Author: des
Date: Thu Mar 19 12:39:13 2009
New Revision: 190030
URL: http://svn.freebsd.org/changeset/base/190030
Log:
Rename two functions to make their purpose clearer. Add tons of comments.
Generated code is identical after stripping .comment section.
Suggested by: Andriy Gapon <a...@icyb.net.ua>
MFC after: 2 weeks
Modified:
head/sys/dev/ichwd/ichwd.c
Modified: head/sys/dev/ichwd/ichwd.c
==============================================================================
--- head/sys/dev/ichwd/ichwd.c Thu Mar 19 12:33:37 2009 (r190029)
+++ head/sys/dev/ichwd/ichwd.c Thu Mar 19 12:39:13 2009 (r190030)
@@ -141,26 +141,55 @@ static devclass_t ichwd_devclass;
device_printf(dev, __VA_ARGS__);\
} while (0)
+/*
+ * Disable the watchdog timeout SMI handler.
+ *
+ * Apparently, some BIOSes install handlers that reset or disable the
+ * watchdog timer instead of resetting the system, so we disable the SMI
+ * (by clearing the SMI_TCO_EN bit of the SMI_EN register) to prevent this
+ * from happening.
+ */
static __inline void
-ichwd_intr_enable(struct ichwd_softc *sc)
+ichwd_smi_disable(struct ichwd_softc *sc)
{
ichwd_write_smi_4(sc, SMI_EN, ichwd_read_smi_4(sc, SMI_EN) &
~SMI_TCO_EN);
}
+/*
+ * Enable the watchdog timeout SMI handler. See above for details.
+ */
static __inline void
-ichwd_intr_disable(struct ichwd_softc *sc)
+ichwd_smi_enable(struct ichwd_softc *sc)
{
ichwd_write_smi_4(sc, SMI_EN, ichwd_read_smi_4(sc, SMI_EN) |
SMI_TCO_EN);
}
+/*
+ * Reset the watchdog status bits.
+ */
static __inline void
ichwd_sts_reset(struct ichwd_softc *sc)
{
+ /*
+ * The watchdog status bits are set to 1 by the hardware to
+ * indicate various conditions. They can be cleared by software
+ * by writing a 1, not a 0.
+ */
ichwd_write_tco_2(sc, TCO1_STS, TCO_TIMEOUT);
+ /*
+ * XXX The datasheet says that TCO_SECOND_TO_STS must be cleared
+ * before TCO_BOOT_STS, not the other way around.
+ */
ichwd_write_tco_2(sc, TCO2_STS, TCO_BOOT_STS);
ichwd_write_tco_2(sc, TCO2_STS, TCO_SECOND_TO_STS);
}
+/*
+ * Enable the watchdog timer by clearing the TCO_TMR_HALT bit in the
+ * TCO1_CNT register. This is complicated by the need to preserve bit 9
+ * of that same register, and the requirement that all other bits must be
+ * written back as zero.
+ */
static __inline void
ichwd_tmr_enable(struct ichwd_softc *sc)
{
@@ -172,6 +201,9 @@ ichwd_tmr_enable(struct ichwd_softc *sc)
ichwd_verbose_printf(sc->device, "timer enabled\n");
}
+/*
+ * Disable the watchdog timer. See above for details.
+ */
static __inline void
ichwd_tmr_disable(struct ichwd_softc *sc)
{
@@ -183,6 +215,11 @@ ichwd_tmr_disable(struct ichwd_softc *sc
ichwd_verbose_printf(sc->device, "timer disabled\n");
}
+/*
+ * Reload the watchdog timer: writing anything to any of the lower five
+ * bits of the TCO_RLD register reloads the timer from the last value
+ * written to TCO_TMR.
+ */
static __inline void
ichwd_tmr_reload(struct ichwd_softc *sc)
{
@@ -194,6 +231,10 @@ ichwd_tmr_reload(struct ichwd_softc *sc)
ichwd_verbose_printf(sc->device, "timer reloaded\n");
}
+/*
+ * Set the initial timeout value. Note that this must always be followed
+ * by a reload.
+ */
static __inline void
ichwd_tmr_set(struct ichwd_softc *sc, unsigned int timeout)
{
@@ -262,7 +303,8 @@ ichwd_clear_noreboot(struct ichwd_softc
}
/*
- * Watchdog event handler.
+ * Watchdog event handler - called by the framework to enable or disable
+ * the watchdog or change the initial timeout value.
*/
static void
ichwd_event(void *arg, unsigned int cmd, int *error)
@@ -426,6 +468,13 @@ ichwd_attach(device_t dev)
device_printf(dev, "%s (ICH%d or equivalent)\n",
device_get_desc(dev), sc->ich_version);
+ /*
+ * XXX we should check the status registers (specifically, the
+ * TCO_SECOND_TO_STS bit in the TCO2_STS register) to see if we
+ * just came back from a watchdog-induced reset, and let the user
+ * know.
+ */
+
/* reset the watchdog status registers */
ichwd_sts_reset(sc);
@@ -435,8 +484,8 @@ ichwd_attach(device_t dev)
/* register the watchdog event handler */
sc->ev_tag = EVENTHANDLER_REGISTER(watchdog_list, ichwd_event, sc, 0);
- /* enable watchdog timeout interrupts */
- ichwd_intr_enable(sc);
+ /* disable the SMI handler */
+ ichwd_smi_disable(sc);
return (0);
fail:
@@ -466,8 +515,8 @@ ichwd_detach(device_t dev)
if (sc->active)
ichwd_tmr_disable(sc);
- /* disable watchdog timeout interrupts */
- ichwd_intr_disable(sc);
+ /* enable the SMI handler */
+ ichwd_smi_enable(sc);
/* deregister event handler */
if (sc->ev_tag != NULL)
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