| Message ID | 20200527135207.1118624-1-arnd@arndb.de (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | hwmon: applesmc: avoid overlong udelay() | expand |
On Wed, May 27, 2020 at 03:51:57PM +0200, Arnd Bergmann wrote: > Building this driver with "clang -O3" produces a link error > after the compiler partially unrolls the loop and 256ms > becomes a compile-time constant that triggers the check > in udelay(): > > ld.lld: error: undefined symbol: __bad_udelay > >>> referenced by applesmc.c > >>> hwmon/applesmc.o:(read_smc) in archive drivers/built-in.a > > I can see no reason against using a sleeping function here, > as no part of the driver runs in atomic context, so instead use > usleep_range() with a wide range and use jiffies for the > end condition. > Me not either. > Signed-off-by: Arnd Bergmann <arnd@arndb.de> Applied. Thanks, Guenter > --- > drivers/hwmon/applesmc.c | 12 +++++++++--- > 1 file changed, 9 insertions(+), 3 deletions(-) > > diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c > index ec93b8d673f5..316618409315 100644 > --- a/drivers/hwmon/applesmc.c > +++ b/drivers/hwmon/applesmc.c > @@ -156,14 +156,19 @@ static struct workqueue_struct *applesmc_led_wq; > */ > static int wait_read(void) > { > + unsigned long end = jiffies + (APPLESMC_MAX_WAIT * HZ) / USEC_PER_SEC; > u8 status; > int us; > + > for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) { > - udelay(us); > + usleep_range(us, us * 16); > status = inb(APPLESMC_CMD_PORT); > /* read: wait for smc to settle */ > if (status & 0x01) > return 0; > + /* timeout: give up */ > + if (time_after(jiffies, end)) > + break; > } > > pr_warn("wait_read() fail: 0x%02x\n", status); > @@ -178,10 +183,11 @@ static int send_byte(u8 cmd, u16 port) > { > u8 status; > int us; > + unsigned long end = jiffies + (APPLESMC_MAX_WAIT * HZ) / USEC_PER_SEC; > > outb(cmd, port); > for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) { > - udelay(us); > + usleep_range(us, us * 16); > status = inb(APPLESMC_CMD_PORT); > /* write: wait for smc to settle */ > if (status & 0x02) > @@ -190,7 +196,7 @@ static int send_byte(u8 cmd, u16 port) > if (status & 0x04) > return 0; > /* timeout: give up */ > - if (us << 1 == APPLESMC_MAX_WAIT) > + if (time_after(jiffies, end)) > break; > /* busy: long wait and resend */ > udelay(APPLESMC_RETRY_WAIT);
diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c index ec93b8d673f5..316618409315 100644 --- a/drivers/hwmon/applesmc.c +++ b/drivers/hwmon/applesmc.c @@ -156,14 +156,19 @@ static struct workqueue_struct *applesmc_led_wq; */ static int wait_read(void) { + unsigned long end = jiffies + (APPLESMC_MAX_WAIT * HZ) / USEC_PER_SEC; u8 status; int us; + for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) { - udelay(us); + usleep_range(us, us * 16); status = inb(APPLESMC_CMD_PORT); /* read: wait for smc to settle */ if (status & 0x01) return 0; + /* timeout: give up */ + if (time_after(jiffies, end)) + break; } pr_warn("wait_read() fail: 0x%02x\n", status); @@ -178,10 +183,11 @@ static int send_byte(u8 cmd, u16 port) { u8 status; int us; + unsigned long end = jiffies + (APPLESMC_MAX_WAIT * HZ) / USEC_PER_SEC; outb(cmd, port); for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) { - udelay(us); + usleep_range(us, us * 16); status = inb(APPLESMC_CMD_PORT); /* write: wait for smc to settle */ if (status & 0x02) @@ -190,7 +196,7 @@ static int send_byte(u8 cmd, u16 port) if (status & 0x04) return 0; /* timeout: give up */ - if (us << 1 == APPLESMC_MAX_WAIT) + if (time_after(jiffies, end)) break; /* busy: long wait and resend */ udelay(APPLESMC_RETRY_WAIT);