Re: [PATCH v3 3/7] of: reserved_mem: add support for named reserved mem nodes

[Rob Herring <robh+dt@kernel.org>]

On Mon, Jan 4, 2016 at 7:57 AM, Marek Szyprowski <m.szyprowski@samsung.com> wrote:
> Hi Rob,
>
>
> On 2015-12-31 00:25, Rob Herring wrote:
>>
>> On Wed, Dec 16, 2015 at 9:37 AM, Marek Szyprowski
>> <m.szyprowski@samsung.com> wrote:
>>>
>>> This patch allows device drivers to initialize more than one reserved
>>> memory region assigned to given device. When driver needs to use more
>>> than one reserved memory region, it should allocate child devices and
>>> initialize regions by index or name for each of its child devices.
>>>
>>> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
>>> ---
>>>   .../bindings/reserved-memory/reserved-memory.txt   |   2 +
>>>   .../devicetree/bindings/resource-names.txt         |   1 +
>>>   drivers/of/of_reserved_mem.c                       | 104
>>> +++++++++++++++++----
>>>   include/linux/of_reserved_mem.h                    |  31 +++++-
>>>   4 files changed, 115 insertions(+), 23 deletions(-)
>>>
>>> diff --git
>>> a/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
>>> b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
>>> index 3da0ebdba8d9..43a14957fd64 100644
>>> ---
>>> a/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
>>> +++
>>> b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
>>> @@ -74,6 +74,8 @@ Regions in the /reserved-memory node may be referenced
>>> by other device
>>>   nodes by adding a memory-region property to the device node.
>>>
>>>   memory-region (optional) - phandle, specifier pairs to children of
>>> /reserved-memory
>>> +memory-region-names (optional) - supplemental names property, provide
>>> array of
>>> +                                names to identify memory regions
>>>
>>>   Example
>>>   -------
>>> diff --git a/Documentation/devicetree/bindings/resource-names.txt
>>> b/Documentation/devicetree/bindings/resource-names.txt
>>> index e280fef6f265..51823e99b983 100644
>>> --- a/Documentation/devicetree/bindings/resource-names.txt
>>> +++ b/Documentation/devicetree/bindings/resource-names.txt
>>> @@ -12,6 +12,7 @@ Resource Property     Supplemental Names Property
>>>   reg                    reg-names
>>>   clocks                 clock-names
>>>   interrupts             interrupt-names
>>> +memory-region          memory-region-names
>>
>> The other cases of *-names should correspond to actual h/w names for a
>> h/w block. memory-regions are not really h/w. So I'd prefer to not add
>> memory-region-names. If you want a name for the region, put it in the
>> region node. The name for each client node is not going to be
>> different.
>
>
> There is a difference between a name in the region node and a name assigned
> in client node. Reserved memory region bindings already allows assigning
> given region to more than one device. In such case the name put in the
> region itself is not really useful.
>
> In my case (Exynos MFC device) the names are related to HW names. The memory
> regions are named in the hw documentation (referred as 'left memory bank'
> and 'right memory bank'). Using those names in the binding is also simply
> convenient (no need to remember which regions is at which index number).
>
> Those names might be also convenient for describing Android's ION related
> regions, although I didn't look deep into details of such use case.


>
> Best regards
> --
> Marek Szyprowski, PhD
> Samsung R&D Institute Poland
>