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105 lines
2.9 KiB
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105 lines
2.9 KiB
Plaintext
========================================
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Writing Device Drivers for Zorro Devices
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========================================
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:Author: Written by Geert Uytterhoeven <geert@linux-m68k.org>
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:Last revised: September 5, 2003
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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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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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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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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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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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