im6 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
    ... ...
}

以MX6Q_PAD_SD1_DAT1__GPIO_1_17举例。
#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 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);