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    SubjectRe: [PATCH v4 7/7] drm/mediatek: mtk_dsi: Create connector for bridges
    Hi, Enric:

    Enric Balletbo i Serra <enric.balletbo@collabora.com> 於 2020年5月15日 週五 上午1:35寫道:
    >
    > Hi again,
    >
    > On 14/5/20 19:12, Enric Balletbo i Serra wrote:
    > > Hi Chun-Kuang,
    > >
    > > On 14/5/20 18:44, Chun-Kuang Hu wrote:
    > >> Hi, Enric:
    > >>
    > >> Enric Balletbo i Serra <enric.balletbo@collabora.com> 於 2020年5月14日 週四 下午11:42寫道:
    > >>>
    > >>> Hi Chun-Kuang,
    > >>>
    > >>> On 14/5/20 16:28, Chun-Kuang Hu wrote:
    > >>>> Hi, Enric:
    > >>>>
    > >>>> Enric Balletbo Serra <eballetbo@gmail.com> 於 2020年5月14日 週四 上午12:41寫道:
    > >>>>>
    > >>>>> Hi Chun-Kuang,
    > >>>>>
    > >>>>> Missatge de Enric Balletbo i Serra <enric.balletbo@collabora.com> del
    > >>>>> dia dv., 1 de maig 2020 a les 17:25:
    > >>>>>>
    > >>>>>> Use the drm_bridge_connector helper to create a connector for pipelines
    > >>>>>> that use drm_bridge. This allows splitting connector operations across
    > >>>>>> multiple bridges when necessary, instead of having the last bridge in
    > >>>>>> the chain creating the connector and handling all connector operations
    > >>>>>> internally.
    > >>>>>>
    > >>>>>> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
    > >>>>>> Acked-by: Sam Ravnborg <sam@ravnborg.org>
    > >>>>>
    > >>>>> A gentle ping on this, I think that this one is the only one that
    > >>>>> still needs a review in the series.
    > >>>>
    > >>>> This is what I reply in patch v3:
    > >>>>
    > >>>
    > >>> Sorry for missing this.
    > >>>
    > >>>> I think the panel is wrapped into next_bridge here,
    > >>>>
    > >>>
    > >>> Yes, you can have for example:
    > >>>
    > >>> 1. drm_bridge (mtk_dsi) -> drm_bridge (ps8640 - dsi-to-edp) -> drm_panel_bridge
    > >>> (edp panel)
    > >>>
    > >>> or a
    > >>>
    > >>> 2. drm_bridge (mtk_dsi)-> drm_panel_bridge (dsi panel)
    > >>>
    > >>> The _first_ one is my use case
    > >>>
    > >>>> if (panel) {
    > >>>
    > >>> This handles the second case, where you attach a dsi panel.
    > >>>
    > >>>> dsi->next_bridge = devm_drm_panel_bridge_add(dev, panel);
    > >>>>
    > >>>> so the next_bridge is a panel_bridge, in its attach function
    > >>>> panel_bridge_attach(),
    > >>>> according to the flag DRM_BRIDGE_ATTACH_NO_CONNECTOR, if not exist,
    > >>>> it would create connector and attach connector to panel.
    > >>>>
    > >>>> I'm not sure this flag would exist or not, but for both case, it's strange.
    > >>>> If exist, you create connector in this patch but no where to attach
    > >>>> connector to panel.
    > >>>
    > >>> Yes, in fact, this is transitional patch needed, as once I converted mtk_dpi,
    > >>> mtk_dsi and mtk_hdmi to the new drm_bridge API the drm_bridge_connector_init()
    > >>> will be done in mtk_drm_drv. We will need to call drm_bridge_connector_init for
    > >>> dpi and dsi pipes and remove that call from mtk_dsi and mtk_dpi drivers. The
    > >>> graphic controller driver should create connectors and CRTCs, as example you can
    > >>> take a look at drivers/gpu/drm/omapdrm/omap_drv.c
    > >>>
    > >>
    > >> I have such question because I've reviewed omap's driver. In omap's
    > >> driver, after it call drm_bridge_connector_init(), it does this:
    > >>
    > >> if (pipe->output->panel) {
    > >> ret = drm_panel_attach(pipe->output->panel,
    > >> pipe->connector);
    > >> if (ret < 0)
    > >> return ret;
    > >> }
    > >>
    > >> In this patch, you does not do this.
    > >>
    > >
    > > I see, so yes, I am probably missing call drm_panel_attach in case there is a
    > > direct panel attached. Thanks for pointing it.
    > >
    > > I'll send a new version adding the drm_panel_attach call.
    > >
    >
    > Wait, shouldn't panel be attached on the call of mtk_dsi_bridge_attach as
    > next_bridge points to a bridge or a panel?
    >
    > static int mtk_dsi_bridge_attach(struct drm_bridge *bridge,
    > enum drm_bridge_attach_flags flags)
    > {
    > struct mtk_dsi *dsi = bridge_to_dsi(bridge);
    >
    > /* Attach the panel or bridge to the dsi bridge */
    > return drm_bridge_attach(bridge->encoder, dsi->next_bridge,
    > &dsi->bridge, flags);
    > }
    >
    > Or I am continuing misunderstanding all this?
    >

    My point is: when do you attach panel to a connector?
    In this patch,

    ret = drm_bridge_attach(&dsi->encoder, &dsi->bridge, NULL,
    DRM_BRIDGE_ATTACH_NO_CONNECTOR);

    it would call into mtk_dsi_bridge_attach() with
    DRM_BRIDGE_ATTACH_NO_CONNECTOR, and call into panel_bridge_attach()
    with DRM_BRIDGE_ATTACH_NO_CONNECTOR.
    If you does not pass DRM_BRIDGE_ATTACH_NO_CONNECTOR into
    panel_bridge_attach(), it would create a connector and attach panel to
    that connector.
    And you pass DRM_BRIDGE_ATTACH_NO_CONNECTOR into
    panel_bridge_attach(), so I thiink you need to create connector and
    attach panel to that connector by yourself (this is what omap does).

