[dpdk-dev] [PATCH] build: add support for detecting march on ARM

[Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>]

Added support for detecting march and mcpu by reading midr_el1 register.
The implementer, primary part number values read can be used to figure
out the underlying arm cpu.

Signed-off-by: Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>
---

 The current method used for reading MIDR_EL1 form userspace might not be
 reliable and can be easily modified by updating config/arm/machine.py.

 More info on midr_el1 can be found at
 http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0500g/BABFEABI.html

 This patch depends on http://dpdk.org/dev/patchwork/patch/32410/

 config/arm/machine.py  | 18 ++++++++++++++++++
 config/arm/meson.build | 20 ++++++++++++++++++++
 config/meson.build     |  3 ++-
 drivers/meson.build    |  2 +-
 examples/meson.build   |  2 +-
 lib/meson.build        |  2 +-
 meson.build            |  2 +-
 7 files changed, 44 insertions(+), 5 deletions(-)
 create mode 100755 config/arm/machine.py

diff --git a/config/arm/machine.py b/config/arm/machine.py
new file mode 100755
index 000000000..3c6e7b6a7
--- /dev/null
+++ b/config/arm/machine.py
@@ -0,0 +1,18 @@
+#!/usr/bin/python
+import pprint
+pp = pprint
+
+ident = []
+fname = '/sys/devices/system/cpu/cpu0/regs/identification/midr_el1'
+with open(fname) as f:
+    content = f.read()
+
+midr_el1 = (int(content.rstrip('\n'), 16))
+
+ident.append(hex((midr_el1 >> 24) & 0xFF))  # Implementer
+ident.append(hex((midr_el1 >> 20) & 0xF))   # Variant
+ident.append(hex((midr_el1 >> 16) & 0XF))   # Architecture
+ident.append(hex((midr_el1 >> 4) & 0xFFF))  # Primary Part number
+ident.append(hex(midr_el1 & 0xF))           # Revision
+
+print(' '.join(ident))
diff --git a/config/arm/meson.build b/config/arm/meson.build
index 250958415..f6ae69c21 100644
--- a/config/arm/meson.build
+++ b/config/arm/meson.build
@@ -41,3 +41,23 @@ else
 endif
 dpdk_conf.set('RTE_CACHE_LINE_SIZE', 128)
 dpdk_conf.set('RTE_FORCE_INTRINSICS', 1)
+
+detect_vendor = find_program(join_paths(meson.current_source_dir(),
+			'machine.py'))
+cmd = run_command(detect_vendor.path())
+if cmd.returncode() != 0
+	message('Unable to read midr_el1')
+else
+	cmd_output = cmd.stdout().strip().split(' ')
+	message('midr_el1 output: \n' + 'Implementor ' + cmd_output[0] +
+			' Variant ' + cmd_output[1] + ' Architecture ' +
+			cmd_output[2] + ' Primary Part number ' + cmd_output[3]
+			+ ' Revision ' + cmd_output[4])
+	if cmd_output[0] == '0x43'
+		message('Implementor : Cavium')
+		dpdk_conf.set('RTE_MACHINE', 'thunderx')
+		machine_arg = []
+	        machine_arg += '-march=' + 'armv8-a+crc+crypto'
+		machine_arg += '-mcpu=' + 'thunderx'
+	endif
+endif
diff --git a/config/meson.build b/config/meson.build
index 86e978fb1..fe8104676 100644
--- a/config/meson.build
+++ b/config/meson.build
@@ -8,7 +8,8 @@ else
 	machine = get_option('machine')
 endif
 dpdk_conf.set('RTE_MACHINE', machine)
-machine_arg = '-march=' + machine
+machine_arg = []
+machine_arg += '-march=' + machine

 # use pthreads
 add_project_link_arguments('-pthread', language: 'c')
diff --git a/drivers/meson.build b/drivers/meson.build
index 9b5039847..f5009aa2e 100644
--- a/drivers/meson.build
+++ b/drivers/meson.build
@@ -22,7 +22,7 @@ foreach class:driver_classes
 		version = 1
 		sources = []
 		objs = []
-		cflags = [machine_arg]
+		cflags = machine_arg
 		includes = [include_directories(drv_path)]
 		# set up internal deps. Drivers can append/override as necessary
 		deps = std_deps
diff --git a/examples/meson.build b/examples/meson.build
index 0abed7169..88df650cf 100644
--- a/examples/meson.build
+++ b/examples/meson.build
@@ -9,7 +9,7 @@ endif
 foreach example: get_option('examples').split(',')
 	name = example
 	sources = []
-	cflags = [machine_arg]
+	cflags = machine_arg
 	ext_deps = []
 	includes = [include_directories(example)]
 	deps = ['eal', 'mempool', 'net', 'mbuf', 'ethdev', 'cmdline']
diff --git a/lib/meson.build b/lib/meson.build
index 0c94d74b9..3c98efa70 100644
--- a/lib/meson.build
+++ b/lib/meson.build
@@ -31,7 +31,7 @@ foreach l:libraries
 	sources = []
 	headers = []
 	includes = []
-	cflags = [machine_arg]
+	cflags = machine_arg
 	objs = [] # other object files to link against, used e.g. for
 	          # instruction-set optimized versions of code

diff --git a/meson.build b/meson.build
index 3dce8579e..493bcc313 100644
--- a/meson.build
+++ b/meson.build
@@ -66,5 +66,5 @@ pkg.generate(name: meson.project_name(),
 			['-Wl,-Bdynamic'] + dpdk_extra_ldflags,
 	description: 'The Data Plane Development Kit (DPDK)',
 	subdirs: [get_option('include_subdir_arch'), '.'],
-	extra_cflags: ['-include "rte_config.h"', machine_arg]
+	extra_cflags: ['-include "rte_config.h"'] + machine_arg
 )
--
2.15.1