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From:   Chun-Kuang Hu <chunkuang.hu@kernel.org>
Date:   Fri, 24 Sep 2021 07:43:38 +0800
Message-ID: <CAAOTY__dgkSnYnEhYaFsF2G9f+iiBYeA4VhV7gBcrGY6NU_bgg@mail.gmail.com>
Subject: Re: [PATCH v2 0/4] CMDQ refinement of Mediatek DRM driver
To:     Enric Balletbo Serra <eballetbo@gmail.com>
Cc:     Chun-Kuang Hu <chunkuang.hu@kernel.org>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Yongqiang Niu <yongqiang.niu@mediatek.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        DRI Development <dri-devel@lists.freedesktop.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@lists.infradead.org>
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Hi, Enric:

Enric Balletbo Serra <eballetbo@gmail.com> =E6=96=BC 2021=E5=B9=B49=E6=9C=
=8824=E6=97=A5 =E9=80=B1=E4=BA=94 =E4=B8=8A=E5=8D=8812:36=E5=AF=AB=E9=81=93=
=EF=BC=9A
>
> Hi Chun-Kuang,
>
> Missatge de Chun-Kuang Hu <chunkuang.hu@kernel.org> del dia dt., 21 de
> set. 2021 a les 15:15:
> >
> > Hi, Enric:
> >
> > Enric Balletbo Serra <eballetbo@gmail.com> =E6=96=BC 2021=E5=B9=B49=E6=
=9C=8821=E6=97=A5 =E9=80=B1=E4=BA=8C =E4=B8=8B=E5=8D=884:36=E5=AF=AB=E9=81=
=93=EF=BC=9A
> > >
> > > Hi Chun-Kuang,
> > >
> > > (again without html format, sorry for the noise)
> > >
> > > Missatge de Chun-Kuang Hu <chunkuang.hu@kernel.org> del dia dj., 12
> > > d=E2=80=99ag. 2021 a les 2:13:
> > > >
> > > > Chun-Kuang Hu <chunkuang.hu@kernel.org> =E6=96=BC 2021=E5=B9=B48=E6=
=9C=889=E6=97=A5 =E9=80=B1=E4=B8=80 =E4=B8=8A=E5=8D=887:47=E5=AF=AB=E9=81=
=93=EF=BC=9A
> > > > >
> > > > > These refinements include using standard mailbox callback interfa=
ce,
> > > > > timeout detection, and a fixed cmdq_handle.
> > > >
> > > > For this series, applied to mediatek-drm-next [1].
> > > >
> > > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/chunkuang.hu/li=
nux.git/log/?h=3Dmediatek-drm-next
> > > >
> > >
> > > These patches seem to break the display on the Acer Chromebook R 13
> > > (MT8173) in the current mainline. After running a bisection it pointe=
d
> > > me to the following commit
> > >
> > > commit f4be17cd5b14dd73545b0e014a63ebe9ab5ef837
> > > Author: Chun-Kuang Hu <chunkuang.hu@kernel.org>
> > > Date:   Sun Jul 4 15:36:48 2021 +0800
> > >
> > >     drm/mediatek: Remove struct cmdq_client
> > >
> > > Reverting this patch alone is not trivial, so I ended up reverting th=
e
> > > full series, and I can confirm that reverting the full series makes
> > > the display work again.
> >
> > I think you could not just revert "drm/mediatek: Remove struct
> > cmdq_client", you should also revert the patches after it, such as
> >
> > "drm/mediatek: Clear pending flag when cmdq packet is done"
> > "drm/mediatek: Add cmdq_handle in mtk_crtc"
> > "drm/mediatek: Detect CMDQ execution timeout"
> >
>
> Yes, in fact I reverted:
>
> 9efb16c2fdd6 drm/mediatek: Clear pending flag when cmdq packet is done
> bc9241be73d9 drm/mediatek: Add cmdq_handle in mtk_crtc
> 8cdcb3653424 drm/mediatek: Detect CMDQ execution timeout
> f4be17cd5b14 drm/mediatek: Remove struct cmdq_client
> c1ec54b7b5af drm/mediatek: Use mailbox rx_callback instead of cmdq_task_c=
b
>
> Without these patches 5.15-rc2 works again on my platform.
>
> The commit 'c1ec54b7b5af drm/mediatek: Use mailbox rx_callback instead
> of cmdq_task_cb' alone introduces lots of warnings in the kernel
>
> WARNING: CPU: 0 PID: 0 at drivers/mailbox/mtk-cmdq-mailbox.c:198
> cmdq_task_exec_done+0xb8/0xe0

