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 <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Documentation/devicetree/bindings/powerpc/ibm,powerpc-cpu-features.txt

+*** NOTE ***
+This document is copied from OPAL firmware
+(skiboot/doc/device-tree/ibm,powerpc-cpu-features/binding.txt)
+
+There is more complete overview and documentation of features in that
+source tree.  All patches and modifications should go there.
+************
+
+ibm,powerpc-cpu-features binding
+================================
+
+This device tree binding describes CPU features available to software, with
+enablement, privilege, and compatibility metadata.
+
+More general description of design and implementation of this binding is
+found in design.txt, which also points to documentation of specific features.
+
+
+/cpus/ibm,powerpc-cpu-features node binding
+-------------------------------------------
+
+Node: ibm,powerpc-cpu-features
+
+Description: Container of CPU feature nodes.
+
+The node name must be "ibm,powerpc-cpu-features".
+
+It is implemented as a child of the node "/cpus", but this must not be
+assumed by parsers.
+
+The node is optional but should be provided by new OPAL firmware.
+
+Properties:
+
+- compatible
+  Usage: required
+  Value type: string
+  Definition: "ibm,powerpc-cpu-features"
+
+  This compatibility refers to backwards compatibility of the overall
+  design with parsers that behave according to these guidelines. This can
+  be extended in a backward compatible manner which would not warrant a
+  revision of the compatible property.
+
+- isa
+  Usage: required
+  Value type: <u32>
+  Definition:
+
+  isa that the CPU is currently running in. This provides instruction set
+  compatibility, less the individual feature nodes. For example, an ISA v3.0
+  implementation that lacks the "transactional-memory" cpufeature node
+  should not use transactional memory facilities.
+
+  Value corresponds to the "Power ISA Version" multiplied by 1000.
+  For example, <3000> corresponds to Version 3.0, <2070> to Version 2.07.
+  The minor digit is available for revisions.
+
+- display-name
+  Usage: optional
+  Value type: string
+  Definition:
+
+  A human readable name for the CPU.
+
+/cpus/ibm,powerpc-cpu-features/example-feature node bindings
+----------------------------------------------------------------
+
+Each child node of cpu-features represents a CPU feature / capability.
+
+Node: A string describing an architected CPU feature, e.g., "floating-point".
+
+Description: A feature or capability supported by the CPUs.
+
+The name of the node is a human readable string that forms the interface
+used to describe features to software. Features are currently documented
+in the code where they are implemented in skiboot/core/cpufeatures.c
+
+Presence of the node indicates the feature is available.
+
+Properties:
+
+- isa
+  Usage: required
+  Value type: <u32>
+  Definition:
+
+  First level of the Power ISA that the feature appears in.
+  Software should filter out features when constraining the
+  environment to a particular ISA version.
+
+  Value is defined similarly to /cpus/features/isa
+
+- usable-privilege
+  Usage: required
+  Value type: <u32> bit mask
+  Definition:
+              Bit numbers are LSB0
+              bit 0 - PR (problem state / user mode)
+              bit 1 - OS (privileged state)
+              bit 2 - HV (hypervisor state)
+              All other bits reserved and should be zero.
+
+  This property describes the privilege levels and/or software components
+  that can use the feature.
+
+  If bit 0 is set, then the hwcap-bit-nr property will exist.
+
+
+- hv-support
+  Usage: optional
+  Value type: <u32> bit mask
+  Definition:
+              Bit numbers are LSB0
+              bit 0 -  HFSCR
+              All other bits reserved and should be zero.
+
+  This property describes the HV privilege support required to enable the
+  feature to lesser privilege levels. If the property does not exist then no
+  support is required.
+
+  If no bits are set, the hypervisor must have explicit/custom support for
+  this feature.
+
+  If the HFSCR bit is set, then the hfscr-bit-nr property will exist and
+  the feature may be enabled by setting this bit in the HFSCR register.
