[PATCH 13/15] MIPS: JZ4770: Workaround for corrupted DMA transfers
From: Paul Cercueil <paul@crapouillou.net>
Date: 2017-06-07 20:06:34
Also in:
linux-clk, linux-mips, lkml
Subsystem:
mips, the rest · Maintainers:
Thomas Bogendoerfer, Linus Torvalds
From: Maarten ter Huurne <redacted> We have seen MMC DMA transfers read corrupted data from SDRAM when a burst interval ends at physical address 0x10000000. To avoid this problem, we remove the final page of low memory from the memory map. Signed-off-by: Maarten ter Huurne <redacted> --- arch/mips/jz4740/setup.c | 24 ++++++++++++++++++++++++ arch/mips/kernel/setup.c | 8 ++++++++ 2 files changed, 32 insertions(+)
diff --git a/arch/mips/jz4740/setup.c b/arch/mips/jz4740/setup.c
index afd84ee966e8..6948b133a15d 100644
--- a/arch/mips/jz4740/setup.c
+++ b/arch/mips/jz4740/setup.c@@ -23,6 +23,7 @@ #include <asm/bootinfo.h> #include <asm/mips_machine.h> +#include <asm/page.h> #include <asm/prom.h> #include <asm/mach-jz4740/base.h>
@@ -102,6 +103,29 @@ void __init arch_init_irq(void) irqchip_init(); } +/* + * We have seen MMC DMA transfers read corrupted data from SDRAM when a burst + * interval ends at physical address 0x10000000. To avoid this problem, we + * remove the final page of low memory from the memory map. + */ +void __init jz4770_reserve_unsafe_for_dma(void) +{ + int i; + + for (i = 0; i < boot_mem_map.nr_map; i++) { + struct boot_mem_map_entry *entry = boot_mem_map.map + i; + + if (entry->type != BOOT_MEM_RAM) + continue; + + if (entry->addr + entry->size != 0x10000000) + continue; + + entry->size -= PAGE_SIZE; + break; + } +} + static int __init jz4740_machine_setup(void) { mips_machine_setup();
diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 89785600fde4..cccfd7ba89fe 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c@@ -838,6 +838,14 @@ static void __init arch_mem_init(char **cmdline_p) parse_early_param(); +#ifdef CONFIG_MACH_JZ4770 + if (current_cpu_type() == CPU_JZRISC && + mips_machtype == MACH_INGENIC_JZ4770) { + extern void __init jz4770_reserve_unsafe_for_dma(void); + jz4770_reserve_unsafe_for_dma(); + } +#endif + if (usermem) { pr_info("User-defined physical RAM map:\n"); print_memory_map();
--
2.11.0