The address that starts with 0x801.... is a physical address and from within the kernel you need to use a virtual address.. If memory serves the devices are mapped at 0xffffd... ,but I can't remember how many bits that corresponds to of the physical address. You should be able to find that in either the dec tsunami documentation or by looking at how the kernel generates an address for the frame buffer device.
Ali On Jun 28, 2011, at 5:53 PM, Alex Edwards wrote: > Great, I will do so. > > As far as trying to trigger the read() function for the device goes, I have > been trying to use an inb() command from the kernel. However, I am not sure > I have the address mapping right. > > I see in /m5/srv/dev/alpha/Tsunami.py:87 that there is already an instance of > a BadDevice as the frame buffer pointer in the Tsunami platform. > > ... > fb = BadDevice(pio_addr=0x801fc0003d0, devicename='FrameBuffer') > ... > > Is there a simple way to trigger the read() function of this frame buffer > BadDevice device? I am trying a simple inb(0x801fc0003d0) from the kernel, > but it seems to cause the OS to hang. > > Thanks again, > Alex Edwards > > > > On Mon, Jun 27, 2011 at 7:20 PM, Ali Saidi <[email protected]> wrote: > You can take a look at the DEC Tsunami documentation and find an address that > is unassigned. > > Ali > > On Jun 27, 2011, at 5:00 PM, Alex Edwards wrote: > > > Hi All, > > > > I am trying to add a simple simple BadDevice device to the ALPHA_FS system, > > but I am not sure what pio_addr to specify in FSConfig.py. > > > > I am going to use BadDevice as a model for a really really simple "read > > from a register"/"write to a register" device, so it seemed like starting > > with the basic BadDevice model that simply panics upon attempting > > read/write was a good start. > > > > Is there a given address range that is unused in the ALPHA_FS system in > > gem5? How should I choose this pio_addr value? I will only need to be > > accessing this "device" from kernel space, so I was hoping to simply > > inb(pio_addr) and that this would cause a panic? > > > > Further, when specifying pio_addr, it must be a physical address, right? > > Thus, I'll need to know its corresponding virtual address when trying to > > read from the "device" in the linux kernel? Or is there some section of > > memory in ALPHA_FS that is an identity mapping when doing address > > translation? Anyone know? > > > > > > Thanks much, > > > > Alex > > _______________________________________________ > > gem5-users mailing list > > [email protected] > > http://m5sim.org/cgi-bin/mailman/listinfo/gem5-users > > _______________________________________________ > gem5-users mailing list > [email protected] > http://m5sim.org/cgi-bin/mailman/listinfo/gem5-users > > _______________________________________________ > gem5-users mailing list > [email protected] > http://m5sim.org/cgi-bin/mailman/listinfo/gem5-users
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