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[PATCH v2 15/17] MIPS: JZ4770: Workaround for corrupted DMA transfers

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From: Maarten ter Huurne <maarten@treewalker.org>

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 <maarten@treewalker.org>
---
 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
+
 	if (usermem) {
 		pr_info("User-defined physical RAM map:\n");
 		print_memory_map();
-- 
2.11.0

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[PATCH v2 01/17] clk: ingenic: Use const pointer to clk_ops in struct Paul Cercueil <paul@crapouillou.net> - 2017-06-20 17:30 +0200
  [PATCH v2 08/17] serial: 8250_ingenic: Parse earlycon options Paul Cercueil <paul@crapouillou.net> - 2017-06-20 17:30 +0200
  [PATCH v2 15/17] MIPS: JZ4770: Workaround for corrupted DMA transfers Paul Cercueil <paul@crapouillou.net> - 2017-06-20 17:30 +0200
    Re: [PATCH v2 15/17] MIPS: JZ4770: Workaround for corrupted DMA  transfers Marcin Nowakowski <marcin.nowakowski@imgtec.com> - 2017-06-22 09:30 +0200
      Re: [PATCH v2 15/17] MIPS: JZ4770: Workaround for corrupted DMA  transfers Paul Cercueil <paul@crapouillou.net> - 2017-06-26 15:40 +0200
  [PATCH v2 03/17] clk: ingenic: support PLLs with no bypass bit Paul Cercueil <paul@crapouillou.net> - 2017-06-20 17:30 +0200
  [PATCH v2 07/17] serial: 8250_ingenic: Add support for the JZ4770 SoC Paul Cercueil <paul@crapouillou.net> - 2017-06-20 17:30 +0200
  [PATCH v2 06/17] serial: core: Make uart_parse_options take const char* argument Paul Cercueil <paul@crapouillou.net> - 2017-06-20 17:30 +0200
  [PATCH v2 05/17] clk: Add Ingenic jz4770 CGU driver Paul Cercueil <paul@crapouillou.net> - 2017-06-20 17:30 +0200
  [PATCH v2 16/17] devicetree/bindings: Add GCW vendor prefix Paul Cercueil <paul@crapouillou.net> - 2017-06-20 17:30 +0200
  Re: [PATCH v2 01/17] clk: ingenic: Use const pointer to clk_ops in  struct Stephen Boyd <sboyd@codeaurora.org> - 2017-06-22 00:00 +0200
    Re: [PATCH v2 01/17] clk: ingenic: Use const pointer to clk_ops in  struct Paul Cercueil <paul@crapouillou.net> - 2017-06-26 15:50 +0200

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