linux-kernel - Re: [RFC LINUX PATCH 0/3] Allow remote to specify shared memory

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Date:   Tue, 28 Mar 2017 18:24:09 -0500
From:   Suman Anna <s-anna@...com>
To:     Wendy Liang <sunnyliangjy@...il.com>
CC:     Wendy Liang <wendy.liang@...inx.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        <linux-remoteproc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Wendy Liang <jliang@...inx.com>
Subject: Re: [RFC LINUX PATCH 0/3] Allow remote to specify shared memory

Hi Wendy,

On 03/28/2017 01:52 PM, Wendy Liang wrote:
> Thanks Suman for your comments.
> 
> On Mon, Mar 27, 2017 at 8:54 AM, Suman Anna <s-anna@...com> wrote:
>> Hi Wendy,
>>
>> On 03/24/2017 02:22 PM, Wendy Liang wrote:
>>> This patch enables the remoteproc to specify the shared memory.
>>> Remoteproc declared this memory as DMA memory.
>>> It can be used for virtio, or shared buffers.
>>
>> You should be able to achieve this without any remoteproc core changes.
>> You can do this by defining a reserved-memory node in your DTS file (can
>> be a CMA pool or a DMA pool), assigning the node using memory-region in
>> your remoteproc DT node and using the function,
>> of_reserved_mem_device_init() in your remoteproc driver.
> 
> The idea to introduce the rproc_mem is to let the remote to specify
> the shared memory.
> I am trying to see if there is a way to specify this software attribute without
> touching the device tree as it doesn't look like it is hardware related.
> And try to see if there is a way that when I change the firmware, i
> don't need to change the device tree.

So is this shared memory going to be accessed through an MMU by the
remote processor? If not, don't you need a specific carveout, which
would then in turn mean boot-time memory reservation?

regards
Suman

> 
> Thanks,
> Wendy
> 
>>
>> regards
>> Suman
>>
>>>
>>> Wendy Liang (3):
>>>   remoteproc: add rproc mem resource entry
>>>   remoteproc: add rproc_mem resource entry handler
>>>   remoteproc: Release DMA declare mem when cleanup rsc
>>>
>>>  drivers/remoteproc/remoteproc_core.c | 40 ++++++++++++++++++++++++++++++++++++
>>>  include/linux/remoteproc.h           | 23 ++++++++++++++++++++-
>>>  2 files changed, 62 insertions(+), 1 deletion(-)
>>>
>>
>> --
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