| Message ID | 20220131193137.3684-4-W_Armin@gmx.de (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | hwmon: (sch56xx) Automatically load on supported hardware | expand |
On 1/31/22 11:31, Armin Wolf wrote: > msleep(1) will often sleep more than 20ms, slowing down sensor > and watchdog reads/writes. Use usleep_range() as recommended > in timers-howto.rst to fix that. > > Tested on a Fujitsu Esprimo P720. > > Signed-off-by: Armin Wolf <W_Armin@gmx.de> > --- > drivers/hwmon/sch56xx-common.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/hwmon/sch56xx-common.c b/drivers/hwmon/sch56xx-common.c > index 0172aa16dc0c..f66e1ed4b1aa 100644 > --- a/drivers/hwmon/sch56xx-common.c > +++ b/drivers/hwmon/sch56xx-common.c > @@ -139,7 +139,7 @@ static int sch56xx_send_cmd(u16 addr, u8 cmd, u16 reg, u8 v) > /* EM Interface Polling "Algorithm" */ > for (i = 0; i < max_busy_polls + max_lazy_polls; i++) { > if (i >= max_busy_polls) > - msleep(1); > + usleep_range(1, 2); This replaces a 1-millisecond sleep with a 1-2 microsecond sleep. Are you sure this is what you want to do ? Given that task switches typically take several microseconds, the new code is pretty much identical to a busy loop, and the maximum sleep time is reduced significantly. Guenter > /* Read Interrupt source Register */ > val = inb(addr + 8); > /* Write Clear the interrupt source bits */ > -- > 2.30.2 >
Hi, On 1/31/22 21:10, Guenter Roeck wrote: > On 1/31/22 11:31, Armin Wolf wrote: >> msleep(1) will often sleep more than 20ms, slowing down sensor >> and watchdog reads/writes. Use usleep_range() as recommended >> in timers-howto.rst to fix that. >> >> Tested on a Fujitsu Esprimo P720. >> >> Signed-off-by: Armin Wolf <W_Armin@gmx.de> >> --- >> drivers/hwmon/sch56xx-common.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/hwmon/sch56xx-common.c b/drivers/hwmon/sch56xx-common.c >> index 0172aa16dc0c..f66e1ed4b1aa 100644 >> --- a/drivers/hwmon/sch56xx-common.c >> +++ b/drivers/hwmon/sch56xx-common.c >> @@ -139,7 +139,7 @@ static int sch56xx_send_cmd(u16 addr, u8 cmd, u16 reg, u8 v) >> /* EM Interface Polling "Algorithm" */ >> for (i = 0; i < max_busy_polls + max_lazy_polls; i++) { >> if (i >= max_busy_polls) >> - msleep(1); >> + usleep_range(1, 2); > > This replaces a 1-millisecond sleep with a 1-2 microsecond sleep. > > Are you sure this is what you want to do ? Given that task switches typically > take several microseconds, the new code is pretty much identical to a busy > loop, and the maximum sleep time is reduced significantly. Ah good catch, I missed that will reviewing v1, sorry about that. The issue is actually worse then busy-waiting the max wait time in this code is expressed in a maximum number of polls, so if usleep_range(1, 2) would really only sleep 1 usec, we would wait much too short and may hit a false-positive timeout condition here. Regards, Hans
diff --git a/drivers/hwmon/sch56xx-common.c b/drivers/hwmon/sch56xx-common.c index 0172aa16dc0c..f66e1ed4b1aa 100644 --- a/drivers/hwmon/sch56xx-common.c +++ b/drivers/hwmon/sch56xx-common.c @@ -139,7 +139,7 @@ static int sch56xx_send_cmd(u16 addr, u8 cmd, u16 reg, u8 v) /* EM Interface Polling "Algorithm" */ for (i = 0; i < max_busy_polls + max_lazy_polls; i++) { if (i >= max_busy_polls) - msleep(1); + usleep_range(1, 2); /* Read Interrupt source Register */ val = inb(addr + 8); /* Write Clear the interrupt source bits */
msleep(1) will often sleep more than 20ms, slowing down sensor and watchdog reads/writes. Use usleep_range() as recommended in timers-howto.rst to fix that. Tested on a Fujitsu Esprimo P720. Signed-off-by: Armin Wolf <W_Armin@gmx.de> --- drivers/hwmon/sch56xx-common.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) -- 2.30.2