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Subject: Re: [PATCH RFC v3 2/6] drm/sprd: add Unisoc's drm kms master
To:     tang pengchuan <kevin3.tang@gmail.com>,
        Sam Ravnborg <sam@ravnborg.org>
Cc:     mark.rutland@arm.com, Baolin Wang <baolin.wang@linaro.org>,
        David Airlie <airlied@linux.ie>,
        Chunyan Zhang <zhang.lyra@gmail.com>,
        "Linux-Kernel@Vger. Kernel. Org" <linux-kernel@vger.kernel.org>,
        ML dri-devel <dri-devel@lists.freedesktop.org>,
        robh+dt@kernel.org, Orson Zhai <orsonzhai@gmail.com>
References: <1582271336-3708-1-git-send-email-kevin3.tang@gmail.com>
 <1582271336-3708-3-git-send-email-kevin3.tang@gmail.com>
 <20200221213652.GD3456@ravnborg.org>
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 <20200222212713.GA30872@ravnborg.org>
 <CAFPSGXZWC7dASrVP3MTWS+oJjcwQEK0T+BLiwZ-cxk2OyeNZQw@mail.gmail.com>
From:   Thomas Zimmermann <tzimmermann@suse.de>
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Date:   Tue, 25 Feb 2020 08:38:47 +0100
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From: Thomas Zimmermann <tzimmermann@suse.de>
To: tang pengchuan <kevin3.tang@gmail.com>, Sam Ravnborg <sam@ravnborg.org>
Cc: mark.rutland@arm.com, Baolin Wang <baolin.wang@linaro.org>,
 David Airlie <airlied@linux.ie>, Chunyan Zhang <zhang.lyra@gmail.com>,
 "Linux-Kernel@Vger. Kernel. Org" <linux-kernel@vger.kernel.org>,
 ML dri-devel <dri-devel@lists.freedesktop.org>, robh+dt@kernel.org,
 Orson Zhai <orsonzhai@gmail.com>
Message-ID: <3acf15ff-6a41-ca13-e219-301fcef983fa@suse.de>
Subject: Re: [PATCH RFC v3 2/6] drm/sprd: add Unisoc's drm kms master
References: <1582271336-3708-1-git-send-email-kevin3.tang@gmail.com>
 <1582271336-3708-3-git-send-email-kevin3.tang@gmail.com>
 <20200221213652.GD3456@ravnborg.org>
 <CAFPSGXacMKTPrxk_FOrwrvH_XfmO3dYCCa_GoPCe_HUfQFPHtw@mail.gmail.com>
 <20200222212713.GA30872@ravnborg.org>
 <CAFPSGXZWC7dASrVP3MTWS+oJjcwQEK0T+BLiwZ-cxk2OyeNZQw@mail.gmail.com>
In-Reply-To: <CAFPSGXZWC7dASrVP3MTWS+oJjcwQEK0T+BLiwZ-cxk2OyeNZQw@mail.gmail.com>