I think the WARN_ON in cmdq driver should be remove because that
warning show that cmdq_task_cb is not used but I that is what I want.

>
> I think is just a leftover or the mentioned warning, but that confused
> me a bit doing the bisection. Then, after commit 'f4be17cd5b14
> drm/mediatek: Remove struct cmdq_client' my system simply gets stuck.
> For now I don't see any obvious mistake but will dig further.
>
> Can I ask you in which platform did you test? And if you can double
> check if your platform is broken too in current mainline?

I've no environment to test code now. I apply this series because I
assume Yongqiang has test his patch "Clear pending flag when cmdq
packet is done".  Before I setup the environment (this may take a long
time), I would find others to fix this problem.
According to your information, "c1ec54b7b5af drm/mediatek: Use mailbox
rx_callback instead of cmdq_task_cb" would cause many warning but
display still work, right? If so, I think we should focus on
"f4be17cd5b14 drm/mediatek: Remove struct cmdq_client".

Regards,
Chun-Kuang.

>
> Thanks,
>   Enric
>
> > If "drm/mediatek: Remove struct cmdq_client" is the patch cause
> > display abnormal, I think you could compare code w/ and w/o this
> > patch. Focus on the value accuracy, such as cmdq_cl and cmdq_chan. And
> > focus on the flow accuracy, such as mtk_drm_crtc_update_config() and
> > ddp_cmdq_cb(). If this could not find the problem, I think the latest
> > way is to break this patch into small patches, changes little in each
> > small patches and we could finally find out the problem.
> >
> > Regards,
> > Chun-Kuang.
> >
> > >
> > > Unfortunately, after the merge window, different things broke for thi=
s
> > > device, and I didn't finish isolating them, and it is not clear to me
> > > yet whether the logs I'm getting are useful for this specific issue o=
r
> > > not. Basically with this series merged the kernel seems to be stuck,
> > > and the display is not working. Latest message is
> > >
> > > [   12.329173] mtk-iommu 10205000.iommu: Partial TLB flush timed out,
> > > falling back to full flush
> > >
> > > Without the series, the kernel goes far and display works, however
> > > there are other issues affecting the cros-ec, but I think that's
> > > another issue.
> > >
> > > I'll try to dig a bit more, but, meanwhile, if you have any idea
> > > please let me know.
> > >
> > > Thanks,
> > >  Enric
> > >
> > >
> > > > Regards,
> > > > Chun-Kuang.
> > > >
> > > > >
> > > > > Changes in v2:
> > > > > 1. Define mtk_drm_cmdq_pkt_create() and mtk_drm_cmdq_pkt_destroy(=
)
> > > > >    when CONFIG_MTK_CMDQ is reachable.
> > > > >
> > > > > Chun-Kuang Hu (4):
> > > > >   drm/mediatek: Use mailbox rx_callback instead of cmdq_task_cb
> > > > >   drm/mediatek: Remove struct cmdq_client
> > > > >   drm/mediatek: Detect CMDQ execution timeout
> > > > >   drm/mediatek: Add cmdq_handle in mtk_crtc
> > > > >
> > > > >  drivers/gpu/drm/mediatek/mtk_drm_crtc.c | 110 ++++++++++++++++++=
++----
> > > > >  1 file changed, 91 insertions(+), 19 deletions(-)
> > > > >
> > > > > --
> > > > > 2.25.1
> > > > >