flash/nor/efr32: fixed lockbits and user data

Changed flash driver to support writing to the user data page, as well as to any portion of the lockbits page above 512 bytes (the amount used for the actual page lock words). The top part of the lockbits page is used on at least the EFR32xG1 chips for the SiLabs bootloader encryption keys.

As presented to the user, the lockbits page is the same size as the other pages, but any attempt to write to its low 512 bytes is an error. To enforce this, efr32x_write is renamed to efm32x_priv_write and a wrapper function is provided in its place. If the user erases the lockbits page, the driver rewrites the cached lock words after the erase. When the driver erases the lockbits page in order to update the lock words, it first takes a copy of anything stored in the top part of the page, and re-programs it after the erase operation.

There are now multiple instances of flash_bank for each target, and the flash_bank instances must share their cached lock words to operate as intended. Therefore, when a bank is created, the global flash bank list is used to find any other banks that share the same target. Since some banks in the global list are invalid at the time free_driver_priv is called, reference counting is used to decide when to free driver_priv.

To avoid the need to find the lockbits flash_bank from another flash_bank, efm32x_priv_write and efm32x_erase_page now take an absolute address.

There didn't seem to be any reason to prohibit unprotecting individual flash pages, so that limitation is removed from efm32x_protect().

This addresses ticket #185.

Valgrind-clean, except for 2x 4kiB not freed/still reachable blocks that were allocated by libudev.
No new Clang analyzer warnings, no new sanitizer warnings.

Signed-off-by: Doug Brunner <doug.a.brunner@gmail.com>
Change-Id: Ifb22e6149939d893f386706e99b928691ec1d41b
Reviewed-on: https://review.openocd.org/c/openocd/+/6665
Tested-by: jenkins
Reviewed-by: Fredrik Hederstierna <fredrik.hederstierna@gmail.com>
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>

doc/openocd.texi

@@ -6351,13 +6351,22 @@ flash bank $_FLASHNAME cc3220sf 0 0 0 0 $_TARGETNAME
 @end deffn
 
 @deffn {Flash Driver} {efm32}
-All members of the EFM32 microcontroller family from Energy Micro include
-internal flash and use ARM Cortex-M3 cores. The driver automatically recognizes
-a number of these chips using the chip identification register, and
+All members of the EFM32/EFR32 microcontroller family from Energy Micro (now Silicon Labs)
+include internal flash and use Arm Cortex-M3 or Cortex-M4 cores. The driver automatically
+recognizes a number of these chips using the chip identification register, and
 autoconfigures itself.
 @example
 flash bank $_FLASHNAME efm32 0 0 0 0 $_TARGETNAME
 @end example
+It supports writing to the user data page, as well as the portion of the lockbits page
+past 512 bytes on chips with larger page sizes. The latter is used by the SiLabs
+bootloader/AppLoader system for encryption keys. Setting protection on these pages is
+currently not supported.
+@example
+flash bank userdata.flash efm32 0x0FE00000 0 0 0 $_TARGETNAME
+flash bank lockbits.flash efm32 0x0FE04000 0 0 0 $_TARGETNAME
+@end example
+
 A special feature of efm32 controllers is that it is possible to completely disable the
 debug interface by writing the correct values to the 'Debug Lock Word'. OpenOCD supports
 this via the following command:

tcl/target/efm32.cfg

@@ -43,6 +43,8 @@ $_TARGETNAME configure -work-area-phys 0x10000000 -work-area-size $_WORKAREASIZE
 
 set _FLASHNAME $_CHIPNAME.flash
 flash bank $_FLASHNAME efm32 0 0 0 0 $_TARGETNAME
+flash bank userdata.flash efm32 0x0FE00000 0 0 0 $_TARGETNAME
+flash bank lockbits.flash efm32 0x0FE04000 0 0 0 $_TARGETNAME
 
 if {![using_hla]} {
    # if srst is not fitted use SYSRESETREQ to