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Subject: Re: [PATCH] of: use hash based search in of_find_node_by_phandle
From: Frank Rowand <frowand.list@gmail.com>
To: Chintan Pandya <cpandya@codeaurora.org>, robh+dt@kernel.org,
        devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org
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Date: Fri, 26 Jan 2018 13:29:59 -0800
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On 01/26/18 13:27, Frank Rowand wrote:
> On 01/26/18 00:22, Chintan Pandya wrote:
>>
>>
>> On 1/26/2018 1:24 AM, Frank Rowand wrote:
>>> On 01/25/18 02:14, Chintan Pandya wrote:
>>>> of_find_node_by_phandle() takes a lot of time finding
>>>> right node when your intended device is too right-side
>>>> in the fdt. Reason is, we search each device serially
>>>> from the fdt, starting from left-most to right-most.
>>> Please give me a pointer to the code that is doing
>>> this search.
>>>
>>> -Frank
>> You can refer include/linux/of.h
>>
>> #define for_each_of_allnodes_from(from, dn) \
>>         for (dn = __of_find_all_nodes(from); dn; dn = __of_find_all_nodes(dn))
>> #define for_each_of_allnodes(dn) for_each_of_allnodes_from(NULL, dn)
>>
>> where __of_find_all_nodes() does
>>
>> struct device_node *__of_find_all_nodes(struct device_node *prev)
>> {
>>         struct device_node *np;
>>         if (!prev) {
>>                 np = of_root;
>>         } else if (prev->child) {
>>                 np = prev->child;
>>         } else {
>>                 /* Walk back up looking for a sibling, or the end of the structure */
>>                 np = prev;
>>                 while (np->parent && !np->sibling)
>>                         np = np->parent;
>>                 np = np->sibling; /* Might be null at the end of the tree */
>>         }
>>         return np;
>> }
>>
> 
> Let me restate my question.
> 
> Can you point me to the driver code that is invoking
> the search?
> 
> -Frank
> 

And also the .dts devicetree source file that you are seeing
large overhead with.