linux-kernel - Re: [PATCH v2 1/2] amdgpu/dc/dml: Consolidate redundant CFLAGS

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Message-ID: <20180208184827.GD116483@google.com>
Date:   Thu, 8 Feb 2018 10:48:27 -0800
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Harry Wentland <harry.wentland@....com>
Cc:     Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        David Zhou <David1.Zhou@....com>,
        David Airlie <airlied@...ux.ie>,
        Felix Kuehling <Felix.Kuehling@....com>,
        Dmytro Laktyushkin <Dmytro.Laktyushkin@....com>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, Guenter Roeck <groeck@...omium.org>,
        Justin TerAvest <teravest@...omium.org>,
        Craig Bergstrom <craigb@...omium.org>
Subject: Re: [PATCH v2 1/2] amdgpu/dc/dml: Consolidate redundant CFLAGS

El Thu, Feb 08, 2018 at 09:33:53AM -0500 Harry Wentland ha dit:

> On 2018-02-07 08:51 PM, Matthias Kaehlcke wrote:
> > Use subdir-ccflags instead of specifying the same flags for every source
> > file.
> > 
> > Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
> > Reviewed-by: Guenter Roeck <groeck@...omium.org>
> > ---
> > Changes in v2:
> > - added 'Reviewed-by: Guenter Roeck <groeck@...omium.org>' tag
> > 
> >  drivers/gpu/drm/amd/display/dc/dml/Makefile | 10 +---------
> >  1 file changed, 1 insertion(+), 9 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/amd/display/dc/dml/Makefile b/drivers/gpu/drm/amd/display/dc/dml/Makefile
> > index 3488af2b5786..b8cadf833e71 100644
> > --- a/drivers/gpu/drm/amd/display/dc/dml/Makefile
> > +++ b/drivers/gpu/drm/amd/display/dc/dml/Makefile
> > @@ -24,15 +24,7 @@
> >  # It provides the general basic services required by other DAL
> >  # subcomponents.
> >  
> > -CFLAGS_display_mode_vba.o := -mhard-float -msse -mpreferred-stack-boundary=4
> > -CFLAGS_display_mode_lib.o := -mhard-float -msse -mpreferred-stack-boundary=4
> > -CFLAGS_display_pipe_clocks.o := -mhard-float -msse -mpreferred-stack-boundary=4
> > -CFLAGS_display_rq_dlg_calc.o := -mhard-float -msse -mpreferred-stack-boundary=4
> > -CFLAGS_dml1_display_rq_dlg_calc.o := -mhard-float -msse -mpreferred-stack-boundary=4
> > -CFLAGS_display_rq_dlg_helpers.o := -mhard-float -msse -mpreferred-stack-boundary=4
> > -CFLAGS_soc_bounding_box.o := -mhard-float -msse -mpreferred-stack-boundary=4
> > -CFLAGS_dml_common_defs.o := -mhard-float -msse -mpreferred-stack-boundary=4
> > -
> > +subdir-ccflags-y += -mhard-float -msse -mpreferred-stack-boundary=4
> 
> Are you sure this will only apply to dc/dml?
> 
> The way the amdgpu build is setup I've seen this flag apply to all of amdgpu, even if specified in a subdirectories build file. The reason being that amdgpu/Makefile recursively includes all other Makefiles in the module.
> 
> According to kbuild/makefiles.txt this will have effect for the kbuild file where it's present and all subdirectories:
> 
> https://www.kernel.org/doc/Documentation/kbuild/makefiles.txt:
> >     subdir-ccflags-y, subdir-asflags-y
> > 	The two flags listed above are similar to ccflags-y and asflags-y.
> > 	The difference is that the subdir- variants have effect for the kbuild
> > 	file where they are present and all subdirectories.
> > 	Options specified using subdir-* are added to the commandline before
> > 	the options specified using the non-subdir variants.
> > 
> > 	Example:
> > 		subdir-ccflags-y := -Werror

Thanks, I didn't realize the recursive inclusion from amdgpu/Makefile,
in this case using subdir-ccflags-y indeed isn't a good idea.

> For your 2nd patch you probably want to make a dml_cflags variable
> that's set different for clang and gcc, and then still set it for
> all files in DML individually.

Yep, that was my first impulse and then I remembered
subdir-ccflags-y. Will go back to that.

> You'll probably also have to do the same for dc/calcs/Makefile.

Thanks for the heads up!