linux-kernel - Re: [PATCH] drm/nouveau/pci: rework AGP dependency

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Message-ID: <CAKMK7uEqztQYkqwuduAwvz_87tq_SBwjSYZF7x5b-aWb-kHVsw@mail.gmail.com>
Date:   Thu, 25 Feb 2021 16:46:48 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Christian König <christian.koenig@....com>
Cc:     Arnd Bergmann <arnd@...nel.org>, Ben Skeggs <bskeggs@...hat.com>,
        David Airlie <airlied@...ux.ie>, Arnd Bergmann <arnd@...db.de>,
        Lyude Paul <lyude@...hat.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Nouveau Dev <nouveau@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/nouveau/pci: rework AGP dependency

On Thu, Feb 25, 2021 at 1:59 PM Christian König
<christian.koenig@....com> wrote:
>
> Am 25.02.21 um 13:52 schrieb Arnd Bergmann:
> > From: Arnd Bergmann <arnd@...db.de>
> >
> > I noticed a warning from 'nm' when CONFIG_TRIM_UNUSED_KSYMS is set
> > and IS_REACHABLE(CONFIG_AGP) is false:
> >
> > drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.o: no symbols
> >
> > I later found this is completely harmless and we should find a way
> > to suppress the warning, but at that point I had already done a
> > cleanup patch to address this instance.
> >
> > It turns out this code could be improved anyway, as the current version
> > behaves unexpectedly when AGP is a loadable module but nouveau is built-in
> > itself, in which case it silently omits agp support.
> >
> > A better way to handle this is with a Kconfig dependency that requires
> > AGP either to be disabled, or forces nouveau to be a module for AGP=m.
> > With this change, the compile-time hack can be removed and lld no
> > longer warns.
> >
> > Fixes: 340b0e7c500a ("drm/nouveau/pci: merge agp handling from nouveau drm")
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> > ---
> >   drivers/gpu/drm/nouveau/Kbuild                 | 1 +
> >   drivers/gpu/drm/nouveau/Kconfig                | 1 +
> >   drivers/gpu/drm/nouveau/nvkm/subdev/pci/Kbuild | 2 +-
> >   drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.c  | 2 --
> >   drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.h  | 9 +++++----
> >   5 files changed, 8 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/nouveau/Kbuild b/drivers/gpu/drm/nouveau/Kbuild
> > index 60586fb8275e..173b8d9d85e3 100644
> > --- a/drivers/gpu/drm/nouveau/Kbuild
> > +++ b/drivers/gpu/drm/nouveau/Kbuild
> > @@ -15,6 +15,7 @@ nouveau-y := $(nvif-y)
> >   #- code also used by various userspace tools/tests
> >   include $(src)/nvkm/Kbuild
> >   nouveau-y += $(nvkm-y)
> > +nouveau-m += $(nvkm-m)
> >
> >   # DRM - general
> >   ifdef CONFIG_X86
> > diff --git a/drivers/gpu/drm/nouveau/Kconfig b/drivers/gpu/drm/nouveau/Kconfig
> > index 278e048235a9..90276a557a70 100644
> > --- a/drivers/gpu/drm/nouveau/Kconfig
> > +++ b/drivers/gpu/drm/nouveau/Kconfig
> > @@ -2,6 +2,7 @@
> >   config DRM_NOUVEAU
> >       tristate "Nouveau (NVIDIA) cards"
> >       depends on DRM && PCI && MMU
> > +     depends on AGP || !AGP
>
> My first thought was WTF? But then I realized that this totally makes sense.

depends on SYM || !SYM

is essentially

optional depends on SYM

when SYM is a tri-state. I think there was even patches to kconfig to
add something like that since it's such a common pattern. Might be
neat to resurrect that for more clarity.
-Daniel

> We should probably have the same for radeon as well.
>
> Apart from that the patch is Acked-by: Christian König
> <christian.koenig@....com>
>
> >       select IOMMU_API
> >       select FW_LOADER
> >       select DRM_KMS_HELPER
> > diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/pci/Kbuild b/drivers/gpu/drm/nouveau/nvkm/subdev/pci/Kbuild
> > index 174bdf995271..a400c680cf65 100644
> > --- a/drivers/gpu/drm/nouveau/nvkm/subdev/pci/Kbuild
> > +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/pci/Kbuild
> > @@ -1,5 +1,5 @@
> >   # SPDX-License-Identifier: MIT
> > -nvkm-y += nvkm/subdev/pci/agp.o
> > +nvkm-$(CONFIG_AGP) += nvkm/subdev/pci/agp.o
> >   nvkm-y += nvkm/subdev/pci/base.o
> >   nvkm-y += nvkm/subdev/pci/pcie.o
> >   nvkm-y += nvkm/subdev/pci/nv04.o
> > diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.c b/drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.c
> > index 385a90f91ed6..86c9e1d658af 100644
> > --- a/drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.c
> > +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.c
> > @@ -20,7 +20,6 @@
> >    * OTHER DEALINGS IN THE SOFTWARE.
> >    */
> >   #include "agp.h"
> > -#ifdef __NVKM_PCI_AGP_H__
> >   #include <core/option.h>
> >
> >   struct nvkm_device_agp_quirk {
> > @@ -172,4 +171,3 @@ nvkm_agp_ctor(struct nvkm_pci *pci)
> >
> >       pci->agp.mtrr = arch_phys_wc_add(pci->agp.base, pci->agp.size);
> >   }
> > -#endif
> > diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.h b/drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.h
> > index ad4d3621d02b..041fe1fbf093 100644
> > --- a/drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.h
> > +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.h
> > @@ -1,15 +1,14 @@
> > -/* SPDX-License-Identifier: MIT */
> > -#include "priv.h"
> > -#if defined(CONFIG_AGP) || (defined(CONFIG_AGP_MODULE) && defined(MODULE))
> >   #ifndef __NVKM_PCI_AGP_H__
> >   #define __NVKM_PCI_AGP_H__
> >
> > +/* SPDX-License-Identifier: MIT */
> > +#include "priv.h"
> > +#if IS_ENABLED(CONFIG_AGP)
> >   void nvkm_agp_ctor(struct nvkm_pci *);
> >   void nvkm_agp_dtor(struct nvkm_pci *);
> >   void nvkm_agp_preinit(struct nvkm_pci *);
> >   int nvkm_agp_init(struct nvkm_pci *);
> >   void nvkm_agp_fini(struct nvkm_pci *);
> > -#endif
> >   #else
> >   static inline void nvkm_agp_ctor(struct nvkm_pci *pci) {}
> >   static inline void nvkm_agp_dtor(struct nvkm_pci *pci) {}
> > @@ -17,3 +16,5 @@ static inline void nvkm_agp_preinit(struct nvkm_pci *pci) {}
> >   static inline int nvkm_agp_init(struct nvkm_pci *pci) { return -ENOSYS; }
> >   static inline void nvkm_agp_fini(struct nvkm_pci *pci) {}
> >   #endif
> > +
> > +#endif
>


-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch