lib/cportlib/cport.c

   1 /*
   2  * PROJECT:         ReactOS ComPort Library
   3  * LICENSE:         BSD - See COPYING.ARM in the top level directory
   4  * FILE:            lib/reactos/cportlib/cport.c
   5  * PURPOSE:         Provides a serial port library for KDCOM, INIT, and FREELDR
   6  * PROGRAMMERS:     ReactOS Portable Systems Group
   7  */
   8
   9 /* NOTE: This library follows the precise serial port intialization steps documented
  10  * by Microsoft in some of their Server hardware guidance. Because they've clearly
  11  * documented their serial algorithms, we use the same ones to stay "compliant".
  12  * Do not change this code to "improve" it. It's done this way on purpose, at least on x86.
  13  * -- sir_richard
  14  */
  15
  16 /* NOTE: This code is used by Headless Support (Ntoskrnl.exe and Osloader.exe) and
  17    Kdcom.dll in Windows. It may be that WinDBG depends on some of these quirks.
  18 */
  19
  20 /* NOTE: The original code supports Modem Control. We currently do not */
  21
  22 /* FIXMEs:
  23         - Make this serial-port specific (NS16550 vs other serial port types)
  24         - Get x64 KDCOM, KDBG, FREELDR, and other current code to use this
  25 */
  26
  27 /* INCLUDES *******************************************************************/
  28
  29 #include <cportlib/cportlib.h>
  30 #include <drivers/serial/ns16550.h>
  31 #include <intrin.h>
  32 #include <ioaccess.h>
  33 #include <debug.h>
  34
  35 /* GLOBALS ********************************************************************/
  36
  37 UCHAR RingIndicator;
  38
  39 /* FUNCTIONS ******************************************************************/
  40
  41 VOID
  42 NTAPI
  43 CpInitialize(IN PCPPORT Port,
  44                          IN PUCHAR Address,
  45                          IN ULONG Rate)
  46 {
  47         /* Reset port data */
  48     Port->Address = Address;
  49     Port->Baud = 0;
  50
  51         /* Set the baud rate */
  52     CpSetBaud(Port, Rate);
  53
  54     /* Enable on DTR and RTS  */
  55     WRITE_PORT_UCHAR(Address + MODEM_CONTROL_REGISTER,
  56                                          SERIAL_MCR_DTR | SERIAL_MCR_RTS);
  57
  58     /* Disable interrupts */
  59     WRITE_PORT_UCHAR(Address + INTERRUPT_ENABLE_REGISTER, 0);
  60 }
  61
  62 VOID
  63 NTAPI
  64 CpEnableFifo(IN PUCHAR Address,
  65                  IN BOOLEAN Enable)
  66 {
  67         /* Set FIFO */
  68     WRITE_PORT_UCHAR(Address + FIFO_CONTROL_REGISTER, Enable ? SERIAL_FCR_ENABLE : 0);
  69 }
  70
  71 BOOLEAN
  72 NTAPI
  73 CpDoesPortExist(IN PUCHAR Address)
  74 {
  75     UCHAR Old;
  76         /*
  77          * See "Building Hardware and Firmware to Complement Microsoft Windows Headless Operation"
  78          * Out-of-Band Management Port Device Requirements:
  79          * The device must act as a 16550 or 16450 UART.
  80          * Windows Server 2003 will test this device using the following process.
  81          *      1. Save off the current modem status register.
  82          *      2. Place the UART into diagnostic mode (The UART is placed into loopback mode
  83          *         by writing SERIAL_MCR_LOOP to the modem control register).
  84          *      3. The modem status register is read and the high bits are checked. This means
  85          *         SERIAL_MSR_CTS, SERIAL_MSR_DSR, SERIAL_MSR_RI and SERIAL_MSR_DCD should
  86          *      all be clear.
  87          *      4. Place the UART in diagnostic mode and turn on OUTPUT (Loopback Mode and
  88          *          OUTPUT are both turned on by writing (SERIAL_MCR_LOOP | SERIAL_MCR_OUT1)
  89          *              to the modem control register).
  90          *      5. The modem status register is read and the ring indicator is checked.
  91          *         This means SERIAL_MSR_RI should be set.
  92          *      6. Restore original modem status register.
