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Specify PCI based UART for earlyprintk
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Add support for specifying PCI based UARTs for earlyprintk
using a syntax like "earlyprintk=pciserial,00:18.1,115200",
where 00:18.1 is the BDF of a UART device.

[Slightly tidied from Stuart's original patch]
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Stuart R. Anderson authored and Greg Kroah-Hartman committed Feb 2, 2015
1 parent d2b6f44 commit ea9e9d8
Showing 1 changed file with 166 additions and 16 deletions.
182 changes: 166 additions & 16 deletions arch/x86/kernel/early_printk.c
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@
#include <linux/usb/ehci_def.h>
#include <linux/efi.h>
#include <asm/efi.h>
#include <asm/pci_x86.h>

/* Simple VGA output */
#define VGABASE (__ISA_IO_base + 0xb8000)
Expand Down Expand Up @@ -76,7 +77,7 @@ static struct console early_vga_console = {

/* Serial functions loosely based on a similar package from Klaus P. Gerlicher */

static int early_serial_base = 0x3f8; /* ttyS0 */
static unsigned long early_serial_base = 0x3f8; /* ttyS0 */

#define XMTRDY 0x20

Expand All @@ -94,13 +95,40 @@ static int early_serial_base = 0x3f8; /* ttyS0 */
#define DLL 0 /* Divisor Latch Low */
#define DLH 1 /* Divisor latch High */

static void mem32_serial_out(unsigned long addr, int offset, int value)
{
uint32_t *vaddr = (uint32_t *)addr;
/* shift implied by pointer type */
writel(value, vaddr + offset);
}

static unsigned int mem32_serial_in(unsigned long addr, int offset)
{
uint32_t *vaddr = (uint32_t *)addr;
/* shift implied by pointer type */
return readl(vaddr + offset);
}

static unsigned int io_serial_in(unsigned long addr, int offset)
{
return inb(addr + offset);
}

static void io_serial_out(unsigned long addr, int offset, int value)
{
outb(value, addr + offset);
}

static unsigned int (*serial_in)(unsigned long addr, int offset) = io_serial_in;
static void (*serial_out)(unsigned long addr, int offset, int value) = io_serial_out;

static int early_serial_putc(unsigned char ch)
{
unsigned timeout = 0xffff;

while ((inb(early_serial_base + LSR) & XMTRDY) == 0 && --timeout)
while ((serial_in(early_serial_base, LSR) & XMTRDY) == 0 && --timeout)
cpu_relax();
outb(ch, early_serial_base + TXR);
serial_out(early_serial_base, TXR, ch);
return timeout ? 0 : -1;
}

Expand All @@ -114,13 +142,28 @@ static void early_serial_write(struct console *con, const char *s, unsigned n)
}
}

static __init void early_serial_hw_init(unsigned divisor)
{
unsigned char c;

serial_out(early_serial_base, LCR, 0x3); /* 8n1 */
serial_out(early_serial_base, IER, 0); /* no interrupt */
serial_out(early_serial_base, FCR, 0); /* no fifo */
serial_out(early_serial_base, MCR, 0x3); /* DTR + RTS */

c = serial_in(early_serial_base, LCR);
serial_out(early_serial_base, LCR, c | DLAB);
serial_out(early_serial_base, DLL, divisor & 0xff);
serial_out(early_serial_base, DLH, (divisor >> 8) & 0xff);
serial_out(early_serial_base, LCR, c & ~DLAB);
}

#define DEFAULT_BAUD 9600

static __init void early_serial_init(char *s)
{
unsigned char c;
unsigned divisor;
unsigned baud = DEFAULT_BAUD;
unsigned long baud = DEFAULT_BAUD;
char *e;

if (*s == ',')
Expand All @@ -145,24 +188,124 @@ static __init void early_serial_init(char *s)
s++;
}

outb(0x3, early_serial_base + LCR); /* 8n1 */
outb(0, early_serial_base + IER); /* no interrupt */
outb(0, early_serial_base + FCR); /* no fifo */
outb(0x3, early_serial_base + MCR); /* DTR + RTS */
if (*s) {
if (kstrtoul(s, 0, &baud) < 0 || baud == 0)
baud = DEFAULT_BAUD;
}

/* Convert from baud to divisor value */
divisor = 115200 / baud;

