| Message ID | 20240909-rockchip-canfd-clang-div-libcall-v1-1-c6037ea0bb2b@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [net-next] can: rockchip_canfd: Use div_s64() in rkcanfd_timestamp_init() | expand |
On Tue. 10 Sep. 2024 at 01:24, Nathan Chancellor <nathan@kernel.org> wrote: > When building with clang for a 32-bit target, such as arm, a libcall is > generated when dividing the result of clocksource_cyc2ns(), which > returns a signed 64-bit integer: > > ERROR: modpost: "__aeabi_ldivmod" [drivers/net/can/rockchip/rockchip_canfd.ko] undefined! > > Use div_s64() to avoid generating the libcall. > > Fixes: 4e1a18bab124 ("can: rockchip_canfd: add hardware timestamping support") > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > --- > This does not happen with GCC, likely because it implements > optimizations for division by a constant that clang does not implement. > --- > drivers/net/can/rockchip/rockchip_canfd-timestamp.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/net/can/rockchip/rockchip_canfd-timestamp.c b/drivers/net/can/rockchip/rockchip_canfd-timestamp.c > index 81cccc5fd8384ee1fec919077db48632f0fe7cc2..4ca01d385ffffdeec964b7fd954d8ba3ba3a1381 100644 > --- a/drivers/net/can/rockchip/rockchip_canfd-timestamp.c > +++ b/drivers/net/can/rockchip/rockchip_canfd-timestamp.c > @@ -71,7 +71,7 @@ void rkcanfd_timestamp_init(struct rkcanfd_priv *priv) > > max_cycles = div_u64(ULLONG_MAX, cc->mult); > max_cycles = min(max_cycles, cc->mask); > - work_delay_ns = clocksource_cyc2ns(max_cycles, cc->mult, cc->shift) / 3; > + work_delay_ns = div_s64(clocksource_cyc2ns(max_cycles, cc->mult, cc->shift), 3); I was surprised at first to see div_s64() instead of div_u64(), but clocksource_cyc2ns() indeed returns a s64. So this looks correct. > priv->work_delay_jiffies = nsecs_to_jiffies(work_delay_ns); > INIT_DELAYED_WORK(&priv->timestamp, rkcanfd_timestamp_work); Reviewed-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
On 09.09.2024 09:24:25, Nathan Chancellor wrote: > When building with clang for a 32-bit target, such as arm, a libcall is > generated when dividing the result of clocksource_cyc2ns(), which > returns a signed 64-bit integer: > > ERROR: modpost: "__aeabi_ldivmod" [drivers/net/can/rockchip/rockchip_canfd.ko] undefined! > > Use div_s64() to avoid generating the libcall. > > Fixes: 4e1a18bab124 ("can: rockchip_canfd: add hardware timestamping support") > Signed-off-by: Nathan Chancellor <nathan@kernel.org> A similar patch by me is mainline: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=9c100bc3ec13914f9911a937ec5b38182a5c3d64 regards, Marc
diff --git a/drivers/net/can/rockchip/rockchip_canfd-timestamp.c b/drivers/net/can/rockchip/rockchip_canfd-timestamp.c index 81cccc5fd8384ee1fec919077db48632f0fe7cc2..4ca01d385ffffdeec964b7fd954d8ba3ba3a1381 100644 --- a/drivers/net/can/rockchip/rockchip_canfd-timestamp.c +++ b/drivers/net/can/rockchip/rockchip_canfd-timestamp.c @@ -71,7 +71,7 @@ void rkcanfd_timestamp_init(struct rkcanfd_priv *priv) max_cycles = div_u64(ULLONG_MAX, cc->mult); max_cycles = min(max_cycles, cc->mask); - work_delay_ns = clocksource_cyc2ns(max_cycles, cc->mult, cc->shift) / 3; + work_delay_ns = div_s64(clocksource_cyc2ns(max_cycles, cc->mult, cc->shift), 3); priv->work_delay_jiffies = nsecs_to_jiffies(work_delay_ns); INIT_DELAYED_WORK(&priv->timestamp, rkcanfd_timestamp_work);
When building with clang for a 32-bit target, such as arm, a libcall is generated when dividing the result of clocksource_cyc2ns(), which returns a signed 64-bit integer: ERROR: modpost: "__aeabi_ldivmod" [drivers/net/can/rockchip/rockchip_canfd.ko] undefined! Use div_s64() to avoid generating the libcall. Fixes: 4e1a18bab124 ("can: rockchip_canfd: add hardware timestamping support") Signed-off-by: Nathan Chancellor <nathan@kernel.org> --- This does not happen with GCC, likely because it implements optimizations for division by a constant that clang does not implement. --- drivers/net/can/rockchip/rockchip_canfd-timestamp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- base-commit: bfba7bc8b7c2c100b76edb3a646fdce256392129 change-id: 20240909-rockchip-canfd-clang-div-libcall-ba9f619434bf Best regards,