Commit 027bc8b0 authored by Tony Lindgren's avatar Tony Lindgren Committed by Tony Luck
Browse files

pstore-ram: Allow optional mapping with pgprot_noncached 



On some ARMs the memory can be mapped pgprot_noncached() and still
be working for atomic operations. As pointed out by Colin Cross
<ccross@android.com>, in some cases you do want to use
pgprot_noncached() if the SoC supports it to see a debug printk
just before a write hanging the system.

On ARMs, the atomic operations on strongly ordered memory are
implementation defined. So let's provide an optional kernel parameter
for configuring pgprot_noncached(), and use pgprot_writecombine() by
default.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rob Herring <robherring2@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Anton Vorontsov <anton@enomsg.org>
Cc: Colin Cross <ccross@android.com>
Cc: Olof Johansson <olof@lixom.net>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: stable@vger.kernel.org
Acked-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarTony Lindgren <tony@atomide.com>
Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
parent 7ae9cb81

Documentation/ramoops.txt

+11 −2
Original line number Diff line number Diff line
@@ -14,11 +14,19 @@ survive after a restart. 


1. Ramoops concepts



Ramoops uses a predefined memory area to store the dump. The start and size of

the memory area are set using two variables:

Ramoops uses a predefined memory area to store the dump. The start and size

and type of the memory area are set using three variables:

  * "mem_address" for the start

  * "mem_size" for the size. The memory size will be rounded down to a

  power of two.

  * "mem_type" to specifiy if the memory type (default is pgprot_writecombine).



Typically the default value of mem_type=0 should be used as that sets the pstore

mapping to pgprot_writecombine. Setting mem_type=1 attempts to use

pgprot_noncached, which only works on some platforms. This is because pstore

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.



The memory area is divided into "record_size" chunks (also rounded down to

power of two) and each oops/panic writes a "record_size" chunk of
@@ -55,6 +63,7 @@ Setting the ramoops parameters can be done in 2 different manners: 
static struct ramoops_platform_data ramoops_data = {

        .mem_size               = <...>,

        .mem_address            = <...>,

        .mem_type               = <...>,

        .record_size            = <...>,

        .dump_oops              = <...>,

        .ecc                    = <...>,

fs/pstore/ram.c

+11 −2
Original line number Diff line number Diff line
@@ -61,6 +61,11 @@ module_param(mem_size, ulong, 0400); 
MODULE_PARM_DESC(mem_size,

		"size of reserved RAM used to store oops/panic logs");



static unsigned int mem_type;

module_param(mem_type, uint, 0600);

MODULE_PARM_DESC(mem_type,

		"set to 1 to try to use unbuffered memory (default 0)");



static int dump_oops = 1;

module_param(dump_oops, int, 0600);

MODULE_PARM_DESC(dump_oops,
@@ -79,6 +84,7 @@ struct ramoops_context { 
	struct persistent_ram_zone *fprz;

	phys_addr_t phys_addr;

	unsigned long size;

	unsigned int memtype;

	size_t record_size;

	size_t console_size;

	size_t ftrace_size;
@@ -366,7 +372,8 @@ static int ramoops_init_przs(struct device *dev, struct ramoops_context *cxt, 
		size_t sz = cxt->record_size;



		cxt->przs[i] = persistent_ram_new(*paddr, sz, 0,

						  &cxt->ecc_info);

						  &cxt->ecc_info,

						  cxt->memtype);

		if (IS_ERR(cxt->przs[i])) {

			err = PTR_ERR(cxt->przs[i]);

			dev_err(dev, "failed to request mem region (0x%zx@0x%llx): %d\n",
@@ -396,7 +403,7 @@ static int ramoops_init_prz(struct device *dev, struct ramoops_context *cxt, 
		return -ENOMEM;

	}



	*prz = persistent_ram_new(*paddr, sz, sig, &cxt->ecc_info);

