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Re: [Qemu-devel] [PATCH qemu] fdc: Exit if ISA controller does not suppo
From: |
Philippe Mathieu-Daudé |
Subject: |
Re: [Qemu-devel] [PATCH qemu] fdc: Exit if ISA controller does not support DMA |
Date: |
Mon, 5 Mar 2018 16:03:57 -0300 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 |
On 03/05/2018 07:29 AM, Philippe Mathieu-Daudé wrote:
> On 10/26/2017 03:46 AM, Alexey Kardashevskiy wrote:
>> A "powernv" machine type defines an ISA bus but it does not add any
>> DMA
>> controller to it so it is possible to hit assert(fdctrl->dma) by
>> adding "-machine powernv -device isa-fdc".
>
> The same happens with the Alpha machine.
>
> On 12/13/2017 03:19 AM, Hervé Poussineau wrote:
>> Le 08/12/2017 à 22:29, John Snow a écrit :
>> [...]
>>>
>>> It looks like Herve was working on decoupling floppies from i8257, but
>>> perhaps didn't get all the way through -- I'm not actually clear on what
>>> work remains to be done here, maybe he can chime in if he's still
>>> interested in the project?
>>>
>>
>> Indeed, I worked on decoupling floppies (and other ISA devices) from
>> i8257, for three reasons:
>> 1) having a working floppy on MIPS Magnum machine. fdc is PC-compatible,
>> but DMA controller is not i8257-compatible.
>> 2) reimplement another ISA bus with a somewhat i8257-compatible DMA
>> 3) for fun, support multiple ISA buses on a same machine but on
>> different PCI bridges.
>>
>> I failed on point 1), mostly due to lack of documentation.
>> I succeeded on point 2), by having locally some patches for a ISAPNP
>> bus, where IO/IRQ/DMA addresses of ISA devices can change dynamically,
>> and devices can be discovered by operating system.
>> About point 3, most of the patches are ready, but some details are still
>> to be fixed.
>
> I'm having hard time refactoring all these PC chipsets, I'll make some
> room to send my current work as RFC before soft freeze.
Sorry I misunderstood the problem; my series only modify the Super I/O
devices, being affected by the same problem Alexey has with the ISA DMA :(