c

@@ -23,7 +23,9 @@
 #include <asm/mmu.h>
 #include <asm/setup.h>
 
-struct cpu_spec* cur_cpu_spec = NULL;
+static struct cpu_spec the_cpu_spec __read_mostly;
+
+struct cpu_spec* cur_cpu_spec __read_mostly = NULL;
 EXPORT_SYMBOL(cur_cpu_spec);
 
 /* The platform string corresponding to the real PVR */
@@ -2179,7 +2181,15 @@ static struct cpu_spec __initdata cpu_specs[] = {
 #endif /* CONFIG_E500 */
 };
 
-static struct cpu_spec the_cpu_spec;
+void __init set_cur_cpu_spec(struct cpu_spec *s)
+{
+	struct cpu_spec *t = &the_cpu_spec;
+
+	t = PTRRELOC(t);
+	*t = *s;
+
+	*PTRRELOC(&cur_cpu_spec) = &the_cpu_spec;
+}
 
 static struct cpu_spec * __init setup_cpu_spec(unsigned long offset,
 					       struct cpu_spec *s)
@@ -2266,6 +2276,29 @@ struct cpu_spec * __init identify_cpu(unsigned long offset, unsigned int pvr)
 	return NULL;
 }
 
+/*
+ * Used by cpufeatures to get the name for CPUs with a PVR table.
+ * If they don't hae a PVR table, cpufeatures gets the name from
+ * cpu device-tree node.
+ */
+void __init identify_cpu_name(unsigned int pvr)
+{
+	struct cpu_spec *s = cpu_specs;
+	struct cpu_spec *t = &the_cpu_spec;
+	int i;
+
+	s = PTRRELOC(s);
+	t = PTRRELOC(t);
+
+	for (i = 0; i < ARRAY_SIZE(cpu_specs); i++,s++) {
+		if ((pvr & s->pvr_mask) == s->pvr_value) {
+			t->cpu_name = s->cpu_name;
+			return;
+		}
+	}
+}
+
+
 #ifdef CONFIG_JUMP_LABEL_FEATURE_CHECKS
 struct static_key_true cpu_feature_keys[NUM_CPU_FTR_KEYS] = {
 			[0 ... NUM_CPU_FTR_KEYS - 1] = STATIC_KEY_TRUE_INIT

arch/powerpc/kernel/prom.c

@@ -57,6 +57,7 @@
 #include <asm/fadump.h>
 #include <asm/epapr_hcalls.h>
 #include <asm/firmware.h>
+#include <asm/dt_cpu_ftrs.h>
 
 #include <mm/mmu_decl.h>
 
@@ -375,23 +376,31 @@ static int __init early_init_dt_scan_cpus(unsigned long node,
 	 * A POWER6 partition in "POWER6 architected" mode
 	 * uses the 0x0f000002 PVR value; in POWER5+ mode
 	 * it uses 0x0f000001.
+	 *
+	 * If we're using device tree CPU feature discovery then we don't
+	 * support the cpu-version property, and it's the responsibility of the
+	 * firmware/hypervisor to provide the correct feature set for the
+	 * architecture level via the ibm,powerpc-cpu-features binding.
 	 */
-	prop = of_get_flat_dt_prop(node, "cpu-version", NULL);
-	if (prop && (be32_to_cpup(prop) & 0xff000000) == 0x0f000000)
-		identify_cpu(0, be32_to_cpup(prop));
+	if (!dt_cpu_ftrs_in_use()) {
+		prop = of_get_flat_dt_prop(node, "cpu-version", NULL);
+		if (prop && (be32_to_cpup(prop) & 0xff000000) == 0x0f000000)
+			identify_cpu(0, be32_to_cpup(prop));
+
+		check_cpu_feature_properties(node);
+		check_cpu_pa_features(node);
+	}
 
 	identical_pvr_fixup(node);
-
-	check_cpu_feature_properties(node);
-	check_cpu_pa_features(node);
 	init_mmu_slb_size(node);
 
 #ifdef CONFIG_PPC64
-	if (nthreads > 1)
-		cur_cpu_spec->cpu_features |= CPU_FTR_SMT;
-	else
+	if (nthreads == 1)
 		cur_cpu_spec->cpu_features &= ~CPU_FTR_SMT;
+	else if (!dt_cpu_ftrs_in_use())
+		cur_cpu_spec->cpu_features |= CPU_FTR_SMT;
 #endif
+
 	return 0;
 }
 
@@ -721,6 +730,8 @@ void __init early_init_devtree(void *params)
 
 	DBG("Scanning CPUs ...\n");
 
+	dt_cpu_ftrs_scan();
+
 	/* Retrieve CPU related informations from the flat tree
 	 * (altivec support, boot CPU ID, ...)
 	 */

arch/powerpc/kernel/setup_64.c

@@ -49,6 +49,7 @@
 #include <asm/paca.h>
 #include <asm/time.h>
 #include <asm/cputable.h>
+#include <asm/dt_cpu_ftrs.h>
 #include <asm/sections.h>
 #include <asm/btext.h>
 #include <asm/nvram.h>
@@ -265,8 +266,10 @@ void __init early_setup(unsigned long dt_ptr)
 
 	/* -------- printk is _NOT_ safe to use here ! ------- */
 
-	/* Identify CPU type */
-	identify_cpu(0, mfspr(SPRN_PVR));
+	/* Try new device tree based feature discovery ... */
+	if (!dt_cpu_ftrs_init(__va(dt_ptr)))
+		/* Otherwise use the old style CPU table */
+		identify_cpu(0, mfspr(SPRN_PVR));
 
 	/* Assume we're on cpu 0 for now. Don't write to the paca yet! */
 	initialise_paca(&boot_paca, 0);
@@ -532,6 +535,9 @@ void __init initialize_cache_info(void)
 	dcache_bsize = ppc64_caches.l1d.block_size;
 	icache_bsize = ppc64_caches.l1i.block_size;
 
+	cur_cpu_spec->dcache_bsize = dcache_bsize;
+	cur_cpu_spec->icache_bsize = icache_bsize;
+
 	DBG(" <- initialize_cache_info()\n");
 }