linux-kernel - Re: [RFC] fdt:free the fdt reserved memory

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Date:	Wed, 24 Sep 2014 15:45:20 +0100
From:	Grant Likely <grant.likely@...aro.org>
To:	"Wang, Yalin" <Yalin.Wang@...ymobile.com>,
	"'robh+dt@...nel.org'" <robh+dt@...nel.org>,
	"'devicetree@...r.kernel.org'" <devicetree@...r.kernel.org>,
	"'pawel.moll@....com'" <pawel.moll@....com>,
	"'mark.rutland@....com'" <mark.rutland@....com>,
	"'ijc+devicetree@...lion.org.uk'" <ijc+devicetree@...lion.org.uk>,
	"'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] fdt:free the fdt reserved memory

On Thu, 18 Sep 2014 17:25:12 +0800, "Wang, Yalin" <Yalin.Wang@...ymobile.com> wrote:
> This patch make some change to unflatten_dt_node(), make sure the
> device_node don't reference to fdt raw blob memory, so that we can
> free the raw blob reserved memory after initcalls.
> 
> Signed-off-by: Yalin Wang <yalin.wang@...ymobile.com>

Do you have any measurements showing a change in available memory before
and after the patch?

g.

> ---
>  drivers/of/fdt.c       | 27 +++++++++++++++++++++++----
>  include/linux/of_fdt.h |  2 ++
>  2 files changed, 25 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 79cb831..e891ef6 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -240,6 +240,7 @@ static void * unflatten_dt_node(void *blob,
>  	     (offset = fdt_next_property_offset(blob, offset))) {
>  		const char *pname;
>  		u32 sz;
> +		int name_len;
>  
>  		if (!(p = fdt_getprop_by_offset(blob, offset, &pname, &sz))) {
>  			offset = -FDT_ERR_INTERNAL;
> @@ -250,10 +251,12 @@ static void * unflatten_dt_node(void *blob,
>  			pr_info("Can't find property name in list !\n");
>  			break;
>  		}
> +		name_len = strlen(pname);
>  		if (strcmp(pname, "name") == 0)
>  			has_name = 1;
> -		pp = unflatten_dt_alloc(&mem, sizeof(struct property),
> -					__alignof__(struct property));
> +		pp = unflatten_dt_alloc(&mem,
> +				ALIGN(sizeof(struct property) + name_len + 1, 4)
> +				+ sz, __alignof__(struct property));
>  		if (allnextpp) {
>  			/* We accept flattened tree phandles either in
>  			 * ePAPR-style "phandle" properties, or the
> @@ -270,9 +273,11 @@ static void * unflatten_dt_node(void *blob,
>  			 * stuff */
>  			if (strcmp(pname, "ibm,phandle") == 0)
>  				np->phandle = be32_to_cpup(p);
> -			pp->name = (char *)pname;
> +			pp->name = (char *)memcpy(pp + 1, pname, name_len + 1);
>  			pp->length = sz;
> -			pp->value = (__be32 *)p;
> +			pp->value = (__be32 *)memcpy((void *)pp +
> +					ALIGN(sizeof(struct property) +
> +						name_len + 1, 4), p, sz);
>  			*prev_pp = pp;
>  			prev_pp = &pp->next;
>  		}
> @@ -564,6 +569,20 @@ void __init early_init_fdt_scan_reserved_mem(void)
>  	fdt_init_reserved_mem();
>  }
>  
> +void __init free_early_init_fdt_scan_reserved_mem(void)
> +{
> +	unsigned long start, end, size;
> +	if (!initial_boot_params)
> +		return;
> +
> +	size = fdt_totalsize(initial_boot_params);
> +	memblock_free(__pa(initial_boot_params), size);
> +	start = round_down((unsigned long)initial_boot_params, PAGE_SIZE);
> +	end = round_up((unsigned long)initial_boot_params + size, PAGE_SIZE);
> +	free_reserved_area((void *)start, (void *)end, 0, "fdt");
> +	initial_boot_params = 0;
> +}
> +
>  /**
>   * of_scan_flat_dt - scan flattened tree blob and call callback on each.
>   * @it: callback function
> diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
> index 0ff360d..21d51ce 100644
> --- a/include/linux/of_fdt.h
> +++ b/include/linux/of_fdt.h
> @@ -62,6 +62,7 @@ extern int early_init_dt_scan_chosen(unsigned long node, const char *uname,
>  extern int early_init_dt_scan_memory(unsigned long node, const char *uname,
>  				     int depth, void *data);
>  extern void early_init_fdt_scan_reserved_mem(void);
> +extern void free_early_init_fdt_scan_reserved_mem(void);
>  extern void early_init_dt_add_memory_arch(u64 base, u64 size);
>  extern int early_init_dt_reserve_memory_arch(phys_addr_t base, phys_addr_t size,
>  					     bool no_map);
> @@ -89,6 +90,7 @@ extern u64 fdt_translate_address(const void *blob, int node_offset);
>  extern void of_fdt_limit_memory(int limit);
>  #else /* CONFIG_OF_FLATTREE */
>  static inline void early_init_fdt_scan_reserved_mem(void) {}
> +static inline void free_early_init_fdt_scan_reserved_mem(void) {}
>  static inline const char *of_flat_dt_get_machine_name(void) { return NULL; }
>  static inline void unflatten_device_tree(void) {}
>  static inline void unflatten_and_copy_device_tree(void) {}
> -- 
> 2.1.0
> --
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