PL050 PS/2 Controller
Another example is the ARM Integrator/CP board which implements the PS/2 interface encapsulated in the PL050 (where the PL050 is analogous to the I8042) except you communicate with the PL050 differently than the I8042. But, after the PL050 is configured you then proceed with the PS/2 mouse protocol. For example:
/*
KMI/PL050 bases under Integrator/CP compatible board.
*/
#define KMI_KB_BASE 0x18000000 // keyboard
#define KMI_MS_BASE 0x19000000 // mouse
typedef struct _KMI_MMIO {
uint32 cr; // control register (rw)
uint32 stat; // status register (r)
uint32 data; // data register (rw)
uint32 clk; // clock divisor register (rw)
uint32 ir; // interrupt control register (r)
} KMI_MMIO;
KMI_MMIO volatile *mmio;
uint32 tmp;
mmio = (KMI_MMIO*)KMI_MS_BASE;
mmio->cr = 0x4;
/* talk to the PS2 controller and enable it */
mmio->data = 0xF4;
/* keyboard sends back ACK */
while(!KMI_TXFULL(mmio->stat));
tmp = mmio->data;
The above uses memory mapped input/output (MMIO), but other architectures may use I/O ports instead or a combination of I/O ports and MMIO for example the X84/64. So understanding your platform is very important to understand how to proceed in talking to the devices.
Above, the PL050 is also called the KMI (Keyboard And Mouse Interface). So first, configure the PL050 by enabling it. Now, it provides a interface to the PS2 interface which then interfaces with the mouse. So, the next thing to do is write the value 0xF4 which you can find in the table above to enable the mouse.
Note that, due to the complexity of the Raspberry Pi's USB interface and Qemu's versatilepb being the go-to Pi emulator before raspi2 was developed, some older Pi programs will use the PL050 to easily enable debugging in Qemu. No Pi device so far has PS/2 compatibility hardware.