iPXE
efi_timer.c
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1 /*
2  * Copyright (C) 2008 Michael Brown <mbrown@fensystems.co.uk>.
3  *
4  * This program is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU General Public License as
6  * published by the Free Software Foundation; either version 2 of the
7  * License, or any later version.
8  *
9  * This program is distributed in the hope that it will be useful, but
10  * WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12  * General Public License for more details.
13  *
14  * You should have received a copy of the GNU General Public License
15  * along with this program; if not, write to the Free Software
16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
17  * 02110-1301, USA.
18  *
19  * You can also choose to distribute this program under the terms of
20  * the Unmodified Binary Distribution Licence (as given in the file
21  * COPYING.UBDL), provided that you have satisfied its requirements.
22  */
23 
24 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
25 
26 #include <string.h>
27 #include <errno.h>
28 #include <unistd.h>
29 #include <ipxe/timer.h>
30 #include <ipxe/init.h>
31 #include <ipxe/efi/efi.h>
32 
33 /** @file
34  *
35  * iPXE timer API for EFI
36  *
37  */
38 
39 /**
40  * Number of jiffies per second
41  *
42  * This is a policy decision.
43  */
44 #define EFI_JIFFIES_PER_SEC 32
45 
46 /** Current tick count */
47 static unsigned long efi_jiffies;
48 
49 /** Timer tick event */
51 
52 /** Colour for debug messages */
53 #define colour &efi_jiffies
54 
55 /**
56  * Delay for a fixed number of microseconds
57  *
58  * @v usecs Number of microseconds for which to delay
59  */
60 static void efi_udelay ( unsigned long usecs ) {
62  EFI_STATUS efirc;
63  int rc;
64 
65  if ( ( efirc = bs->Stall ( usecs ) ) != 0 ) {
66  rc = -EEFI ( efirc );
67  DBGC ( colour, "EFI could not delay for %ldus: %s\n",
68  usecs, strerror ( rc ) );
69  /* Probably screwed */
70  }
71 }
72 
73 /**
74  * Get current system time in ticks
75  *
76  * @ret ticks Current time, in ticks
77  */
78 static unsigned long efi_currticks ( void ) {
80 
81  /* UEFI manages to ingeniously combine the worst aspects of
82  * both polling and interrupt-driven designs. There is no way
83  * to support proper interrupt-driven operation, since there
84  * is no way to hook in an interrupt service routine. A
85  * mockery of interrupts is provided by UEFI timers, which
86  * trigger at a preset rate and can fire at any time.
87  *
88  * We therefore have all of the downsides of a polling design
89  * (inefficiency and inability to sleep until something
90  * interesting happens) combined with all of the downsides of
91  * an interrupt-driven design (the complexity of code that
92  * could be preempted at any time).
93  *
94  * The UEFI specification expects us to litter the entire
95  * codebase with calls to RaiseTPL() as needed for sections of
96  * code that are not reentrant. Since this doesn't actually
97  * gain us any substantive benefits (since even with such
98  * calls we would still be suffering from the limitations of a
99  * polling design), we instead choose to run at TPL_CALLBACK
100  * almost all of the time, dropping to a lower TPL to allow
101  * timer ticks to occur.
102  *
103  * We record the external TPL at the point of entry into iPXE,
104  * and drop back only as far as this external TPL. This
105  * avoids the unexpected behaviour that may arise from having
106  * iPXE temporarily drop to TPL_APPLICATION in the middle of
107  * an entry point invoked at TPL_CALLBACK. The side effect is
108  * that iPXE's view of the system time is effectively frozen
109  * for the duration of any call made in to iPXE at
110  * TPL_CALLBACK or higher.
111  *
112  *
113  * For added excitement, UEFI provides no clean way for device
114  * drivers to shut down in preparation for handover to a
115  * booted operating system. The platform firmware simply
116  * doesn't bother to call the drivers' Stop() methods.
