From: Michael Ellerman <mpe@ellerman.id.au>
To: Michael Neuling <mikey@neuling.org>,
        "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        "Shreyas B. Prabhu" <shreyasbp@gmail.com>,
        Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>,
        Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>,
        Anton Blanchard <anton@samba.org>,
        Balbir Singh <bsingharora@gmail.com>,
        Akshay Adiga <akshay.adiga@linux.vnet.ibm.com>,
        Nicholas Piggin <npiggin@gmail.com>,
        Mahesh J Salgaonkar <mahesh@linux.vnet.ibm.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] powernv:idle: Use correct IDLE_THREAD_BITS in POWER8/9
In-Reply-To: <1492065380.4624.50.camel@neuling.org>
References: <cover.1491996797.git.ego@linux.vnet.ibm.com> <1b89d07b1a7ea140501a86b1ed246c5af1b0ce83.1491996797.git.ego@linux.vnet.ibm.com> <1492065380.4624.50.camel@neuling.org>
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Date: Thu, 13 Apr 2017 20:00:47 +1000
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Michael Neuling <mikey@neuling.org> writes:

> On Wed, 2017-04-12 at 17:16 +0530, Gautham R. Shenoy wrote:
>> From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
>> 
>> This patch ensures that POWER8 and POWER9 processors use the correct
>> value of IDLE_THREAD_BITS as POWER8 has 8 threads per core and hence
>> the IDLE_THREAD_BITS should be 0xFF while POWER9 has only 4 threads
>> per core and hence the IDLE_THREAD_BITS should be 0xF.
>
> Why don't we derive this from the device tree rather than hard wiring it per cpu
> type?

Right.

In fact we already have threads_per_core which is exactly that.

cheers