minix/kernel/arch/earm/omap_serial.c

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#include <assert.h>
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#include <sys/types.h>
#include <machine/cpu.h>
#include <minix/type.h>
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#include <io.h>
#include "kernel/kernel.h"
#include "kernel/proc.h"
#include "kernel/vm.h"
#include "kernel/proto.h"
#include "arch_proto.h"
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#include "omap_serial.h"
struct omap_serial {
vir_bytes base;
vir_bytes size;
};
static struct omap_serial omap_serial = {
.base = 0,
};
static kern_phys_map serial_phys_map;
/*
* 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
omap_serial.size = 0x1000 ; /* 4k */
kern_phys_map_ptr(omap_serial.base,omap_serial.size,
&serial_phys_map, (vir_bytes) &omap_serial.base);
assert(omap_serial.base);
}
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void omap3_ser_putc(char c)
{
assert(omap_serial.base);
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int i;
/* Wait until FIFO's empty */
for (i = 0; i < 100000; i++)
if (mmio_read(omap_serial.base + OMAP3_LSR) & OMAP3_LSR_THRE)
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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;
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}