lkml.org 
[lkml]   [2020]   [May]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] hwmon: applesmc: avoid overlong udelay()
Date
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>
---
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);
--
2.26.2
\
 
 \ /
  Last update: 2020-05-27 15:52    [W:0.037 / U:10.688 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site