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[realtek] Enable DAC only when built as a 64-bit binary

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Some RTL8169 cards (observed with an RTL8169SC) crash and burn if DAC
is enabled, even if only 32-bit addresses are used.  Observed
behaviour includes system lockups and repeated transmission of garbage
data onto the wire.

This seems to be a known problem.  The Linux r8169 driver disables DAC
by default and provides a "use_dac" module parameter.

There appears to be no known test for determining whether or not DAC
will work.  As a workaround, enable DAC only if we are built as as
64-bit binary.  This at least eliminates the problem in the common
case of a 32-bit build, which will never use 64-bit addresses anyway.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown 2012-08-23 13:35:19 +01:00
parent 0e61beb26f
commit 0dacd54174
1 changed files with 7 additions and 2 deletions
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9
src/drivers/net/realtek.c
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@ -878,10 +878,15 @@ static void realtek_detect ( struct realtek_nic *rtl ) {
/* The C+ Command register is present only on 8169 and 8139C+.
* Try to enable C+ mode and PCI Dual Address Cycle (for
* 64-bit systems), if supported.
*
* Note that enabling DAC seems to cause bizarre behaviour
* (lockups, garbage data on the wire) on some systems, even
* if only 32-bit addresses are used.
*/
cpcr = readw ( rtl->regs + RTL_CPCR );
cpcr |= ( RTL_CPCR_DAC | RTL_CPCR_MULRW | RTL_CPCR_CPRX |
RTL_CPCR_CPTX );
cpcr |= ( RTL_CPCR_MULRW | RTL_CPCR_CPRX | RTL_CPCR_CPTX );
if ( sizeof ( physaddr_t ) > sizeof ( uint32_t ) )
cpcr |= RTL_CPCR_DAC;
writew ( cpcr, rtl->regs + RTL_CPCR );
check_cpcr = readw ( rtl->regs + RTL_CPCR );