Incorrect flash usage report

[Pedro]

Hi,

I'm having an issue with flash usage reporting when building app. I'm using MCUBoot, so 2 images are generated.

First of all, my definition of partitions in an overlay file is the following (Original board is arduino nicla sense me).

I'm defining just slot0_partition as I will only update fw in serial recovery mode.

&flash0 {
	partitions {
		compatible = "fixed-partitions";
		#address-cells = <1>;
		#size-cells = <1>;

		boot_partition: partition@0 {
			label = "mcuboot";
			reg = <0x0 0xc000>;
		};
		slot0_partition: partition@c000 {
			label = "image-0";
			reg = <0xc000 0x6e000>;
		};
		storage_partition: partition@7a000 {
			label = "storage";
			reg = <0x7a000 0x6000>;
		};
	};
};

When I build the code, I receive these 2 memory usage reports:

Memory region         Used Size  Region Size  %age Used
           FLASH:       35288 B        48 KB     71.79%
            SRAM:       24800 B        64 KB     37.84%
        IDT_LIST:          0 GB         2 KB      0.00%

First one has sense and I suppose it corresponds to MCUboot, as 48KB is exactly 0xc000.

Memory region         Used Size  Region Size  %age Used
           FLASH:      186104 B     232960 B     79.89%
            SRAM:       63497 B        64 KB     96.89%
        IDT_LIST:          0 GB         2 KB      0.00%

However, in the second one I can not understand the source of 232960 B region size. Shouldn't be 440KB (0x6e000)??

I also tried splitting into slot0 and slot1 but 232960 B region size keeps unmodified.

Thanks and best regards,

Pedro.

[Hung Bui]

Hi Pedro, 

When you enable MCUBoot, Partition Manager will also be used and the overlay dts partition will not be used. Instead, you will find a file called partitions.yml  in the build folder which is the actual partition used. 
You will have something like this: 

app:
  address: 0xc200
  end_address: 0x46000
  region: flash_primary
  size: 0x39e00
mcuboot:
  address: 0x0
  end_address: 0xc000
  placement:
    before:
    - mcuboot_primary
  region: flash_primary
  size: 0xc000
mcuboot_pad:
  address: 0xc000
  end_address: 0xc200
  placement:
    align:
      start: 0x1000
    before:
    - mcuboot_primary_app
  region: flash_primary
  size: 0x200
mcuboot_primary:
  address: 0xc000
  end_address: 0x46000
  orig_span: &id001
  - mcuboot_pad
  - app
  region: flash_primary
  sharers: 0x1
  size: 0x3a000
  span: *id001
mcuboot_primary_app:
  address: 0xc200
  end_address: 0x46000
  orig_span: &id002
  - app
  region: flash_primary
  size: 0x39e00
  span: *id002
mcuboot_secondary:
  address: 0x46000
  end_address: 0x80000
  placement:
    after:
    - mcuboot_primary
    align:
      start: 0x1000
    align_next: 0x1000
  region: flash_primary
  share_size:
  - mcuboot_primary
  size: 0x3a000
sram_primary:
  address: 0x20000000
  end_address: 0x20010000
  region: sram_primary
  size: 0x10000

You can see the mcuboot_primary_app size will be 0x39e00 or 0x38E00 . 

By default the MCUBoot will configure the main flash into two partitions : primary and secondary. This is to support dual bank DFU update. 
I'm not sure if there is a way to disable this, but one work around is to copy the file partitions.yml and call it pm_static.yml. Put it to the root folder of the project and then modify the mcuboot_primary and mcuboot_secondary to make the size of mcuboot_primary  cover the whole flash and mcuboot_secondary  has zero size. 

[Pedro]

Hi Hung,

Thank you for your answer. I've deleted partitions definition in overlay dts and used pm_static.yml instead and it works.

I have a question about different sections of this file, because for me it seems to be redundant information.

What are the differences between app, mcuboot_primary and mcuboot_primary_app sections? I changed addresses and size in the 3, but I also noticed changing just mcuboot_primary also works (Seems to be ignoring app and mcuboot_primary_app). 

Why there is mcuboot_secondary but no mcuboot_secondary_app?

Regards,

Pedro.

[Hung Bui]

Hi Pedro, 

As far as I know, MCUBoot expects two partititions, mcuboot_primary and mcuboot_secondary. 

mcuboot_primary contains the mcuboot_primary_app (where the application located) and the mcuboot_pad (where the padding is) 

The app partition could be a redundancy here because it would be identical to the mcuboot_primary_app. 

 There is no point of having mcuboot_secondary_app because the app is not executed at the secondary lot. And padding not needed. It's simply the place where the new image is copied to. 

[Pedro]

Now It's clear for me. Thank you!