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Subject: Re: [PATCH v4 7/7] drm/mediatek: mtk_dsi: Create connector for
 bridges
To:     Chun-Kuang Hu <chunkuang.hu@kernel.org>,
        Enric Balletbo Serra <eballetbo@gmail.com>
Cc:     linux-kernel <linux-kernel@vger.kernel.org>,
        Collabora Kernel ML <kernel@collabora.com>,
        Nicolas Boichat <drinkcat@chromium.org>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        David Airlie <airlied@linux.ie>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@lists.infradead.org>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Hsin-Yi Wang <hsinyi@chromium.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Sam Ravnborg <sam@ravnborg.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>
References: <20200501152335.1805790-1-enric.balletbo@collabora.com>
 <20200501152335.1805790-8-enric.balletbo@collabora.com>
 <CAFqH_53h=3OXzwLnw1XT3rHYkMPOPNFBdQdPeFmNubN9qq_Twg@mail.gmail.com>
 <CAAOTY_-pOUuM7LQ1jm6gqpg8acMqDWOHxGucY5XOjq0ctGUkzA@mail.gmail.com>
From:   Enric Balletbo i Serra <enric.balletbo@collabora.com>
Message-ID: <53683f2d-23c7-57ab-2056-520c50795ffe@collabora.com>
Date:   Thu, 14 May 2020 17:42:15 +0200
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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

> 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?

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