    Regards,
    Chun-Kuang.

    > >>>> If not exist, the next_brige would create one connector and this brige
    > >>>> would create another connector.
    > >>>>
    > >>>> I think in your case, mtk_dsi does not directly connect to a panel, so
    > >>>
    > >>> Exactly
    > >>>
    > >>>> I need a exact explain. Or someone could test this on a
    > >>>> directly-connect-panel platform.
    > >>>
    > >>> I don't think I am breaking this use case but AFAICS there is no users in
    > >>> mainline that directly connect a panel using the mediatek driver. As I said my
    > >>> use case is the other so I can't really test. Do you know anyone that can test this?
    > >>
    > >> I'm not sure who can test this, but [1], which is sent by YT Shen in a
    > >> series, is a patch to support dsi command mode so dsi could directly
    > >> connect to panel.
    > >>
    > >> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/gpu/drm/mediatek?h=v5.7-rc5&id=21898816831fc60c92dd634ab4316a24da7eb4af
    > >>
    > >> It's better that someone could test this case, but if no one would
    > >> test this, I could also accept a good-look patch.
    > >>
    > >> Regards,
    > >> Chun-Kuang.
    > >>
    > >>>
    > >>> Thanks,
    > >>> Enric
    > >>>
    > >>>>
    > >>>> Regards,
    > >>>> Chun-Kuang.
    > >>>>
    > >>>>>
    > >>>>> Thanks,
    > >>>>> Enric
    > >>>>>
    > >>>>>> ---
    > >>>>>>
    > >>>>>> Changes in v4: None
    > >>>>>> Changes in v3:
    > >>>>>> - Move the bridge.type line to the patch that adds drm_bridge support. (Laurent Pinchart)
    > >>>>>>
    > >>>>>> Changes in v2: None
    > >>>>>>
    > >>>>>> drivers/gpu/drm/mediatek/mtk_dsi.c | 13 ++++++++++++-
    > >>>>>> 1 file changed, 12 insertions(+), 1 deletion(-)
    > >>>>>>
    > >>>>>> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
    > >>>>>> index 4f3bd095c1ee..471fcafdf348 100644
    > >>>>>> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
    > >>>>>> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
    > >>>>>> @@ -17,6 +17,7 @@
    > >>>>>>
    > >>>>>> #include <drm/drm_atomic_helper.h>
    > >>>>>> #include <drm/drm_bridge.h>
    > >>>>>> +#include <drm/drm_bridge_connector.h>
    > >>>>>> #include <drm/drm_mipi_dsi.h>
    > >>>>>> #include <drm/drm_of.h>
    > >>>>>> #include <drm/drm_panel.h>
    > >>>>>> @@ -183,6 +184,7 @@ struct mtk_dsi {
    > >>>>>> struct drm_encoder encoder;
    > >>>>>> struct drm_bridge bridge;
    > >>>>>> struct drm_bridge *next_bridge;
    > >>>>>> + struct drm_connector *connector;
    > >>>>>> struct phy *phy;
    > >>>>>>
    > >>>>>> void __iomem *regs;
    > >>>>>> @@ -977,10 +979,19 @@ static int mtk_dsi_encoder_init(struct drm_device *drm, struct mtk_dsi *dsi)
    > >>>>>> */
    > >>>>>> dsi->encoder.possible_crtcs = 1;
    > >>>>>>
    > >>>>>> - ret = drm_bridge_attach(&dsi->encoder, &dsi->bridge, NULL, 0);
    > >>>>>> + ret = drm_bridge_attach(&dsi->encoder, &dsi->bridge, NULL,
    > >>>>>> + DRM_BRIDGE_ATTACH_NO_CONNECTOR);
    > >>>>>> if (ret)
    > >>>>>> goto err_cleanup_encoder;
    > >>>>>>
    > >>>>>> + dsi->connector = drm_bridge_connector_init(drm, &dsi->encoder);
    > >>>>>> + if (IS_ERR(dsi->connector)) {
    > >>>>>> + DRM_ERROR("Unable to create bridge connector\n");
    > >>>>>> + ret = PTR_ERR(dsi->connector);
    > >>>>>> + goto err_cleanup_encoder;
    > >>>>>> + }
    > >>>>>> + drm_connector_attach_encoder(dsi->connector, &dsi->encoder);
    > >>>>>> +
    > >>>>>> return 0;
    > >>>>>>
    > >>>>>> err_cleanup_encoder:
    > >>>>>> --
    > >>>>>> 2.26.2
    > >>>>>>
    > >>>>>>
    > >>>>>> _______________________________________________
    > >>>>>> Linux-mediatek mailing list
    > >>>>>> Linux-mediatek@lists.infradead.org
    > >>>>>> http://lists.infradead.org/mailman/listinfo/linux-mediatek
    > >

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