arch/powerpc/boot/mpc8xx.c

Source file repositories/reference/linux-study-clean/arch/powerpc/boot/mpc8xx.c

File Facts

System
Linux kernel
Corpus path
arch/powerpc/boot/mpc8xx.c
Extension
.c
Size
1511 bytes
Lines
79
Domain
Architecture Layer
Bucket
arch/powerpc
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0-only
/*
 * MPC8xx support functions
 *
 * Author: Scott Wood <scottwood@freescale.com>
 *
 * Copyright (c) 2007 Freescale Semiconductor, Inc.
 */

#include "ops.h"
#include "types.h"
#include "fsl-soc.h"
#include "mpc8xx.h"
#include "stdio.h"
#include "io.h"

#define MPC8XX_PLPRCR (0x284/4) /* PLL and Reset Control Register */

/* Return system clock from crystal frequency */
u32 mpc885_get_clock(u32 crystal)
{
	u32 *immr;
	u32 plprcr;
	int mfi, mfn, mfd, pdf;
	u32 ret;

	immr = fsl_get_immr();
	if (!immr) {
		printf("mpc885_get_clock: Couldn't get IMMR base.\r\n");
		return 0;
	}

	plprcr = in_be32(&immr[MPC8XX_PLPRCR]);

	mfi = (plprcr >> 16) & 15;
	if (mfi < 5) {
		printf("Warning: PLPRCR[MFI] value of %d out-of-bounds\r\n",
		       mfi);
		mfi = 5;
	}

	pdf = (plprcr >> 1) & 0xf;
	mfd = (plprcr >> 22) & 0x1f;
	mfn = (plprcr >> 27) & 0x1f;

	ret = crystal * mfi;

	if (mfn != 0)
		ret += crystal * mfn / (mfd + 1);

	return ret / (pdf + 1);
}

/* Set common device tree fields based on the given clock frequencies. */
void mpc8xx_set_clocks(u32 sysclk)
{
	void *node;

	dt_fixup_cpu_clocks(sysclk, sysclk / 16, sysclk);

	node = finddevice("/soc/cpm");
	if (node)
		setprop(node, "clock-frequency", &sysclk, 4);

	node = finddevice("/soc/cpm/brg");
	if (node)
		setprop(node, "clock-frequency", &sysclk, 4);
}

int mpc885_fixup_clocks(u32 crystal)
{
	u32 sysclk = mpc885_get_clock(crystal);
	if (!sysclk)
		return 0;

	mpc8xx_set_clocks(sysclk);
	return 1;
}

Annotation

Implementation Notes