Subject: Re: [PATCH 3/3] of/fdt: Rework early_init_dt_scan_memory() to call
 directly
To:     Rob Herring <robh@kernel.org>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        John Crispin <john@phrozen.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Paul Mackerras <paulus@samba.org>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc:     devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
References: <20211118181213.1433346-1-robh@kernel.org>
 <20211118181213.1433346-4-robh@kernel.org>
From:   Frank Rowand <frowand.list@gmail.com>
Message-ID: <49f32685-11e2-efba-5a8f-279b69a041d0@gmail.com>
Date:   Wed, 24 Nov 2021 11:58:58 -0500
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On 11/18/21 1:12 PM, Rob Herring wrote:
> Use of the of_scan_flat_dt() function predates libfdt and is discouraged
> as libfdt provides a nicer set of APIs. Rework
> early_init_dt_scan_memory() to be called directly and use libfdt.
> 
> Cc: John Crispin <john@phrozen.org>
> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Frank Rowand <frowand.list@gmail.com>
> Cc: linux-mips@vger.kernel.org
> Cc: linuxppc-dev@lists.ozlabs.org
> Signed-off-by: Rob Herring <robh@kernel.org>
> ---
>  arch/mips/ralink/of.c      | 16 ++-------
>  arch/powerpc/kernel/prom.c | 16 ++++-----
>  drivers/of/fdt.c           | 68 ++++++++++++++++++++------------------
>  include/linux/of_fdt.h     |  3 +-
>  4 files changed, 47 insertions(+), 56 deletions(-)
> 
> diff --git a/arch/mips/ralink/of.c b/arch/mips/ralink/of.c
> index 0135376c5de5..e1d79523343a 100644
> --- a/arch/mips/ralink/of.c
> +++ b/arch/mips/ralink/of.c
> @@ -53,17 +53,6 @@ void __init device_tree_init(void)
>  	unflatten_and_copy_device_tree();
>  }
>  
> -static int memory_dtb;
> -
> -static int __init early_init_dt_find_memory(unsigned long node,
> -				const char *uname, int depth, void *data)
> -{
> -	if (depth == 1 && !strcmp(uname, "memory@0"))
> -		memory_dtb = 1;
> -
> -	return 0;
> -}
> -
>  void __init plat_mem_setup(void)
>  {
>  	void *dtb;
> @@ -77,9 +66,8 @@ void __init plat_mem_setup(void)
>  	dtb = get_fdt();
>  	__dt_setup_arch(dtb);
>  
> -	of_scan_flat_dt(early_init_dt_find_memory, NULL);
> -	if (memory_dtb)
> -		of_scan_flat_dt(early_init_dt_scan_memory, NULL);
> +	if (!early_init_dt_scan_memory())
> +		return;
>  	else if (soc_info.mem_detect)

The previous chunk is now:

   if (XXX)
      return;

instead of:

   if (XXX)
      YYY();

so "else if (soc_info.mem_detect)" should be:

  if (soc_info.mem_detect)

>  		soc_info.mem_detect();
>  	else if (soc_info.mem_size)
> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
> index 6e1a106f02eb..63762a3b75e8 100644
> --- a/arch/powerpc/kernel/prom.c
> +++ b/arch/powerpc/kernel/prom.c
> @@ -532,19 +532,19 @@ static int  __init early_init_drmem_lmb(struct drmem_lmb *lmb,
>  }
>  #endif /* CONFIG_PPC_PSERIES */
>  
> -static int __init early_init_dt_scan_memory_ppc(unsigned long node,
> -						const char *uname,
> -						int depth, void *data)
> +static int __init early_init_dt_scan_memory_ppc(void)
>  {
>  #ifdef CONFIG_PPC_PSERIES
> -	if (depth == 1 &&
> -	    strcmp(uname, "ibm,dynamic-reconfiguration-memory") == 0) {
> +	const void *fdt = initial_boot_params;
> +	int node = fdt_path_offset(fdt, "/ibm,dynamic-reconfiguration-memory");
> +
> +	if (node > 0) {
>  		walk_drmem_lmbs_early(node, NULL, early_init_drmem_lmb);
>  		return 0;
>  	}
>  #endif
>  	
> -	return early_init_dt_scan_memory(node, uname, depth, data);
> +	return early_init_dt_scan_memory();
>  }
>  
>  /*
> @@ -749,7 +749,7 @@ void __init early_init_devtree(void *params)
>  
>  	/* Scan memory nodes and rebuild MEMBLOCKs */
>  	early_init_dt_scan_root();
> -	of_scan_flat_dt(early_init_dt_scan_memory_ppc, NULL);
> +	early_init_dt_scan_memory_ppc();
>  
>  	parse_early_param();
>  
> @@ -858,7 +858,7 @@ void __init early_get_first_memblock_info(void *params, phys_addr_t *size)
>  	 */
>  	add_mem_to_memblock = 0;
>  	early_init_dt_scan_root();
> -	of_scan_flat_dt(early_init_dt_scan_memory_ppc, NULL);
> +	early_init_dt_scan_memory_ppc();
>  	add_mem_to_memblock = 1;
>  
>  	if (size)
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 5e216555fe4f..a799117886f4 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -1078,49 +1078,53 @@ u64 __init dt_mem_next_cell(int s, const __be32 **cellp)
>  /*
>   * early_init_dt_scan_memory - Look for and parse memory nodes
>   */
> -int __init early_init_dt_scan_memory(unsigned long node, const char *uname,
> -				     int depth, void *data)
> +int __init early_init_dt_scan_memory(void)
>  {
> -	const char *type = of_get_flat_dt_prop(node, "device_type", NULL);
> -	const __be32 *reg, *endp;
> -	int l;
> -	bool hotpluggable;
> +	int node;
> +	const void *fdt = initial_boot_params;
>  
> -	/* We are scanning "memory" nodes only */
> -	if (type == NULL || strcmp(type, "memory") != 0)
> -		return 0;
> +	fdt_for_each_subnode(node, fdt, 0) {
> +		const char *type = of_get_flat_dt_prop(node, "device_type", NULL);
> +		const __be32 *reg, *endp;
> +		int l;
> +		bool hotpluggable;
>  
> -	reg = of_get_flat_dt_prop(node, "linux,usable-memory", &l);
> -	if (reg == NULL)
> -		reg = of_get_flat_dt_prop(node, "reg", &l);
> -	if (reg == NULL)
> -		return 0;
> +		/* We are scanning "memory" nodes only */
> +		if (type == NULL || strcmp(type, "memory") != 0)
> +			continue;
>  
> -	endp = reg + (l / sizeof(__be32));
> -	hotpluggable = of_get_flat_dt_prop(node, "hotpluggable", NULL);
> +		reg = of_get_flat_dt_prop(node, "linux,usable-memory", &l);
> +		if (reg == NULL)
> +			reg = of_get_flat_dt_prop(node, "reg", &l);
> +		if (reg == NULL)
> +			return 0;

