imx6 gpio分析

本文主要介绍如何配置IOMUX寄存器，设置IO复用寄存器，配置为GPIO功能。
参考：
　　http://www.jianshu.com/p/3c2053508342
　　http://www.embest-tech.com/community/index.php?topic=2822.0

查看板级文件
kernel/arch/arm/mach-mx6/board_mx6q_sabresd.c

MACHINE_START(MX6Q_SABRESD, "Freescale i.MX 6Quad/DualLite/Solo Sabre-SD Board")
    /* Maintainer: Freescale Semiconductor, Inc. */
    .boot_params = MX6_PHYS_OFFSET + 0x100,
    .fixup = fixup_mxc_board,
    .map_io = mx6_map_io,
    .init_irq = mx6_init_irq,
    .init_machine = mx6_sabresd_board_init,　　　　//-------------------------------->>>  mx6_sabresd_board_init
    .timer = &mx6_sabresd_timer,
    .reserve = mx6q_sabresd_reserve,
MACHINE_END


static void __init mx6_sabresd_board_init(void)　　//<<<--------------------------------  mx6_sabresd_board_init
{
    ... ...
    //这里这里已经将大部分寄存器都进行了配置。
    if (cpu_is_mx6q())
        mxc_iomux_v3_setup_multiple_pads(mx6q_sabresd_pads,　　　　// ------------------>>> mxc_iomux_v3_setup_multiple_pads
            ARRAY_SIZE(mx6q_sabresd_pads));　　　　　　　　　　　　　//  ----------------->>> mx6q_sabresd_pads
    else if (cpu_is_mx6dl()) {
        mxc_iomux_v3_setup_multiple_pads(mx6dl_sabresd_pads,
            ARRAY_SIZE(mx6dl_sabresd_pads));
    }
    ... ...
}

mx6q_sabresd_pads结构体。
kernel/arch/arm/mach-mx6/board_mx6q_sabresd.h
static iomux_v3_cfg_t mx6q_sabresd_pads[] = {　　　　　　　　　　// <<<---------------------  mx6q_sabresd_pads
    /* AUDMUX */
    MX6Q_PAD_CSI0_DAT4__AUDMUX_AUD3_TXC,
    MX6Q_PAD_CSI0_DAT5__AUDMUX_AUD3_TXD,
    MX6Q_PAD_CSI0_DAT6__AUDMUX_AUD3_TXFS,
    MX6Q_PAD_CSI0_DAT7__AUDMUX_AUD3_RXD,

    MX6Q_PAD_SD1_DAT1__GPIO_1_17,       /* FT5X06 RESET */

    MX6Q_PAD_NANDF_CS3__GPIO_6_16,      //FT5X06_INT
    ... ...
}

文件：kernel/arch/arm/plat-mxc/include/mach/iomux-mx6q.h
以MX6Q_PAD_SD1_DAT1__GPIO_1_17举例。 
//MX6Q_PAD_SD1_DAT1表示寄存器，表示IOMUXC_IOMUXC_SW_MUX_CTL_PAD_SD1_DAT1。芯片手册2160页。
//后面的GPIO_1_17表示将该引脚复用为GPIO17.
//0x0724,0x003c表示寄存器地址的偏移量。具体查看上面的参考链接和芯片手册。
#define  MX6Q_PAD_SD1_DAT1__GPIO_1_17       
        (_MX6Q_PAD_SD1_DAT1__GPIO_1_17 | MUX_PAD_CTRL(MX6Q_HIGH_DRV))
#define _MX6Q_PAD_SD1_DAT1__GPIO_1_17           
        IOMUX_PAD(0x0724, 0x033C, 5, 0x0000, 0, 0)
#define MUX_PAD_CTRL(x)     ((iomux_v3_cfg_t)(x) << MUX_PAD_CTRL_SHIFT)

