linux-kernel - Re: [PATCH v3 2/4] remoteproc: add a rproc ops for performing address translation

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Date:	Mon, 11 May 2015 09:55:09 -0500
From:	Suman Anna <s-anna@...com>
To:	Ohad Ben-Cohen <ohad@...ery.com>, Dave Gerlach <d-gerlach@...com>
CC:	linux-arm <linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Kevin Hilman <khilman@...aro.org>,
	Tony Lindgren <tony@...mide.com>
Subject: Re: [PATCH v3 2/4] remoteproc: add a rproc ops for performing address
 translation

Hi Ohad,

On 05/09/2015 02:54 AM, Ohad Ben-Cohen wrote:
> Hi Dave,
> 
> On Wed, Apr 1, 2015 at 10:37 PM, Dave Gerlach <d-gerlach@...com> wrote:
>> From: Suman Anna <s-anna@...com>
>>
>> The rproc_da_to_va API is currently used to perform any device to
>> kernel address translations to meet the different needs of the remoteproc
>> core/drivers (eg: loading). The functionality is achieved within the
>> remoteproc core, and is limited only for carveouts allocated within the
>> core.
>>
>> A new rproc ops, da_to_va, is added to provide flexibility to platform
>> implementations to perform the address translation themselves when the
>> above conditions cannot be met by the implementations. The rproc_da_to_va()
>> API is extended to invoke this ops if present, and fallback to regular
>> processing if the platform implementation cannot provide the translation.
>> This will allow any remoteproc implementations to translate addresses for
>> dedicated memories like internal memories.
> 
> Can you please provide specific examples where this is needed and how
> it is going to be used?

We will be using this for the WkupM3 remoteproc driver, and also using
it for a PRUSS remoteproc driver (on downstream kernel for now) on TI
AM335x/AM437x SoCs. The driver uses a firmware where all segments are
placed only in internal RAMs (nothing in DDR), and we use the remoteproc
core's ELF loader code to perform the loading. We need a way for the
remoteproc elf loader core to be able to translate these device
addresses into a kernel mapped addresses so that the loader code can
copy the firmware segments.

The previous attempt on this was to use a new resource type through the
resource table, whereby we are publishing and storing the internal
memory translations were stored in the remoteproc core [1].

regards
Suman

[1] https://patchwork.kernel.org/patch/5602981/

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