On 2018-02-12 07:27, frowand.list@xxxxxxxxx wrote:
> From: Frank Rowand <frank.rowand@xxxxxxxx>
>
> Create a cache of the nodes that contain a phandle property. Use this
> cache to find the node for a given phandle value instead of scanning
> the devicetree to find the node. If the phandle value is not found
> in the cache, of_find_node_by_phandle() will fall back to the tree
> scan algorithm.
>
> The cache is initialized in of_core_init().
>
> The cache is freed via a late_initcall_sync() if modules are not
> enabled.
Maybe a few words about the memory consumption of this solution versus
the other proposed ones. Other nits below.
> +static void of_populate_phandle_cache(void)
> +{
> + unsigned long flags;
> + phandle max_phandle;
> + u32 nodes = 0;
> + struct device_node *np;
> +
> + if (phandle_cache)
> + return;
What's the point of that check? And shouldn't it be done inside the
spinlock if at all?
> + max_phandle = live_tree_max_phandle();
> +
> + raw_spin_lock_irqsave(&devtree_lock, flags);
> +
> + for_each_of_allnodes(np)
> + nodes++;
Why not save a walk over all nodes and a spin_lock/unlock pair by
combining the node count with the max_phandle computation? But you've
just moved the existing live_tree_max_phandle, so probably better as a
followup patch.
> + /* sanity cap for malformed tree */
> + if (max_phandle > nodes)
> + max_phandle = nodes;
> +
> + phandle_cache = kzalloc((max_phandle + 1) * sizeof(*phandle_cache),
> + GFP_ATOMIC);
Maybe kcalloc. Sure, you've capped max_phandle so there's no real risk
of overflow.
> + for_each_of_allnodes(np)
> + if (np->phandle != OF_PHANDLE_ILLEGAL &&
> + np->phandle <= max_phandle &&
> + np->phandle)
I'd reverse the order of these conditions so that for all the nodes with
no phandle we only do the np->phandle check. Also, extra whitespace
before &&.
> + phandle_cache[np->phandle] = np;
> +
> + max_phandle_cache = max_phandle;
> +
> + raw_spin_unlock_irqrestore(&devtree_lock, flags);
> +}
> +
Rasmus
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