  #define _MX6Q_PAD_SD2_DAT1__USDHC2_DAT1
          IOMUX_PAD(0x0360, 0x004C, 0, 0x0000, 0, 0)
  #define _MX6Q_PAD_SD2_DAT1__ECSPI5_SS0
        　IOMUX_PAD(0x0360, 0x004C, 1, 0x0834, 0, 0)
  #define _MX6Q_PAD_SD2_DAT1__WEIM_WEIM_CS_2
　　　　　　IOMUX_PAD(0x0360, 0x004C, 2, 0x0000, 0, 0)
  #define _MX6Q_PAD_SD2_DAT1__AUDMUX_AUD4_TXFS
　　　　　　IOMUX_PAD(0x0360, 0x004C, 3, 0x07C8, 0, 0)
  #define _MX6Q_PAD_SD2_DAT1__KPP_COL_7
　　　　　　IOMUX_PAD(0x0360, 0x004C, 4, 0x08F0, 0, 0)
  #define _MX6Q_PAD_SD2_DAT1__GPIO_1_14
　　　　　　IOMUX_PAD(0x0360, 0x004C, 5, 0x0000, 0, 0)
  #define _MX6Q_PAD_SD2_DAT1__CCM_WAIT
　　　　　　IOMUX_PAD(0x0360, 0x004C, 6, 0x0000, 0, 0)
  #define _MX6Q_PAD_SD2_DAT1__ANATOP_ANATOP_TESTO_0
　　　　　　IOMUX_PAD(0x0360, 0x004C, 7, 0x0000, 0, 0)

文件：kernel/arch/arm/plat-mxc/include/mach/iomux-v3.h
#define IOMUX_PAD(_pad_ctrl_ofs, _mux_ctrl_ofs, _mux_mode, _sel_input_ofs, 
        _sel_input, _pad_ctrl)                  
    (((iomux_v3_cfg_t)(_mux_ctrl_ofs) << MUX_CTRL_OFS_SHIFT) |  
        ((iomux_v3_cfg_t)(_mux_mode) << MUX_MODE_SHIFT) |   
        ((iomux_v3_cfg_t)(_pad_ctrl_ofs) << MUX_PAD_CTRL_OFS_SHIFT) | 
        ((iomux_v3_cfg_t)(_pad_ctrl) << MUX_PAD_CTRL_SHIFT) |   
        ((iomux_v3_cfg_t)(_sel_input_ofs) << MUX_SEL_INPUT_OFS_SHIFT) | 
        ((iomux_v3_cfg_t)(_sel_input) << MUX_SEL_INPUT_SHIFT))


int mxc_iomux_v3_setup_multiple_pads(iomux_v3_cfg_t *pad_list, unsigned count)　　　//　<<<-------- mxc_iomux_v3_setup_multiple_pads()
{
    iomux_v3_cfg_t *p = pad_list;
    int i;
    int ret;

    for (i = 0; i < count; i++) {
        ret = mxc_iomux_v3_setup_pad(*p);　　　　　　　　　　// ------------------------------>>>  mxc_iomux_v3_setup_pad()
        if (ret)
            return ret;
        p++;
    }   
    return 0;
}
EXPORT_SYMBOL(mxc_iomux_v3_setup_multiple_pads);

/* 将定义的宏解析，提取其中数据，设置到寄存器中 */
int mxc_iomux_v3_setup_pad(iomux_v3_cfg_t pad)　　　　　　　// <<<---------------------------- mxc_iomux_v3_setup_pad()
{
    u32 mux_ctrl_ofs = (pad & MUX_CTRL_OFS_MASK) >> MUX_CTRL_OFS_SHIFT;
    u32 mux_mode = (pad & MUX_MODE_MASK) >> MUX_MODE_SHIFT;
    u32 sel_input_ofs = (pad & MUX_SEL_INPUT_OFS_MASK) >> MUX_SEL_INPUT_OFS_SHIFT;
    u32 sel_input = (pad & MUX_SEL_INPUT_MASK) >> MUX_SEL_INPUT_SHIFT;
    u32 pad_ctrl_ofs = (pad & MUX_PAD_CTRL_OFS_MASK) >> MUX_PAD_CTRL_OFS_SHIFT;
    u32 pad_ctrl = (pad & MUX_PAD_CTRL_MASK) >> MUX_PAD_CTRL_SHIFT;

    if (mux_ctrl_ofs)
        __raw_writel(mux_mode, base + mux_ctrl_ofs);

    if (sel_input_ofs)
        __raw_writel(sel_input, base + sel_input_ofs);

    if (!(pad_ctrl & NO_PAD_CTRL) && pad_ctrl_ofs)
        __raw_writel(pad_ctrl, base + pad_ctrl_ofs);

    return 0;
}
EXPORT_SYMBOL(mxc_iomux_v3_setup_pad);