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166 lines
8.1 KiB
C
166 lines
8.1 KiB
C
/** @file
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I2C Bus Configuration Management Protocol as defined in the PI 1.3 specification.
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The EFI I2C bus configuration management protocol provides platform specific
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services that allow the I2C host protocol to reconfigure the switches and multiplexers
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and set the clock frequency for the I2C bus. This protocol also enables the I2C host protocol
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to reset an I2C device which may be locking up the I2C bus by holding the clock or data line low.
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Copyright (c) 2013 - 2018, Intel Corporation. All rights reserved.<BR>
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SPDX-License-Identifier: BSD-2-Clause-Patent
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@par Revision Reference:
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This protocol is from PI Version 1.3.
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**/
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#ifndef __I2C_BUS_CONFIGURATION_MANAGEMENT_H__
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#define __I2C_BUS_CONFIGURATION_MANAGEMENT_H__
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#define EFI_I2C_BUS_CONFIGURATION_MANAGEMENT_PROTOCOL_GUID \
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{ 0x55b71fb5, 0x17c6, 0x410e, { 0xb5, 0xbd, 0x5f, 0xa2, 0xe3, 0xd4, 0x46, 0x6b }}
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///
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/// I2C bus configuration management protocol
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///
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/// The EFI I2C bus configuration management protocol provides platform
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/// specific services that allow the I2C host protocol to reconfigure the
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/// switches and multiplexers and set the clock frequency for the I2C bus.
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/// This protocol also enables the I2C host protocol to reset an I2C device
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/// which may be locking up the I2C bus by holding the clock or data line
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/// low.
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///
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/// The I2C protocol stack uses the concept of an I2C bus configuration as
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/// a way to describe a particular state of the switches and multiplexers
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/// in the I2C bus.
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///
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/// A simple I2C bus does not have any multiplexers or switches is described
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/// to the I2C protocol stack with a single I2C bus configuration which
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/// specifies the I2C bus frequency.
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///
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/// An I2C bus with switches and multiplexers use an I2C bus configuration
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/// to describe each of the unique settings for the switches and multiplexers
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/// and the I2C bus frequency. However the I2C bus configuration management
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/// protocol only needs to define the I2C bus configurations that the software
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/// uses, which may be a subset of the total.
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///
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/// The I2C bus configuration description includes a list of I2C devices
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/// which may be accessed when this I2C bus configuration is enabled. I2C
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/// devices before a switch or multiplexer must be included in one I2C bus
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/// configuration while I2C devices after a switch or multiplexer are on
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/// another I2C bus configuration.
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///
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/// The I2C bus configuration management protocol is an optional protocol.
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/// When the I2C bus configuration protocol is not defined the I2C host
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/// protocol does not start and the I2C master protocol may be used for
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/// other purposes such as SMBus traffic. When the I2C bus configuration
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/// protocol is available, the I2C host protocol uses the I2C bus
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/// configuration protocol to call into the platform specific code to set
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/// the switches and multiplexers and set the maximum I2C bus frequency.
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///
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/// The platform designers determine the maximum I2C bus frequency by
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/// selecting a frequency which supports all of the I2C devices on the
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/// I2C bus for the setting of switches and multiplexers. The platform
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/// designers must validate this against the I2C device data sheets and
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/// any limits of the I2C controller or bus length.
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///
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/// During I2C device enumeration, the I2C bus driver retrieves the I2C
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/// bus configuration that must be used to perform I2C transactions to
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/// each I2C device. This I2C bus configuration value is passed into
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/// the I2C host protocol to identify the I2C bus configuration required
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/// to access a specific I2C device. The I2C host protocol calls
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/// EnableBusConfiguration() to set the switches and multiplexers in the
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/// I2C bus and the I2C clock frequency. The I2C host protocol may
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/// optimize calls to EnableBusConfiguration() by only making the call
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/// when the I2C bus configuration value changes between I2C requests.
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///
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/// When I2C transactions are required on the same I2C bus to change the
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/// state of multiplexers or switches, the I2C master protocol must be
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/// used to perform the necessary I2C transactions.
