9bb0e9cb04
This commit gets rid of some minor errors in Documentation/: * cputopology.txt: drawes -> drawers * debugging-via-ohci1394.txt: remove an unnecessary line break * static-keys: statemnts -> statements * zorro.txt: busses -> buses Signed-off-by: Stan Drozd <drozdziak1@gmail.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
103 lines
2.9 KiB
Text
103 lines
2.9 KiB
Text
Writing Device Drivers for Zorro Devices
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----------------------------------------
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Written by Geert Uytterhoeven <geert@linux-m68k.org>
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Last revised: September 5, 2003
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1. Introduction
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---------------
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The Zorro bus is the bus used in the Amiga family of computers. Thanks to
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AutoConfig(tm), it's 100% Plug-and-Play.
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There are two types of Zorro buses, Zorro II and Zorro III:
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- The Zorro II address space is 24-bit and lies within the first 16 MB of the
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Amiga's address map.
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- Zorro III is a 32-bit extension of Zorro II, which is backwards compatible
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with Zorro II. The Zorro III address space lies outside the first 16 MB.
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2. Probing for Zorro Devices
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----------------------------
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Zorro devices are found by calling `zorro_find_device()', which returns a
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pointer to the `next' Zorro device with the specified Zorro ID. A probe loop
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for the board with Zorro ID `ZORRO_PROD_xxx' looks like:
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struct zorro_dev *z = NULL;
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while ((z = zorro_find_device(ZORRO_PROD_xxx, z))) {
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if (!zorro_request_region(z->resource.start+MY_START, MY_SIZE,
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"My explanation"))
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...
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}
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`ZORRO_WILDCARD' acts as a wildcard and finds any Zorro device. If your driver
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supports different types of boards, you can use a construct like:
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struct zorro_dev *z = NULL;
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while ((z = zorro_find_device(ZORRO_WILDCARD, z))) {
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if (z->id != ZORRO_PROD_xxx1 && z->id != ZORRO_PROD_xxx2 && ...)
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continue;
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if (!zorro_request_region(z->resource.start+MY_START, MY_SIZE,
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"My explanation"))
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...
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}
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3. Zorro Resources
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------------------
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Before you can access a Zorro device's registers, you have to make sure it's
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not yet in use. This is done using the I/O memory space resource management
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functions:
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request_mem_region()
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release_mem_region()
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Shortcuts to claim the whole device's address space are provided as well:
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zorro_request_device
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zorro_release_device
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4. Accessing the Zorro Address Space
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------------------------------------
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The address regions in the Zorro device resources are Zorro bus address
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regions. Due to the identity bus-physical address mapping on the Zorro bus,
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they are CPU physical addresses as well.
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The treatment of these regions depends on the type of Zorro space:
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- Zorro II address space is always mapped and does not have to be mapped
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explicitly using z_ioremap().
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Conversion from bus/physical Zorro II addresses to kernel virtual addresses
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and vice versa is done using:
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virt_addr = ZTWO_VADDR(bus_addr);
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bus_addr = ZTWO_PADDR(virt_addr);
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- Zorro III address space must be mapped explicitly using z_ioremap() first
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before it can be accessed:
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virt_addr = z_ioremap(bus_addr, size);
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...
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z_iounmap(virt_addr);
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5. References
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-------------
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linux/include/linux/zorro.h
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linux/include/uapi/linux/zorro.h
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linux/include/uapi/linux/zorro_ids.h
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linux/arch/m68k/include/asm/zorro.h
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linux/drivers/zorro
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/proc/bus/zorro
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