On Mon, Jan 08, 2018 at 01:43:07PM +0530, Jerin Jacob wrote:

-----Original Message-----

quoted

Date: Sat, 30 Dec 2017 22:07:54 +0530
From: Pavan Nikhilesh <redacted>
To: bruce.richardson@intel.com, bluca@debian.org,
 harry.van.haaren@intel.com, jerin.jacob@caviumnetworks.com
Cc: dev@dpdk.org, Pavan Nikhilesh <redacted>
Subject: [dpdk-dev] [PATCH] build: add support for detecting march on ARM
X-Mailer: git-send-email 2.14.1

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 <redacted>
---

<snip>

quoted

+cmd = run_command(detect_vendor.path())
+if cmd.returncode() != 0
+	message('Unable to read midr_el1')

Instead of this "unable to read midr_el1", We could fallback to
"message('Implementer : Generic arm64')" message

Some thoughts,
1) From the Linux documentation[1] this sysfs entries are available
from the kernels > June 2016

[1]
What:		/sys/devices/system/cpu/cpuX/regs/
		/sys/devices/system/cpu/cpuX/regs/identification/
		/sys/devices/system/cpu/cpuX/regs/identification/midr_el1
		/sys/devices/system/cpu/cpuX/regs/identification/revidr_el1
Date: 		June 2016
Contact:      	Linux ARM Kernel Mailing list [off-list ref]
Description:   	AArch64 CPU registers 'identification' directory exposes the CPU ID registers or
                identifying model and revision of the CPU.

2) This scheme is not available in Freebsd.
3) I guess, we anyway need a meta file to store this information for cross compilation case.

If so,
1) Can we introduce something similar to T= for cross compilation case and
use the same scheme to override for native compilation flags if required.
2) If above scheme is not chosen and
a) if /sys/devices/system/cpu/cpuX/regs/identification/midr_el1 avilable then derive
machine_arg based on that
b) if /sys/devices/system/cpu/cpuX/regs/identification/midr_el1 not available then fallback to generic arm64 compilation.

Thoughts?

[1&2] Agreed, when midr_el1 file is unavailable should continue with generic arm32/64.
This would cover freebsd too and if we need we can use the meta stored in cross
compilation case for native compilation.

It would be good if we start agreeing in directory structure where cross-compile
meta files are stored so that we can start adding and experiment with them.

The meta files would have info as mentioned in
http://dpdk.org/dev/patchwork/patch/32410/

Thanks,
Pavan.

quoted

+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'

1) Instead of changing the code for each Vendors and the multiple
variants, Can we put some framework to just define this information some
where?
2) Please add the another mcpu variables for the Cavium produces like
81xx and 83xx etc

quoted

+	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