Re: [PATCH v9 20/23] drm/rockchip: Make VOP driver optional

Sascha Hauer
2022-04-05T09:05:17Z

On Sat, Apr 02, 2022 at 09:25:33AM +0800, Andy Yan wrote:
> Hi Sascha:
>
> On 4/1/22 20:55, Sascha Hauer wrote:
> > On Thu, Mar 31, 2022 at 07:00:34PM +0800, Andy Yan wrote:
> > > Hi:
> > >
> > > On 3/31/22 16:18, Sascha Hauer wrote:
> > > > On Thu, Mar 31, 2022 at 03:20:37PM +0800, Andy Yan wrote:
> > > > > Hi Sascha:
> > > > >
> > > > > On 3/31/22 15:06, Sascha Hauer wrote:
> > > > > > On Wed, Mar 30, 2022 at 08:50:09PM +0800, Andy Yan wrote:
> > > > > > > Hi Sascha:
> > > > > > >
> > > > > > > On 3/30/22 14:39, Sascha Hauer wrote:
> > > > > > > > Hi Andy,
> > > > > > > >
> > > > > > > > On Tue, Mar 29, 2022 at 07:56:27PM +0800, Andy Yan wrote:
> > > > > > > > > Hi Sascha:
> > > > > > > > >
> > > > > > > > > On 3/28/22 23:11, Sascha Hauer wrote:
> > > > > > > > > > With upcoming VOP2 support VOP won't be the only choice anymore, so make
> > > > > > > > > > the VOP driver optional.
> > > > > > > > > >
> > > > > > > > > > Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> > > > > > > > > > ---
> > > > > > > > > > drivers/gpu/drm/rockchip/Kconfig | 8 ++++++++
> > > > > > > > > > drivers/gpu/drm/rockchip/Makefile | 3 ++-
> > > > > > > > > > drivers/gpu/drm/rockchip/rockchip_drm_drv.c | 2 +-
> > > > > > > > > > 3 files changed, 11 insertions(+), 2 deletions(-)
> > > > > > > > > >
> > > > > > > > > > diff --git a/drivers/gpu/drm/rockchip/Kconfig b/drivers/gpu/drm/rockchip/Kconfig
> > > > > > > > > > index fa5cfda4e90e3..7d22e2997a571 100644
> > > > > > > > > > --- a/drivers/gpu/drm/rockchip/Kconfig
> > > > > > > > > > +++ b/drivers/gpu/drm/rockchip/Kconfig
> > > > > > > > > > @@ -23,8 +23,16 @@ config DRM_ROCKCHIP
> > > > > > > > > > if DRM_ROCKCHIP
> > > > > > > > > > +config ROCKCHIP_VOP
> > > > > > > > > > + bool "Rockchip VOP driver"
> > > > > > > > > > + default y
> > > > > > > > > > + help
> > > > > > > > > > + This selects support for the VOP driver. You should enable it
> > > > > > > > > > + on all older SoCs up to RK3399.
> > > > > > > > That reminds me that I wanted to rephrase this. Will change in next
> > > > > > > > round.
> > > > > > > >
> > > > > > > > > > +
> > > > > > > > > > config ROCKCHIP_ANALOGIX_DP
> > > > > > > > > > bool "Rockchip specific extensions for Analogix DP driver"
> > > > > > > > > > + depends on ROCKCHIP_VOP
> > > > > > > > > Aanlogix dp is also on vop2 base soc such as  rk356x and rk3588.
> > > > > > BTW I just looked at the downstream driver. Here we have the same
> > > > > > situation that the analogix dp driver calls rockchip_drm_wait_vact_end()
> > > > > > which is implemented in the VOP driver, so when the analogix dp driver
> > > > > > is actually used on a VOP2 SoC then it is either used in a way that
> > > > > > rockchip_drm_wait_vact_end() will never be called or it explodes in all
> > > > > > colours.
> > > > > >
> > > > > > > > I added the dependency because analogix_dp-rockchip.c calls
> > > > > > > > rockchip_drm_wait_vact_end() which is implemented in the VOP driver,
> > > > > > > > so this driver currenty can't work with the VOP2 driver and can't
> > > > > > > > be linked without the VOP driver being present.
> > > > > > > > I'll add a few words to the commit message.
> > > > > > > Maybe a better direction is move rockchip_drm_wait_vact_end from the VOP
> > > > > > > driver to rockchip_drm_drv.c
> > > > > > I am not sure if that's really worth it. Yes, the direction might be the
> > > > > > right one, but I would really prefer when somebody does the change who
> > > > > > can test and confirm that the analogix dp really works with VOP2 in the
> > > > > > end.
> > > > > If follow this point, the current DW_MIPI also has not been tested for
> > > > > confirm that it
> > > > >
> > > > > can really work with VOP2, so you should also make it depends on
> > > > > ROCKCHIP_VOP.

Here you are suggesting to add even more Kconfig dependencies.

> > > > Well at least I have patches here which make DW_MIPI work with VOP2 ;)
> > >
> > > But you DW_MIPI patches for rk356x didn't come. So this is not keep
> > > consistency with this point.
> > >
> > > > What about the others, like LVDS and RGB?
> > >
> > > Yes, we also have other interface , RK356X has LVDS/RGB/BT1120/BT656, RK3588
> > > has BT1120/BT656, no LVDS or RGB.
> > >
> > > > > I think the current solution is just a workaround to make your patch pass
> > > > > the kernel compile
> > > > Indeed.
> > > >
> > > > I agree that it would be good to add a note somewhere which outputs
> > > > work with the VOP2 driver (currently only HDMI), but I wonder if Kconfig
> > > > dependencies is the right place for it, because only people who deliberately
> > > > disable VOP support will see this information.
> > > > Maybe we should rather add it to the Kconfig help text?
> > >
> > > If a device is supported for this soc, we will add dt node at the dtsi file.
> > >
> > > A Kconfig dependencies don't seems a good idea.

Here you say Kconfig dependencies are no good idea.

> > Ok, this means we can keep my current approach with just letting
> > ROCKCHIP_ANALOGIX_DP depend on ROCKCHIP_VOP to avoid having a non
>
> Excuse me? How do you get this conclusion ?

Given that you say that you want to have both more and less Kconfig
dependencies I came to the conclusion that I only add one where it's
necessary to compile the driver.

>
> I said before,  vop and vop2 based platforms both have ROCKCHIP_ANALOGIX_DP.

Maybe, but vop2 with ROCKCHIP_ANALOGIX_DP doesn't even work in the
Rockchip downstream kernel, so I wonder how relevant this usecase really
is.

>
> If this patch will cause the compile error, please do a real fix, not a

I can't, because I don't have any hardware to test the Analogix DP on a
VOP hardware, and given that Analogix DP in conjunction with VOP2 hardware is
not even supported in the downstream Kernel I am not sure if it's really
worth doing that.

Moving rockchip_drm_wait_vact_end() to rockchip_drm_drv.c doesn't work
with mainline currently, we first would have to add a struct crtc_funcs
to struct rockchip_drm_private. Yes, that could be done.

>
> workaround that may deliver misleading information.

The Kconfig dependency quite clearly says that the Analogix DP currently
doesn't work with the VOP2. Anyone who wants to change that can use that
information as a starting point and implement whatever is necessary and
likely has the hardware to verify the work. I don't want to solve
problems that *might* arise in the future, and in this case it's not a
direction decision that we might regret in the future.

Sascha

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