On Tue, Sep 24, 2019 at 12:36:44PM -0700, Nick Desaulniers wrote: > On Tue, Sep 24, 2019 at 11:38 AM Nathan Chancellor > <natechancellor@xxxxxxxxx> wrote: > > > > On Tue, Sep 24, 2019 at 10:47:28AM -0700, Nick Desaulniers wrote: > > > Fixes the following 2 issues in the driver: > > > 1. Left shifting a signed integer is undefined behavior. Unsigned > > > integral types should be used for bitwise operations. > > > 2. The delay scales from 0x0010 to 0x20000 by powers of 2, but udelay > > > will result in a linkage failure when given a constant that's greater > > > than 20000 (0x4E20). Agressive loop unrolling can fully unroll the > > > loop, resulting in later iterations overflowing the call to udelay. > > > > > > 2 is fixed via splitting the loop in two, iterating the first up to the > > > point where udelay would overflow, then switching to mdelay, as > > > suggested in Documentation/timers/timers-howto.rst. > > > > > > Reported-by: Tomasz Paweł Gajc <tpgxyz@xxxxxxxxx> > > > Link: https://github.com/ClangBuiltLinux/linux/issues/678 > > > Debugged-by: Nathan Chancellor <natechancellor@xxxxxxxxx> > > > Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > > > --- > > > Changes V1 -> V2: > > > * The first loop in send_byte() needs to break out on the same condition > > > now. Technically, the loop condition could even be removed. The diff > > > looks funny because of the duplicated logic between existing and newly > > > added for loops. > > > > > > drivers/hwmon/applesmc.c | 35 +++++++++++++++++++++++++++++++---- > > > 1 file changed, 31 insertions(+), 4 deletions(-) > > > > > > diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c > > > index 183ff3d25129..c76adb504dff 100644 > > > --- a/drivers/hwmon/applesmc.c > > > +++ b/drivers/hwmon/applesmc.c > > > @@ -46,6 +46,7 @@ > > > #define APPLESMC_MIN_WAIT 0x0010 > > > #define APPLESMC_RETRY_WAIT 0x0100 > > > #define APPLESMC_MAX_WAIT 0x20000 > > > +#define APPLESMC_UDELAY_MAX 20000 > > > > > > #define APPLESMC_READ_CMD 0x10 > > > #define APPLESMC_WRITE_CMD 0x11 > > > @@ -157,14 +158,23 @@ static struct workqueue_struct *applesmc_led_wq; > > > static int wait_read(void) > > > { > > > u8 status; > > > - int us; > > > - for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) { > > > + unsigned int us; > > > + > > > + for (us = APPLESMC_MIN_WAIT; us < APPLESMC_UDELAY_MAX; us <<= 1) { > > > udelay(us); > > > status = inb(APPLESMC_CMD_PORT); > > > /* read: wait for smc to settle */ > > > if (status & 0x01) > > > return 0; > > > } > > > + /* switch to mdelay for longer sleeps */ > > > + for (; us < APPLESMC_MAX_WAIT; us <<= 1) { > > > + mdelay(us); > > > + status = inb(APPLESMC_CMD_PORT); > > > + /* read: wait for smc to settle */ > > > + if (status & 0x01) > > > + return 0; > > > + } > > > > > > pr_warn("wait_read() fail: 0x%02x\n", status); > > > return -EIO; > > > @@ -177,10 +187,10 @@ static int wait_read(void) > > > static int send_byte(u8 cmd, u16 port) > > > { > > > u8 status; > > > - int us; > > > + unsigned int us; > > > > > > outb(cmd, port); > > > - for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) { > > > + for (us = APPLESMC_MIN_WAIT; us < APPLESMC_UDELAY_MAX; us <<= 1) { > > > udelay(us); > > > status = inb(APPLESMC_CMD_PORT); > > > /* write: wait for smc to settle */ > > > @@ -190,6 +200,23 @@ static int send_byte(u8 cmd, u16 port) > > > if (status & 0x04) > > > return 0; > > > /* timeout: give up */ > > > + if (us << 1 == APPLESMC_UDELAY_MAX) > > > + break; > > > + /* busy: long wait and resend */ > > > + udelay(APPLESMC_RETRY_WAIT); > > > + outb(cmd, port); > > > + } > > > + /* switch to mdelay for longer sleeps */ > > > + for (; us < APPLESMC_MAX_WAIT; us <<= 1) { > > > + mdelay(us); > > > + status = inb(APPLESMC_CMD_PORT); > > > + /* write: wait for smc to settle */ > > > + if (status & 0x02) > > > + continue; > > > + /* ready: cmd accepted, return */ > > > + if (status & 0x04) > > > + return 0; > > > + /* timeout: give up */ > > > if (us << 1 == APPLESMC_MAX_WAIT) > > > break; > > > /* busy: long wait and resend */ > > > -- > > > 2.23.0.351.gc4317032e6-goog > > > > > > > This resolves the __bad_udelay appearance at -O3 for me. I am not > > familiar enough with this code to give a reviewed by though! > > Does that constitute a Tested-by tag? Given that this could have real implications for the hardware, I would think tested by would imply running this on said hardware. FWIW: Build-tested-by: Nathan Chancellor <natechancellor@xxxxxxxxx> > > > > Also, for some odd reason, I couldn't apply your patch with 'git apply': > > > > % curl -LSs https://lore.kernel.org/lkml/20190924174728.201464-1-ndesaulniers@xxxxxxxxxx/raw | git apply > > error: corrupt patch at line 117 > > > > It looks like some of the '=' got changed into =3D and some spaces got > > changed into =20. Weird encoding glitch? > > The text in my email client shows no encoding error; the link above > shows the issue. Attaching a copy here, in case git-send-email > related. Yes, appears git send-email related because your attached patch applies just fine. Cheers, Nathan
