I am writing an Ethernet driver for a Internal PCI cable modem with
some onboard memory that I have mapped using ioremap.
But I have problem reading the memory, more accurately, I can read it
once, write it many, but not read it a second time.
It is mapped using:
// Remap physical PCI controller LCR memory to virtual memory
if(((char*)(global_lcr_vmemaddr = (u32) ioremap(global_pci_lcr_memaddr, LCR_MEMORY_RANGE)))==NULL)
return -EAGAIN;
// Remap physical PCI memory to virtual memory
if((((char*)global_vmemaddr = (u32) ioremap(global_pci_memaddr,MODEM_MEMORY_RANGE))) == NULL) {
iounmap((char*)global_lcr_vmemaddr); return -EAGAIN;
}
The following silly code then works fine:
Byte byArgh;
byArgh = *((Byte*)global_vmemaddr);
if(byArgh==0) printk(KERN_DEBUG "byArgh\n");
*((Byte*)global_vmemaddr) = 0x5a;
byArgh = *((Byte*)global_vmemaddr);
While the PC freezes completely at the last conditional statement
at the following, almost identical, code fragment:
Byte byArgh;
byArgh = *((Byte*)global_vmemaddr);
if(byArgh==0) printk(KERN_DEBUG "byArgh\n");
*((Byte*)global_vmemaddr) = 0x5a;
byArgh = *((Byte*)global_vmemaddr);
if(byArgh==0) printk(KERN_DEBUG "byArgh\n"); // DEATH HERE
- as if the bus had not finished the transfer the second time I read.
I have in a similar way mapped PCI LCR memory in the PLX9052 PCI
controller (that by the way does not support master mode). And I can
read and write that LCR memory as much as I want.
I have tried changing compiler (to gcc 2.7.2.3), changing the
modem board with one that works with my WinNT driver, adding
udelay(60) between accesses, using readb() instead of direct access -
no change.
If I do _extensive_ memory testing, writing all the memory twice, then
reading all, writing all again, reading all, writing all again -
there is no problem reading, but later in the driver when just
accessing a single byte like in the second example I freeze again.
A small sample code is available at http://www.zorland.dk/jimbo/hw.c
This is my first SW project of any kind on linux, so please be gentle
with me :-) Maybe I am mapping the memory in a wrong way ?
I am using kernel 2.2.9.
PS: I am in no way acting on behalf of COCOM A/S, this is purely a
spare time project.
--
Best regards, Klaus.
----------------------------------------------------
Klaus J. O. Nielsen
System Engineer, COCOM A/S, www.cocom.dk
Personal web: http://www.zorland.dk/jimbo
PGP public key: http://www.zorland.dk/jimbo/kjn.asc
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