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authorArnd Bergmann <arnd@arndb.de>2020-05-27 16:51:57 +0300
committerGuenter Roeck <linux@roeck-us.net>2020-05-27 19:18:13 +0300
commitfff2d0f701e6753591609739f8ab9be1c8e80ebb (patch)
treeee91b58d6b14c7e435e4550025c6fc1b4668f0ee /drivers/hwmon
parent156ad7f9e0b39cfa0ed02e42c6e1c258c4e81e05 (diff)
downloadlinux-fff2d0f701e6753591609739f8ab9be1c8e80ebb.tar.xz
hwmon: (applesmc) avoid overlong udelay()
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>
Diffstat (limited to 'drivers/hwmon')
-rw-r--r--drivers/hwmon/applesmc.c12
1 files 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);