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///
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/// It is up to the platform specific code to choose the proper I2C bus
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/// configuration when ExitBootServices() is called. Some operating systems
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/// are not able to manage the I2C bus configurations and must use the I2C
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/// bus configuration that is established by the platform firmware before
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/// ExitBootServices() returns.
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///
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typedef struct _EFI_I2C_BUS_CONFIGURATION_MANAGEMENT_PROTOCOL EFI_I2C_BUS_CONFIGURATION_MANAGEMENT_PROTOCOL;
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/**
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Enable access to an I2C bus configuration.
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This routine must be called at or below TPL_NOTIFY. For synchronous
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requests this routine must be called at or below TPL_CALLBACK.
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Reconfigure the switches and multiplexers in the I2C bus to enable
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access to a specific I2C bus configuration. Also select the maximum
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clock frequency for this I2C bus configuration.
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This routine uses the I2C Master protocol to perform I2C transactions
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on the local bus. This eliminates any recursion in the I2C stack for
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configuration transactions on the same I2C bus. This works because the
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local I2C bus is idle while the I2C bus configuration is being enabled.
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If I2C transactions must be performed on other I2C busses, then the
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EFI_I2C_HOST_PROTOCOL, the EFI_I2C_IO_PROTCOL, or a third party I2C
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driver interface for a specific device must be used. This requirement
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is because the I2C host protocol controls the flow of requests to the
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I2C controller. Use the EFI_I2C_HOST_PROTOCOL when the I2C device is
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not enumerated by the EFI_I2C_ENUMERATE_PROTOCOL. Use a protocol
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produced by a third party driver when it is available or the
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EFI_I2C_IO_PROTOCOL when the third party driver is not available but
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the device is enumerated with the EFI_I2C_ENUMERATE_PROTOCOL.
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When Event is NULL, EnableI2cBusConfiguration operates synchronously
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and returns the I2C completion status as its return value.
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@param[in] This Pointer to an EFI_I2C_BUS_CONFIGURATION_MANAGEMENT_PROTOCOL
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structure.
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@param[in] I2cBusConfiguration Index of an I2C bus configuration. All
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values in the range of zero to N-1 are
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valid where N is the total number of I2C
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bus configurations for an I2C bus.
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@param[in] Event Event to signal when the transaction is complete
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@param[out] I2cStatus Buffer to receive the transaction status.
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@return When Event is NULL, EnableI2cBusConfiguration operates synchrouously
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and returns the I2C completion status as its return value. In this case it is
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recommended to use NULL for I2cStatus. The values returned from
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EnableI2cBusConfiguration are:
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@retval EFI_SUCCESS The asynchronous bus configuration request
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was successfully started when Event is not
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NULL.
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@retval EFI_SUCCESS The bus configuration request completed
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successfully when Event is NULL.
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@retval EFI_DEVICE_ERROR The bus configuration failed.
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@retval EFI_NO_MAPPING Invalid I2cBusConfiguration value
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**/
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typedef
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EFI_STATUS
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(EFIAPI *EFI_I2C_BUS_CONFIGURATION_MANAGEMENT_PROTOCOL_ENABLE_I2C_BUS_CONFIGURATION) (
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IN CONST EFI_I2C_BUS_CONFIGURATION_MANAGEMENT_PROTOCOL *This,
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IN UINTN I2cBusConfiguration,
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IN EFI_EVENT Event OPTIONAL,
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IN EFI_STATUS *I2cStatus OPTIONAL
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);
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///
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/// I2C bus configuration management protocol
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///
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struct _EFI_I2C_BUS_CONFIGURATION_MANAGEMENT_PROTOCOL {
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///
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/// Enable an I2C bus configuration for use.
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///
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EFI_I2C_BUS_CONFIGURATION_MANAGEMENT_PROTOCOL_ENABLE_I2C_BUS_CONFIGURATION EnableI2cBusConfiguration;
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};
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///
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/// Reference to variable defined in the .DEC file
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///
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extern EFI_GUID gEfiI2cBusConfigurationManagementProtocolGuid;
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#endif // __I2C_BUS_CONFIGURATION_MANAGEMENT_H__
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