                        Should be "continue" instead of "return 0"?

>  
> -	pr_debug("memory scan node %s, reg size %d,\n", uname, l);
> +		endp = reg + (l / sizeof(__be32));
> +		hotpluggable = of_get_flat_dt_prop(node, "hotpluggable", NULL);
>  
> -	while ((endp - reg) >= (dt_root_addr_cells + dt_root_size_cells)) {
> -		u64 base, size;
> +		pr_debug("memory scan node %s, reg size %d,\n",
> +			fdt_get_name(fdt, node, NULL), l);

Second line of pr_debug() should be indented one more space.

>  
> -		base = dt_mem_next_cell(dt_root_addr_cells, &reg);
> -		size = dt_mem_next_cell(dt_root_size_cells, &reg);
> +		while ((endp - reg) >= (dt_root_addr_cells + dt_root_size_cells)) {
> +			u64 base, size;
>  
> -		if (size == 0)
> -			continue;
> -		pr_debug(" - %llx, %llx\n", base, size);
> +			base = dt_mem_next_cell(dt_root_addr_cells, &reg);
> +			size = dt_mem_next_cell(dt_root_size_cells, &reg);
>  
> -		early_init_dt_add_memory_arch(base, size);
> +			if (size == 0)
> +				continue;
> +			pr_debug(" - %llx, %llx\n", base, size);
>  
> -		if (!hotpluggable)
> -			continue;
> +			early_init_dt_add_memory_arch(base, size);
>  
> -		if (memblock_mark_hotplug(base, size))
> -			pr_warn("failed to mark hotplug range 0x%llx - 0x%llx\n",
> -				base, base + size);
> -	}
> +			if (!hotpluggable)
> +				continue;
>  
> +			if (memblock_mark_hotplug(base, size))
> +				pr_warn("failed to mark hotplug range 0x%llx - 0x%llx\n",
> +					base, base + size);
> +		}
> +	}
>  	return 0;
>  }
>  
> @@ -1271,7 +1275,7 @@ void __init early_init_dt_scan_nodes(void)
>  		pr_warn("No chosen node found, continuing without\n");
>  
>  	/* Setup memory, calling early_init_dt_add_memory_arch */
> -	of_scan_flat_dt(early_init_dt_scan_memory, NULL);
> +	early_init_dt_scan_memory();
>  
>  	/* Handle linux,usable-memory-range property */
>  	memblock_cap_memory_range(cap_mem_addr, cap_mem_size);
> diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
> index df3d31926c3c..914739f3c192 100644
> --- a/include/linux/of_fdt.h
> +++ b/include/linux/of_fdt.h
> @@ -59,8 +59,7 @@ extern unsigned long of_get_flat_dt_root(void);
>  extern uint32_t of_get_flat_dt_phandle(unsigned long node);
>  
>  extern int early_init_dt_scan_chosen(char *cmdline);
> -extern int early_init_dt_scan_memory(unsigned long node, const char *uname,
> -				     int depth, void *data);
> +extern int early_init_dt_scan_memory(void);
>  extern int early_init_dt_scan_chosen_stdout(void);
>  extern void early_init_fdt_scan_reserved_mem(void);
>  extern void early_init_fdt_reserve_self(void);
>