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From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Date:   Wed, 15 Nov 2023 21:33:05 +0200
Message-ID: <CAA8EJpoyC=paF1ZuznXgJAkT1fne0RwYfqJh-cdz0WLt02i+bw@mail.gmail.com>
Subject: Re: [PATCH v2] Remove custom dumb_map_offset implementation in msm driver
To:     Dipam Turkar <dipamt1729@gmail.com>
Cc:     robdclark@gmail.com, quic_abhinavk@quicinc.com, sean@poorly.run,
        marijn.suijten@somainline.org, airlied@gmail.com, daniel@ffwll.ch,
        linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org,
        freedreno@lists.freedesktop.org, linux-kernel@vger.kernel.org
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On Wed, 15 Nov 2023 at 20:46, Dipam Turkar <dipamt1729@gmail.com> wrote:
>
> They are not outdated, my bad. I went through the locks' code and saw tha=
t they have been updated. But they are probably not necessary here as most =
of the drivers do not use any form of locking in their implementations. The=
 generic implementations drm_gem_dumb_map_offset() and drm_gem_ttm_dumb_map=
_offset() do not have any locking mechanisms either.

Excuse me, but this doesn't sound right to me. There are different
drivers with different implementations. So either we'd need a good
explanation of why it is not necessary, or this patch is NAKed.

>
> Thanks and regards
> Dipam Turkar
>
> On Wed, Nov 15, 2023 at 8:37=E2=80=AFPM Dmitry Baryshkov <dmitry.baryshko=
v@linaro.org> wrote:
>>
>> On Wed, 15 Nov 2023 at 16:30, Dipam Turkar <dipamt1729@gmail.com> wrote:
>> >
>> > Make msm use drm_gem_create_map_offset() instead of its custom
>> > implementation for associating GEM object with a fake offset. Since,
>> > we already have this generic implementation, we don't need the custom
>> > implementation and it is better to standardize the code for GEM based
>> > drivers. This also removes the outdated locking leftovers.
>>
>> Why are they outdated?
>>
>> >
>> > Signed-off-by: Dipam Turkar <dipamt1729@gmail.com>
>> > ---
>> >  drivers/gpu/drm/msm/msm_drv.c |  2 +-
>> >  drivers/gpu/drm/msm/msm_gem.c | 21 ---------------------
>> >  drivers/gpu/drm/msm/msm_gem.h |  2 --
>> >  3 files changed, 1 insertion(+), 24 deletions(-)
>> >
>> > Changes in v2:
>> > Modify commit message to include the absence of internal locking lefto=
vers
>> > around allocating a fake offset in msm_gem_mmap_offset() in the generi=
c
>> > implementation drm_gem_create_map_offset().
>> >
>> > diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_d=
rv.c
>> > index a428951ee539..86a15992c717 100644
>> > --- a/drivers/gpu/drm/msm/msm_drv.c
>> > +++ b/drivers/gpu/drm/msm/msm_drv.c
>> > @@ -1085,7 +1085,7 @@ static const struct drm_driver msm_driver =3D {
>> >         .open               =3D msm_open,
>> >         .postclose          =3D msm_postclose,
>> >         .dumb_create        =3D msm_gem_dumb_create,
>> > -       .dumb_map_offset    =3D msm_gem_dumb_map_offset,
>> > +       .dumb_map_offset    =3D drm_gem_dumb_map_offset,
>> >         .gem_prime_import_sg_table =3D msm_gem_prime_import_sg_table,
>> >  #ifdef CONFIG_DEBUG_FS
>> >         .debugfs_init       =3D msm_debugfs_init,
>> > diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_g=
em.c
>> > index db1e748daa75..489694ef79cb 100644
>> > --- a/drivers/gpu/drm/msm/msm_gem.c
>> > +++ b/drivers/gpu/drm/msm/msm_gem.c
>> > @@ -671,27 +671,6 @@ int msm_gem_dumb_create(struct drm_file *file, st=
ruct drm_device *dev,
>> >                         MSM_BO_SCANOUT | MSM_BO_WC, &args->handle, "du=
mb");
>> >  }
>> >
>> > -int msm_gem_dumb_map_offset(struct drm_file *file, struct drm_device =
*dev,
>> > -               uint32_t handle, uint64_t *offset)
>> > -{
>> > -       struct drm_gem_object *obj;
>> > -       int ret =3D 0;
>> > -
>> > -       /* GEM does all our handle to object mapping */
>> > -       obj =3D drm_gem_object_lookup(file, handle);
>> > -       if (obj =3D=3D NULL) {
>> > -               ret =3D -ENOENT;
>> > -               goto fail;
>> > -       }
>> > -
>> > -       *offset =3D msm_gem_mmap_offset(obj);
>> > -
>> > -       drm_gem_object_put(obj);
>> > -
>> > -fail:
>> > -       return ret;
>> > -}
>> > -
>> >  static void *get_vaddr(struct drm_gem_object *obj, unsigned madv)
>> >  {
>> >         struct msm_gem_object *msm_obj =3D to_msm_bo(obj);
>> > diff --git a/drivers/gpu/drm/msm/msm_gem.h b/drivers/gpu/drm/msm/msm_g=
em.h
>> > index 8ddef5443140..dc74a0ef865d 100644
>> > --- a/drivers/gpu/drm/msm/msm_gem.h
>> > +++ b/drivers/gpu/drm/msm/msm_gem.h
>> > @@ -139,8 +139,6 @@ struct page **msm_gem_pin_pages(struct drm_gem_obj=
ect *obj);
>> >  void msm_gem_unpin_pages(struct drm_gem_object *obj);
>> >  int msm_gem_dumb_create(struct drm_file *file, struct drm_device *dev=
,
>> >                 struct drm_mode_create_dumb *args);
>> > -int msm_gem_dumb_map_offset(struct drm_file *file, struct drm_device =
*dev,
>> > -               uint32_t handle, uint64_t *offset);
>> >  void *msm_gem_get_vaddr_locked(struct drm_gem_object *obj);
>> >  void *msm_gem_get_vaddr(struct drm_gem_object *obj);
>> >  void *msm_gem_get_vaddr_active(struct drm_gem_object *obj);
>> > --
>> > 2.34.1
>> >
>>
>>
>> --
>> With best wishes
>> Dmitry


--=20
With best wishes
Dmitry