Messages in this thread | | | Date | Fri, 25 Jan 2002 13:43:27 -0500 (EST) | From | "Richard B. Johnson" <> | Subject | Re: PCI #LOCK assertion |
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On Fri, 25 Jan 2002, chus Medina wrote:
> > Hola, > > I need to create module to perform atomic transactions through the PCI bus > between the processor and an IDE hard disk. The PCI bus specifications 2.2 > point to the #LOCK signal to perform such a transaction. Is possible to > assert the #LOCK signal of the PCI bus using the Linux Kernel? How? I didnt > see any pointers in include/pci.h or anywhere in the source code. > > I will truly appreciate any help/pointers, > > Jesus >
On Intel machines, you precede a memory access with the 'lock' instruction. With CPUs i486, and later, only the accessed page is locked at that instant. Earlier CPUs locked the whole bus.
The PCI/Bus controller handles the #LOCK signal itself to guarantee the atomicity of a transaction. You should never have to do this yourself. If you think you have to, just precede each PCI/Bus address-space access with the 'lock' instruction. You just make your own version of the readl/readw/readb/etc macros that are provided. You may find that this deadlocks, though, and all bets are off. You may have just locked the PCI/Bus off the bus when you needed it most!!
If you are finding something 'strange' in your PCI/Bus accesses, it is probably because you didn't use 'nocache' when you obtained address-space for your PCI Device, i.e., ioremap_nocache() instead of ioremap().
Cheers, Dick Johnson
Penguin : Linux version 2.4.1 on an i686 machine (797.90 BogoMips).
I was going to compile a list of innovations that could be attributed to Microsoft. Once I realized that Ctrl-Alt-Del was handled in the BIOS, I found that there aren't any.
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