riotboot/flashwrite: use flashpage_raw when available

[fjmolinas]

Contribution description

The following PR allows using flashpage_write_raw() to finish an update process. The main objective of this is to support OTA on stm32f4/2/7. Since the flash is sector based if at the finish we are to perform an erase operation the whole sector would be erased (sectors that go from 16KB to 256KB). The idea is that since we only need to write 4 bytes if flashpage_write_raw() is available erasing the sector again can be avoided since it was already erased at the start of the flashwrite process. So as long as the first 4 bytes are kept in an erased state '0xFF' flashpage_write_raw() can be used.

Testing procedure

1. Verify that everything still works on supported board that support and don't support flashpage. Applying this diff can help in testing over ethos:

diff --git a/tests/riotboot_flashwrite/Makefile b/tests/riotboot_flashwrite/Makefile
index 32f127d70..d3c9f20b4 100644
--- a/tests/riotboot_flashwrite/Makefile
+++ b/tests/riotboot_flashwrite/Makefile
@@ -39,11 +39,17 @@ LOW_MEMORY_BOARDS := nucleo-f334r8
 GNRC_NETIF_NUMOF := 2
 
 # uncomment these to use ethos
-#USEMODULE += ethos gnrc_uhcpc
+USEMODULE += ethos gnrc_uhcpc  stdio_uart_rx
 #
 ## ethos baudrate can be configured from make command
-#ETHOS_BAUDRATE ?= 115200
-#CFLAGS += -DETHOS_BAUDRATE=$(ETHOS_BAUDRATE) -DUSE_ETHOS_FOR_STDIO
+ETHOS_BAUDRATE ?= 115200
+CFLAGS += -DETHOS_BAUDRATE=$(ETHOS_BAUDRATE) -DUSE_ETHOS_FOR_STDIO
+
+TAP ?= tap0
+IPV6_PREFIX ?= 2001:db8::/64
+
+TERMPROG ?= sudo sh $(RIOTTOOLS)/ethos/start_network.sh
+TERMFLAGS ?= $(PORT) $(TAP) $(IPV6_PREFIX)
 
 ifneq (,$(filter $(BOARD),$(LOW_MEMORY_BOARDS)))
   $(info Using low-memory configuration for microcoap_server.)

for nucleo-l073rz:

• provided the node make -C tests/riotboot_flashwrite/ BOARD= nucleo-l073rz riotboot/flash term
• compile new firmware: make -C tests/riotboot_flashwrite/ BOARD= nucleo-l073rzriotboot
• launch an updated: coap-client -m post coap://[fe80::2%tap0]/flashwrite -f tests/riotboot_flashwrite/bin/ nucleo-l073rz/tests_riotboot_flashwrite-slot1.riot.bin -b 64

for samr21-xpro:

• provided the node make -C tests/riotboot_flashwrite/ BOARD= samr21-xpro riotboot/flash term
• compile new firmware: make -C tests/riotboot_flashwrite/ BOARD= samr21-xpro rzriotboot
• launch an updated: coap-client -m post coap://[fe80::2%tap0]/flashwrite -f tests/riotboot_flashwrite/bin/ samr21-xpro/tests_riotboot_flashwrite-slot1.riot.bin -b 64

When the update finished reboot the node manually it should have started from a different slot.

2. rebase on top of cpu/stm32f4: add riotboot requirements #11682 and cpu/stm32f7/4/2: add flashpage and flashpage_raw #11681 and test over an stm32f4 board, e.g. nucleo-f446re

• provided the node make -C tests/riotboot_flashwrite/ BOARD=nucleo-f446re riotboot/flash term
• compile new firmware: make -C tests/riotboot_flashwrite/ BOARD=nucleo-f446re riotboot
• launch an updated: coap-client -m post coap://[fe80::2%tap0]/flashwrite -f tests/riotboot_flashwrite/bin/ nucleo-f446retests_riotboot_flashwrite-slot1.riot.bin -b 64

Issues/PRs references

Related to #11682 and #1168

[kaspar030]

Code looks fine. Will try to test tomorrow.

(Some of the alignment changes were a little off, fixing from too little spaces to too many.)

[kaspar030]

hmmmm ;)

[kaspar030]

Hm, shouldn't flashpage_raw allow to not allocate a whole flash page as buffer?
The idea would be to erase a page on first write, but then write in FLASHPAGE_RAW_BLOCKSIZE sized chunks.

[fjmolinas]

Closed in favor of #11705