src/superio/fintek/common/early_serial.c

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2
   3 /*
   4  * A generic romstage (pre-ram) driver for Fintek variant Super I/O chips.
   5  *
   6  * The following is derived directly from the vendor Fintek's data-sheets:
   7  *
   8  * To toggle between `configuration mode` and `normal operation mode` as to
   9  * manipulation the various LDN's in Fintek Super I/O's we are required to pass
  10  * magic numbers `passwords keys`.
  11  *
  12  *  FINTEK_ENTRY_KEY :=  enable  configuration : 0x87
  13  *  FINTEK_EXIT_KEY  :=  disable configuration : 0xAA
  14  *
  15  * To modify a LDN's configuration register, we use the index port to select
  16  * the index of the LDN and then writing to the data port to alter the
  17  * parameters. A default index, data port pair is 0x4E, 0x4F respectively, a
  18  * user modified pair is 0x2E, 0x2F respectively.
  19  *
  20  */
  21
  22 #include <arch/io.h>
  23 #include <device/pnp_ops.h>
  24 #include <device/pnp.h>
  25 #include <stdint.h>
  26 #include "fintek.h"
  27
  28 #define FINTEK_ENTRY_KEY 0x87
  29 #define FINTEK_EXIT_KEY 0xAA
  30
  31 /* Enable configuration: pass entry key '0x87' into index port dev. */
  32 void pnp_enter_conf_state(pnp_devfn_t dev)
  33 {
  34         u16 port = dev >> 8;
  35         outb(FINTEK_ENTRY_KEY, port);
  36         outb(FINTEK_ENTRY_KEY, port);
  37 }
  38
  39 /* Disable configuration: pass exit key '0xAA' into index port dev. */
  40 void pnp_exit_conf_state(pnp_devfn_t dev)
  41 {
  42         u16 port = dev >> 8;
  43         outb(FINTEK_EXIT_KEY, port);
  44 }
  45
  46 /* Bring up early serial debugging output before the RAM is initialized. */
  47 void fintek_enable_serial(pnp_devfn_t dev, u16 iobase)
  48 {
  49         pnp_enter_conf_state(dev);
  50         pnp_set_logical_device(dev);
  51         pnp_set_enable(dev, 0);
  52         pnp_set_iobase(dev, PNP_IDX_IO0, iobase);
  53         pnp_set_enable(dev, 1);
  54         pnp_exit_conf_state(dev);
  55 }