Hello.
Ashlesha Shintre wrote:
I m working on porting the 2.6.14.6 kernel to the Encore M3 (AU1500)
board --
The kernel mounts the NFS root and executes the init=/bin/sh program --
however I dont see it on the console (standard 8250 UART)
The reason is that there was no platform_device structure defined for
the serial console in the platform.c file.
I therefore added the following to the
arch/mips/au1000/common/platform.c file,
I doubt this is fitting place, since it only registers SoC devices. Move
this to the *board* specific code instead.
#ifdef CONFIG_MIPS_AMPRO_M3
static struct plat_serial8250_port encm3_via_uart_data[] = {
{
.mapbase = 0x50000000 + 0x3f8,
I highly doubt this is correct -- the address 0x3f8 is in I/O space. And
since 0x50000000 is mips_io_port_base, you do *not* need to add it here.
.membase = (char *)(0x50000000 +0x3f8),
This needs a kernel address, i.e. in KSEG1. As the UARTs are in the I/O
space, you just don't need to set this.
static struct resource encm3_via_uart_resource = {
.start = VIA_COM1_ADDR, // this is 0x3f8
.end = VIA_COM1_ADDR + 0x7,
.flags = IORESOURCE_IO,
};
static struct platform_device encm3_via_uart = {
.name = "serial8250",
.id = 1,
.dev = {
.platform_data = encm3_via_uart_data,
},
.num_resources = 1,
Where the IRQ is declared?
.resource = &encm3_via_uart_resource,
};
#endif
Well, I doubt that you need to also decalre the UART as platform_device in
addition to registering it with 8250.x -- it'll do everything for you.
I have a these queries about the above entries:
1) The serial console is on a VIA 686B southbridge which is on the PCI
bus -- however, because of the way the VIA is designed, any references
from the processor to port 0x3f8 are routed to the console --
- the 0x50000000 is the mips_io_port_base address for the Southbridge
so should the resource.flags be IORESOURCE_IO or IORESOURCE_MEM -- what
does this signify exactly?
On x86 the hardware on the busses is accessible via both memory and I/O
address space (the 2nd method was historically preferred) -- so, all archs
that want to reuse the standard x86 h/w have to adapt to its ways,
implementing I/O address space accesses by some means, usually by dedicating
the certain range of the physical addresses to it....
I tried both and neither makes a difference
to the output from the log buffer which I have pasted below. Does this
have to do with whether the ports are i/o or memory mapped -- cus in
This has to do with improper UART addresses you were passing.
that case it should be IORESOURCE_MEM as all io ports on MIPS processors
are memory mapped -- right?
No, it should be IORESOURCE_IO.
2) in the platform_device structure, does the name of the device have to
be coherent with a name given to it elsewhere, if yes, where?
You just don't need it in this case.
3) control goes into the serial8250_probe function and assigns values
from the plat_serial8250_port encm3_via_uart_data to the port..so what
is the basic difference between registration of "probe device" versus
"platform bus" devices in the 2.6 kernel?
I'm not sure I follow you here.
WBR, Sergei