/* These will always be IO based ports */
serial_in = io_serial_in;
serial_out = io_serial_out;

/* Set up the HW */
early_serial_hw_init(divisor);
}

#ifdef CONFIG_PCI
/*
* early_pci_serial_init()
*
* This function is invoked when the early_printk param starts with "pciserial"
* The rest of the param should be ",B:D.F,baud" where B, D & F describe the
* location of a PCI device that must be a UART device.
*/
static __init void early_pci_serial_init(char *s)
{
unsigned divisor;
unsigned long baud = DEFAULT_BAUD;
u8 bus, slot, func;
uint32_t classcode, bar0;
uint16_t cmdreg;
char *e;


/*
* First, part the param to get the BDF values
*/
if (*s == ',')
++s;

if (*s == 0)
return;

bus = (u8)simple_strtoul(s, &e, 16);
s = e;
if (*s != ':')
return;
++s;
slot = (u8)simple_strtoul(s, &e, 16);
s = e;
if (*s != '.')
return;
++s;
func = (u8)simple_strtoul(s, &e, 16);
s = e;

/* A baud might be following */
if (*s == ',')
s++;

/*
* Second, find the device from the BDF
*/
cmdreg = read_pci_config(bus, slot, func, PCI_COMMAND);
classcode = read_pci_config(bus, slot, func, PCI_CLASS_REVISION);
bar0 = read_pci_config(bus, slot, func, PCI_BASE_ADDRESS_0);

/*
* Verify it is a UART type device
*/
if (((classcode >> 16 != PCI_CLASS_COMMUNICATION_MODEM) &&
(classcode >> 16 != PCI_CLASS_COMMUNICATION_SERIAL)) ||
(((classcode >> 8) & 0xff) != 0x02)) /* 16550 I/F at BAR0 */
return;

/*
* Determine if it is IO or memory mapped
*/
if (bar0 & 0x01) {
/* it is IO mapped */
serial_in = io_serial_in;
serial_out = io_serial_out;
early_serial_base = bar0&0xfffffffc;
write_pci_config(bus, slot, func, PCI_COMMAND,
cmdreg|PCI_COMMAND_IO);
} else {
/* It is memory mapped - assume 32-bit alignment */
serial_in = mem32_serial_in;
serial_out = mem32_serial_out;
/* WARNING! assuming the address is always in the first 4G */
early_serial_base =
(unsigned long)early_ioremap(bar0 & 0xfffffff0, 0x10);
write_pci_config(bus, slot, func, PCI_COMMAND,
cmdreg|PCI_COMMAND_MEMORY);
}

/*
* Lastly, initalize the hardware
*/
if (*s) {
baud = simple_strtoul(s, &e, 0);
if (baud == 0 || s == e)
if (strcmp(s, "nocfg") == 0)
/* Sometimes, we want to leave the UART alone
* and assume the BIOS has set it up correctly.
* "nocfg" tells us this is the case, and we
* should do no more setup.
*/
return;
if (kstrtoul(s, 0, &baud) < 0 || baud == 0)
baud = DEFAULT_BAUD;
}

/* Convert from baud to divisor value */
divisor = 115200 / baud;
c = inb(early_serial_base + LCR);
outb(c | DLAB, early_serial_base + LCR);
outb(divisor & 0xff, early_serial_base + DLL);
outb((divisor >> 8) & 0xff, early_serial_base + DLH);
outb(c & ~DLAB, early_serial_base + LCR);

/* Set up the HW */
early_serial_hw_init(divisor);
}
#endif

static struct console early_serial_console = {
.name = "earlyser",
Expand Down Expand Up @@ -210,6 +353,13 @@ static int __init setup_early_printk(char *buf)
early_serial_init(buf + 4);
early_console_register(&early_serial_console, keep);
}
#ifdef CONFIG_PCI
if (!strncmp(buf, "pciserial", 9)) {
early_pci_serial_init(buf + 9);
early_console_register(&early_serial_console, keep);
buf += 9; /* Keep from match the above "serial" */
}
#endif
if (!strncmp(buf, "vga", 3) &&
boot_params.screen_info.orig_video_isVGA == 1) {
max_xpos = boot_params.screen_info.orig_video_cols;
Expand Down

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