Messages in this thread | | | Date | Sat, 17 Apr 1999 15:04:04 +0200 (MET DST) | From | Gerard Roudier <> | Subject | Re: Weird PCI problem |
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On Sat, 17 Apr 1999, Rogier Wolff wrote:
> Gerard Roudier wrote: > > If you can do that, then, I will recommend you to do at least: > > > > - Read this base address register > > - Warn if any of bit 1, 2 or 3 is set. > > - Mask all the bits that should have read zero (bit 0,1,2,3) > > - Rewrite this base address register > > - Read it again and warn if any bit 0, 1, 2 or 3 is still set. > > In my opinion that last one should be "bail out if any of the > addressing type bits is still set".
Indeed. It was just a minimal recommendation against just silently trying to clear the offending bits. I didn't encourage to let the driver blindly attach the device and tamper the address as a memory mapped address. I obviously assumed this not to happen if the last read of the bits returned wrong values.
> The PLX (which I understand is the PCI bridge for the card) is capable > of mapping stuff into IO space as well as into memory space. It will > simply do whatever the bit is set at. You're supposed to program the > eeprom in such a way that the bit becomes read-only, but it is > certainly writeable in hardware, and the device will honour whatever > it is set at. > > Telling the chip you want a 64k IOmapped window is probably going to > crash the machine sooner or later.
If this window does not conflict and no driver will tamper the window and the chip hasn't exploded at the time this bit 0 has been set, then nothing bad should happen when attempting to clear this bit 0, in my opinion. :-)
Regards, Gérard.
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