117  * Instead, all non-trivial drivers must register an
118  * EVT_SIGNAL_EXIT_BOOT_SERVICES event to be signalled when
119  * ExitBootServices() is called, and clean up without any
120  * reference to the EFI driver model.
121  *
122  * Unfortunately, all timers silently stop working when
123  * ExitBootServices() is called. Even more unfortunately, and
124  * for no discernible reason, this happens before any
125  * EVT_SIGNAL_EXIT_BOOT_SERVICES events are signalled. The
126  * net effect of this entertaining design choice is that any
127  * timeout loops on the shutdown path (e.g. for gracefully
128  * closing outstanding TCP connections) may wait indefinitely.
129  *
130  * There is no way to report failure from currticks(), since
131  * the API lazily assumes that the host system continues to
132  * travel through time in the usual direction. Work around
133  * EFI's violation of this assumption by falling back to a
134  * simple free-running monotonic counter during shutdown.
135  */
136  if ( efi_shutdown_in_progress ) {
137  efi_jiffies++;
138  } else {
140  bs->RaiseTPL ( TPL_CALLBACK );
141  }
142 
143  return ( efi_jiffies * ( TICKS_PER_SEC / EFI_JIFFIES_PER_SEC ) );
144 }
145 
146 /**
147  * Timer tick
148  *
149  * @v event Timer tick event
150  * @v context Event context
151  */
152 static EFIAPI void efi_tick ( EFI_EVENT event __unused,
153  void *context __unused ) {
154 
155  /* Increment tick count */
156  efi_jiffies++;
157 }
158 
159 /**
160  * Start timer tick
161  *
162  */
163 static void efi_tick_startup ( void ) {
165  EFI_STATUS efirc;
166  int rc;
167 
168  /* Create timer tick event */
169  if ( ( efirc = bs->CreateEvent ( ( EVT_TIMER | EVT_NOTIFY_SIGNAL ),
171  &efi_tick_event ) ) != 0 ) {
172  rc = -EEFI ( efirc );
173  DBGC ( colour, "EFI could not create timer tick: %s\n",
174  strerror ( rc ) );
175  /* Nothing we can do about it */
176  return;
177  }
178 
179  /* Start timer tick */
180  if ( ( efirc = bs->SetTimer ( efi_tick_event, TimerPeriodic,
181  ( 10000000 / EFI_JIFFIES_PER_SEC ) ))!=0){
182  rc = -EEFI ( efirc );
183  DBGC ( colour, "EFI could not start timer tick: %s\n",
184  strerror ( rc ) );
185  /* Nothing we can do about it */
186  return;
187  }
188  DBGC ( colour, "EFI timer started at %d ticks per second\n",
190 }
191 
192 /**
193  * Stop timer tick
194  *
195  * @v booting System is shutting down in order to boot
196  */
197 static void efi_tick_shutdown ( int booting __unused ) {
199  EFI_STATUS efirc;
200  int rc;
201 
202  /* Stop timer tick */
203  if ( ( efirc = bs->SetTimer ( efi_tick_event, TimerCancel, 0 ) ) != 0 ){
204  rc = -EEFI ( efirc );
205  DBGC ( colour, "EFI could not stop timer tick: %s\n",
206  strerror ( rc ) );
207  /* Self-destruct initiated */
208  return;
209  }
210  DBGC ( colour, "EFI timer stopped\n" );
211 
212  /* Destroy timer tick event */
213  if ( ( efirc = bs->CloseEvent ( efi_tick_event ) ) != 0 ) {
214  rc = -EEFI ( efirc );
215  DBGC ( colour, "EFI could not destroy timer tick: %s\n",
216  strerror ( rc ) );
217  /* Probably non-fatal */
218  return;
219  }
220 }
221 
222 /** Timer tick startup function */
223 struct startup_fn efi_tick_startup_fn __startup_fn ( STARTUP_EARLY ) = {
224  .name = "efi_tick",
225  .startup = efi_tick_startup,
226  .shutdown = efi_tick_shutdown,
227 };
228 
229 /** EFI timer */
230 struct timer efi_timer __timer ( TIMER_NORMAL ) = {
231  .name = "efi",
232  .currticks = efi_currticks,
233  .udelay = efi_udelay,
234 };
static void efi_udelay(unsigned long usecs)
Delay for a fixed number of microseconds.
