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[serial] Improve serial driver chip detect and FIFO handling #575

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Apr 23, 2020
Merged

[serial] Improve serial driver chip detect and FIFO handling #575

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103 changes: 18 additions & 85 deletions elks/arch/i86/drivers/char/serial.c
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@
#include <arch/ports.h>

#define NEW 1 /* set =0 for old driver code if needed*/
#define FIFO 0 /* set =1 to enable new FIFO code for testing*/
#define FIFO 1 /* set =1 to enable new FIFO code for testing*/

#if defined (CONFIG_CHAR_DEV_RS) || defined (CONFIG_CONSOLE_SERIAL)

Expand Down Expand Up @@ -92,14 +92,15 @@ static unsigned int divisors[] = {
/* Flush input fifo */
static void flush_input_fifo(register struct serial_info *sp)
{
#if !FIFO /* HW FIFO cleared when reset or enabled*/
int i = MAX_RX_BUFFER_SIZE;

do {
inb_p(sp->io + UART_RX);
} while (--i && (inb_p(sp->io + UART_LSR) & UART_LSR_DR));
#endif
}

#if NEW
static int rs_probe(register struct serial_info *sp)
{
int status, type;
Expand All @@ -117,19 +118,21 @@ static int rs_probe(register struct serial_info *sp)

/* then read FIFO status*/
status = inb_p(sp->io + UART_IIR);
if (status & 0x40) {
if (status & 0x80) { /* FIFO enabled*/
if (status & 0x20) /* 64 byte FIFO enabled*/
type = ST_16750;
else type = ST_16550A;
} else type = ST_16550;
if (status & 0x80) { /* FIFO available*/
if (status & 0x20) /* 64 byte FIFO enabled*/
type = ST_16750;
else if (status & 0x40) /* 16 byte FIFO OK */
type = ST_16550A;
else
type = ST_16550; /* Non-functional FIFO */
} else {
/* no FIFO, try writing arbitrary value to scratch reg*/
outb_p(0x2A, sp->io + UART_SCR);
if (inb_p(sp->io + UART_SCR) == 0x2a)
type = ST_16450;
else type = ST_8250;
}

sp->flags = SERF_EXIST | type;

/*
Expand All @@ -146,76 +149,6 @@ static int rs_probe(register struct serial_info *sp)
return 0;
}

#else

static int rs_probe(register struct serial_info *sp)
{
int status1, status2;
unsigned char scratch;

inb(sp->io + UART_IER);
outb_p(0, sp->io + UART_IER);
scratch = inb_p(sp->io + UART_IER);
outb_p(scratch, sp->io + UART_IER);
if (scratch)
return -1;

/* this code is weird, IMO */
scratch = inb_p(sp->io + UART_LCR);
outb_p(scratch | UART_LCR_DLAB, sp->io + UART_LCR);
outb_p(0, sp->io + UART_EFR);
outb_p(scratch, sp->io + UART_LCR);

outb_p(UART_FCR_ENABLE_FIFO, sp->io + UART_FCR);

/* upper two bits of IIR define UART type, but according to both RB's
* intlist and HelpPC this code is wrong, see comments marked with [*]
*/
scratch = inb_p(sp->io + UART_IIR) >> 6;
switch (scratch) {
case 0:
sp->flags = (unsigned char) (SERF_EXIST | ST_16450);
break;
case 1: /* [*] this denotes broken 16550 UART,
* not 16550A or any newer type */
sp->flags = (unsigned char) (ST_UNKNOWN);
break;
case 2: /* invalid combination */
case 3: /* Could be a 16650.. we dont care */
/* [*] 16550A or newer with enabled FIFO buffers
*/
sp->flags = (unsigned char) (SERF_EXIST | ST_16550);
}

/* 8250 UART if scratch register isn't present */
if (!scratch) {
scratch = inb_p(sp->io + UART_SCR);
outb_p(0xA5, sp->io + UART_SCR);
status1 = inb_p(sp->io + UART_SCR);
outb_p(0x5A, sp->io + UART_SCR);
status2 = inb_p(sp->io + UART_SCR);
outb_p(scratch, sp->io + UART_SCR);
if ((status1 != 0xA5) || (status2 != 0x5A))
sp->flags = (unsigned char) (SERF_EXIST | ST_8250);
}

/*
* Reset the chip
*/

outb_p(0x00, sp->io + UART_MCR);

/* clear RX and TX FIFOs */
outb_p((unsigned char) (UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT),
sp->io + UART_FCR);

/* clear RX register */
flush_input_fifo(sp);

return 0;
}
#endif /* old rs_probe function*/

static void update_port(register struct serial_info *port)
{
tcflag_t cflags;
Expand Down Expand Up @@ -272,7 +205,7 @@ void rs_irq(int irq, struct pt_regs *regs, void *dev_id)
struct ch_queue *q;
int i, j, status;
char *io;
unsigned char buf[10];
unsigned char buf[MAX_RX_BUFFER_SIZE];

i = 0;
sp = &ports[(int)irq_port[irq - 2]];
Expand All @@ -288,9 +221,9 @@ void rs_irq(int irq, struct pt_regs *regs, void *dev_id)
//if (status & UART_LSR_DR) /* Receiver buffer full? */
do {
buf[i++] = inb_p(io + UART_RX); /* Read received data */
} while ((inb_p(io + UART_LSR) & UART_LSR_DR) && i < 10);
} while ((inb_p(io + UART_LSR) & UART_LSR_DR) && i < MAX_RX_BUFFER_SIZE);
//}
//} while (!(inb_p(io + UART_IIR) & UART_IIR_NO_INT) && i < 10);
//} while (!(inb_p(io + UART_IIR) & UART_IIR_NO_INT) && i < MAX_RX_BUFFER_SIZE);

if (status & UART_LSR_OE)
printk("serial: data overrun\n");
Expand Down Expand Up @@ -375,10 +308,10 @@ static int rs_open(struct tty *tty)
#define UART_FCR_ENABLE_FIFO14 (UART_FCR_ENABLE_FIFO | 0xC0)
#define UART_FCR_ENABLE_FIFO8 (UART_FCR_ENABLE_FIFO | 0x80)
#define UART_FCR_ENABLE_FIFO4 (UART_FCR_ENABLE_FIFO | 0x40)
/* enable FIFO with 8 byte trigger */
/* enable FIFO with 14 byte trigger */
#if FIFO
if ((port->flags & SERF_TYPE) > ST_16450)
outb_p(UART_FCR_ENABLE_FIFO8, port->io + UART_FCR);
if ((port->flags & SERF_TYPE) > ST_16550)
outb_p(UART_FCR_ENABLE_FIFO14, port->io + UART_FCR);
#endif

inb_p(port->io + UART_IIR);
Expand Down Expand Up @@ -487,7 +420,7 @@ int rs_init(void)
do {
if (sp->tty != NULL) {
printk("ttyS%d at 0x%x, irq %d is a%s\n", ttyno,
sp->io, sp->irq, serial_type[sp->flags & 0x3]);
sp->io, sp->irq, serial_type[sp->flags & SERF_TYPE]);
}
sp++;
} while (++ttyno < NR_SERIAL);
Expand Down