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Subject: Re: [RFC PATCH 0/5] Add smp booting support for Qualcomm ARMv8 SoCs
From: Kumar Gala <galak@codeaurora.org>
In-Reply-To: <20150410100529.GA6854@e104818-lin.cambridge.arm.com>
Date: Fri, 10 Apr 2015 10:24:46 -0500
Cc: linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        Device Tree Mailing List <devicetree@vger.kernel.org>,
        Abhimanyu Kapur <abhimany@codeaurora.org>,
        Will Deacon <will.deacon@arm.com>, linux-kernel@vger.kernel.org,
        arm@kernel.org, linux-arm-kernel@lists.infradead.org
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To: Catalin Marinas <catalin.marinas@arm.com>
Sender: linux-kernel-owner@vger.kernel.org
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On Apr 10, 2015, at 5:05 AM, Catalin Marinas <catalin.marinas@arm.com> wrote:

> On Thu, Apr 09, 2015 at 12:37:06PM -0500, Kumar Gala wrote:
>> This patch set adds support for SMP boot on the MSM8x16 family of Qualcomm SoCs.
>> 
>> To support SMP on the MSM8x16 SoCs we need to add ARMv8/64-bit SCM interfaces to
>> setup the boot/release addresses for the secondary CPUs.  In addition we need
>> a uniquie set of cpu ops.  I'm aware the desired methods for booting secondary
>> CPUs is either via spintable or PSCI.  However, these SoCs are shipping with a
>> firmware that does not support those methods.
> 
> And the reason is? Some guesses:
> 
> a) QC doesn't think boot interface (and cpuidle) standardisation is
>   worth the effort (to put it nicely)
> b) The hardware was available before we even mentioned PSCI
> c) PSCI is not suitable for the QC's SCM interface
> d) Any combination of the above
> 
> I strongly suspect it's point (a). Should we expect future QC hardware
> to do the same?
> 
> You could argue the reason was (b), though we've been discussing PSCI
> for at least two years and, according to QC press releases, MSM8916
> started sampling in 2014.
> 
> The only valid reason is (c) and if that's the case, I would expect a
> proposal for a new firmware interface protocol (it could be PSCI-based),
> well documented, that can be shared with others that may encounter the
> same shortcomings.
> 
> -- 
> Catalin

Does it matter?  I?ve always felt the kernel was a place of inclusion.  Qualcomm choose for whatever reason to not use PSCI or spin table.  You don?t like it, I might not like it, but it is what it is.

- k

-- 
Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

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