linux - ioremap 返回 NULL

Question

我正在尝试为 Raspberry PI 创建自定义 UART 驱动程序。 我尝试重新映射 MMIO。但是ioremap总是返回NULL。

#define UART_REG_BASE_ADDR  0x7E20100

pUart = ioremap(UART_REG_BASE_ADDR, 1024);
if (pUart==NULL)
{
    printk("Couldn't remap UART MMIO\n");
    return -EIO;
}

dmesg 转储以下内容:

[ 2906.579848] CPU: 0 PID: 4983 Comm: insmod Tainted: G      D W  O   3.18.5+ #1
[ 2906.590783] [<c0014b64>] (unwind_backtrace) from [<c00120ec>] (show_stack+0x20/0x24)
[ 2906.614046] [<c00120ec>] (show_stack) from [<c0549008>] (dump_stack+0x20/0x28)
[ 2906.624803] [<c0549008>] (dump_stack) from [<c0022620>] (warn_slowpath_common+0x7c/0x9c)
[ 2906.647925] [<c0022620>] (warn_slowpath_common) from [<c002266c>] (warn_slowpath_null+0x2c/0x34)
[ 2906.668656] [<c002266c>] (warn_slowpath_null) from [<c001a888>] (__arm_ioremap_pfn_caller+0x240/0x25c)
[ 2906.691936] [<c001a888>] (__arm_ioremap_pfn_caller) from [<c001a934>] (__arm_ioremap_caller+0x68/0x70)
[ 2906.713171] [<c001a934>] (__arm_ioremap_caller) from [<c001a3d0>] (__arm_ioremap+0x24/0x2c)
[ 2906.735043] [<c001a3d0>] (__arm_ioremap) from [<bf19c028>] (hello_init+0x28/0x88 [domotx])
[ 2906.755780] [<bf19c028>] (hello_init [domotx]) from [<c000873c>] (do_one_initcall+0x94/0x1e4)
[ 2906.778165] [<c000873c>] (do_one_initcall) from [<c0087e70>] (load_module+0x1848/0x1e38)
[ 2906.799410] [<c0087e70>] (load_module) from [<c008854c>] (SyS_init_module+0xec/0xf0)
[ 2906.822660] [<c008854c>] (SyS_init_module) from [<c000e980>] (ret_fast_syscall+0x0/0x48)
[ 2906.844558] ---[ end trace c7cdd8b3d5007a1b ]---
[ 2906.856382] Couldn't remap UART MMIO

我做错了什么？

Answer 1

我找到了上述问题的解决方案。实际上解决方案有两个:

• BCM2835 数据表未在其数据表中公布物理地址: 外设的物理地址范围为 0x20000000 到 0x20FFFFFF。外设的总线地址设置为映射到从 0x7E000000 开始的外设总线地址范围。因此，此处在总线地址 0x7Ennnnnnn 处公布的外设可在物理地址 0x20nnnnnn 处使用。
• 数据表中有一个拼写错误: PL011 USRT 映射到基地址 0x7E20100。 必须是PL011 USRT 映射到基地址 0x7E201000。