  93          */
  94     Old = READ_PORT_UCHAR(Address + MODEM_CONTROL_REGISTER);
  95     WRITE_PORT_UCHAR(Address + MODEM_CONTROL_REGISTER, SERIAL_MCR_LOOP);
  96     WRITE_PORT_UCHAR(Address + MODEM_CONTROL_REGISTER, SERIAL_MCR_LOOP);
  97     if (!(READ_PORT_UCHAR(Address + MODEM_STATUS_REGISTER) &
  98                  (SERIAL_MSR_CTS | SERIAL_MSR_DSR | SERIAL_MSR_RI | SERIAL_MSR_DCD)))
  99         {
 100             WRITE_PORT_UCHAR(Address + MODEM_CONTROL_REGISTER,
 101                                                  (SERIAL_MCR_OUT1 | SERIAL_MCR_LOOP));
 102             if (READ_PORT_UCHAR(Address + MODEM_STATUS_REGISTER) & SERIAL_MSR_RI)
 103                 {
 104                         WRITE_PORT_UCHAR(Address + MODEM_CONTROL_REGISTER, Old);
 105                         return TRUE;
 106             }
 107         }
 108     WRITE_PORT_UCHAR(Address + MODEM_CONTROL_REGISTER, Old);
 109     return FALSE;
 110 }
 111
 112 UCHAR
 113 NTAPI
 114 CpReadLsr(IN PCPPORT Port,
 115           IN UCHAR ExpectedValue)
 116 {
 117         UCHAR Lsr, Msr;
 118
 119         /* Read the LSR and check if the expected value is present */
 120     Lsr = READ_PORT_UCHAR(Port->Address + LINE_STATUS_REGISTER);
 121     if (!(Lsr & ExpectedValue))
 122         {
 123                 /* Check the MSR for ring indicator toggle */
 124         Msr = READ_PORT_UCHAR(Port->Address + MODEM_STATUS_REGISTER);
 125
 126                 /* If the indicator reaches 3, we've seen this on/off twice */
 127         RingIndicator |= (Msr & SERIAL_MSR_RI) ? 1 : 2;
 128         if (RingIndicator == 3) Port->Flags |= CPPORT_FLAG_MODEM_CONTROL;
 129     }
 130
 131     return Lsr;
 132 }
 133
 134 VOID
 135 NTAPI
 136 CpSetBaud(IN PCPPORT Port,
 137           IN ULONG Rate)
 138 {
 139         UCHAR Lcr;
 140         USHORT Mode;
 141
 142     /* Add DLAB */
 143         Lcr = READ_PORT_UCHAR(Port->Address + LINE_CONTROL_REGISTER);
 144     WRITE_PORT_UCHAR(Port->Address + LINE_CONTROL_REGISTER, Lcr | SERIAL_LCR_DLAB);
 145
 146     /* Set baud rate */
 147     Mode = 115200 / Rate;
 148     WRITE_PORT_UCHAR(Port->Address + DIVISOR_LATCH_MSB, (UCHAR)((Mode >> 8) & 0xff));
 149     WRITE_PORT_UCHAR(Port->Address + DIVISOR_LATCH_LSB, (UCHAR)(Mode & 0xff));
 150
 151     /* Reset DLAB and set 8 data bits, 1 stop bit, no parity, no break */
 152     WRITE_PORT_UCHAR(Port->Address + LINE_CONTROL_REGISTER,
 153                                          SERIAL_8_DATA | SERIAL_1_STOP | SERIAL_NONE_PARITY);
 154
 155         /* Save baud rate in port */
 156     Port->Baud = Rate;
 157 }
 158
 159 USHORT
 160 NTAPI
 161 CpGetByte(IN PCPPORT Port,
 162               IN PUCHAR Byte,
 163                   IN BOOLEAN Wait,
 164                   IN BOOLEAN Poll)
 165 {
 166         UCHAR Lsr;
 167         ULONG i;
 168
 169         /* Handle early read-before-init */
 170         if (!Port->Address) return CP_GET_NODATA;
 171
 172         /* If "wait" mode enabled, spin many times, otherwise attempt just once */
 173         i = Wait ? 204800 : 1;
 174     while (i--)
 175         {
 176                 /* Read LSR for data ready */
 177         Lsr = CpReadLsr(Port, SERIAL_LSR_DR);
 178         if ((Lsr & SERIAL_LSR_DR) == SERIAL_LSR_DR)
 179                 {
 180                         /* If an error happened, clear the byte and fail */
 181             if (Lsr & (SERIAL_LSR_FE | SERIAL_LSR_PE))
 182                         {
 183                 *Byte = 0;
 184                 return CP_GET_ERROR;
 185             }
 186
 187                         /* If only polling was requested by caller, return now */
 188             if (Poll) return CP_GET_SUCCESS;
 189
 190                         /* Otherwise read the byte and return it */
 191             *Byte = READ_PORT_UCHAR(Port->Address + RECEIVE_BUFFER_REGISTER);
 192
 193                         /* Handle CD if port is in modem control mode */
 194             if (Port->Flags & CPPORT_FLAG_MODEM_CONTROL)
 195                         {
 196                                 /* Not implemented yet */
 197                                 DPRINT1("CP: CPPORT_FLAG_MODEM_CONTROL unexpected\n");
 198             }
 199
 200                         /* Byte was read */
 201             return CP_GET_SUCCESS;
 202         }
 203     }
 204
 205         /* Reset LSR, no data was found */
 206     CpReadLsr(Port, 0);
 207     return CP_GET_NODATA;
 208 }
 209
 210 VOID
 211 NTAPI
 212 CpPutByte(IN PCPPORT Port,
 213           IN UCHAR Byte)
 214 {
 215         /* Check if port is in modem control to handle CD */
 216     while (Port->Flags & CPPORT_FLAG_MODEM_CONTROL)
 217         {
 218                 /* Not implemented yet */
 219                 DPRINT1("CP: CPPORT_FLAG_MODEM_CONTROL unexpected\n");
 220     }
 221
 222         /* Wait for LSR to say we can go ahead */
 223     while (!(CpReadLsr(Port, SERIAL_LSR_THRE) & SERIAL_LSR_THRE));
 224
 225     /* Send the byte */
 226     WRITE_PORT_UCHAR(Port->Address + RECEIVE_BUFFER_REGISTER, Byte);
 227 }