| Message ID | alpine.LFD.2.20.1511031653580.630@knanqh.ubzr |
|---|---|
| State | Accepted |
| Commit | 8cb87c0407cb55277d8b9aa50f0e29201b90a88d |
| Headers | show |
On Fri, 4 Dec 2015, Thierry Reding wrote: > On Tue, Nov 03, 2015 at 05:01:46PM -0500, Nicolas Pitre wrote: > > do_div() must only be used with a u64 dividend. > > > > Signed-off-by: Nicolas Pitre <nico@linaro.org> > > > > diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c b/drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c > > index 254094ab7f..5da2aa8cc3 100644 > > --- a/drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c > > +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c > > @@ -141,9 +141,8 @@ gk20a_pllg_calc_rate(struct gk20a_clk *clk) > > > > rate = clk->parent_rate * clk->n; > > divider = clk->m * pl_to_div[clk->pl]; > > - do_div(rate, divider); > > > > - return rate / 2; > > + return rate / divider / 2; > > } > > > > static int > > This causes build breakage on 32-bit ARM. Funny, because the above _fixes_ build warnings on 32-bit ARM for me. > I'm also confused by the commit message because the code that I'm > looking at has u64 rate and u32 divider, If I look at drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c in v4.4-rc3 between line 137 and line 147, I see this: gk20a_pllg_calc_rate(struct gk20a_clk *clk) { u32 rate; u32 divider; rate = clk->parent_rate * clk->n; divider = clk->m * pl_to_div[clk->pl]; do_div(rate, divider); return rate / 2; } So clearly both rate and divider are u32 variables and do_div() should not be used. Here's the warning: drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c: In function 'gk20a_pllg_calc_rate': include/asm-generic/div64.h:207:28: warning: comparison of distinct pointer types lacks a cast (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \ ^ drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c:144:2: note: in expansion of macro 'do_div' do_div(rate, divider); ^ The corresponding line number in vanilla v4.4-rc3 for include/asm-generic/div64.h is line 43. Nicolas
diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c b/drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c index 254094ab7f..5da2aa8cc3 100644 --- a/drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/clk/gk20a.c @@ -141,9 +141,8 @@ gk20a_pllg_calc_rate(struct gk20a_clk *clk) rate = clk->parent_rate * clk->n; divider = clk->m * pl_to_div[clk->pl]; - do_div(rate, divider); - return rate / 2; + return rate / divider / 2; } static int
do_div() must only be used with a u64 dividend. Signed-off-by: Nicolas Pitre <nico@linaro.org>