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at_rtc: check in ACPI FADT boot flags if the RTC is present

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Or else disable the device. Note that the detection can be bypassed by
setting the hw.atrtc.enable option in the loader configuration file.
More information can be found on atrtc(4).

Sponsored by:		Citrix Systems R&D
Reviewed by:		ian
Differential revision:	https://reviews.freebsd.org/D14399
This commit is contained in:
Roger Pau Monné 2018-03-13 09:42:33 +00:00
parent c2272faa06
commit 4a6d4e7b58
2 changed files with 48 additions and 2 deletions
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7
share/man/man4/atrtc.4
View File

@ -33,13 +33,18 @@
.Sh SYNOPSIS
This driver is a mandatory part of i386/amd64 kernels.
.Pp
The following tunable is settable from the
The following tunables are settable from the
.Xr loader 8 :
.Bl -ohang
.It Va hint.atrtc. Ns Ar X Ns Va .clock
controls event timers functionality support.
Setting to 0, disables it.
Default value is 1.
.It Va hw.atrtc.enable
Forces enabling or disabling of the device(s).
Setting to 0 disables it, setting to 1 enables it, bypassing any platform
configuration hints.
Default value is -1 (autodetect).
.El
.Sh DESCRIPTION
This driver uses RTC hardware to supply kernel with time-of-day clock

43
sys/x86/isa/atrtc.c
View File

@ -32,6 +32,7 @@
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_acpi.h"
#include "opt_isa.h"
#include <sys/param.h>
@ -55,6 +56,10 @@ __FBSDID("$FreeBSD$");
#include <machine/intr_machdep.h>
#include "clock_if.h"
#ifdef DEV_ACPI
#include <contrib/dev/acpica/include/acpi.h>
#endif
/*
* atrtc_lock protects low-level access to individual hardware registers.
* atrtc_time_lock protects the entire sequence of accessing multiple registers
@ -63,6 +68,10 @@ __FBSDID("$FreeBSD$");
static struct mtx atrtc_lock;
MTX_SYSINIT(atrtc_lock_init, &atrtc_lock, "atrtc", MTX_SPIN);
/* Force RTC enabled/disabled. */
static int atrtc_enabled = -1;
TUNABLE_INT("hw.atrtc.enabled", &atrtc_enabled);
struct mtx atrtc_time_lock;
MTX_SYSINIT(atrtc_time_lock_init, &atrtc_time_lock, "atrtc_time", MTX_DEF);
@ -249,11 +258,43 @@ static struct isa_pnp_id atrtc_ids[] = {
{ 0 }
};
static bool
atrtc_acpi_disabled(void)
{
#ifdef DEV_ACPI
ACPI_TABLE_FADT *fadt;
vm_paddr_t physaddr;
uint16_t flags;
physaddr = acpi_find_table(ACPI_SIG_FADT);
if (physaddr == 0)
return (false);
fadt = acpi_map_table(physaddr, ACPI_SIG_FADT);
if (fadt == NULL) {
printf("at_rtc: unable to map FADT ACPI table\n");
return (false);
}
flags = fadt->BootFlags;
acpi_unmap_table(fadt);
if (flags & ACPI_FADT_NO_CMOS_RTC)
return (true);
#endif
return (false);
}
static int
atrtc_probe(device_t dev)
{
int result;
if ((atrtc_enabled == -1 && atrtc_acpi_disabled()) ||
(atrtc_enabled == 0))
return (ENXIO);
result = ISA_PNP_PROBE(device_get_parent(dev), dev, atrtc_ids);
/* ENOENT means no PnP-ID, device is hinted. */
if (result == ENOENT) {