Definition: efi_timer.c:60
EFI_BOOT_SERVICES * BootServices
A pointer to the EFI Boot Services Table.
Definition: UefiSpec.h:2000
struct arbelprm_rc_send_wqe rc
Definition: arbel.h:14
static EFI_EVENT efi_tick_event
Timer tick event.
Definition: efi_timer.c:50
#define TICKS_PER_SEC
Number of ticks per second.
Definition: timer.h:15
#define EEFI(efirc)
Convert an EFI status code to an iPXE status code.
Definition: efi.h:167
EFI_RAISE_TPL RaiseTPL
Definition: UefiSpec.h:1845
An event is to be signaled periodically at a specified interval from the current time.
Definition: UefiSpec.h:489
EFI_STALL Stall
Definition: UefiSpec.h:1893
#define colour
Colour for debug messages.
Definition: efi_timer.c:53
Error codes.
VOID * EFI_EVENT
Handle to an event structure.
Definition: UefiBaseType.h:43
static unsigned long efi_jiffies
Current tick count.
Definition: efi_timer.c:47
#define STARTUP_EARLY
Early startup.
Definition: init.h:62
#define DBGC(...)
Definition: compiler.h:505
EFI_CLOSE_EVENT CloseEvent
Definition: UefiSpec.h:1864
EFI_SET_TIMER SetTimer
Definition: UefiSpec.h:1861
iPXE timers
const char * name
Definition: init.h:42
A timer.
Definition: timer.h:28
A startup/shutdown function.
Definition: init.h:41
An event's timer settings is to be cancelled and not trigger time is to be set/.
Definition: UefiSpec.h:485
static void efi_tick_shutdown(int booting __unused)
Stop timer tick.
Definition: efi_timer.c:197
static void efi_tick_startup(void)
Start timer tick.
Definition: efi_timer.c:163
EFI_CREATE_EVENT CreateEvent
Definition: UefiSpec.h:1860
char * strerror(int errno)
Retrieve string representation of error number.
Definition: strerror.c:78
#define EFIAPI
EFI Boot Services Table.
Definition: UefiSpec.h:1836
#define TPL_CALLBACK
Definition: UefiSpec.h:591
#define EVT_NOTIFY_SIGNAL
Definition: UefiSpec.h:394
EFI API.
#define __unused
Declare a variable or data structure as unused.
Definition: compiler.h:573
const char * name
Name.
Definition: timer.h:30
FILE_LICENCE(GPL2_OR_LATER_OR_UBDL)
struct startup_fn efi_tick_startup_fn __startup_fn(STARTUP_EARLY)
Timer tick startup function.
RETURN_STATUS EFI_STATUS
Function return status for EFI API.
Definition: UefiBaseType.h:35
#define EFI_JIFFIES_PER_SEC
Number of jiffies per second.
Definition: efi_timer.c:44
EFI_SYSTEM_TABLE * efi_systab
EFI_RESTORE_TPL RestoreTPL
Definition: UefiSpec.h:1846
struct timer efi_timer __timer(TIMER_NORMAL)
EFI timer.
static unsigned long efi_currticks(void)
Get current system time in ticks.
Definition: efi_timer.c:78
#define NULL
NULL pointer (VOID *)
Definition: Base.h:362
String functions.
static EFIAPI void efi_tick(EFI_EVENT event __unused, void *context __unused)
Timer tick.
Definition: efi_timer.c:152
#define TIMER_NORMAL
Normal timer.
Definition: timer.h:63
int efi_shutdown_in_progress
EFI shutdown is in progress.
Definition: efi_init.c:54
#define EVT_TIMER
Definition: UefiSpec.h:391
EFI_TPL efi_external_tpl
External task priority level.
Definition: efi_init.c:51