Hello everyone, I have arm SoC AM3517 (Cortex-A8) running linux 2.6.32. I am trying to access hardware registers using kgdb. I can connect to the board via RS232, can read variables in kernel space, control processes using breakpoints, but I can't read hardware register. For example, I am trying to read UART3 registers. Information about UART3 is saved in structure: static struct plat_serial8250_port serial_platform_data2[] = { { .mapbase = OMAP_UART3_BASE, .irq = 74, .iotype = UPIO_MEM, .regshift = 2, ... } } mapbase is a physical address. According to the Technical Reference Manual is should be 0x49020000. I checked this field using kgdb: (gdb) p/x serial_platform_data2[0].mapbase $34 = 0x49020000 This structure has the field membase. As I understand, it contains virtual address of the mapbase physical address. This field is initialized on UART init via function ioremap(). I checked this field as well: (gdb) p/x serial_platform_data2[0].membase $35 = 0xfb020000 Now I am trying to read register MCR_REG, that has offset 0x10 from the base address. (gdb) x serial_platform_data2[0].membase+0x10 0xfb020010: Cannot access memory at address 0xfb020010 (gdb) x serial_platform_data2[0].mapbase+0x10 0x49020010: Cannot access memory at address 0x49020010 As I understand, the membase address should work. Right? Why has access failed? Is it kgdb limitation? -- Best regards, Andrey Skvortsov