+
+
+- os-support
+  Usage: optional
+  Value type: <u32> bit mask
+  Definition:
+              Bit numbers are LSB0
+              bit 0 -  FSCR
+              All other bits reserved and should be zero.
+
+  This property describes the OS privilege support required to enable the
+  feature to lesser privilege levels. If the property does not exist then no
+  support is required.
+
+  If no bits are set, the operating system must have explicit/custom support
+  for this feature.
+
+  If the FSCR bit is set, then the fscr-bit-nr property will exist and
+  the feature may be enabled by setting this bit in the FSCR register.
+
+
+- hfscr-bit-nr
+  Usage: optional
+  Value type: <u32>
+  Definition: HFSCR bit position (LSB0)
+
+  This property exists when the hv-support property HFSCR bit is set. This
+  property describes the bit number in the HFSCR register that the
+  hypervisor must set in order to enable this feature.
+
+  This property also exists if an HFSCR bit corresponds with this feature.
+  This makes CPU feature parsing slightly simpler.
+
+
+- fscr-bit-nr
+  Usage: optional
+  Value type: <u32>
+  Definition: FSCR bit position (LSB0)
+
+  This property exists when the os-support property FSCR bit is set. This
+  property describes the bit number in the FSCR register that the
+  operating system must set in order to enable this feature.
+
+  This property also exists if an FSCR bit corresponds with this feature.
+  This makes CPU feature parsing slightly simpler.
+
+
+- hwcap-bit-nr
+  Usage: optional
+  Value type: <u32>
+  Definition: Linux ELF AUX vector bit position (LSB0)
+
+  This property may exist when the usable-privilege property value has PR bit set.
+  This property describes the bit number that should be set in the ELF AUX
+  hardware capability vectors in order to advertise this feature to userspace.
+  Bits 0-31 correspond to bits 0-31 in AT_HWCAP vector. Bits 32-63 correspond
+  to 0-31 in AT_HWCAP2 vector, and so on.  Missing AT_HWCAPx vectors implies
+  that the feature is not enabled or can not be advertised. Operating systems
+  may provide a number of unassigned hardware capability bits to allow for new
+  features to be advertised.
+
+  Some properties representing features created before this binding are
+  advertised to userspace without a one-to-one hwcap bit number may not specify
+  this bit. Operating system will handle those bits specifically.  All new
+  features usable by userspace will have a hwcap-bit-nr property.
+
+
+- dependencies
+  Usage: optional
+  Value type: <prop-encoded-array>
+  Definition:
+
+  If this property exists then it is a list of phandles to cpu feature
+  nodes that must be enabled for this feature to be enabled.
+
+
+Example
+-------
+
+	/cpus/ibm,powerpc-cpu-features {
+		compatible = "ibm,powerpc-cpu-features";
+
+		isa = <3020>;
+
+		darn {
+			isa = <3000>;
+			usable-privilege = <1 | 2 | 4>;
+			hwcap-bit-nr = <xx>;
+		};
+
+		scv {
+			isa = <3000>;
+			usable-privilege = <1 | 2>;
+			os-support = <0>;
+			hwcap-bit-nr = <xx>;
+		};
+
+		stop {
+			isa = <3000>;
+			usable-privilege = <2 | 4>;
+			hv-support = <0>;
+			os-support = <0>;
+		};
+
+		vsx2 (hypothetical) {
+			isa = <3010>;
+			usable-privilege = <1 | 2 | 4>;
+			hv-support = <0>;
+			os-support = <0>;
+			hwcap-bit-nr = <xx>;
+		};
+
+		vsx2-newinsns {
+			isa = <3020>;
+			usable-privilege = <1 | 2 | 4>;
+			os-support = <1>;
+			fscr-bit-nr = <xx>;
+			hwcap-bit-nr = <xx>;
+			dependencies = <&vsx2>;
+		};
+
+	};

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

-#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

+#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.
 	 */
+	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));
 
-	identical_pvr_fixup(node);
-
 		check_cpu_feature_properties(node);
 		check_cpu_pa_features(node);
+	}
+
+	identical_pvr_fixup(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>
@@ -265,7 +266,9 @@ void __init early_setup(unsigned long dt_ptr)
 
 	/* -------- printk is _NOT_ safe to use here ! ------- */
 
-	/* Identify CPU type */
+	/* 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! */
@@ -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");
 }