Hi,

Le 2017-06-22 09:21, Marcin Nowakowski a écrit :

Hi Paul, Maarten,

On 20.06.2017 17:18, Paul Cercueil wrote:

quoted

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(+)

  v2: No change

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
+

This part doesn't look good in the platform-agnostic code ... is there
a reason why you wouldn't do that from within plat_mem_setup()?

I agree, but, doing it in plat_mem_setup() is too early, as the 'boot 
mem map' hasn't been initialized yet then...

quoted

  	if (usermem) {
  		pr_info("User-defined physical RAM map:\n");
  		print_memory_map();

Marcin