After reboot, reset or even short power off, DRAM typically retains
the old stale data for some period of time (for this type of memory,
the bits of data are stored in slowly discharging capacitors).
The current sun6i/sun8i DRAM size detection logic, which is
inherited from the Allwinner code, relies on using a large magic
signature with the hope that it is unique enough and unlikely to
ever accidentally match this leftover garbage data in RAM. But
this approach is inherently unsafe, as can be demonstrated using
the following test program:
/***** A testcase for reproducing the problem ******/
void main(int argc, char *argv[])
{
size_t size, i;
uint32_t *buf;
/* Allocate the buffer */
if (argc < 2 || !(size = (size_t)atoi(argv[1]) * 1048576) ||
!(buf = malloc(size))) {
printf("Need buffer size in MiB as a cmdline argument\n");
exit(1);
}
/* Fill it with the Allwinner DRAM "magic" values */
for (i = 0; i < size / 4; i++)
buf[i] = 0xaa55aa55 + ((uintptr_t)&buf[i] / 4) % 64;
/* Try to reboot */
system("reboot");
/* And wait */
for (;;) {}
}
/***************************************************/
If this test program is run on the device (giving it a large
chunk of memory), then the DRAM size detection logic in u-boot
gets confused after reboot and fails to initialize DRAM properly.
A better approach is not to rely on luck and abstain from making
any assumptions about the properties of the leftover garbage
data in RAM. Instead just use a more reliable code for testing
whether two different addresses refer to the same memory location.
Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
The sun8i boot0 code fills the DRAM with a "random" pattern before comparing
it at different offsets to do columns, etc. detection. The sun6i boot0 code
does not do it, instead relying on the memory contents being random enough
to begin with for the memcmp to properly detect the wrap-around address, iow
it is working purely by chance. Since our sun6i dram code was modelled after
the boot0 code it contained the same issue.
This commit fixes this by filling the memory with a unique, distinct pattern.
The new mctl_mem_fill function this introduces is added as an inline helper
in dram.h, so that it can be shared with the sun8i dram code.
While at it move mctl_mem_matches to dram.h for re-use in sun8i too.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
The await_completion helper is already copy pasted between the sun4i and sun6i
dram code, and we need it for sun8i too, so lets make it an inline helper in
dram.h, rather then adding yet another copy.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
The sun8i dram code sometimes wants to enable sigma delta mode,
add a parameter to allow this.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
The A31s only has one dram channel, so do not bother with trying to initialize
a second channel.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
It turns out that there is a too large spread between boards to handle this
with a default value, turn this into Kconfig options, and set the values
the factory images are using for the Colombus and Mele_M9 boards.
Note this changes the ZQ default when not overriden through defconfig from
120 to 123, as that is what most boards seem to actually use.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
Allwinner tells us that this bit of code is the rtc ram being used to detect
coming out of "super-standby" mode, and if that is the case, going out of
self-refresh mode.
Since we do not support "super-standby" mode, this can be dropped.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
Add full support for dram initialization, using a fixed clock and autodetection
of the memory organization (numbers of channels, bus-width, etc.).
This is based on dram_sun6i.c and dram.h from u-boot in the Allwinner A31 SDK,
extended with extra initialization sequences and the autodetect algorithm
from boot0.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
