Documentation: Minor changes to men-chameleon-bus.txt
Change men-chameleon-bus.txt according to the comments made by Randy Dunlap in https://lkml.org/lkml/2015/7/17/691. These are: * Some minor gramatical changes * Spelling fixes * Write the word "Chameleon" capitalized throughout the whole document * Explain MEN as MEN Mikro Elektronik GmbH. Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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@ -13,7 +13,7 @@ Table of Contents
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3 Resource handling
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3.1 Memory Resources
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3.2 IRQs
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4 Writing a MCB driver
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4 Writing an MCB driver
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4.1 The driver structure
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4.2 Probing and attaching
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4.3 Initializing the driver
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1.1 Scope of this Document
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---------------------------
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This document is intended to be a short overview of the current
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implementation and does by no means describe to complete possibilities of MCB
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implementation and does by no means describe the complete possibilities of MCB
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based devices.
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1.2 Limitations of the current implementation
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2 Architecture
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===============
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MCB is divided in 3 functional blocks:
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MCB is divided into 3 functional blocks:
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- The MEN Chameleon Bus itself,
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- drivers for MCB Carrier Devices and
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- the parser for the Chameleon table.
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2.1 MEN Chameleon Bus
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----------------------
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The MEN Chameleon Bus is an artificial bus system that attaches to an MEN
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Chameleon FPGA device. These devices are multi-function devices implemented
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in a single FPGA and usually attached via some sort of PCI or PCIe link. Each
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FPGA contains a header section describing the content of the FPGA. The header
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lists the device id, PCI BAR, offset from the beginning of the PCI BAR, size
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in the FPGA, interrupt number and some other properties currently not handled
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by the MCB implementation.
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The MEN Chameleon Bus is an artificial bus system that attaches to a so
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called Chameleon FPGA device found on some hardware produced my MEN Mikro
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Elektronik GmbH. These devices are multi-function devices implemented in a
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single FPGA and usually attached via some sort of PCI or PCIe link. Each
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FPGA contains a header section describing the content of the FPGA. The
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header lists the device id, PCI BAR, offset from the beginning of the PCI
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BAR, size in the FPGA, interrupt number and some other properties currently
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not handled by the MCB implementation.
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2.2 Carrier Devices
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--------------------
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A carrier device is just an abstraction for the real world physical bus the
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chameleon FPGA is attached to. Some IP Core drivers may need to interact with
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Chameleon FPGA is attached to. Some IP Core drivers may need to interact with
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properties of the carrier device (like querying the IRQ number of a PCI
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device). To provide abstraction from the real hardware bus, an MCB carrier
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device provides callback methods to translate the driver's MCB function calls
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to hardware related function calls. For example a carrier device may
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implement the get_irq() method which can be translate into a hardware bus
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implement the get_irq() method which can be translated into a hardware bus
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query for the IRQ number the device should use.
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2.3 Parser
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-----------
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The parser reads the 1st 512 bytes of a chameleon device and parses the
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chameleon table. Currently the parser only supports the Chameleon v2 variant
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of the chameleon table but can easily be adopted to support an older or
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The parser reads the first 512 bytes of a Chameleon device and parses the
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Chameleon table. Currently the parser only supports the Chameleon v2 variant
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of the Chameleon table but can easily be adopted to support an older or
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possible future variant. While parsing the table's entries new MCB devices
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are allocated and their resources are assigned according to the resource
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assignment in the chameleon table. After resource assignment is finished, the
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assignment in the Chameleon table. After resource assignment is finished, the
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MCB devices are registered at the MCB and thus at the driver core of the
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Linux kernel.
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Each MCB device has exactly one IRQ resource, which can be requested from the
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MCB bus. If a carrier device driver implements the ->get_irq() callback
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method, the IRQ number assigned by the carrier device will be returned,
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otherwise the IRQ number inside the chameleon table will be returned. This
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otherwise the IRQ number inside the Chameleon table will be returned. This
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number is suitable to be passed to request_irq().
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4 Writing a MCB driver
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4 Writing an MCB driver
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=======================
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4.1 The driver structure
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-------------------------
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Each MCB driver has a structure to identify the device driver as well as
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device ids which identify the IP Core inside the FPGA. The driver structure
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also contaings callback methods which get executed on driver probe and
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also contains callback methods which get executed on driver probe and
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removal from the system.
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