Commit 9d843e8f authored by Mukesh Ojha's avatar Mukesh Ojha Committed by Kees Cook
Browse files

pstore: Add mem_type property DT parsing support 



There could be a scenario where we define some region
in normal memory and use them store to logs which is later
retrieved by bootloader during warm reset.

In this scenario, we wanted to treat this memory as normal
cacheable memory instead of default behaviour which
is an overhead. Making it cacheable could improve
performance.

This commit gives control to change mem_type from Device
tree, and also documents the value for normal memory.

Signed-off-by: default avatarMukesh Ojha <mojha@codeaurora.org>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/1616438537-13719-1-git-send-email-mojha@codeaurora.org
parent a38fd874

Documentation/admin-guide/ramoops.rst

+3 −1
Original line number Diff line number Diff line
@@ -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

+8 −2
Original line number Diff line number Diff line
@@ -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

+6 −1
Original line number Diff line number Diff line
@@ -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

+16 −2
Original line number Diff line number Diff line
@@ -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) {