| Message ID | 20231206123717.524009-1-arnd@kernel.org (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Commit | 73380e2573c34a45e01786750a4a2efafc2248bd |
| Headers | show |
| Series | [1/2] soc: qcom: stats: fix 64-bit division | expand |
Hallo Arnd, On Wed, Dec 06, 2023 at 01:37:06PM +0100, Arnd Bergmann wrote: > Unguarded 64-bit division is not allowed on 32-bit kernels because this > is very slow. The result of trying anyway is a link failure: > > arm-linux-gnueabi-ld: drivers/soc/qcom/qcom_stats.o: in function `qcom_ddr_stats_show': > qcom_stats.c:(.text+0x334): undefined reference to `__aeabi_uldivmod' > > As this function is only used for debugging and not performance critical, > rewrite it to use div_u64() instead. ARCH_TIMER_FREQ is a multiple of > MSEC_PER_SEC anyway, so there is no loss in precisison. Maybe add this information in a comment? We have #define ARCH_TIMER_FREQ 19200000 so it's a multiple of MSEC_PER_SEC (= 1000) indeed. Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Best regards Uwe
On Wed, Dec 06, 2023 at 01:37:06PM +0100, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@arndb.de> > > Unguarded 64-bit division is not allowed on 32-bit kernels because this > is very slow. The result of trying anyway is a link failure: > > arm-linux-gnueabi-ld: drivers/soc/qcom/qcom_stats.o: in function `qcom_ddr_stats_show': > qcom_stats.c:(.text+0x334): undefined reference to `__aeabi_uldivmod' > > As this function is only used for debugging and not performance critical, > rewrite it to use div_u64() instead. ARCH_TIMER_FREQ is a multiple of > MSEC_PER_SEC anyway, so there is no loss in precisison. > > Fixes: e84e61bdb97c ("soc: qcom: stats: Add DDR sleep stats") > Signed-off-by: Arnd Bergmann <arnd@arndb.de> I had [1] lined up already, but hadn't pushed the branch out out... Like your version better, so dropping mine. [1] https://lore.kernel.org/all/20231205-qcom_stats-aeabi_uldivmod-fix-v1-1-f94ecec5e894@quicinc.com/ Thanks, Bjorn > --- > drivers/soc/qcom/qcom_stats.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/soc/qcom/qcom_stats.c b/drivers/soc/qcom/qcom_stats.c > index 4763d62a8cb0..5ec8a754b22b 100644 > --- a/drivers/soc/qcom/qcom_stats.c > +++ b/drivers/soc/qcom/qcom_stats.c > @@ -221,7 +221,7 @@ static int qcom_ddr_stats_show(struct seq_file *s, void *unused) > > for (i = 0; i < ddr.entry_count; i++) { > /* Convert the period to ms */ > - entry[i].dur = mult_frac(MSEC_PER_SEC, entry[i].dur, ARCH_TIMER_FREQ); > + entry[i].dur = div_u64(entry[i].dur, ARCH_TIMER_FREQ / MSEC_PER_SEC); > } > > for (i = 0; i < ddr.entry_count; i++) > -- > 2.39.2 >
On Wed, 06 Dec 2023 13:37:06 +0100, Arnd Bergmann wrote: > Unguarded 64-bit division is not allowed on 32-bit kernels because this > is very slow. The result of trying anyway is a link failure: > > arm-linux-gnueabi-ld: drivers/soc/qcom/qcom_stats.o: in function `qcom_ddr_stats_show': > qcom_stats.c:(.text+0x334): undefined reference to `__aeabi_uldivmod' > > As this function is only used for debugging and not performance critical, > rewrite it to use div_u64() instead. ARCH_TIMER_FREQ is a multiple of > MSEC_PER_SEC anyway, so there is no loss in precisison. > > [...] Applied, thanks! [1/2] soc: qcom: stats: fix 64-bit division commit: 73380e2573c34a45e01786750a4a2efafc2248bd Best regards,
diff --git a/drivers/soc/qcom/qcom_stats.c b/drivers/soc/qcom/qcom_stats.c index 4763d62a8cb0..5ec8a754b22b 100644 --- a/drivers/soc/qcom/qcom_stats.c +++ b/drivers/soc/qcom/qcom_stats.c @@ -221,7 +221,7 @@ static int qcom_ddr_stats_show(struct seq_file *s, void *unused) for (i = 0; i < ddr.entry_count; i++) { /* Convert the period to ms */ - entry[i].dur = mult_frac(MSEC_PER_SEC, entry[i].dur, ARCH_TIMER_FREQ); + entry[i].dur = div_u64(entry[i].dur, ARCH_TIMER_FREQ / MSEC_PER_SEC); } for (i = 0; i < ddr.entry_count; i++)