OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.c

   1 /** @file
   2   Xen console SerialPortLib instance
   3
   4   Copyright (c) 2015, Linaro Ltd. All rights reserved.<BR>
   5
   6   This program and the accompanying materials
   7   are licensed and made available under the terms and conditions of the BSD License
   8   which accompanies this distribution.  The full text of the license may be found at
   9   http://opensource.org/licenses/bsd-license.php
  10
  11   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  12   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  13
  14 **/
  15
  16 #include <Base.h>
  17 #include <Uefi/UefiBaseType.h>
  18
  19 #include <Library/BaseLib.h>
  20 #include <Library/SerialPortLib.h>
  21 #include <Library/XenHypercallLib.h>
  22
  23 #include <IndustryStandard/Xen/io/console.h>
  24 #include <IndustryStandard/Xen/hvm/params.h>
  25 #include <IndustryStandard/Xen/event_channel.h>
  26
  27 //
  28 // We can't use DebugLib due to a constructor dependency cycle between DebugLib
  29 // and ourselves.
  30 //
  31 #define ASSERT(Expression)      \
  32   do {                          \
  33     if (!(Expression)) {        \
  34       CpuDeadLoop ();           \
  35     }                           \
  36   } while (FALSE)
  37
  38 //
  39 // The code below expects these global variables to be mutable, even in the case
  40 // that we have been incorporated into SEC or PEIM phase modules (which is
  41 // allowed by our INF description). While this is a dangerous assumption to make
  42 // in general, it is actually fine for the Xen domU (guest) environment that
  43 // this module is intended for, as UEFI always executes from DRAM in that case.
  44 //
  45 STATIC evtchn_send_t              mXenConsoleEventChain;
  46 STATIC struct xencons_interface   *mXenConsoleInterface;
  47
  48 /**
  49   Initialize the serial device hardware.
  50
  51   If no initialization is required, then return RETURN_SUCCESS.
  52   If the serial device was successfully initialized, then return RETURN_SUCCESS.
  53   If the serial device could not be initialized, then return RETURN_DEVICE_ERROR.
  54
  55   @retval RETURN_SUCCESS        The serial device was initialized.
  56   @retval RETURN_DEVICE_ERROR   The serial device could not be initialized.
  57
  58 **/
  59 RETURN_STATUS
  60 EFIAPI
  61 SerialPortInitialize (
  62   VOID
  63   )
  64 {
  65   if (! XenHypercallIsAvailable ()) {
  66     return RETURN_DEVICE_ERROR;
  67   }
  68
  69   if (!mXenConsoleInterface) {
  70     mXenConsoleEventChain.port = (UINT32)XenHypercallHvmGetParam (HVM_PARAM_CONSOLE_EVTCHN);
  71     mXenConsoleInterface = (struct xencons_interface *)(UINTN)
  72       (XenHypercallHvmGetParam (HVM_PARAM_CONSOLE_PFN) << EFI_PAGE_SHIFT);
  73
  74     //
  75     // No point in ASSERT'ing here as we won't be seeing the output
  76     //
  77   }
  78   return RETURN_SUCCESS;
  79 }
  80
  81 /**
  82   Write data from buffer to serial device.
  83
  84   Writes NumberOfBytes data bytes from Buffer to the serial device.
  85   The number of bytes actually written to the serial device is returned.
  86   If the return value is less than NumberOfBytes, then the write operation failed.
  87   If Buffer is NULL, then ASSERT().
  88   If NumberOfBytes is zero, then return 0.
  89
  90   @param  Buffer           Pointer to the data buffer to be written.
  91   @param  NumberOfBytes    Number of bytes to written to the serial device.
  92
  93   @retval 0                NumberOfBytes is 0.
  94   @retval >0               The number of bytes written to the serial device.
  95                            If this value is less than NumberOfBytes, then the write operation failed.
  96
  97 **/
  98 UINTN
  99 EFIAPI
 100 SerialPortWrite (
 101   IN UINT8     *Buffer,
 102   IN UINTN     NumberOfBytes
 103   )
 104 {
 105   XENCONS_RING_IDX  Consumer, Producer;
 106   UINTN             Sent;
 107
 108   ASSERT (Buffer != NULL);
 109
 110   if (NumberOfBytes == 0) {
 111     return 0;
 112   }
 113
 114   if (!mXenConsoleInterface) {
 115     return 0;
 116   }
 117
 118   Sent = 0;
 119   do {
 120     Consumer = mXenConsoleInterface->out_cons;
 121     Producer = mXenConsoleInterface->out_prod;
 122
 123     MemoryFence ();
 124
 125     while (Sent < NumberOfBytes && ((Producer - Consumer) < sizeof (mXenConsoleInterface->out)))
 126       mXenConsoleInterface->out[MASK_XENCONS_IDX(Producer++, mXenConsoleInterface->out)] = Buffer[Sent++];
 127
 128     MemoryFence ();
 129
 130     mXenConsoleInterface->out_prod = Producer;
 131
 132     XenHypercallEventChannelOp (EVTCHNOP_send, &mXenConsoleEventChain);
 133
 134   } while (Sent < NumberOfBytes);
 135
 136   return Sent;
 137 }
 138
 139 /**
 140   Read data from serial device and save the datas in buffer.
 141
 142   Reads NumberOfBytes data bytes from a serial device into the buffer
 143   specified by Buffer. The number of bytes actually read is returned.
 144   If Buffer is NULL, then ASSERT().
 145   If NumberOfBytes is zero, then return 0.
 146
 147   @param  Buffer           Pointer to the data buffer to store the data read from the serial device.
 148   @param  NumberOfBytes    Number of bytes which will be read.
 149
 150   @retval 0                Read data failed, no data is to be read.
 151   @retval >0               Actual number of bytes read from serial device.
 152
 153 **/
 154 UINTN
 155 EFIAPI
 156 SerialPortRead (
 157   OUT UINT8     *Buffer,
 158   IN  UINTN     NumberOfBytes
 159 )
 160 {
 161   XENCONS_RING_IDX  Consumer, Producer;
 162   UINTN             Received;
 163
 164   ASSERT (Buffer != NULL);
 165
 166   if (NumberOfBytes == 0) {
 167     return 0;
 168   }
 169
 170   if (!mXenConsoleInterface) {
 171     return 0;
 172   }
 173
 174   Consumer = mXenConsoleInterface->in_cons;
 175   Producer = mXenConsoleInterface->in_prod;
 176
 177   MemoryFence ();
 178
 179   Received = 0;
 180   while (Received < NumberOfBytes && Consumer < Producer)
 181      Buffer[Received++] = mXenConsoleInterface->in[MASK_XENCONS_IDX(Consumer++, mXenConsoleInterface->in)];
 182
 183   MemoryFence ();
 184
 185   mXenConsoleInterface->in_cons = Consumer;
 186
 187   XenHypercallEventChannelOp (EVTCHNOP_send, &mXenConsoleEventChain);
 188
 189   return Received;
 190 }
 191
 192 /**
 193   Polls a serial device to see if there is any data waiting to be read.
 194
 195   @retval TRUE             Data is waiting to be read from the serial device.
 196   @retval FALSE            There is no data waiting to be read from the serial device.
 197
 198 **/
 199 BOOLEAN
 200 EFIAPI
 201 SerialPortPoll (
 202   VOID
 203   )
 204 {
 205   return mXenConsoleInterface &&
 206     mXenConsoleInterface->in_cons != mXenConsoleInterface->in_prod;
 207 }