linux-kernel - Re: [PATCH 1/3] powernv:idle: Use correct IDLE_THREAD

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Message-Id: <20170413113513.GA2425@in.ibm.com>
Date:   Thu, 13 Apr 2017 17:05:13 +0530
From:   Gautham R Shenoy <ego@...ux.vnet.ibm.com>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Michael Neuling <mikey@...ling.org>,
        "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        "Shreyas B. Prabhu" <shreyasbp@...il.com>,
        Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
        Anton Blanchard <anton@...ba.org>,
        Balbir Singh <bsingharora@...il.com>,
        Akshay Adiga <akshay.adiga@...ux.vnet.ibm.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Mahesh J Salgaonkar <mahesh@...ux.vnet.ibm.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] powernv:idle: Use correct IDLE_THREAD_BITS in
 POWER8/9

On Thu, Apr 13, 2017 at 08:00:47PM +1000, Michael Ellerman wrote:
> Michael Neuling <mikey@...ling.org> writes:
> 
> > On Wed, 2017-04-12 at 17:16 +0530, Gautham R. Shenoy wrote:
> >> From: "Gautham R. Shenoy" <ego@...ux.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.

Ok. I will convert IDLE_THREAD_BITS to a variable instead of a
macro so that the variable holds the value
(1 << threads_per_core) - 1.



> 
> cheers
>