linux-kernel - Re: [PATCH V2 03/10] irqchip,GICv3,ACPI: Add redistributor support via GICC structures.

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Message-ID: <56960C3B.8030105@arm.com>
Date:	Wed, 13 Jan 2016 08:35:07 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Hanjun Guo <hanjun.guo@...aro.org>,
	Tomasz Nowicki <tn@...ihalf.com>, tglx@...utronix.de,
	jason@...edaemon.net, rjw@...ysocki.net, lorenzo.pieralisi@....com,
	robert.richter@...iumnetworks.com, shijie.huang@....com,
	guohanjun@...wei.com, Suravee.Suthikulpanit@....com
CC:	mw@...ihalf.com, graeme.gregory@...aro.org,
	Catalin.Marinas@....com, will.deacon@....com,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, ddaney.cavm@...il.com
Subject: Re: [PATCH V2 03/10] irqchip,GICv3,ACPI: Add redistributor support
 via GICC structures.

On 13/01/16 01:52, Hanjun Guo wrote:
> 
> 
> On 2016/1/13 0:45, Tomasz Nowicki wrote:
>> On 12.01.2016 13:03, Marc Zyngier wrote:
>>
>>  > +    typer = readq_relaxed(redist_base + GICR_TYPER);
>>  > +    /* don't map reserved page as it's buggy to access it */
>>  > +    size = (typer & GICR_TYPER_VLPIS) ? SZ_64K * 3 : SZ_64K * 2;
>>
>> [...]
>>
>>> Also, please map the whole region for the
>>> redistributor as we have on the DT side (4 64kB pages for VLPIS capable
>>> redistributors).
>>
>> Hanjun, is it something you had problem with?
> 
> Yes, for D02, it use 3 64kB pages for GICv4, it removed the reserved
> page. In DT case, it has "stride" binding so it can support no standard
> cases, seems that we can introduce "stride" for ACPI too.

I don't think there is any need for that, assuming this system only
exposes its redistributors via the ACPI GICC structure. In which case, I
don't think it hurts to have overlapping mappings: For redistributors A
and B, we never touch A[3] (the reserved page), but we will access B[0].

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...