Re: [PATCH] drm: rcar-du: crtc: force depends on cmm

Jackie Liu <liu.yun@xxxxxxxxx> · Wed, 28 Jul 2021 20:14:06 +0800

在 2021/7/28 下午7:30, Laurent Pinchart 写道:
On Wed, Jul 28, 2021 at 12:09:34PM +0100, Kieran Bingham wrote:
Hi Jackie,

On 28/07/2021 10:57, Jackie Liu wrote:
Hi Kieran.

How about this.

diff --git a/drivers/gpu/drm/rcar-du/Kconfig
b/drivers/gpu/drm/rcar-du/Kconfig
index b47e74421e34..14cf3e6415d7 100644
--- a/drivers/gpu/drm/rcar-du/Kconfig
+++ b/drivers/gpu/drm/rcar-du/Kconfig
@@ -1,7 +1,7 @@
  # SPDX-License-Identifier: GPL-2.0
  config DRM_RCAR_DU
         tristate "DRM Support for R-Car Display Unit"
-       depends on DRM && OF
+       depends on DRM && OF && m
         depends on ARM || ARM64
         depends on ARCH_RENESAS || COMPILE_TEST
         imply DRM_RCAR_CMM


Of course, this is not a good way, in fact, as long as rcar-du built-in,
cmm must also be built-in, otherwise an error will be reported.

Correct, ideally we should enforce that if the RCAR_DU is built in (y),
then the CMM can only be y/n and not m.

I thought that the depends on DRM_RCAR_DU should do that, but it appears
it doesn't enforce the built-in rule to match...

Do you have a good way?

Kconfig-language.rst says:

   Note: If the combination of FOO=y and BAR=m causes a link error,
   you can guard the function call with IS_REACHABLE()::

         foo_init()
         {
                 if (IS_REACHABLE(CONFIG_BAZ))
                         baz_register(&foo);
                 ...
         }


But that seems redundant, so I suspect we could/should change the
drivers/gpu/drm/rcar-du/rcar_cmm.h from:


#if IS_ENABLED(CONFIG_DRM_RCAR_CMM)
to
#if IS_REACHABLE(CONFIG_DRM_RCAR_CMM)

...


Seems odd that we might allow the module to be compiled at all if it
won't be reachable and that we can't enforce that at the KConfig level -
but at least IS_REACHABLE would prevent the linker error..

This has been discussed before:

https://lore.kernel.org/dri-devel/20200408202711.1198966-6-arnd@xxxxxxxx/

Hi Laurent.

Thanks for tell me this.

--
Jackie Liu


在 2021/7/28 下午4:58, Kieran Bingham 写道:
On 28/07/2021 09:42, Jackie Liu wrote:
From: Jackie Liu <liuyun01@xxxxxxxxxx>

After the patch 78b6bb1d24db ("drm: rcar-du: crtc: Control CMM
operations"),
the cmm module must be included in the crtc. We cannot remove this
configuration option separately. Therefore, simply linking them together
is the best solution, otherwise some errors will be reported.


Yikes, I'm sure we've had plenty of problems with the config options on
this module. The churn alone makes me wonder if it should just be part
of the overall module to simplify things... but...

   rcar_du_crtc.c:(.text+0x194): undefined reference to `rcar_cmm_setup'
   rcar_du_crtc.c:(.text+0x11bc): undefined reference to
`rcar_cmm_enable'
   rcar_du_crtc.c:(.text+0x1604): undefined reference to
`rcar_cmm_disable'
   rcar_du_kms.c:(.text+0x768): undefined reference to `rcar_cmm_init'

Those are guarded by #if IS_ENABLED in the header.

So from that - perhaps we can assume that the config attempted here was
a built-in DU - but a module CMM which wouldn't be supported?



Fixes: 78b6bb1d24db ("rm: rcar-du: crtc: Control CMM operations")

That fixes tag is missing a 'd', but that's trivial.


Reported-by: kernel-bot <k2ci@xxxxxxxxxx>
Signed-off-by: Jackie Liu <liuyun01@xxxxxxxxxx>
---
   drivers/gpu/drm/rcar-du/Kconfig  | 8 --------
   drivers/gpu/drm/rcar-du/Makefile | 2 +-
   2 files changed, 1 insertion(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/rcar-du/Kconfig
b/drivers/gpu/drm/rcar-du/Kconfig
index b47e74421e34..bc71ad2a472f 100644
--- a/drivers/gpu/drm/rcar-du/Kconfig
+++ b/drivers/gpu/drm/rcar-du/Kconfig
@@ -4,7 +4,6 @@ config DRM_RCAR_DU
       depends on DRM && OF
       depends on ARM || ARM64
       depends on ARCH_RENESAS || COMPILE_TEST
-    imply DRM_RCAR_CMM
       imply DRM_RCAR_LVDS
       select DRM_KMS_HELPER
       select DRM_KMS_CMA_HELPER
@@ -14,13 +13,6 @@ config DRM_RCAR_DU
         Choose this option if you have an R-Car chipset.
         If M is selected the module will be called rcar-du-drm.
   -config DRM_RCAR_CMM
-    tristate "R-Car DU Color Management Module (CMM) Support"
-    depends on DRM && OF
-    depends on DRM_RCAR_DU
-    help
-      Enable support for R-Car Color Management Module (CMM).
-

I suspect the issue lies somewhere in this config that the CMM is not
being enforced to be a built in when the DU is built in ?


   config DRM_RCAR_DW_HDMI
       tristate "R-Car Gen3 and RZ/G2 DU HDMI Encoder Support"
       depends on DRM && OF
diff --git a/drivers/gpu/drm/rcar-du/Makefile
b/drivers/gpu/drm/rcar-du/Makefile
index 4d1187ccc3e5..76ff2e15bc2d 100644
--- a/drivers/gpu/drm/rcar-du/Makefile
+++ b/drivers/gpu/drm/rcar-du/Makefile
@@ -5,6 +5,7 @@ rcar-du-drm-y := rcar_du_crtc.o \
            rcar_du_group.o \
            rcar_du_kms.o \
            rcar_du_plane.o \
+         rcar_cmm.o
     rcar-du-drm-$(CONFIG_DRM_RCAR_LVDS)    += rcar_du_of.o \
                          rcar_du_of_lvds_r8a7790.dtb.o \
@@ -15,7 +16,6 @@ rcar-du-drm-$(CONFIG_DRM_RCAR_LVDS)    +=
rcar_du_of.o \
   rcar-du-drm-$(CONFIG_DRM_RCAR_VSP)    += rcar_du_vsp.o
   rcar-du-drm-$(CONFIG_DRM_RCAR_WRITEBACK) += rcar_du_writeback.o
   -obj-$(CONFIG_DRM_RCAR_CMM)        += rcar_cmm.o
   obj-$(CONFIG_DRM_RCAR_DU)        += rcar-du-drm.o
   obj-$(CONFIG_DRM_RCAR_DW_HDMI)        += rcar_dw_hdmi.o
   obj-$(CONFIG_DRM_RCAR_LVDS)        += rcar_lvds.o







