Re: [PATCH 06/19] drm/amd/display/dc/calcs/dce_calcs: Move some large variables from the stack to the heap

[Christian König]

Am 19.03.21 um 19:26 schrieb Harry Wentland:
> On 2021-03-19 2:13 p.m., Alex Deucher wrote:
> > + Harry, Nick
> >
> > On Fri, Mar 19, 2021 at 4:24 AM Lee Jones <lee.jones@xxxxxxxxxx> wrote:
> > > Fixes the following W=1 kernel build warning(s):
> > >
> > >   drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dce_calcs.c: In 
> > > function ‘calculate_bandwidth’:
> > > drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dce_calcs.c:2016:1: 
> > > warning: the frame size of 1216 bytes is larger than 1024 bytes 
> > > [-Wframe-larger-than=]
> > >
> > > Cc: Harry Wentland <harry.wentland@xxxxxxx>
> > > Cc: Leo Li <sunpeng.li@xxxxxxx>
> > > Cc: Alex Deucher <alexander.deucher@xxxxxxx>
> > > Cc: "Christian König" <christian.koenig@xxxxxxx>
> > > Cc: David Airlie <airlied@xxxxxxxx>
> > > Cc: Daniel Vetter <daniel@xxxxxxxx>
> > > Cc: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> > > Cc: amd-gfx@xxxxxxxxxxxxxxxxxxxxx
> > > Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > > Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
> > > ---
> > >   .../gpu/drm/amd/display/dc/calcs/dce_calcs.c  | 32 
> > > ++++++++++++++++---
> > >   1 file changed, 28 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c 
> > > b/drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c
> > > index e633f8a51edb6..9d8f2505a61c2 100644
> > > --- a/drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c
> > > +++ b/drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c
> > > @@ -98,16 +98,16 @@ static void calculate_bandwidth(
> > >          int32_t num_cursor_lines;
> > >
> > >          int32_t i, j, k;
> > > -       struct bw_fixed yclk[3];
> > > -       struct bw_fixed sclk[8];
> > > +       struct bw_fixed *yclk;
> > > +       struct bw_fixed *sclk;
> > >          bool d0_underlay_enable;
> > >          bool d1_underlay_enable;
> > >          bool fbc_enabled;
> > >          bool lpt_enabled;
> > >          enum bw_defines sclk_message;
> > >          enum bw_defines yclk_message;
> > > -       enum bw_defines tiling_mode[maximum_number_of_surfaces];
> > > -       enum bw_defines surface_type[maximum_number_of_surfaces];
> > > +       enum bw_defines *tiling_mode;
> > > +       enum bw_defines *surface_type;
> > >          enum bw_defines voltage;
> > >          enum bw_defines pipe_check;
> > >          enum bw_defines hsr_check;
> > > @@ -122,6 +122,22 @@ static void calculate_bandwidth(
> > >          int32_t number_of_displays_enabled_with_margin = 0;
> > >          int32_t number_of_aligned_displays_with_no_margin = 0;
> > >
> > > +       yclk = kcalloc(3, sizeof(*yclk), GFP_KERNEL);
> > > +       if (!yclk)
> > > +               return;
> > > +
> > > +       sclk = kcalloc(8, sizeof(*sclk), GFP_KERNEL);
> > > +       if (!sclk)
> > > +               goto free_yclk;
> > > +
> > > +       tiling_mode = kcalloc(maximum_number_of_surfaces, 
> > > sizeof(*tiling_mode), GFP_KERNEL);
> > > +       if (!tiling_mode)
> > > +               goto free_sclk;
> > > +
> > > +       surface_type = kcalloc(maximum_number_of_surfaces, 
> > > sizeof(*surface_type), GFP_KERNEL);
> > > +       if (!surface_type)
> > > +               goto free_tiling_mode;
> > > +
> >
> >
> > Harry or Nick can correct me if I'm wrong, but for this patch and the
> > next one, I think this can be called from an atomic context.
>
> From what I can see this doesn't seem the case. If I'm missing 
> something someone please correct me.

Have you taken into account that using FP functions require atomic 
context as well?

We had quite a bunch of problems with that and had to replace some 
GFP_KERNEL with GFP_ATOMIC in the DC code because of this.

Could of course be that this code here isn't affected by that, but 
better save than sorry.

Christian.

> This and the next (06/19) patch are both
> Reviewed-by: Harry Wentland <harry.wentland@xxxxxxx>
>
> Harry
>
> > Alex
> >
> > >          yclk[low] = vbios->low_yclk;
> > >          yclk[mid] = vbios->mid_yclk;
> > >          yclk[high] = vbios->high_yclk;
> > > @@ -2013,6 +2029,14 @@ static void calculate_bandwidth(
> > >                          }
> > >                  }
> > >          }
> > > +
> > > +       kfree(surface_type);
> > > +free_tiling_mode:
> > > +       kfree(tiling_mode);
> > > +free_yclk:
> > > +       kfree(yclk);
> > > +free_sclk:
> > > +       kfree(sclk);
> > >   }
> > >
> > > /*******************************************************************************
> > > --
> > > 2.27.0
> > >
> > > _______________________________________________
> > > dri-devel mailing list
> > > dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > > https://lists.freedesktop.org/mailman/listinfo/dri-devel>