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hwmon: (applesmc) avoid overlong udelay()

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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.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20200527135207.1118624-1-arnd@arndb.de
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Arnd Bergmann 2020-05-27 15:51:57 +02:00 committed by Guenter Roeck
parent 156ad7f9e0
commit fff2d0f701
1 changed files with 9 additions and 3 deletions
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12
drivers/hwmon/applesmc.c
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@ -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);