[PATCH v5 08/17] arm64: mm: Add dynamic ramoops region support through command line

[Mukesh Ojha <quic_mojha@quicinc.com>]

The reserved memory region for ramoops is assumed to be at a fixed
and known location when read from the devicetree. This may not be
required for something like Qualcomm's minidump which is interested
in knowing addresses of ramoops region but it does not put hard
requirement of address being fixed as most of it's SoC does not
support warm reset and does not use pstorefs at all instead it has
firmware way of collecting ramoops region if it gets to know the
address and register it with apss minidump table which is sitting
in shared memory region in DDR and firmware will have access to
these table during reset and collects it on crash of SoC.

So, add the support of reserving ramoops region to be dynamically
allocated early during boot if it is request through command line
via 'dyn_ramoops_size=' and fill up reserved resource structure and
export the structure, so that it can be read by ramoops driver.

Signed-off-by: Mukesh Ojha <quic_mojha@quicinc.com>
---
 arch/arm64/mm/init.c       | 94 ++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/pstore_ram.h |  2 +
 2 files changed, 96 insertions(+)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index d31c3a9290c5..14d7086758bf 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -31,6 +31,7 @@
 #include <linux/hugetlb.h>
 #include <linux/acpi_iort.h>
 #include <linux/kmemleak.h>
+#include <linux/pstore_ram.h>
 
 #include <asm/boot.h>
 #include <asm/fixmap.h>
@@ -73,6 +74,93 @@ phys_addr_t __ro_after_init arm64_dma_phys_limit;
 
 #define DEFAULT_CRASH_KERNEL_LOW_SIZE	(128UL << 20)
 
+#define RAMOOPS_ADDR_HIGH_MAX		(PHYS_MASK + 1)
+
+/* Location of the reserved area for the dynamic ramoops */
+struct resource dyn_ramoops_res = {
+	.name  = "ramoops",
+	.start = 0,
+	.end   = 0,
+	.flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM,
+	.desc  = IORES_DESC_NONE,
+};
+EXPORT_SYMBOL(dyn_ramoops_res);
+
+static int __init parse_dynamic_ramoops(char *cmdline, unsigned long long *size)
+{
+	const char *name = "dyn_ramoops_size=";
+	char *p = NULL;
+	char *q = NULL;
+	char *tmp;
+
+	if (!cmdline)
+		return -ENOENT;
+
+	/* Check for "dyn_ramoops_size" and use the later if there are more */
+	p = strstr(cmdline, name);
+	while (p) {
+		q = p;
+		p = strchr(p, ' ');
+		if (!p)
+			break;
+
+		p = strstr(p + 1, name);
+	}
+
+	if (!q) {
+		pr_err("ramoops: No entry found for %s\n", name);
+		return -ENOENT;
+	}
+
+	p = q + strlen(name);
+	*size = memparse(p, &tmp);
+	if (p == tmp) {
+		pr_err("ramoops: memory value expected\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int __init parse_dyn_ramoops_size_dummy(char *arg)
+{
+	return 0;
+}
+early_param("dyn_ramoops_size", parse_dyn_ramoops_size_dummy);
+
+/*
+ * reserve_dynamic_ramoops() - reserves memory for dynamic ramoops
+ *
+ * This enable dynamic reserve memory support for ramoops through
+ * command line.
+ */
+static void __init reserve_dynamic_ramoops(void)
+{
+	char *cmdline = boot_command_line;
+	unsigned long long ramoops_base;
+	unsigned long long ramoops_size;
+
+	if (!IS_ENABLED(CONFIG_PSTORE_RAM))
+		return;
+
+	if (parse_dynamic_ramoops(cmdline, &ramoops_size))
+		return;
+
+	ramoops_base = memblock_phys_alloc_range(ramoops_size, SMP_CACHE_BYTES,
+						 0, RAMOOPS_ADDR_HIGH_MAX);
+	if (!ramoops_base) {
+		pr_err("cannot allocate ramoops dynamic memory (size:0x%llx).\n",
+			ramoops_size);
+		return;
+	}
+
+	kmemleak_ignore_phys(ramoops_base);
+
+	dyn_ramoops_res.start = ramoops_base;
+	dyn_ramoops_res.end = ramoops_base + ramoops_size - 1;
+	insert_resource(&iomem_resource, &dyn_ramoops_res);
+}
+
 static int __init reserve_crashkernel_low(unsigned long long low_size)
 {
 	unsigned long long low_base;
@@ -456,6 +544,12 @@ void __init bootmem_init(void)
 	 */
 	reserve_crashkernel();
 
+	/*
+	 * Reserving ramoops region resource dynamically in case it is
+	 * requested from command line.
+	 */
+	reserve_dynamic_ramoops();
+
 	memblock_dump_all();
 }
 
diff --git a/include/linux/pstore_ram.h b/include/linux/pstore_ram.h
index 9d65ff94e216..07d700b7649d 100644
--- a/include/linux/pstore_ram.h
+++ b/include/linux/pstore_ram.h
@@ -10,6 +10,8 @@
 
 #include <linux/pstore.h>
 
+extern struct resource dyn_ramoops_res;
+
 struct persistent_ram_ecc_info {
 	int block_size;
 	int ecc_size;
-- 
2.7.4