drivers/watchdog/npcm_wdt.c

File Facts

System

Linux kernel

Corpus path

drivers/watchdog/npcm_wdt.c

Extension

.c

Size

6040 bytes

Lines

264

Domain

Driver Families

Bucket

drivers/watchdog

Inferred role

Driver Families: implementation source

Status

source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

• Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.
• Touches IRQ or DMA behavior; this matters for the representative real-device path.
• Allocates kernel memory; connect allocation flags and lifetime to context constraints.
• Defines or uses C structs; map object ownership, embedded links, reference counts, and lock ownership.

Dependency Surface

• linux/bitops.h
• linux/clk.h
• linux/delay.h
• linux/interrupt.h
• linux/kernel.h
• linux/module.h
• linux/of_irq.h
• linux/platform_device.h
• linux/slab.h
• linux/watchdog.h

Detected Declarations

• struct npcm_wdt
• function npcm_wdt_ping
• function npcm_wdt_start
• function npcm_wdt_stop
• function npcm_wdt_set_timeout
• function npcm_wdt_interrupt
• function npcm_wdt_restart
• function npcm_is_running
• function npcm_wdt_probe

Annotated Snippet

struct npcm_wdt {
	struct watchdog_device  wdd;
	void __iomem		*reg;
	struct clk		*clk;
};

static inline struct npcm_wdt *to_npcm_wdt(struct watchdog_device *wdd)
{
	return container_of(wdd, struct npcm_wdt, wdd);
}

static int npcm_wdt_ping(struct watchdog_device *wdd)
{
	struct npcm_wdt *wdt = to_npcm_wdt(wdd);
	u32 val;

	val = readl(wdt->reg);
	writel(val | NPCM_WTR, wdt->reg);

	return 0;
}

static int npcm_wdt_start(struct watchdog_device *wdd)
{
	struct npcm_wdt *wdt = to_npcm_wdt(wdd);
	u32 val;

	clk_prepare_enable(wdt->clk);

	if (wdd->timeout < 2)
		val = 0x800;
	else if (wdd->timeout < 3)
		val = 0x420;
	else if (wdd->timeout < 6)
		val = 0x810;
	else if (wdd->timeout < 11)
		val = 0x430;
	else if (wdd->timeout < 22)
		val = 0x820;
	else if (wdd->timeout < 44)
		val = 0xC00;
	else if (wdd->timeout < 87)
		val = 0x830;
	else if (wdd->timeout < 173)
		val = 0xC10;
	else if (wdd->timeout < 688)
		val = 0xC20;
	else
		val = 0xC30;

	val |= NPCM_WTRE | NPCM_WTE | NPCM_WTR | NPCM_WTIE;

	writel(val, wdt->reg);

	return 0;
}

static int npcm_wdt_stop(struct watchdog_device *wdd)
{
	struct npcm_wdt *wdt = to_npcm_wdt(wdd);

	writel(0, wdt->reg);

	clk_disable_unprepare(wdt->clk);

	return 0;
}

static int npcm_wdt_set_timeout(struct watchdog_device *wdd,
				unsigned int timeout)
{
	if (timeout < 2)
		wdd->timeout = 1;
	else if (timeout < 3)
		wdd->timeout = 2;
	else if (timeout < 6)
		wdd->timeout = 5;
	else if (timeout < 11)
		wdd->timeout = 10;
	else if (timeout < 22)
		wdd->timeout = 21;
	else if (timeout < 44)
		wdd->timeout = 43;
	else if (timeout < 87)
		wdd->timeout = 86;
	else if (timeout < 173)
		wdd->timeout = 172;
	else if (timeout < 688)
		wdd->timeout = 687;
	else

Annotation

• Immediate include surface: `linux/bitops.h`, `linux/clk.h`, `linux/delay.h`, `linux/interrupt.h`, `linux/kernel.h`, `linux/module.h`, `linux/of_irq.h`, `linux/platform_device.h`.
• Detected declarations: `struct npcm_wdt`, `function npcm_wdt_ping`, `function npcm_wdt_start`, `function npcm_wdt_stop`, `function npcm_wdt_set_timeout`, `function npcm_wdt_interrupt`, `function npcm_wdt_restart`, `function npcm_is_running`, `function npcm_wdt_probe`.
• Atlas domain: Driver Families / drivers/watchdog.
• Implementation status: source implementation candidate.
• IRQ or DMA behavior appears here, which is relevant to the selected PCIe/NVMe device path.

Implementation Notes

• This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
• Core OS pages should be promoted from atlas-only to deep-reviewed when they explain data structures, invariants, locking, lifecycle, and C implementation snippets.
• Driver-family pages are intentionally pattern-oriented unless they are part of the selected PCIe/NVMe representative device path.