On 4/20/21 12:02 PM, Maciej W. Rozycki wrote: > On Mon, 19 Apr 2021, Khalid Aziz wrote: > >>> Khalid: I have skimmed over these documents and I infer 24-bit addressing >>> can be verified with any MultiMaster adapter, including ones that do have >>> 32-bit addressing implemented, by using the legacy Initialize Mailbox HBA >>> command. That could be used to stop Christoph's recent changes for older >>> adapter support removal and replace them with proper fixes for whatever >>> has become broken. Is that something you'd be willing as the driver's >>> maintainer to look into, or shall I? >> >> Do you mean use OpCode 01 (INITIALIZE MAILBOX) to set a 24-bit address >> for mailbox in place of OpCode 81? Verifying the change would be a >> challenge. Do you have an old adapter to test it with? If you do, go >> ahead and make the changes. I will be happy to review. I have only a >> BT-757 adapter. > > Yes, but upon inspection it looks like our driver doesn't use that opcode > and relies solely on 32-bit Mode Initialize Mailbox (0x81) even with ISA > devices. That makes sense as documentation indicates the firmware has > been designed to be unified so that the same binary microcontroller code > runs across all BusLogic MultiMaster devices. > > Anyway given the unified API it should be straightforward to simulate an > older adapter with a newer one, except for host bus protocol differences. > So verifying the workaround for broken BT-445S adapters continues to work > once modernised is not going to be a problem as it can be unconditionally > activated in a debug environment. That would verify correct DMA bounce > buffer operation under the new scheme. > > Verifying actual ISA operations (third-party DMA, etc.) cannot be made > this way, but as I understand the issue there is merely with passing data > structures around and that may not require too much attention beyond > getting things syntactically correct, which I gather someone forgot to do > with a change made a while ago. So that should be doable as well. In theory this sounds reasonable, but without being able to test with a real hardware I would be concerned about making this change. > > NB as noted before I only have a BT-958 readily wired for operation. I > don't expect I have any other BusLogic hardware, but I may yet have to > double-check a stash of hardware I have accumulated over the years. But > that is overseas, so I won't be able to get at it before we're at least > somewhat closer to normality. If all else fails I could possibly buy one. > > I have respun the series now as promised. Does your BT-757 adapter avoid > the issue with trailing allocation somehow? > Well, my only test machine with a legacy PCI slot died some time back. I have been working on putting together a replacement and have now been able to get a working machine with a BT-950 adapter. I have not seen issue with trailing allocation upto 5.12-rc8. I am going to try the top of tree as well to make sure I do not run into this issue. -- Khalid
