Re: [PATCH 2/2] of: reserved_mem: allocate and map the reserved_mem array early

[Marek Szyprowski]

On 08.10.2026 16:05, Rob Herring wrote:
> On Thu, Oct 08, 2026 at 11:41:23AM +0200, Marek Szyprowski wrote:
>> Get rid of the static, limited-size reserved_mem array and replace it
>> with array allocated by memblock_alloc_raw() and accessed through a
>> temporary early_memremap() mapping. Such mapping is needed for some
>> architectures (like ARM64), where linear map is not yet available during
>> early boot scan. Having a single, writeable array with all reserved
>> regions removes the need to perform two step initialization introduced
>> by commit 8a6e02d0c00e ("of: reserved_mem: Restructure how the reserved
>> memory regions are processed"), so all regions can be processed
>> directly during the early scan again.
>>
>> Suggested-by: Mike Rapoport <rppt@xxxxxxxxxx>
>> Link: https://lore.kernel.org/all/asc6brs_g0ky0wOM@xxxxxxxxxx/
>> Assisted-By: Claude Opus 5.5 <noreply@xxxxxxxxxxxxx>
> Assisted-by: LLM
>
> is the new way...
>
>> Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
>> ---
>>  drivers/of/fdt.c             |   3 -
>>  drivers/of/of_private.h      |   2 -
>>  drivers/of/of_reserved_mem.c | 251 ++++++++++++++---------------------
>>  3 files changed, 96 insertions(+), 160 deletions(-)
>>
>> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
>> index ecc923102622..a58efdcbac7f 100644
>> --- a/drivers/of/fdt.c
>> +++ b/drivers/of/fdt.c
>> @@ -1283,9 +1283,6 @@ void __init unflatten_device_tree(void)
>>  {
>>  	void *fdt = initial_boot_params;
>>  
>> -	/* Save the statically-placed regions in the reserved_mem array */
>> -	fdt_scan_reserved_mem_late();
>> -
>>  	/* Populate an empty root node when bootloader doesn't provide one */
>>  	if (!fdt) {
>>  		fdt = (void *) __dtb_empty_root_begin;
>> diff --git a/drivers/of/of_private.h b/drivers/of/of_private.h
>> index 0ae16da066e2..895f868b4cfa 100644
>> --- a/drivers/of/of_private.h
>> +++ b/drivers/of/of_private.h
>> @@ -9,7 +9,6 @@
>>   */
>>  
>>  #define FDT_ALIGN_SIZE 8
>> -#define MAX_RESERVED_REGIONS    64
>>  
>>  /**
>>   * struct alias_prop - Alias property in 'aliases' node
>> @@ -186,7 +185,6 @@ static inline struct device_node *__of_get_dma_parent(const struct device_node *
>>  #endif
>>  
>>  int fdt_scan_reserved_mem(void);
>> -void __init fdt_scan_reserved_mem_late(void);
>>  
>>  bool of_fdt_device_is_available(const void *blob, unsigned long node);
>>  
>> diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
>> index 300fb236ab59..6a5e53243bb7 100644
>> --- a/drivers/of/of_reserved_mem.c
>> +++ b/drivers/of/of_reserved_mem.c
>> @@ -24,12 +24,14 @@
>>  #include <linux/slab.h>
>>  #include <linux/memblock.h>
>>  #include <linux/kmemleak.h>
>> +#ifdef CONFIG_GENERIC_EARLY_IOREMAP
>> +#include <asm/early_ioremap.h>
>> +#endif
> These ifdefs are the only thing I don't like. early_ioremap.h is always 
> in asm-generic, so do we need the ifdef here? Or does the arch have to 
> do something to pick it up? I don't remember.

Those ifdefs seems to be some hallucinations I missed to fix. I will send v2 in a few
minutes.

> ...

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland