From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Cercueil Subject: [PATCH v2 15/17] MIPS: JZ4770: Workaround for corrupted DMA transfers Date: Tue, 20 Jun 2017 17:18:53 +0200 Message-ID: <20170620151855.19399-15-paul@crapouillou.net> References: <20170607200439.24450-2-paul@crapouillou.net> <20170620151855.19399-1-paul@crapouillou.net> Return-path: In-Reply-To: <20170620151855.19399-1-paul@crapouillou.net> Sender: linux-kernel-owner@vger.kernel.org To: Ralf Baechle , Michael Turquette , Stephen Boyd , Rob Herring Cc: Paul Burton , Maarten ter Huurne , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mips@linux-mips.org, linux-clk@vger.kernel.org List-Id: devicetree@vger.kernel.org From: Maarten ter Huurne 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 --- 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 #include +#include #include #include @@ -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