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Subject: Re: [PATCH] of: add early boot allocation of
 of_find_node_by_phandle() cache
To:     frowand.list@gmail.com, Rob Herring <robh+dt@kernel.org>
Cc:     devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
References: <1518655465-10759-1-git-send-email-frowand.list@gmail.com>
From:   Chintan Pandya <cpandya@codeaurora.org>
Message-ID: <25deaf48-6590-4ca2-e0db-adaef1f49c5d@codeaurora.org>
Date:   Fri, 16 Feb 2018 14:37:55 +0530
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On 2/15/2018 6:14 AM, frowand.list@gmail.com wrote:
> From: Frank Rowand <frank.rowand@sony.com>
> 
> The initial implementation of the of_find_node_by_phandle() cache
> allocates the cache using kcalloc().  Add an early boot allocation
> of the cache so it will be usable during early boot.  Switch over
> to the kcalloc() based cache once normal memory allocation
> becomes available.
> 
> Signed-off-by: Frank Rowand <frank.rowand@sony.com>
> ---
> 
> This patch is optional, to be added at Rob's discretion.  The
> extra complexity is not as much as I had feared, but the boot
> speed up is also likely small.
> 
>   drivers/of/base.c       | 33 +++++++++++++++++++++++++++++++++
>   drivers/of/fdt.c        |  2 ++
>   drivers/of/of_private.h |  2 ++
>   3 files changed, 37 insertions(+)
> 
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index ab545dfa9173..d7b1ff1209e8 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -16,9 +16,11 @@
>   
>   #define pr_fmt(fmt)	"OF: " fmt
>   
> +#include <linux/bootmem.h>
>   #include <linux/console.h>
>   #include <linux/ctype.h>
>   #include <linux/cpu.h>
> +#include <linux/memblock.h>
>   #include <linux/module.h>
>   #include <linux/of.h>
>   #include <linux/of_device.h>
> @@ -131,6 +133,29 @@ static void of_populate_phandle_cache(void)
>   	raw_spin_unlock_irqrestore(&devtree_lock, flags);
>   }
>   
> +void __init of_populate_phandle_cache_early(void)
> +{
> +	u32 cache_entries;
> +	struct device_node *np;
> +	u32 phandles = 0;
> +	size_t size;
> +
> +	for_each_of_allnodes(np)
> +		if (np->phandle && np->phandle != OF_PHANDLE_ILLEGAL)
> +			phandles++;
> +
> +	cache_entries = roundup_pow_of_two(phandles);
> +	phandle_cache_mask = cache_entries - 1;
> +
> +	size = cache_entries * sizeof(*phandle_cache);
> +	phandle_cache = memblock_virt_alloc(size, 4);
> +	memset(phandle_cache, 0, size);
> +
> +	for_each_of_allnodes(np)
> +		if (np->phandle && np->phandle != OF_PHANDLE_ILLEGAL)
> +			phandle_cache[np->phandle & phandle_cache_mask] = np;
> +}

There is a lot of code duplication in this function with
of_populate_phandle_cache. Would you think of taking out
common code or differ the function with extra bool parameter
to say 'early' or 'not early'.

> +
>   #ifndef CONFIG_MODULES
>   static int __init of_free_phandle_cache(void)
>   {
> @@ -150,7 +175,15 @@ static int __init of_free_phandle_cache(void)
>   
>   void __init of_core_init(void)
>   {
> +	unsigned long flags;
>   	struct device_node *np;
> +	phys_addr_t size;
> +
> +	raw_spin_lock_irqsave(&devtree_lock, flags);
> +	size = (phandle_cache_mask + 1) * sizeof(*phandle_cache);
> +	memblock_free(__pa(phandle_cache), size);
> +	phandle_cache = NULL;
> +	raw_spin_unlock_irqrestore(&devtree_lock, flags);
>   
>   	of_populate_phandle_cache();
>   
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 84aa9d676375..cb320df23f26 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -1264,6 +1264,8 @@ void __init unflatten_device_tree(void)
>   	of_alias_scan(early_init_dt_alloc_memory_arch);
>   
>   	unittest_unflatten_overlay_base();
> +
> +	of_populate_phandle_cache_early();
>   }
>   
>   /**
> diff --git a/drivers/of/of_private.h b/drivers/of/of_private.h
> index fa70650136b4..6720448c84cc 100644
> --- a/drivers/of/of_private.h
> +++ b/drivers/of/of_private.h
> @@ -134,6 +134,8 @@ extern void __of_sysfs_remove_bin_file(struct device_node *np,
>   /* illegal phandle value (set when unresolved) */
>   #define OF_PHANDLE_ILLEGAL	0xdeadbeef
>   
> +extern void __init of_populate_phandle_cache_early(void);
> +
>   /* iterators for transactions, used for overlays */
>   /* forward iterator */
>   #define for_each_transaction_entry(_oft, _te) \
> 

Chintan
-- 
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