pstore update for v5.13-rc1

- Add mem_type property to expand support for >2 memory types (Mukesh Ojha)
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Merge tag 'pstore-v5.13-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull pstore update from Kees Cook:

 - Add mem_type property to expand support for >2 memory types (Mukesh Ojha)

* tag 'pstore-v5.13-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  pstore: Add mem_type property DT parsing support

Documentation/admin-guide/ramoops.rst

@@ -3,7 +3,7 @@ Ramoops oops/panic logger
 
 Sergiu Iordache <sergiu@chromium.org>
 
-Updated: 17 November 2011
+Updated: 10 Feb 2021
 
 Introduction
 ------------
@@ -30,6 +30,8 @@ mapping to pgprot_writecombine. Setting ``mem_type=1`` attempts to use
 depends on atomic operations. At least on ARM, pgprot_noncached causes the
 memory to be mapped strongly ordered, and atomic operations on strongly ordered
 memory are implementation defined, and won't work on many ARMs such as omaps.
+Setting ``mem_type=2`` attempts to treat the memory region as normal memory,
+which enables full cache on it. This can improve the performance.
 
 The memory area is divided into ``record_size`` chunks (also rounded down to
 power of two) and each kmesg dump writes a ``record_size`` chunk of

Documentation/devicetree/bindings/reserved-memory/ramoops.txt

@@ -42,8 +42,14 @@ Optional properties:
 - pmsg-size: size in bytes of log buffer reserved for userspace messages
   (defaults to 0: disabled)
 
-- unbuffered: if present, use unbuffered mappings to map the reserved region
-  (defaults to buffered mappings)
+- mem-type: if present, sets the type of mapping is to be used to map the
+  reserved region. mem-type: 0 = write-combined (default), 1 = unbuffered,
+  2 = cached.
+
+- unbuffered: deprecated, use mem_type instead. If present, and mem_type is
+  not specified, it is equivalent to mem_type = 1 and uses unbuffered mappings
+  to map the reserved region (defaults to buffered mappings mem_type = 0). If
+  both are specified -- "mem_type" overrides "unbuffered".
 
 - max-reason: if present, sets maximum type of kmsg dump reasons to store
   (defaults to 2: log Oopses and Panics). This can be set to INT_MAX to

fs/pstore/ram.c

@@ -56,7 +56,7 @@ MODULE_PARM_DESC(mem_size,
 static unsigned int mem_type;
 module_param(mem_type, uint, 0400);
 MODULE_PARM_DESC(mem_type,
-		"set to 1 to try to use unbuffered memory (default 0)");
+		"memory type: 0=write-combined (default), 1=unbuffered, 2=cached");
 
 static int ramoops_max_reason = -1;
 module_param_named(max_reason, ramoops_max_reason, int, 0400);
@@ -648,6 +648,10 @@ static int ramoops_parse_dt(struct platform_device *pdev,
 
 	pdata->mem_size = resource_size(res);
 	pdata->mem_address = res->start;
+	/*
+	 * Setting "unbuffered" is deprecated and will be ignored if
+	 * "mem_type" is also specified.
+	 */
 	pdata->mem_type = of_property_read_bool(of_node, "unbuffered");
 	/*
 	 * Setting "no-dump-oops" is deprecated and will be ignored if
@@ -666,6 +670,7 @@ static int ramoops_parse_dt(struct platform_device *pdev,
 		field = value;						\
 	}
 
+	parse_u32("mem-type", pdata->record_size, pdata->mem_type);
 	parse_u32("record-size", pdata->record_size, 0);
 	parse_u32("console-size", pdata->console_size, 0);
 	parse_u32("ftrace-size", pdata->ftrace_size, 0);

fs/pstore/ram_core.c

@@ -396,6 +396,10 @@ void persistent_ram_zap(struct persistent_ram_zone *prz)
 	persistent_ram_update_header_ecc(prz);
 }
 
+#define MEM_TYPE_WCOMBINE	0
+#define MEM_TYPE_NONCACHED	1
+#define MEM_TYPE_NORMAL		2
+
 static void *persistent_ram_vmap(phys_addr_t start, size_t size,
 		unsigned int memtype)
 {
@@ -409,10 +413,20 @@ static void *persistent_ram_vmap(phys_addr_t start, size_t size,
 	page_start = start - offset_in_page(start);
 	page_count = DIV_ROUND_UP(size + offset_in_page(start), PAGE_SIZE);
 
-	if (memtype)
+	switch (memtype) {
+	case MEM_TYPE_NORMAL:
+		prot = PAGE_KERNEL;
+		break;
+	case MEM_TYPE_NONCACHED:
 		prot = pgprot_noncached(PAGE_KERNEL);
-	else
+		break;
+	case MEM_TYPE_WCOMBINE:
 		prot = pgprot_writecombine(PAGE_KERNEL);
+		break;
+	default:
+		pr_err("invalid mem_type=%d\n", memtype);
+		return NULL;
+	}
 
 	pages = kmalloc_array(page_count, sizeof(struct page *), GFP_KERNEL);
 	if (!pages) {