From e39b3da82e65da93934df483903464b2c3c3510a Mon Sep 17 00:00:00 2001
From: Sudarshan Rajagopalan <sudaraja@codeaurora.org>
Date: Fri, 27 Apr 2018 14:41:03 -0700
Subject: [PATCH] arm64: Override memory limit set by boot parameter

To guarantee successful hot-plugging of memory blocks, these blocks
should belong to ZONE_MOVABLE which has migratable pages. Linux kernel
during boot initializes all the available memory blocks to ZONE_DMA and
ZONE_NORMAL. Hence, boot the system with less memory whose percentage
is given by mem-offline DT property 'mem-percent' and override any memory
limit imposed by kernel boot params and let mem-offline driver initialize
the remaining with ZONE_MOVABLE. The memory blocks in this zone are
applicable for memory offlining.

Change-Id: Ia7b804522fe9425101ee83d1ee354ed09483df13
Signed-off-by: Sudarshan Rajagopalan <sudaraja@codeaurora.org>
[swatsrid@codeaurora.org: Fix merge conflicts]
Signed-off-by: Swathi Sridhar <swatsrid@codeaurora.org>
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>
---
 arch/arm64/mm/init.c     | 48 ++++++++++++++++++++++++++++++++++++++++
 drivers/soc/qcom/Kconfig | 10 +++++++++
 2 files changed, 58 insertions(+)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 3184ceccc288..3710fb71b50b 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -28,6 +28,8 @@
 #include <linux/mm.h>
 #include <linux/kexec.h>
 #include <linux/crash_dump.h>
+#include <linux/memory.h>
+#include <linux/libfdt.h>
 
 #include <asm/boot.h>
 #include <asm/fixmap.h>
@@ -259,6 +261,51 @@ EXPORT_SYMBOL(pfn_valid);
 static phys_addr_t memory_limit = PHYS_ADDR_MAX;
 phys_addr_t bootloader_memory_limit;
 
+#ifdef CONFIG_OVERRIDE_MEMORY_LIMIT
+static void __init update_memory_limit(void)
+{
+	unsigned long dt_root = of_get_flat_dt_root();
+	unsigned long node, mp;
+	const char *p;
+	unsigned long long ram_sz, sz;
+	int ret;
+
+	ram_sz = memblock_end_of_DRAM() - memblock_start_of_DRAM();
+	node = of_get_flat_dt_subnode_by_name(dt_root, "mem-offline");
+	if (node == -FDT_ERR_NOTFOUND) {
+		pr_err("mem-offine node not found in FDT\n");
+		return;
+	}
+	p = of_get_flat_dt_prop(node, "mem-percent", NULL);
+	if (!p) {
+		pr_err("mem-offine: mem-percent property not found in FDT\n");
+		return;
+	}
+
+	ret = kstrtoul(p, 10, &mp);
+	if (ret) {
+		pr_err("mem-offine: kstrtoul failed\n");
+		return;
+	}
+
+	if (mp > 100) {
+		pr_err("mem-offine: Invalid mem-percent DT property\n");
+		return;
+	}
+	sz = ram_sz - ((ram_sz * mp) / 100);
+	memory_limit = (phys_addr_t)sz;
+	memory_limit = ALIGN(memory_limit, MIN_MEMORY_BLOCK_SIZE);
+
+	pr_notice("Memory limit set/overridden to %lldMB\n",
+							memory_limit >> 20);
+}
+#else
+static void __init update_memory_limit(void)
+{
+
+}
+#endif
+
 /*
  * Limit the memory size that was specified via FDT.
  */
@@ -350,6 +397,7 @@ void __init arm64_memblock_init(void)
 		memblock_remove(0, memstart_addr);
 	}
 
+	update_memory_limit();
 	/*
 	 * Save bootloader imposed memory limit before we overwirte
 	 * memblock.
diff --git a/drivers/soc/qcom/Kconfig b/drivers/soc/qcom/Kconfig
index 717163231ccd..67f6406240c8 100644
--- a/drivers/soc/qcom/Kconfig
+++ b/drivers/soc/qcom/Kconfig
@@ -66,6 +66,16 @@ config QCOM_GENI_SE
 	  driver is also used to manage the common aspects of multiple Serial
 	  Engines present in the QUP.
 
+config OVERRIDE_MEMORY_LIMIT
+	bool "Override memory limit set by the kernel boot parameter"
+	depends on QCOM_MEM_OFFLINE
+	help
+	  Override any memory limit set by the kernel boot parameter with
+	  limit set by mem-offline dt entry so that memory offline framework
+	  can initialize remaining memory with movable pages for memory
+	  hot-plugging.
+	  If unsure, say N
+
 config QCOM_GLINK_SSR
 	tristate "Qualcomm Glink SSR driver"
 	depends on RPMSG