minix/kernel/arch/earm/omap_serial.c
Kees Jongenburger c40df92bf2 arm:add AM335X serial
Change-Id: I728622ddd4f59529d15e8ac2499c41fa815eee3b
2013-05-24 11:17:52 +02:00

61 lines
1.8 KiB
C

#include <assert.h>
#include <sys/types.h>
#include <machine/cpu.h>
#include <minix/type.h>
#include <io.h>
#include "omap_serial.h"
struct omap_serial {
vir_bytes base;
};
static struct omap_serial omap_serial = {
.base = 0,
};
/*
* In kernel serial for the omap. The serial driver like most other
* drivers needs to be started early and even before the MMU is turned on.
* We start by directly accessing the hardware memory address. Later on
* a when the MMU is turned on we still use a 1:1 mapping for these addresses.
*
* Pretty soon we are going to remap these addresses at later stage. And this
* requires us to use a dynamic base address. The idea is to receive a callback
* from VM with the new address to use.
*
* We also anticipate on the beaglebone port an try to keep the differences between
* the drivers to a minimum by initializing a struct here and not using (to much)
* constants in the code.
*
* The serial driver also gets used in the "pre_init" stage before the kernel is loaded
* in high memory so keep in mind there are two copies of this code in the kernel.
*/
void omap3_ser_init(){
#ifdef DM37XX
omap_serial.base = OMAP3_DM37XX_DEBUG_UART_BASE;
#endif
#ifdef AM335X
omap_serial.base = OMAP3_AM335X_DEBUG_UART_BASE;
#endif
assert(omap_serial.base);
}
void omap3_ser_putc(char c)
{
assert(omap_serial.base);
int i;
/* Wait until FIFO's empty */
for (i = 0; i < 100000; i++)
if (mmio_read(omap_serial.base + OMAP3_LSR) & OMAP3_LSR_THRE)
break;
/* Write character */
mmio_write(omap_serial.base + OMAP3_THR, c);
/* And wait again until FIFO's empty to prevent TTY from overwriting */
for (i = 0; i < 100000; i++)
if (mmio_read(omap_serial.base + OMAP3_LSR) & (OMAP3_LSR_THRE | OMAP3_LSR_TEMT))
break;
}