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dev/ichsmb: use hardware semaphore for smbus_callback #1990

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dev/ichsmb: use hardware semaphore for smbus_callback #1990

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f4829d9
dev/smbus: properly wait for bus request
ckoehne Jan 23, 2026
69b1828
dev/smbus: add timeout while waiting for bus request
ckoehne Jan 23, 2026
36e781e
dev/ichsmb: release semaphore on spurios interrupts
ckoehne Jan 22, 2026
36b86b1
dev/ichsmb: use hardware semaphore for smbus_callback
ckoehne Jan 22, 2026
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18 changes: 15 additions & 3 deletions sys/dev/ichsmb/ichsmb.c
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Original file line number Diff line number Diff line change
Expand Up @@ -145,13 +145,17 @@
int
ichsmb_callback(device_t dev, int index, void *data)
{
const sc_p sc = device_get_softc(dev);
int smb_error = 0;

DBG("index=%d how=%d\n", index, data ? *(int *)data : -1);
switch (index) {
case SMB_REQUEST_BUS:
if ((bus_read_1(sc->io_res, ICH_HST_STA) & ICH_HST_STA_INUSE_STS) != 0)

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return (EBUSY);
break;
case SMB_RELEASE_BUS:
bus_write_1(sc->io_res, ICH_HST_STA, ICH_HST_STA_INUSE_STS);
break;
default:
smb_error = SMB_EABORT; /* XXX */
Expand Down Expand Up @@ -507,10 +511,18 @@
DBG("%d stat=0x%02x\n", count, status);
}
#endif
status &= ~(ICH_HST_STA_INUSE_STS | ICH_HST_STA_HOST_BUSY |
ICH_HST_STA_SMBALERT_STS);
if (status == 0)
status &= ~(ICH_HST_STA_HOST_BUSY | ICH_HST_STA_SMBALERT_STS);
if ((status & ~ICH_HST_STA_INUSE_STS) == 0) {
// We're not the target of the interrupt. In that case,
// reading the status register can acquire the
// semaphore which will lock subsequent accesses to the

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// SMBus. For that reason, release the semaphore if
// we've acquired it.
if ((status & ICH_HST_STA_INUSE_STS) == 0)
bus_write_1(sc->io_res, ICH_HST_STA, ICH_HST_STA_INUSE_STS);
break;
}
status &= ~ICH_HST_STA_INUSE_STS;

/* Check for unexpected interrupt */
ok_bits = ICH_HST_STA_SMBALERT_STS;
Expand Down
23 changes: 21 additions & 2 deletions sys/dev/smbus/smbconf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,7 @@

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/module.h>
#include <sys/mutex.h>
Expand Down Expand Up @@ -118,6 +119,8 @@
struct smbus_softc *sc = device_get_softc(bus);
device_t parent;
int error;
int retries = 0;
int max_retries = 20;

/* first, ask the underlying layers if the request is ok */
parent = device_get_parent(bus);
Expand All @@ -127,8 +130,24 @@
error = SMBUS_CALLBACK(parent, SMB_REQUEST_BUS, &how);
mtx_lock(&sc->lock);

if (error)
error = smbus_poll(sc, how);
/* Check if we've successfully got bus access. */
if (error == 0)
break;
/* Check for timeout.*/
if (retries++ < max_retries)

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return (EBUSY);

switch (how) {

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case SMB_WAIT | SMB_INTR:
error = msleep(sc, &sc->lock, SMBPRI|PCATCH, "smbreq", hz / 100);
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@kostikbel kostikbel Jan 27, 2026

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What if hz < 100?

break;
case SMB_WAIT | SMB_NOINTR:
error = msleep(sc, &sc->lock, SMBPRI, "smbreq", hz / 100);
break;
default:
/* We're in non blocking mode, so exit early. */
return (EWOULDBLOCK);
}
} while (error == EWOULDBLOCK);

while (error == 0) {
Expand Down
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