	*prz = persistent_ram_new(*paddr, sz, sig, &cxt->ecc_info, cxt->memtype);

	if (IS_ERR(*prz)) {

		int err = PTR_ERR(*prz);
@@ -443,6 +450,7 @@ static int ramoops_probe(struct platform_device *pdev) 


	cxt->size = pdata->mem_size;

	cxt->phys_addr = pdata->mem_address;

	cxt->memtype = pdata->mem_type;

	cxt->record_size = pdata->record_size;

	cxt->console_size = pdata->console_size;

	cxt->ftrace_size = pdata->ftrace_size;
@@ -572,6 +580,7 @@ static void ramoops_register_dummy(void) 


	dummy_data->mem_size = mem_size;

	dummy_data->mem_address = mem_address;

	dummy_data->mem_type = 0;

	dummy_data->record_size = record_size;

	dummy_data->console_size = ramoops_console_size;

	dummy_data->ftrace_size = ramoops_ftrace_size;

fs/pstore/ram_core.c

+22 −9
Original line number Diff line number Diff line
@@ -380,7 +380,8 @@ void persistent_ram_zap(struct persistent_ram_zone *prz) 
	persistent_ram_update_header_ecc(prz);

}



static void *persistent_ram_vmap(phys_addr_t start, size_t size)

static void *persistent_ram_vmap(phys_addr_t start, size_t size,

		unsigned int memtype)

{

	struct page **pages;

	phys_addr_t page_start;
@@ -392,6 +393,9 @@ 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)

		prot = pgprot_noncached(PAGE_KERNEL);

	else

		prot = pgprot_writecombine(PAGE_KERNEL);



	pages = kmalloc_array(page_count, sizeof(struct page *), GFP_KERNEL);
@@ -411,8 +415,11 @@ static void *persistent_ram_vmap(phys_addr_t start, size_t size) 
	return vaddr;

}



static void *persistent_ram_iomap(phys_addr_t start, size_t size)

static void *persistent_ram_iomap(phys_addr_t start, size_t size,

		unsigned int memtype)

{

	void *va;



	if (!request_mem_region(start, size, "persistent_ram")) {

		pr_err("request mem region (0x%llx@0x%llx) failed\n",

			(unsigned long long)size, (unsigned long long)start);
@@ -422,19 +429,24 @@ static void *persistent_ram_iomap(phys_addr_t start, size_t size) 
	buffer_start_add = buffer_start_add_locked;

	buffer_size_add = buffer_size_add_locked;



	return ioremap_wc(start, size);

	if (memtype)

		va = ioremap(start, size);

	else

		va = ioremap_wc(start, size);



	return va;

}



static int persistent_ram_buffer_map(phys_addr_t start, phys_addr_t size,

		struct persistent_ram_zone *prz)

		struct persistent_ram_zone *prz, int memtype)

{

	prz->paddr = start;

	prz->size = size;



	if (pfn_valid(start >> PAGE_SHIFT))

		prz->vaddr = persistent_ram_vmap(start, size);

		prz->vaddr = persistent_ram_vmap(start, size, memtype);

	else

		prz->vaddr = persistent_ram_iomap(start, size);

		prz->vaddr = persistent_ram_iomap(start, size, memtype);



	if (!prz->vaddr) {

		pr_err("%s: Failed to map 0x%llx pages at 0x%llx\n", __func__,
@@ -500,7 +512,8 @@ void persistent_ram_free(struct persistent_ram_zone *prz) 
}



struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t size,

			u32 sig, struct persistent_ram_ecc_info *ecc_info)

			u32 sig, struct persistent_ram_ecc_info *ecc_info,

			unsigned int memtype)

{

	struct persistent_ram_zone *prz;

	int ret = -ENOMEM;
@@ -511,7 +524,7 @@ struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t size, 
		goto err;

	}



	ret = persistent_ram_buffer_map(start, size, prz);

	ret = persistent_ram_buffer_map(start, size, prz, memtype);

	if (ret)

		goto err;

include/linux/pstore_ram.h

+3 −1
Original line number Diff line number Diff line
@@ -53,7 +53,8 @@ struct persistent_ram_zone { 
};



struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t size,

			u32 sig, struct persistent_ram_ecc_info *ecc_info);

			u32 sig, struct persistent_ram_ecc_info *ecc_info,

			unsigned int memtype);

void persistent_ram_free(struct persistent_ram_zone *prz);

void persistent_ram_zap(struct persistent_ram_zone *prz);
@@ -76,6 +77,7 @@ ssize_t persistent_ram_ecc_string(struct persistent_ram_zone *prz, 
struct ramoops_platform_data {

	unsigned long	mem_size;

	unsigned long	mem_address;

	unsigned int	mem_type;

	unsigned long	record_size;

	unsigned long	console_size;

	unsigned long	ftrace_size;

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