[PATCH v3] common: fdt: Remove additional 4k space for fdt allocation

[Michal Simek]

On 18. 06. 20 12:48, Heinrich Schuchardt wrote:
> On 6/18/20 10:51 AM, Michal Simek wrote:
>> From: Ashok Reddy Soma <ashok.reddy.soma at xilinx.com>
>>
>> There is no technical reason to add additional 4k space for FDT. This
>> space
>> is completely unused and just increase memory requirements. This is
>> problematic on systems with limited memory resources as Xilinx Zynq
>> CSE/ZynqMP mini and Versal mini configurations.
>>
>> The patch is removing additional 4k space.
>>
>> EFI code is using copy_fdt() which copy FDT to different location.
>> And all boot commands in case of using U-Boot's FDT pointed by
>> $fdtcontroladdr are copying FDT to different locations by
>> image_setup_libfdt().
>> That's why in proper flow none should modified DTB used by U-Boot that's
>> why there is no need for additional space.
>>
>> Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma at xilinx.com>
>> Signed-off-by: Michal Simek <michal.simek at xilinx.com>
>> ---
>>
>> Changes in v3:
>> - Remove alignment change and keep it as 32
>>
>> Changes in v2:
>> - Change subject (was: common: Add Kconfig option for FDT mem alignment)
>> - Remove Kconfig symbol
>> - Extend description
>>
>> I have tested it on zcu104.
>> Outcome from v2 review was to remove that alignment part and if that
>> works
>> on all boards then it is ready to go. The best as early as possible.
>>
>> Tom: Would be good to add it to your queue for testing to spot any issue
>> earlier.
>>
>> ---
>>   common/board_f.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/common/board_f.c b/common/board_f.c
>> index 01194eaa0e4d..dcad551ae434 100644
>> --- a/common/board_f.c
>> +++ b/common/board_f.c
>> @@ -537,7 +537,7 @@ static int reserve_fdt(void)
>>        * will be relocated with other data.
>>        */
>>       if (gd->fdt_blob) {
>> -        gd->fdt_size = ALIGN(fdt_totalsize(gd->fdt_blob) + 0x1000, 32);
>> +        gd->fdt_size = ALIGN(fdt_totalsize(gd->fdt_blob), 32);
> 
> reserve_stack_aligned() already rounds the size up to a multiple of 16.
> The ALIGN() here is simply wasting 16 bytes of memory in half of the cases.

As we discussed in v2. Let's just deal with alignment in separate patch.

Thanks,
Michal