[PATCH] drm: aspeed: Select CMA only if available

[PATCH] drm: aspeed: Select CMA only if available

[Joel Stanley]

When building this driver for architectures where CMA is not available.

Fixes: 4f2a8f5898ec ("drm: Add ASPEED GFX driver")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>
---
This fixes the build break.

Another question is if we need to select this at all, as we have a
reserved memory region to allocate from. I am not familiar with this
area, so advice is welcome.

 drivers/gpu/drm/aspeed/Kconfig | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/aspeed/Kconfig b/drivers/gpu/drm/aspeed/Kconfig
index 42b74d18a41b..1775fb85ec74 100644
--- a/drivers/gpu/drm/aspeed/Kconfig
+++ b/drivers/gpu/drm/aspeed/Kconfig
@@ -4,8 +4,8 @@ config DRM_ASPEED_GFX
 	select DRM_KMS_HELPER
 	select DRM_KMS_CMA_HELPER
 	select DRM_PANEL
-	select DMA_CMA
-	select CMA
+	select DMA_CMA if HAVE_DMA_CONTIGUOUS
+	select CMA if HAVE_DMA_CONTIGUOUS
 	select MFD_SYSCON
 	help
 	  Chose this option if you have an ASPEED AST2500 SOC Display
-- 
2.20.1

Re: [PATCH] drm: aspeed: Select CMA only if available

[Noralf Trønnes]

Den 05.04.2019 07.28, skrev Joel Stanley:
> When building this driver for architectures where CMA is not available.
> 
> Fixes: 4f2a8f5898ec ("drm: Add ASPEED GFX driver")
> Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Joel Stanley <joel@jms.id.au>
> ---
> This fixes the build break.
> 
> Another question is if we need to select this at all, as we have a
> reserved memory region to allocate from. I am not familiar with this
> area, so advice is welcome.
> 
>  drivers/gpu/drm/aspeed/Kconfig | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/aspeed/Kconfig b/drivers/gpu/drm/aspeed/Kconfig
> index 42b74d18a41b..1775fb85ec74 100644
> --- a/drivers/gpu/drm/aspeed/Kconfig
> +++ b/drivers/gpu/drm/aspeed/Kconfig
> @@ -4,8 +4,8 @@ config DRM_ASPEED_GFX
>  	select DRM_KMS_HELPER
>  	select DRM_KMS_CMA_HELPER
>  	select DRM_PANEL
> -	select DMA_CMA
> -	select CMA
> +	select DMA_CMA if HAVE_DMA_CONTIGUOUS
> +	select CMA if HAVE_DMA_CONTIGUOUS

I'm no expert on this, but the rule is that you should not select
options that are user visible which both of these are. The user should
select them. So I believe that you should remove them.

Docs: Documentation/kbuild/kconfig-language.txt

Noralf.

>  	select MFD_SYSCON
>  	help
>  	  Chose this option if you have an ASPEED AST2500 SOC Display
> 

Re: [PATCH] drm: aspeed: Select CMA only if available

[Joel Stanley]

On Fri, 5 Apr 2019 at 11:20, Noralf Trønnes <noralf@tronnes.org> wrote:
>
>
>
> Den 05.04.2019 07.28, skrev Joel Stanley:
> > When building this driver for architectures where CMA is not available.
> >
> > Fixes: 4f2a8f5898ec ("drm: Add ASPEED GFX driver")
> > Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
> > Reported-by: kernel test robot <lkp@intel.com>
> > Signed-off-by: Joel Stanley <joel@jms.id.au>
> > ---
> > This fixes the build break.
> >
> > Another question is if we need to select this at all, as we have a
> > reserved memory region to allocate from. I am not familiar with this
> > area, so advice is welcome.
> >
> >  drivers/gpu/drm/aspeed/Kconfig | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/aspeed/Kconfig b/drivers/gpu/drm/aspeed/Kconfig
> > index 42b74d18a41b..1775fb85ec74 100644
> > --- a/drivers/gpu/drm/aspeed/Kconfig
> > +++ b/drivers/gpu/drm/aspeed/Kconfig
> > @@ -4,8 +4,8 @@ config DRM_ASPEED_GFX
> >       select DRM_KMS_HELPER
> >       select DRM_KMS_CMA_HELPER
> >       select DRM_PANEL
> > -     select DMA_CMA
> > -     select CMA
> > +     select DMA_CMA if HAVE_DMA_CONTIGUOUS
> > +     select CMA if HAVE_DMA_CONTIGUOUS
>
> I'm no expert on this, but the rule is that you should not select
> options that are user visible which both of these are. The user should
> select them. So I believe that you should remove them.
>
> Docs: Documentation/kbuild/kconfig-language.txt

I agree with your point, I was following what etnaviv did in this case.

As it's written the driver requires CMA to be enabled, or else it
fails to probe:

 [    3.398247] aspeed_gfx 1e6e6000.display: failed to initialize
reserved mem: -22
 [    3.410471] aspeed_gfx: probe of 1e6e6000.display failed with error -22

It was suggested by Michael that 'imply' might be appropriate here.
However, in my testing 'imply' does not set CMA=y . If I start from
both CMA and ASPEED_GFX disabled, and then use menuconfig to enable
ASPEED_GFX, I expected CMA to be enabled. It does not.

In v2[1] of this patch I make the driver depend on ARCH_ASPEED, which
being ARM means it has CMA available. The other case is when enabling
COMPILE_TEST, where the test for HAVE_DMA_CONTIGUOUS will stop the
build break.

CMA only depends on MMU, so we should be safe to select it. I'm open
to other suggstions though.

Cheers,

Joel

[1] https://lore.kernel.org/linux-arm-kernel/20190405081117.27339-1-joel@jms.id.au/