Hi, list
Does anyone here familiar to the serial 8250 driver?
I enabled two uart ports in my board definition, but the ports doesn't
appear after I loaded the kernel (3.4.19). I discovered, it failed at
the UART port auto configuration stage, the exact function is
autoconfig(...) in drivers/tty/serial/8250.c.
...
if (!(port->flags & UPF_BUGGY_UART)) {
scratch = serial_in(up, UART_IER);
serial_out(up, UART_IER, 0);
#ifdef __i386__
outb(0xff, 0x080);
#endif
/*
* Mask out IER[7:4] bits for test as some UARTs (e.g. TL
* 16C754B) allow only to modify them if an EFR bit is set.
*/
scratch2 = serial_in(up, UART_IER) & 0x0f;
serial_out(up, UART_IER, 0x0F);
#ifdef __i386__
outb(0, 0x080);
#endif
scratch3 = serial_in(up, UART_IER) & 0x0f;
serial_out(up, UART_IER, scratch);
if (scratch2 != 0 || scratch3 != 0x0F) {
/*
* We failed; there's nothing here
*/
DEBUG_AUTOCONF("IER test failed (%02x, %02x) ",
scratch2, scratch3);
goto out;
}
}
By enabling the debug output, I found it failed because values in scratch2 and
scratch3 are all zeros.
In my board definition, what I configured are something like:
#define SERIAL_BASE (0xe1400000)
#define SERIAL_FLAGS (UPF_BOOT_AUTOCONF | UPF_IOREMAP | UPF_SHARE_IRQ)
#define SERIAL_CLK (14745600)
static struct plat_serial8250_port lgf2410_urts_data[] = {
[0] = {
.mapbase = SERIAL_BASE + 0x00,
.irq = 16,
.flags = SERIAL_FLAGS,
.iotype = UPIO_MEM,
.regshift = 0,
.uartclk = SERIAL_CLK,
},
[1] = {
.mapbase = SERIAL_BASE + 0x10,
.irq = 17,
.flags = SERIAL_FLAGS,
.iotype = UPIO_MEM,
.regshift = 0,
.uartclk = SERIAL_CLK,
},
};
static struct platform_device lgf2410_urts = {
.name = "serial8250",
.id = PLAT8250_DEV_PLATFORM,
.dev = {
.platform_data = &lgf2410_urts_data,
},
};
I think the mapbase addresses are corrected. Since I copied these addresse from
a old kernel log output from a 2.6.16 linux. For the old 2.6.16 kernel, which
run the exact same board, I have no information how it was configured.
Below is the 2.6.16 kernel output, it successfully detected the UART
ports:
serial8250: tts0 at MMIO 0xe1400000 (irq = 16) is a 16550A
serial8250: tts1 at MMIO 0xe1400008 (irq = 16) is a 16550A
serial8250: tts2 at MMIO 0xe1400010 (irq = 17) is a 16550A
serial8250: tts3 at MMIO 0xe1400018 (irq = 17) is a 16550A
Now I expect the same result from my self tailored 3.4.19 kernel.
Hope I can get your kind support! Thanks.
--
woody
I can't go back to yesterday - because I was a different person then.
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