MdePkg/Include/Protocol/I2cBusConfigurationManagement.h

   1 /** @file
   2   I2C Bus Configuration Management Protocol as defined in the PI 1.3 specification.
   3
   4   The EFI I2C bus configuration management protocol provides platform specific
   5   services that allow the I2C host protocol to reconfigure the switches and multiplexers
   6   and set the clock frequency for the I2C bus. This protocol also enables the I2C host protocol
   7   to reset an I2C device which may be locking up the I2C bus by holding the clock or data line low.
   8
   9   Copyright (c) 2013, Intel Corporation. All rights reserved.<BR>
  10   This program and the accompanying materials
  11   are licensed and made available under the terms and conditions of the BSD License
  12   which accompanies this distribution.  The full text of the license may be found at
  13   http://opensource.org/licenses/bsd-license.php
  14
  15   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  16   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  17
  18   @par Revision Reference:
  19   This protocol is from PI Version 1.3.
  20
  21 **/
  22
  23 #ifndef __I2C_BUS_CONFIGURATION_MANAGEMENT_H__
  24 #define __I2C_BUS_CONFIGURATION_MANAGEMENT_H__
  25
  26 #define EFI_I2C_BUS_CONFIGURATION_MANAGEMENT_PROTOCOL_GUID \
  27   { 0x55b71fb5, 0x17c6, 0x410e, { 0xb5, 0xbd, 0x5f, 0xa2, 0xe3, 0xd4, 0x46, 0x6b }}
  28
  29 ///
  30 /// I2C bus configuration management protocol
  31 ///
  32 /// The EFI I2C bus configuration management protocol provides platform
  33 /// specific services that allow the I2C host protocol to reconfigure the
  34 /// switches and multiplexers and set the clock frequency for the I2C bus.
  35 /// This protocol also enables the I2C host protocol to reset an I2C device
  36 /// which may be locking up the I2C bus by holding the clock or data line
  37 /// low.
  38 ///
  39 /// The I2C protocol stack uses the concept of an I2C bus configuration as
  40 /// a way to describe a particular state of the switches and multiplexers
  41 /// in the I2C bus.
  42 ///
  43 /// A simple I2C bus does not have any multiplexers or switches is described
  44 /// to the I2C protocol stack with a single I2C bus configuration which
  45 /// specifies the I2C bus frequency.
  46 ///
  47 /// An I2C bus with switches and multiplexers use an I2C bus configuration
  48 /// to describe each of the unique settings for the switches and multiplexers
  49 /// and the I2C bus frequency.  However the I2C bus configuration management
  50 /// protocol only needs to define the I2C bus configurations that the software
  51 /// uses, which may be a subset of the total.
  52 ///
  53 /// The I2C bus configuration description includes a list of I2C devices
  54 /// which may be accessed when this I2C bus configuration is enabled.  I2C
  55 /// devices before a switch or multiplexer must be included in one I2C bus
  56 /// configuration while I2C devices after a switch or multiplexer are on
  57 /// another I2C bus configuration.
  58 ///
  59 /// The I2C bus configuration management protocol is an optional protocol.
  60 /// When the I2C bus configuration protocol is not defined the I2C host
  61 /// protocol does not start and the I2C master protocol may be used for
  62 /// other purposes such as SMBus traffic.  When the I2C bus configuration
  63 /// protocol is available, the I2C host protocol uses the I2C bus
  64 /// configuration protocol to call into the platform specific code to set
  65 /// the switches and multiplexers and set the maximum I2C bus frequency.
  66 ///
  67 /// The platform designers determine the maximum I2C bus frequency by
  68 /// selecting a frequency which supports all of the I2C devices on the
  69 /// I2C bus for the setting of switches and multiplexers.  The platform
  70 /// designers must validate this against the I2C device data sheets and
  71 /// any limits of the I2C controller or bus length.
  72 ///
  73 /// During I2C device enumeration, the I2C bus driver retrieves the I2C
  74 /// bus configuration that must be used to perform I2C transactions to
  75 /// each I2C device.  This I2C bus configuration value is passed into
  76 /// the I2C host protocol to identify the I2C bus configuration required
  77 /// to access a specific I2C device.  The I2C host protocol calls
  78 /// EnableBusConfiguration() to set the switches and multiplexers in the
  79 /// I2C bus and the I2C clock frequency.  The I2C host protocol may
  80 /// optimize calls to EnableBusConfiguration() by only making the call
  81 /// when the I2C bus configuration value changes between I2C requests.
  82 ///
  83 /// When I2C transactions are required on the same I2C bus to change the
  84 /// state of multiplexers or switches, the I2C master protocol must be
  85 /// used to perform the necessary I2C transactions.
