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sunxi: restore modified memory

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Current sunxi DRAM initialisation code does several test accesses to the
DRAM array to detect aliasing effects and so determine the correct
row/column configuration. This changes the DRAM content, which breaks
use cases like soft reset and Linux's ramoops mechanism.

Fix this problem by saving and restoring the content of the DRAM cells
that is used for the test writes.

Signed-off-by: Andrey Skvortsov <andrej.skvortzov@gmail.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
This commit is contained in:
Andrey Skvortsov 2023-12-28 00:28:43 +03:00 committed by Andre Przywara
parent 978808d2b9
commit f1e6a718eb
1 changed files with 14 additions and 2 deletions
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16
arch/arm/mach-sunxi/dram_helpers.c
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@ -33,13 +33,25 @@ void mctl_await_completion(u32 *reg, u32 mask, u32 val)
#ifndef CONFIG_MACH_SUNIV
bool mctl_mem_matches_base(u32 offset, ulong base)
{
u32 val_base;
u32 val_offset;
bool ret;
/* Save original values */
val_base = readl(base);
val_offset = readl(base + offset);
/* Try to write different values to RAM at two addresses */
writel(0, base);
writel(0xaa55aa55, base + offset);
dsb();
/* Check if the same value is actually observed when reading back */
return readl(base) ==
readl(base + offset);
ret = readl(base) == readl(base + offset);
/* Restore original values */
writel(val_base, base);
writel(val_offset, base + offset);
return ret;
}
/*