freeze when reading a PCI bridge register
nicolas.lavocat at fr.thalesgroup.com
Wed Apr 22 18:04:29 EST 2009
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
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;
puts("PCI1 reading PCI VENDOR and DEVICE ID\n");
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
-Do you think that my MMU is under the control of an evil spirit? ^^
thank you for your help
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