  86 ///
  87 /// It is up to the platform specific code to choose the proper I2C bus
  88 /// configuration when ExitBootServices() is called. Some operating systems
  89 /// are not able to manage the I2C bus configurations and must use the I2C
  90 /// bus configuration that is established by the platform firmware before
  91 /// ExitBootServices() returns.
  92 ///
  93 typedef struct _EFI_I2C_BUS_CONFIGURATION_MANAGEMENT_PROTOCOL EFI_I2C_BUS_CONFIGURATION_MANAGEMENT_PROTOCOL;
  94
  95
  96 /**
  97   Enable access to an I2C bus configuration.
  98
  99   This routine must be called at or below TPL_NOTIFY.  For synchronous
 100   requests this routine must be called at or below TPL_CALLBACK.
 101
 102   Reconfigure the switches and multiplexers in the I2C bus to enable
 103   access to a specific I2C bus configuration.  Also select the maximum
 104   clock frequency for this I2C bus configuration.
 105
 106   This routine uses the I2C Master protocol to perform I2C transactions
 107   on the local bus.  This eliminates any recursion in the I2C stack for
 108   configuration transactions on the same I2C bus.  This works because the
 109   local I2C bus is idle while the I2C bus configuration is being enabled.
 110
 111   If I2C transactions must be performed on other I2C busses, then the
 112   EFI_I2C_HOST_PROTOCOL, the EFI_I2C_IO_PROTCOL, or a third party I2C
 113   driver interface for a specific device must be used.  This requirement
 114   is because the I2C host protocol controls the flow of requests to the
 115   I2C controller.  Use the EFI_I2C_HOST_PROTOCOL when the I2C device is
 116   not enumerated by the EFI_I2C_ENUMERATE_PROTOCOL.  Use a protocol
 117   produced by a third party driver when it is available or the
 118   EFI_I2C_IO_PROTOCOL when the third party driver is not available but
 119   the device is enumerated with the EFI_I2C_ENUMERATE_PROTOCOL.
 120
 121   When Event is NULL, EnableI2cBusConfiguration operates synchronously
 122   and returns the I2C completion status as its return value.
 123
 124   @param[in]  This            Pointer to an EFI_I2C_BUS_CONFIGURATION_MANAGEMENT_PROTOCOL
 125                               structure.
 126   @param[in]  I2cBusConfiguration Index of an I2C bus configuration.  All
 127                                   values in the range of zero to N-1 are
 128                                   valid where N is the total number of I2C
 129                                   bus configurations for an I2C bus.
 130   @param[in]  Event           Event to signal when the transaction is complete
 131   @param[out] I2cStatus       Buffer to receive the transaction status.
 132
 133   @return  When Event is NULL, EnableI2cBusConfiguration operates synchrouously
 134   and returns the I2C completion status as its return value.  In this case it is
 135   recommended to use NULL for I2cStatus.  The values returned from
 136   EnableI2cBusConfiguration are:
 137
 138   @retval EFI_SUCCESS           The asynchronous bus configuration request
 139                                 was successfully started when Event is not
 140                                 NULL.
 141   @retval EFI_SUCCESS           The bus configuration request completed
 142                                 successfully when Event is NULL.
 143   @retval EFI_DEVICE_ERROR      The bus configuration failed.
 144   @retval EFI_NO_MAPPING        Invalid I2cBusConfiguration value
 145
 146 **/
 147 typedef
 148 EFI_STATUS
 149 (EFIAPI *EFI_I2C_BUS_CONFIGURATION_MANAGEMENT_PROTOCOL_ENABLE_I2C_BUS_CONFIGURATION) (
 150   IN CONST EFI_I2C_BUS_CONFIGURATION_MANAGEMENT_PROTOCOL *This,
 151   IN UINTN                                               I2cBusConfiguration,
 152   IN EFI_EVENT                                           Event      OPTIONAL,
 153   IN EFI_STATUS                                          *I2cStatus OPTIONAL
 154   );
 155
 156 ///
 157 /// I2C bus configuration management protocol
 158 ///
 159 struct _EFI_I2C_BUS_CONFIGURATION_MANAGEMENT_PROTOCOL {
 160   ///
 161   /// Enable an I2C bus configuration for use.
 162   ///
 163   EFI_I2C_BUS_CONFIGURATION_MANAGEMENT_PROTOCOL_ENABLE_I2C_BUS_CONFIGURATION EnableI2cBusConfiguration;
 164 };
 165
 166 ///
 167 /// Reference to variable defined in the .DEC file
 168 ///
 169 extern EFI_GUID gEfiI2cBusConfigurationManagementProtocolGuid;
 170
 171 #endif  //  __I2C_BUS_CONFIGURATION_MANAGEMENT_H__