So the host bridge is important, what is the bridge?
Marvell or Tundra chipset?
________________________________
From: Nicolas Lavocat [mailto:[email protected]]
Sent: Wednesday, April 22, 2009 4:32 PM
To: Liu Dave-R63238
Cc: linuxppc-dev
Subject: Re: freeze when reading a PCI bridge register
a 7448
Liu Dave-R63238 a écrit :
I' am trying to configure a PCI bridge on a private
board, with a
powerpc . In a first time, I tried to get informations
about PCI
devices, in order to be sure that my read and write
methods work (
using 2 configuration registers, like on an x86
architecture.) . 2
configuration registers are used, for example we
write an encoded
address (it is a request to a PCI device) in the first
and
the answer of
the PCI device can be read in the second register (it
is a
configuration
cycle)
Firstly, I did it by JTAG: it works. Then, under uboot,
it is ok.
For example, the code used under u-boot:
volatile u32* addr;
u32 vendor_device_ID;
puts("PCI1 reading PCI VENDOR and DEVICE ID\n");
addr=CFG_ADDR_PCI1;
*addr=0x80007800;
addr= CFG_DATA_PCI1;
vendor_device_ID= *addr;
printf("PCI1: PCI1_VENDOR_DEVICE_ID= %08x \n"
,vendor_device_ID);
Therefore, when I do the same thing under Linux, the
system
crash when I
try to read the second register...
Linux is frozen, and there is no error message.
Under Linux, I made an ioremap before use the registers
and access to
these registers thanks to functions "in_be32" and
"out_be32".
I tried with different endianness to avoid an error of
this type.
If I understand, the main difference between u-boot and
Linux (about
registers access) is the activation of the MMU.
So I thought that problem could come from it.
I think the problem could came from the configuration
of DBAT
and IBATS
registers of the MMU, but I didn't found any
information
about the MMU
configuration under Linux.
So after this novel, I have some questions:
-Is the MMU configuration generic under Linux?
-Does somebody think that the problem doesn't come from
MMU?
-How does work ioremap? Is it a fully software
function, or does it
speaks to MMU to get the effective address from
physical address?
-Does somebody have an idea, or a documentation about
MMU
configuration
under linux?
-Do you think that my MMU is under the control of an
evil spirit? ^^
What is the PowerPC you are using?
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