linux-kernel - Re: [PATCH v2 50/76] ARC: SMP support

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Date:	Tue, 22 Jan 2013 14:27:03 +0530
From:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	<linux-arch@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	Rajeshwar Ranga <rajeshwar.ranga@...il.com>,
	Noam Camus <noamc@...hip.com>,
	Gilad Ben-Yossef <gilad@...yossef.com>
Subject: Re: [PATCH v2 50/76] ARC: SMP support

On Friday 18 January 2013 08:23 PM, Arnd Bergmann wrote:
> On Friday 18 January 2013, Vineet Gupta wrote:
>> +# If a plat can do IPI, same core(s) can do minimal SMP
>> +config ARC_HAS_IPI
>> +       bool
>> +
> I think it would be better to turn the logic around here,
> otherwise you get into trouble when enabling multiple
> platforms, out of which some have IPI support and others
> don't.
>
> Instead, you can mark the platforms that lack IPI support
> (or multiple CPUs) as 'depends on !SMP'.

Or slightly different way - something like below:

The only issue is platform specific SMP extensions - instead of helping enable
CONFIG_SMP are now dependent on it (so hidden if SMP is not enabled at top level)
- but given that CONFIG_SMP is the only common denominator across platforms,
that's how it will work in multi-platform-img paradigm.


diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 6729480..ab854af 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -126,14 +126,9 @@ config CPU_BIG_ENDIAN
 config ARC_PLAT_NEEDS_CPU_TO_DMA
        bool
 
-# If a plat can do IPI, same core(s) can do minimal SMP
-config ARC_HAS_IPI
-       bool
-
 config SMP
        bool "Symmetric Multi-Processing (Incomplete)"
        default y
-       depends on ARC_HAS_IPI
        select USE_GENERIC_SMP_HELPERS
        help
          This enables support for systems with more than one CPU. If you have
diff --git a/arch/arc/plat-arcfpga/Kconfig b/arch/arc/plat-arcfpga/Kconfig
index 6001784..526cdfe 100644
--- a/arch/arc/plat-arcfpga/Kconfig
+++ b/arch/arc/plat-arcfpga/Kconfig
@@ -8,6 +8,7 @@
 
 menuconfig ARC_PLAT_FPGA_LEGACY
        bool "\"Legacy\" ARC FPGA dev Boards"
+       select ISS_SMP_EXTN if SMP
        help
          Support for ARC development boards, provided by Synopsys.
          These are based on FPGA or ISS. e.g.
@@ -30,8 +31,7 @@ config ARC_BOARD_ML509
 
 config ISS_SMP_EXTN
        bool "ARC SMP Extensions (ISS Models only)"
-       default n
-       select ARC_HAS_IPI
+       depends on SMP
        select ARC_HAS_COH_RTSC
        help
          SMP Extensions to ARC700, in a "simulation only" Model, supported in


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