At the moment the "stemmy" board attempts to detect the RAM size with
a simple memory test (get_ram_size()). Unfortunately, this does not work
correctly for devices with 768 MiB RAM (e.g. Samsung Galaxy Ace 2
(GT-I8160), "codina"). Reading/writing memory after the 768 MiB RAM
succeeds but actually overwrites some earlier parts of the memory.
For U-Boot this does not result in any major problems, but on Linux
this will eventually lead to strange crashes because of the memory
corruption.
Since the "stemmy" U-Boot port is designed to be chainloaded from
the original Samsung bootloader, the most reliable way to get the
available amount of RAM is to look at the ATAGS passed by the Samsung
bootloader. Fortunately, the header used to generate ATAGS in U-Boot
(asm/setup.h) can also be easily used to parse them.
Also clarify and simplify stemmy.h a bit to make it more clear where
some of the magic values in there are actually coming from.
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
The ST-Ericsson U8500 SoC has been used in mass-production for
some Android smartphones released around 2012.
In particular, Samsung has released more than 5 different
smartphones based on U8500, e.g.
- Samsung Galaxy S III mini (GT-I8190) "golden"
- Samsung Galaxy S Advance (GT-I9070) "janice"
- Samsung Galaxy Xcover 2 (GT-S7710) "skomer"
and a few others.
Mainline Linux has great support for the Ux500 SoC, so these
smartphones can also run Linux mainline quite well.
Unfortunately, the original Samsung bootloader used on these devices
has limitations that prevent booting Linux mainline directly.
It keeps the L2 cache enabled, which causes Linux to crash very early,
shortly after decompressing the kernel.
Using U-Boot allows to circumvent these limitations. We can let the
Samsung bootloader chain-load U-Boot and U-Boot locks the L2 cache
before booting into Linux. U-Boot has several other advantages
- it supports device-trees directly and we are no longer limited to
flashing Android boot images through Samsung's proprietary download
mode.
The Samsung "stemmy" board covers all Samsung devices based on U8500.
Add minimal support for "stemmy". For now only UART is supported but
this will be extended later.
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
