linux-kernel - Re: [PATCH 0/2] arm64, cma, gicv3-its: Use CMA for allocation of large device tables

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Message-ID: <56D42199.7040207@arm.com>
Date:	Mon, 29 Feb 2016 10:46:49 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Robert Richter <rrichter@...iumnetworks.com>,
	Will Deacon <will.deacon@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Cc:	Tirumalesh Chalamarla <tchalamarla@...ium.com>,
	linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Robert Richter <rrichter@...ium.com>
Subject: Re: [PATCH 0/2] arm64, cma, gicv3-its: Use CMA for allocation of
 large device tables

Hi Robert,

On 25/02/16 11:02, Robert Richter wrote:
> From: Robert Richter <rrichter@...ium.com>
> 
> This series implements the use of CMA for allocation of large device
> tables for the arm64 gicv3 interrupt controller.
> 
> There are 2 patches, the first is for early activation of cma, which
> needs to be done before interrupt initialization to make it available
> to the gicv3. The second implements the use of CMA to allocate
> gicv3-its device tables.
> 
> This solves the problem where mem allocation is limited to 4MB. A
> previous patch sent to the list to address this that instead increases
> FORCE_MAX_ZONEORDER becomes obsolete.

I think you're looking at the problem the wrong way. Instead of going
through CMA directly, I'd rather go through the normal DMA API
(dma_alloc_coherent), which can itself try CMA (should it be enabled).

That will give you all the benefit of the CMA allocation, and also make
the driver more robust. I meant to do this for a while, and never found
the time. Any chance you could have a look?

Thanks,

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