[ipxe-devel] iPXE 5719/5720 TX DMA workaround

Atif Faheem afaheem at btisystems.com
Fri Nov 15 04:39:19 UTC 2013

Hi. I have a question about the 5719 / 5720 TX DMA workaround fix that was committed to the tg3 driver in the Linux kernel. The iPXE's tg3 driver variant for 5719 / 5270 does not contain this. I have a system where I do see the TX DMA stall when Linux loads the regular tg3 driver, but haven’t been able to reproduce it when running iPXE on the same device.  I’m trying to ascertain why iPXE will not fail with the same error - is there a fundamental difference in how iPXE uses TX DMA compared to the mainstream tg3 driver?

Thanks - Atif

 After Power-on-reset, the 5719's TX DMA length registers may contain
uninitialized values and cause TX DMA to stall.  Check for invalid
values and set a register bit to flush the TX channels.  The bit
needs to be turned off after the DMA channels have been flushed
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