| Message ID | 1423065755-19337-1-git-send-email-geert@linux-m68k.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Geert, On 02/05/2015 01:02 AM, Geert Uytterhoeven wrote: > On 32-bit platforms using asm-generic/div64.h: > > drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c: In function 'gk20a_pllg_calc_rate': > drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c:147:79: warning: comparison of distinct pointer types lacks a cast > do_div(rate, divider); > ^ > drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c:147:2: warning: right shift count >= width of type > do_div(rate, divider); > ^ > drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c:147:238: warning: passing argument 1 of '__div64_32' from incompatible pointer type > do_div(rate, divider); > ^ > In file included from arch/parisc/include/generated/asm/div64.h:1:0, > from include/linux/kernel.h:124, > from include/linux/list.h:8, > from include/linux/preempt.h:10, > from include/linux/spinlock.h:50, > from include/linux/mmzone.h:7, > from include/linux/gfp.h:5, > from include/linux/slab.h:14, > from drivers/gpu/drm/nouveau/include/nvif/os.h:5, > from drivers/gpu/drm/nouveau/include/nvkm/core/os.h:3, > from drivers/gpu/drm/nouveau/include/nvkm/core/object.h:3, > from drivers/gpu/drm/nouveau/include/nvkm/core/subdev.h:3, > from drivers/gpu/drm/nouveau/include/nvkm/subdev/clk.h:3, > from drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c:25: > include/asm-generic/div64.h:35:17: note: expected 'uint64_t *' but argument is of type 'u32 *' > extern uint32_t __div64_32(uint64_t *dividend, uint32_t divisor); > ^ > > do_div() is meant for 64-bit by 32-bit division, but both the dividend > and divisor are 32-bit here. Hence use plain "/" instead. > > Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> > --- > Compile-tested only. > > parisc/allmodconfig: > http://kisskb.ellerman.id.au/kisskb/buildresult/12358386/ > --- > drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c b/drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c > index 65c532742b08d1c6..022595876ea4dc85 100644 > --- a/drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c > +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c > @@ -144,9 +144,8 @@ gk20a_pllg_calc_rate(struct gk20a_clk_priv *priv) > > rate = priv->parent_rate * priv->n; > divider = priv->m * pl_to_div[priv->pl]; > - do_div(rate, divider); > > - return rate / 2; > + return rate / divider / 2; I agree there is a problem here, but considering the theoretical values that rate can take, could we rather fix this by making rate a u64? With the current maximum values of priv->parent_rate and priv->n, rate might approach dangerously to the u32 limit and I believe casting it to u64 would be safer.
Hi Alexandre, On Fri, Feb 6, 2015 at 7:50 AM, Alexandre Courbot <acourbot@nvidia.com> wrote: > On 02/05/2015 01:02 AM, Geert Uytterhoeven wrote: >> On 32-bit platforms using asm-generic/div64.h: >> drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c: In function >> 'gk20a_pllg_calc_rate': >> drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c:147:79: warning: >> comparison of distinct pointer types lacks a cast >> do_div(rate, divider); >> >> ^ >> drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c:147:2: warning: right >> shift count >= width of type >> do_div(rate, divider); >> ^ >> drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c:147:238: warning: passing >> argument 1 of '__div64_32' from incompatible pointer type >> do_div(rate, divider); >> >> ^ >> In file included from arch/parisc/include/generated/asm/div64.h:1:0, >> from include/linux/kernel.h:124, >> from include/linux/list.h:8, >> from include/linux/preempt.h:10, >> from include/linux/spinlock.h:50, >> from include/linux/mmzone.h:7, >> from include/linux/gfp.h:5, >> from include/linux/slab.h:14, >> from drivers/gpu/drm/nouveau/include/nvif/os.h:5, >> from drivers/gpu/drm/nouveau/include/nvkm/core/os.h:3, >> from >> drivers/gpu/drm/nouveau/include/nvkm/core/object.h:3, >> from >> drivers/gpu/drm/nouveau/include/nvkm/core/subdev.h:3, >> from >> drivers/gpu/drm/nouveau/include/nvkm/subdev/clk.h:3, >> from drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c:25: >> include/asm-generic/div64.h:35:17: note: expected 'uint64_t *' but >> argument is of type 'u32 *' >> extern uint32_t __div64_32(uint64_t *dividend, uint32_t divisor); >> ^ >> >> do_div() is meant for 64-bit by 32-bit division, but both the dividend >> and divisor are 32-bit here. Hence use plain "/" instead. >> >> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> >> --- >> Compile-tested only. >> >> parisc/allmodconfig: >> http://kisskb.ellerman.id.au/kisskb/buildresult/12358386/ >> --- >> drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c | 3 +-- >> 1 file changed, 1 insertion(+), 2 deletions(-) >> >> diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c >> b/drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c >> index 65c532742b08d1c6..022595876ea4dc85 100644 >> --- a/drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c >> +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c >> @@ -144,9 +144,8 @@ gk20a_pllg_calc_rate(struct gk20a_clk_priv *priv) >> >> rate = priv->parent_rate * priv->n; >> divider = priv->m * pl_to_div[priv->pl]; >> - do_div(rate, divider); >> >> - return rate / 2; >> + return rate / divider / 2; > > > I agree there is a problem here, but considering the theoretical values that > rate can take, could we rather fix this by making rate a u64? With the > current maximum values of priv->parent_rate and priv->n, rate might approach > dangerously to the u32 limit and I believe casting it to u64 would be safer. Yes, that's better. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c b/drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c index 65c532742b08d1c6..022595876ea4dc85 100644 --- a/drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c @@ -144,9 +144,8 @@ gk20a_pllg_calc_rate(struct gk20a_clk_priv *priv) rate = priv->parent_rate * priv->n; divider = priv->m * pl_to_div[priv->pl]; - do_div(rate, divider); - return rate / 2; + return rate / divider / 2; } static int
On 32-bit platforms using asm-generic/div64.h: drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c: In function 'gk20a_pllg_calc_rate': drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c:147:79: warning: comparison of distinct pointer types lacks a cast do_div(rate, divider); ^ drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c:147:2: warning: right shift count >= width of type do_div(rate, divider); ^ drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c:147:238: warning: passing argument 1 of '__div64_32' from incompatible pointer type do_div(rate, divider); ^ In file included from arch/parisc/include/generated/asm/div64.h:1:0, from include/linux/kernel.h:124, from include/linux/list.h:8, from include/linux/preempt.h:10, from include/linux/spinlock.h:50, from include/linux/mmzone.h:7, from include/linux/gfp.h:5, from include/linux/slab.h:14, from drivers/gpu/drm/nouveau/include/nvif/os.h:5, from drivers/gpu/drm/nouveau/include/nvkm/core/os.h:3, from drivers/gpu/drm/nouveau/include/nvkm/core/object.h:3, from drivers/gpu/drm/nouveau/include/nvkm/core/subdev.h:3, from drivers/gpu/drm/nouveau/include/nvkm/subdev/clk.h:3, from drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c:25: include/asm-generic/div64.h:35:17: note: expected 'uint64_t *' but argument is of type 'u32 *' extern uint32_t __div64_32(uint64_t *dividend, uint32_t divisor); ^ do_div() is meant for 64-bit by 32-bit division, but both the dividend and divisor are 32-bit here. Hence use plain "/" instead. Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> --- Compile-tested only. parisc/allmodconfig: http://kisskb.ellerman.id.au/kisskb/buildresult/12358386/ --- drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)