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Hi

Am 23.02.20 um 05:26 schrieb tang pengchuan:
>=20
>=20
> On Sun, Feb 23, 2020 at 5:27 AM Sam Ravnborg <sam@ravnborg.org
> <mailto:sam@ravnborg.org>> wrote:
>=20
>     Hi Kevin/tang.
>=20
>     Thanks for the quick and detailed feedback.
>     Your questions are addressed below.
>=20
>     =C2=A0 =C2=A0 =C2=A0 =C2=A0 Sam
>=20
>=20
>     > > > +static int sprd_drm_bind(struct device *dev)
>     > > > +{
>     > > > +=C2=A0 =C2=A0 =C2=A0struct drm_device *drm;
>     > > > +=C2=A0 =C2=A0 =C2=A0struct sprd_drm *sprd;
>     > > > +=C2=A0 =C2=A0 =C2=A0int err;
>     > > > +
>     > > > +=C2=A0 =C2=A0 =C2=A0drm =3D drm_dev_alloc(&sprd_drm_drv, dev=
);
>     > > > +=C2=A0 =C2=A0 =C2=A0if (IS_ERR(drm))
>     > > > +=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0return PTR_E=
RR(drm);
>     > > You should embed drm_device in struct sprd_drm.
>     > > See example code in drm/drm_drv.c
>     > >
>     > > This is what modern drm drivers do.
>     > >
>     > > I *think* you can drop the component framework if you do this.
>     > >
>     > I have read it(drm/drm_drv.c) carefully, if drop the component
>     framework,
>     > the whole our drm driver maybe need to redesign, so i still want
>     to keep
>     > current design.
>     OK, fine.
>=20
>     > > > +=C2=A0 =C2=A0 =C2=A0sprd_drm_mode_config_init(drm);
>     > > > +
>     > > > +=C2=A0 =C2=A0 =C2=A0/* bind and init sub drivers */
>     > > > +=C2=A0 =C2=A0 =C2=A0err =3D component_bind_all(drm->dev, drm=
);
>     > > > +=C2=A0 =C2=A0 =C2=A0if (err) {
>     > > > +=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0DRM_ERROR("f=
ailed to bind all component.\n");
>     > > > +=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0goto err_dc_=
cleanup;
>     > > > +=C2=A0 =C2=A0 =C2=A0}
>     > > When you have a drm_device - which you do here.
>     > > Then please use drm_err() and friends for error messages.
>     > > Please verify all uses of DRM_XXX
>     > >
>     >=C2=A0 =C2=A0modern drm drivers need drm_xxx to replace DRM_XXX?
>     Yes, use of DRM_XXX is deprecated - when you have a drm_device.
>=20
>     > >
>     > > > +=C2=A0 =C2=A0 =C2=A0/* with irq_enabled =3D true, we can use=
 the vblank
>     feature. */
>     > > > +=C2=A0 =C2=A0 =C2=A0drm->irq_enabled =3D true;
>     > > I cannot see any irq being installed. This looks wrong.
>     > >
>     > Our display controller isr is been register on crtc
>     driver(sprd_dpu.c), not
>     > here.
>=20
>     I think you just need to move this to next patch and then it is fin=
e.
>=20
> Here is the advice given by Thomas Zimmermann, similar to the advice yo=
u
> gave.
> I have given thomas feedback about my questions, maybe thomas didn't se=
e
> my email, so there is no reply.

I have been busy last week. Sorry for not getting back to you.

>=20
> But I've always been confused, because irq is initialized in drm driver=

> for other guys, why not for me?

Do you have an example?

Best regards
Thomas

> Can you help to tell the reason in detail, looking forward to your answ=
ers.
>=20
> Thomas's suggestion=EF=BC=9A
> -----------------------------------------------------------------------=
--------------------
>=20
> This line indicates the problem's design. The irq is initialized in the=

> sub-device code, but the device state is set here. Instead both should
> be set in the same place.
>=20
>> +
>> +=C2=A0 =C2=A0 =C2=A0/* reset all the states of crtc/plane/encoder/con=
nector */
>> +=C2=A0 =C2=A0 =C2=A0drm_mode_config_reset(drm);
>> +
>> +=C2=A0 =C2=A0 =C2=A0/* init kms poll for handling hpd */
>> +=C2=A0 =C2=A0 =C2=A0drm_kms_helper_poll_init(drm);
>=20
> Most of this function's code should be moved into the sub-device bind
> function.
>=20
> Here, maybe do:
>=20
> =C2=A0* allocate device structures
> =C2=A0* call component_bind_all()
> =C2=A0* on success, register device
>=20
> The sub-device function should then do
>=20
> =C2=A0* init modesetting, crtc, planes, etc.
> =C2=A0* do drm_mode_config_reset()
> =C2=A0* init vblanking
> =C2=A0* init the irq
> =C2=A0* do drm_kms_helper_poll_init()
>=20
> roughtly in that order. It makes sense to call drm_vblank_init() after
> drm_mode_config_reset(), as vblanking uses some of the mode-config fiel=
ds.=C2=A0
> -----------------------------------------------------------------------=
-------------------------------
>=20
>=20
>     =C2=A0 =C2=A0 =C2=A0 =C2=A0 Sam
>=20
>=20
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>=20

--=20
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 N=C3=BCrnberg, Germany
(HRB 36809, AG N=C3=BCrnberg)
Gesch=C3=A4ftsf=C3=BChrer: Felix Imend=C3=B6rffer


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