Undrer S3C6410, Setting ARM cpu frequency 667MHz.

最新推荐文章于 2022-02-25 19:38:17 发布

Wenxy1

最新推荐文章于 2022-02-25 19:38:17 发布

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分类专栏： 1. Linux/Uninx 文章标签： c features output image linux java

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本文介绍如何通过修改Linux内核源代码将S3C6410 CPU的运行频率从默认的532MHz提高到667MHz。文中详细展示了修改注册表“APLL_CON/MPLL_CON”的步骤，并提供了计算输出频率的公式。

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1. Undrer S3C6410, Setting ARM cpu frequency 667MHz
Because default freqency is 532MHz.
6410 CPU can run up to 667MHz, modiry Linux kernel source code:

/* arch/arm/plat-s3c64xx/s3c6400-clock.c */

void __init_or_cpufreq s3c6400_setup_clocks(void)
{
    /* ... */
    __raw_writel((__raw_readl(S3C_APLL_CON) & 0xfc00ffff) | (0x14d <<16), S3C_APLL_CON); /* wenxy test, 333*2 MHz */
    apll = s3c6400_get_pll(xtal, __raw_readl(S3C_APLL_CON));

    printk(KERN_INFO "Wenxy: S3C_APLL_CON value: 0x%x\n", (unsigned int)__raw_readl(S3C_APLL_CON));

    fclk = apll / GET_DIV(clkdiv0, S3C6410_CLKDIV0_ARM);

    printk(KERN_INFO "S3C64XX: PLL settings, A=%ld, M=%ld, E=%ld\n",
           apll, mpll, epll);
    /* ... */    
}

I setting register "APLL_CON / MPLL_CON" according to S3C6410X.pdf manual, page 141, 142.
The output frequency is calculated using the following equation:
FOUT = MDIV X FIN / (PDIV X 2SDIV)

2. Then compile new kernel image, run it.
[root@EmbedSky /]# cat /proc/cpuinfo
Processor       : ARMv6-compatible processor rev 6 (v6l)
BogoMIPS        : 665.19
Features        : swp half thumb fastmult vfp edsp java
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x0
CPU part        : 0xb76
CPU revision    : 6

Hardware        : SMDK6410
Revision        : 0000
Serial          : 0000000000000000
[root@EmbedSky /]#