[U-Boot-Users] Protect an area in RAM

[Wolfgang Denk]

In message <DC6F86A94046A64094043D44A3A708F7A148D4 at sestoex02.enea.se> you wrote:
> 
> Many hardware manufactures provide their development platform with
> u-boot. I was wondering if there is a feature (did not find anything) in
> u-boot to protect a specific area in the RAM from being overwritten when
> u-boot boots a microcontroller? The reason for this is that we store
> debug information between restarts from our software and using u-boot
> this is destroyed.

I'm seriously surprised that you  did  not  find  anything.  Did  you
actually search for "protected RAM"?

-> grep -ir 'protected ram' *
README:- Protected RAM:
README:         "protected RAM", i. e. RAM which is not overwritten
README: ...             eventually: pRAM (Protected RAM - unchanged by reset)
board/netstal/hcu5/README.txt:   *  - protected RAM
include/configs/CCM.h:#define   CONFIG_PRAM             512     /* reserve 512kB "protected RAM"*/
include/configs/CMS700.h:#undef  CONFIG_PRAM                    /* no "protected RAM"           */
include/configs/DP405.h:#define CONFIG_PRAM             2       /* reserve 2 kB "protected RAM" */
include/configs/PCI405.h:#define CONFIG_PRAM            2048    /* reserve 2 MB "protected RAM" */
include/configs/PN62.h:#define CONFIG_PRAM              1024            /* reserve 1 MB protected RAM*/
include/configs/VOM405.h:#undef  CONFIG_PRAM                    /* no "protected RAM"           */
include/configs/pcu_e.h:#define CONFIG_PRAM             2048    /* reserve 2 MB "protected RAM" */
lib_m68k/board.c:        *      - protected RAM
lib_m68k/board.c:        * reserve protected RAM
lib_m68k/board.c:       debug ("Reserving %ldk for protected RAM at %08lx\n", reg, addr);
lib_m68k/board.c:        * taking into account the protected RAM at top of memory
lib_ppc/board.c:         *  - protected RAM
lib_ppc/board.c:         * reserve protected RAM
lib_ppc/board.c:        debug ("Reserving %ldk for protected RAM at %08lx\n", reg, addr);
lib_ppc/board.c:         * taking into account the protected RAM at top of memory


> If this feature does not exist, one general solution would be to add a
> system parameter in which areas that are not to be destroyed could be
> added as a default feature of u-boot. Would this be a feature that
> others need as well? If so I will start to investigate what could be
> done.

This feature has been available for a long, long time, as well  as  a
log  driver  which  is  intended  to  pass  for  example  U-Boot POST
information to the OS (Linux), or to allow U-Boot to dump Linux'  log
buffer after a crash.

I guess you should refine your search methods.

Best regards,

Wolfgang Denk

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