nvram.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  c 2001 PPC 64 Team, IBM Corp
 *
 * /dev/nvram driver for PPC
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/uaccess.h>
#include <linux/of.h>
#include <asm/machdep.h>
#include <asm/rtas.h>
#include "chrp.h"

static unsigned int nvram_size;
static unsigned char nvram_buf[4];
static DEFINE_SPINLOCK(nvram_lock);

static unsigned char chrp_nvram_read_val(int addr)
{
	unsigned int done;
	unsigned long flags;
	unsigned char ret;

	if (addr >= nvram_size) {
		printk(KERN_DEBUG "%s: read addr %d > nvram_size %u\n",
		       current->comm, addr, nvram_size);
		return 0xff;
	}
	spin_lock_irqsave(&nvram_lock, flags);
	if ((rtas_call(rtas_function_token(RTAS_FN_NVRAM_FETCH), 3, 2, &done, addr,
		       __pa(nvram_buf), 1) != 0) || 1 != done)
		ret = 0xff;
	else
		ret = nvram_buf[0];
	spin_unlock_irqrestore(&nvram_lock, flags);

	return ret;
}

static void chrp_nvram_write_val(int addr, unsigned char val)
{
	unsigned int done;
	unsigned long flags;

	if (addr >= nvram_size) {
		printk(KERN_DEBUG "%s: write addr %d > nvram_size %u\n",
		       current->comm, addr, nvram_size);
		return;
	}
	spin_lock_irqsave(&nvram_lock, flags);
	nvram_buf[0] = val;
	if ((rtas_call(rtas_function_token(RTAS_FN_NVRAM_STORE), 3, 2, &done, addr,
		       __pa(nvram_buf), 1) != 0) || 1 != done)
		printk(KERN_DEBUG "rtas IO error storing 0x%02x at %d", val, addr);
	spin_unlock_irqrestore(&nvram_lock, flags);
}

static ssize_t chrp_nvram_size(void)
{
	return nvram_size;
}

void __init chrp_nvram_init(void)
{
	struct device_node *nvram;
	const __be32 *nbytes_p;
	unsigned int proplen;

	nvram = of_find_node_by_type(NULL, "nvram");
	if (nvram == NULL)
		return;

	nbytes_p = of_get_property(nvram, "#bytes", &proplen);
	if (nbytes_p == NULL || proplen != sizeof(unsigned int)) {
		of_node_put(nvram);
		return;
	}

	nvram_size = be32_to_cpup(nbytes_p);

	printk(KERN_INFO "CHRP nvram contains %u bytes\n", nvram_size);
	of_node_put(nvram);

	ppc_md.nvram_read_val  = chrp_nvram_read_val;
	ppc_md.nvram_write_val = chrp_nvram_write_val;
	ppc_md.nvram_size      = chrp_nvram_size;

	return;
}

MODULE_DESCRIPTION("PPC NVRAM device driver");
MODULE_LICENSE("GPL v2");