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From:   Damian Kos <dkos@cadence.com>
To:     Heiko Stuebner <heiko@sntech.de>,
        Artur Jedrysek <jartur@cadence.com>,
        "jbergsagel@ti.com" <jbergsagel@ti.com>
CC:     David Airlie <airlied@linux.ie>, Rob Herring <robh+dt@kernel.org>,
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        Archit Taneja <architt@codeaurora.org>,
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        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Gustavo Padovan <gustavo@padovan.org>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Sean Paul <sean@poorly.run>, Sandy Huang <hjc@rock-chips.com>,
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        Piotr Sroka <piotrs@cadence.com>,
        Quentin Schulz <quentin.schulz@free-electrons.com>
Subject: RE: [PATCH v4 5/5] drm: bridge: add support for Cadence MHDP DPI/DP
 bridge
Thread-Topic: [PATCH v4 5/5] drm: bridge: add support for Cadence MHDP DPI/DP
 bridge
Thread-Index: AQHUUPIalRFVqo98AEqNqiK3AF19GqT6bAeAgATn/2CAAA4tgIAABRGw
Date:   Mon, 24 Sep 2018 12:47:39 +0000
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Heiko,

> Hi Damian,
>=20
> Am Montag, 24. September 2018, 13:40:03 CEST schrieb Damian Kos:
> > > Am Donnerstag, 20. September 2018, 16:54:40 CEST schrieb Damian Kos:
> > > > From: Quentin Schulz <quentin.schulz@free-electrons.com>
> > > >=20
> > > > This adds basic support for Cadence MHDP DPI to DP bridge.
> > > >=20
> > > > Basically, it takes a DPI stream as input and output it encoded in=
=20
> > > > DP format. It's missing proper HPD, HDCP and currently supports=20
> > > > only SST mode.
> > > >=20
> > > > Changes made in the low level driver (cdn-dp-reg.*):
> > > > - moved it to from drivers/gpu/drm/rockchip to
> > > >   drivers/gpu/drm/bridge/cdns-mhdp-common.*
> > > > - functions for sending/receiving commands are now public
> > > > - added functions for reading registers and link training
> > > >   adjustment
> > > >=20
> > > > Changes made in RK's driver (cdn-dp-core.*):
> > > > - Moved audio_info and audio_pdev fields from cdn_dp_device to
> > > >   cdns_mhdp_device structure.
> > > >=20
> > > > Signed-off-by: Quentin Schulz <quentin.schulz@free-electrons.com>
> > > > Signed-off-by: Damian Kos <dkos@cadence.com>
> > >=20
> > > [...]
> > >=20
> > > > diff --git a/drivers/gpu/drm/rockchip/Kconfig
> > > > b/drivers/gpu/drm/rockchip/Kconfig
> > > > index 0ccc76217ee4..129b0529f3e1 100644
> > > > --- a/drivers/gpu/drm/rockchip/Kconfig
> > > > +++ b/drivers/gpu/drm/rockchip/Kconfig
> > > > @@ -27,7 +27,9 @@ config ROCKCHIP_ANALOGIX_DP
> > > > =20
> > > >  config ROCKCHIP_CDN_DP
> > > >          bool "Rockchip cdn DP"
> > > > -	depends on EXTCON=3Dy || (EXTCON=3Dm && DRM_ROCKCHIP=3Dm)
> > > > +	depends on DRM_ROCKCHIP=3Dm
> > >=20
> > > Sorry, I wasn't fast enough in my reply to you mail to catch that bef=
ore your v4, but I don't think this is necessary.
> > > Instead I do guess, the select below should do the right thing by mak=
ing EXTCON=3Dy if DRM_ROCKCHIP=3Dy.
> > >=20
> > > Somewhat clumsily verified by making EXTCON=3Dm in my defconfig and s=
eeing get changed to y upon build, which I guess comes from a different "se=
lect" in the config.
> > >=20
> >=20
> > I've changed it to:
> >=20
> > config ROCKCHIP_CDN_DP
> >         bool "Rockchip cdn DP"
> >         depends on DRM_ROCKCHIP
> >         select EXTCON if DRM_ROCKCHIP=3Dy
> >         select DRM_CDNS_MHDP
> >         help...
> >=20
> > and it seems that there are no issues. At least for me.
> >=20
> > Please let me know if that's OK.
>=20
> nope, just do "select EXTCON" . It works nicely and the above would not s=
elect EXTCON at all if the the rockchip-drm driver gets built into the kern=
el.

That's weird. I'm pretty sure that I've tried that and got circular depende=
ncy error, but now it's working fine. Anyway:

config ROCKCHIP_CDN_DP
        bool "Rockchip cdn DP"
        depends on DRM_ROCKCHIP
        select EXTCON
        select DRM_CDNS_MHDP
        help...

>=20
> To be sure I just did a little experiment and added:
>=20
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kcon=
fig index 4ad85c046dcd..64e2b096afd8 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -154,4 +154,11 @@ source "drivers/gpu/drm/bridge/ite/Kconfig"
> =20
>  source "drivers/gpu/drm/bridge/synopsys/Kconfig"
> =20
> +config DRM_TMP1
> +       tristate "option to select"
> +
> +config DRM_TMP2
> +       tristate "option doing the selecting"
> +       select DRM_TMP1
> +
>=20
> If I select DRM_TMP2=3Dm as module I end up with CONFIG_DRM_TMP1=3Dm CONF=
IG_DRM_TMP2=3Dm in the defconfig and wit DRM_TMP2=3Dy it changes to CONFIG_=
DRM_TMP1=3Dy CONFIG_DRM_TMP2=3Dy
>=20
> so all is well with just doing "select EXTCON" above and will select the =
correct "m" or "y" stance as needed.
>=20
>=20
> Heiko

--
Damian