Subject: Re: [PATCH 2/3] of/fdt: Rework early_init_dt_scan_root() 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>
 <20211118181213.1433346-3-robh@kernel.org>
From:   Frank Rowand <frowand.list@gmail.com>
Message-ID: <13f402bb-933d-a5e0-4f45-24e5f5b3b1f1@gmail.com>
Date:   Wed, 24 Nov 2021 11:20:24 -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_root()
> to be called directly and use libfdt.
> 
> 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: linuxppc-dev@lists.ozlabs.org
> Signed-off-by: Rob Herring <robh@kernel.org>
> ---
>  arch/powerpc/kernel/prom.c |  4 ++--
>  drivers/of/fdt.c           | 14 +++++++-------
>  include/linux/of_fdt.h     |  3 +--
>  3 files changed, 10 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
> index c6c398ccd98a..6e1a106f02eb 100644
> --- a/arch/powerpc/kernel/prom.c
> +++ b/arch/powerpc/kernel/prom.c
> @@ -748,7 +748,7 @@ void __init early_init_devtree(void *params)
>  	of_scan_flat_dt(early_init_dt_scan_chosen_ppc, boot_command_line);
>  
>  	/* Scan memory nodes and rebuild MEMBLOCKs */
> -	of_scan_flat_dt(early_init_dt_scan_root, NULL);
> +	early_init_dt_scan_root();
>  	of_scan_flat_dt(early_init_dt_scan_memory_ppc, NULL);
>  
>  	parse_early_param();
> @@ -857,7 +857,7 @@ void __init early_get_first_memblock_info(void *params, phys_addr_t *size)
>  	 * mess the memblock.
>  	 */
>  	add_mem_to_memblock = 0;
> -	of_scan_flat_dt(early_init_dt_scan_root, NULL);
> +	early_init_dt_scan_root();
>  	of_scan_flat_dt(early_init_dt_scan_memory_ppc, NULL);
>  	add_mem_to_memblock = 1;
>  
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 1f1705f76263..5e216555fe4f 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -1042,13 +1042,14 @@ int __init early_init_dt_scan_chosen_stdout(void)
>  /*
>   * early_init_dt_scan_root - fetch the top level address and size cells
>   */
> -int __init early_init_dt_scan_root(unsigned long node, const char *uname,
> -				   int depth, void *data)
> +int __init early_init_dt_scan_root(void)
>  {
>  	const __be32 *prop;
> +	const void *fdt = initial_boot_params;
> +	int node = fdt_path_offset(fdt, "/");
>  
> -	if (depth != 0)
> -		return 0;
> +	if (node < 0)
> +		return -ENODEV;
>  
>  	dt_root_size_cells = OF_ROOT_NODE_SIZE_CELLS_DEFAULT;
>  	dt_root_addr_cells = OF_ROOT_NODE_ADDR_CELLS_DEFAULT;
> @@ -1063,8 +1064,7 @@ int __init early_init_dt_scan_root(unsigned long node, const char *uname,
>  		dt_root_addr_cells = be32_to_cpup(prop);
>  	pr_debug("dt_root_addr_cells = %x\n", dt_root_addr_cells);
>  
> -	/* break now */
> -	return 1;
> +	return 0;
>  }
>  
>  u64 __init dt_mem_next_cell(int s, const __be32 **cellp)
> @@ -1263,7 +1263,7 @@ void __init early_init_dt_scan_nodes(void)
>  	int rc;
>  
>  	/* Initialize {size,address}-cells info */
> -	of_scan_flat_dt(early_init_dt_scan_root, NULL);
> +	early_init_dt_scan_root();
>  
>  	/* Retrieve various information from the /chosen node */
>  	rc = early_init_dt_scan_chosen(boot_command_line);
> diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
> index 654722235df6..df3d31926c3c 100644
> --- a/include/linux/of_fdt.h
> +++ b/include/linux/of_fdt.h
> @@ -68,8 +68,7 @@ extern void early_init_dt_add_memory_arch(u64 base, u64 size);
>  extern u64 dt_mem_next_cell(int s, const __be32 **cellp);
>  
>  /* Early flat tree scan hooks */
> -extern int early_init_dt_scan_root(unsigned long node, const char *uname,
> -				   int depth, void *data);
> +extern int early_init_dt_scan_root(void);
>  
>  extern bool early_init_dt_scan(void *params);
>  extern bool early_init_dt_verify(void *params);
> 

Reviewed-by: Frank Rowand <frank.rowand@sony.com>