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ARM: uniphier: do not use RAM that exceeds 32 bit address range

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LD20 / PXs3 boards are equipped with a large amount of memory beyond
the 32 bit address range.  U-Boot relocates itself to the end of the
available RAM.

This is a problem for DMA engines that only support 32 bit physical
address, like the SDMA of SDHCI controllers.

In fact, U-Boot does not need to run at the very end of RAM.  It is
rather troublesome for drivers with DMA engines because U-Boot does
not have API like dma_set_mask(), so DMA silently fails, making the
driver debugging difficult.

Hide the memory region that exceeds the 32 bit address range.  It can
be done by simply carving out gd->ram_size.  It would also possible to
override get_effective_memsize() or to define CONFIG_MAX_MEM_MAPPED,
but dram_init() is a good enough place to do this job.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
This commit is contained in:
Masahiro Yamada 2018-01-06 22:59:24 +09:00
parent f3dd87e0b9
commit be893a5c09
1 changed files with 17 additions and 0 deletions
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17
arch/arm/mach-uniphier/dram_init.c
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@ -205,6 +205,7 @@ int dram_init(void)
return ret;
for (i = 0; i < ARRAY_SIZE(dram_map); i++) {
unsigned long max_size;
if (!dram_map[i].size)
break;
@ -218,6 +219,22 @@ int dram_init(void)
dram_map[i].base)
break;
/*
* Do not use memory that exceeds 32bit address range. U-Boot
* relocates itself to the end of the effectively available RAM.
* This could be a problem for DMA engines that do not support
* 64bit address (SDMA of SDHCI, UniPhier AV-ether, etc.)
*/
if (dram_map[i].base >= 1ULL << 32)
break;
max_size = (1ULL << 32) - dram_map[i].base;
if (dram_map[i].size > max_size) {
gd->ram_size += max_size;
break;
}
gd->ram_size += dram_map[i].size;
}