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SubjectRe: [PATCH 2/2] of/fdt: skip unflattening of disabled nodes
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On 10/03/17 11:46, Nicolas Pitre wrote:
> On Tue, 3 Oct 2017, Rob Herring wrote:
>
>> For static DT usecases, we don't need the disabled nodes and can skip
>> unflattening. This saves a significant amount of RAM in memory constrained
>> cases. In one example on STM32F469, the RAM usage goes from 118K to 26K.
>>
>> There are a few cases in the kernel that modify the status property
>> dynamically. These all are changes from enabled to disabled, depend on
>> OF_DYNAMIC or are not FDT based (PDT based).
>>
>> Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
>> Cc: Frank Rowand <frowand.list@gmail.com>
>> Signed-off-by: Rob Herring <robh@kernel.org>
>
> Tested-by: Nicolas Pitre <nico@linaro.org>
>
>> ---
>> For more background, see this presentation from Nico:
>>
>> https://connect.linaro.org/resource/sfo17/sfo17-100/
>
> Oh my ... this is horrible ...

I found the presentation to be quite good and useful.
The Linaro site does not have the slides, could you please send
me a copy?

Thanks,

Frank

>
> /me hides in shame
>
>>
>> drivers/of/fdt.c | 4 ++++
>> 1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
>> index f8c39705418b..efe91c6856a0 100644
>> --- a/drivers/of/fdt.c
>> +++ b/drivers/of/fdt.c
>> @@ -396,6 +396,10 @@ static int unflatten_dt_nodes(const void *blob,
>> if (WARN_ON_ONCE(depth >= FDT_MAX_DEPTH))
>> continue;
>>
>> + if (!IS_ENABLED(CONFIG_OF_DYNAMIC) &&
>> + !of_fdt_device_is_available(blob, offset))
>> + continue;
>> +
>> if (!populate_node(blob, offset, &mem, nps[depth],
>> &nps[depth+1], dryrun))
>> return mem - base;
>> --
>> 2.11.0
>>
>>
>

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