[SeaBIOS] non-emulated AHCI hardware

Scott Duplichan scott at notabs.org
Thu May 26 20:09:50 CEST 2011

Gerd Hoffmann wrote:

]   Hi,
]> Attached is a two part version of the previous patch. Stage1 is enough
]> to get through most OS installs. Stage2 adds unaligned buffer support
]> needed for MS-DOS.
]Hmm, patch #1 is still a collection of multiple changes, looks a bit 
]like trying this and that until it somehow worked, without figuring 
]which changes where needed to make the box boot.

Thank you for the feedback. This is a pretty harsh assessment of work
that transforms non-functioning code into something usable on real hardware.
Have you ever written code for real hardware or do work strictly with
software models?

]  Also the changelog 
]should describe what was changed and why, not only the effect of the

These documents will help you understand the changes:

]Polling the IRQ status looks like a sensible thing to do.  Note that 
]there might be multiple bits set in the IRQ status register, so you 
]can't use irqbits == 0x01 to check the status.  qemu fails to boot 
]because of that bug.

Have you considered the possibility that the reason this works on real
hardware and not qemu is that the qemu AHCI model has an erratum?

]  Also it isn't obvious why you are looking for 
]others than the "Device to Host Register FIS" interrupt.  Care to explain?

I don't understand this question.

]I've attached a patch which switches ahci over to irq status polling, 
]based on your patch.  Works nicely in qemu.  Can you give it a spin on 
]real hardware?

It fails on real (AMD) hardware.

I am surprised by qemu bias of your questions. The type of question I
expected is "great to hear it works on AMD hardware, but what about Intel
hardware?" My answer would be that I cannot easily test the code on Intel


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