I.MX6 U-boot GPIO hacking

/*******************************************************************************
 *                          I.MX6 U-boot GPIO hacking
 * 说明：
 *     本文主要记录I.MX6 U-boot是如何设置GPIO口输入输出的，主要是考虑到这个阶段
 * 并没有像Linux内核中的gpio_request一系列函数使用。
 *
 *                                          2016-3-7 深圳 南山平山村 曾剑锋
 ******************************************************************************/

cat bootable/bootloader/uboot-imx/board/freescale/mx6q_sabresd/mx6q_sabresd.c
    ......
    #ifdef CONFIG_LCD
    void lcd_enable(void)
    {
        ......
        mxc_iomux_v3_setup_pad(MX6DL_PAD_SD1_DAT2__GPIO_1_19);   ---+
        reg = readl(GPIO1_BASE_ADDR + GPIO_GDIR);                ---*---------------+
        reg |= ( << );                                           |               |
        writel(reg, GPIO1_BASE_ADDR + GPIO_GDIR);                   |               |
                                                                    |               |
        reg = readl(GPIO1_BASE_ADDR + GPIO_DR);                     |               |
        reg &= ~( << );                                          |               |
        writel(reg, GPIO1_BASE_ADDR + GPIO_DR);                     |               |
        ......                                                      |               |
    }                                                               |               |
    ......                                                          |               |
                                                                    |               |
#define MX6DL_PAD_SD1_DAT2__GPIO_1_19                           <---+          \    |
    IOMUX_PAD(0x06D4, 0x02EC, , 0x0000, , NO_PAD_CTRL)            |               |
                                                                    |               |
/*                                                                  |               |
 * configures a single pad in the iomuxer                           |               |
 */                                                                 |               |
int mxc_iomux_v3_setup_pad(iomux_v3_cfg_t 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 ;                                                                       |
}                                                                                   |
EXPORT_SYMBOL(mxc_iomux_v3_setup_pad);                                              |
                                                                                    |
                                                                                    |
/**                                                                                 |
 * 1. 参考文档：                                                                    |
 *     i.MX 6Dual/6Quad Multimedia Applications Processor Reference Manual          |
 * 2. 30.4 Programmable Registers                                                   |
 *     +------------------------------------------------------+                     |
 *     |                      GPIO memory map                 |                     |
 *     +-----------+-------------------------------+----------+                     |
 *     | Absolute  | Register name                 | Section/ |                     |
 *     | address   |                               | page     |                     |
 *     | (hex)     |                               |          |                     |
 *     +-----------+-------------------------------+----------+                     |
 *     | 0209_C000 | GPIO data register (GPIO1_DR) | 30.4.1/  |                     |
 *     |           |                               |          |                     |
 *     +-----------+-------------------------------+----------+                     |
 * 3. GPIO1_BASE_ADDR = 0x1C000 + 0x80000 + 0x02000000                              |
 *    GPIO1_BASE_ADDR = 0x0209C000                                                  |
 */                                                                                 |
#define GPIO1_BASE_ADDR            (AIPS1_OFF_BASE_ADDR + 0x1C000)         <--------+
#define AIPS1_OFF_BASE_ADDR        (ATZ1_BASE_ADDR + 0x80000)                       |
#define ATZ1_BASE_ADDR            AIPS1_ARB_BASE_ADDR                               |
#define AIPS1_ARB_BASE_ADDR        0x02000000                                       |
                                                                                    |
#define GPIO_GDIR               0x04                                       <--------+
#define GPIO_DR                 0x00