linux-kernel - Re: [PATCH v15 1/3] drm: rockchip: Add basic drm driver

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Date:	Wed, 16 Mar 2016 16:23:58 +0100
From:	Tomeu Vizoso <tomeu@...euvizoso.net>
To:	Mark yao <mark.yao@...k-chips.com>
Cc:	Heiko Stübner <heiko@...ech.de>,
	Boris BREZILLON <boris.brezillon@...e-electrons.com>,
	David Airlie <airlied@...il.com>,
	Rob Clark <robdclark@...il.com>,
	Daniel Vetter <daniel@...ll.ch>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	Grant Likely <grant.likely@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	John Stultz <john.stultz@...aro.org>,
	Rom Lemarchand <romlem@...gle.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	Douglas Anderson <dianders@...omium.org>,
	Stéphane Marchesin <marcheu@...omium.org>,
	Dominik Behr <dbehr@...omium.org>,
	Olof Johansson <olof@...om.net>,
	Daniel Kurtz <djkurtz@...omium.org>,
	Eddie Cai <cf@...k-chips.com>, simon xue <xxm@...k-chips.com>,
	Tao Huang <huangtao@...k-chips.com>,
	Kever Yang <kever.yang@...k-chips.com>, yxj@...k-chips.com,
	xw@...k-chips.com
Subject: Re: [PATCH v15 1/3] drm: rockchip: Add basic drm driver

On 15 March 2016 at 02:30, Mark yao <mark.yao@...k-chips.com> wrote:
> On 2016年03月14日 21:35, Tomeu Vizoso wrote:
>>
>> On 2 December 2014 at 10:15, Mark Yao <mark.yao@...k-chips.com> wrote:
>>>
>>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>>> b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>>> new file mode 100644
>>> index 0000000..e7ca25b
>>> --- /dev/null
>>> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>>> @@ -0,0 +1,1455 @@
>>
>> ...
>>>
>>> +static bool vop_crtc_mode_fixup(struct drm_crtc *crtc,
>>> +                               const struct drm_display_mode *mode,
>>> +                               struct drm_display_mode *adjusted_mode)
>>> +{
>>> +       if (adjusted_mode->htotal == 0 || adjusted_mode->vtotal == 0)
>>> +               return false;
>>
>> Hi Mark,
>>
>> what's the rationale for this?
>>
>> Disabling a CRTC as in [0] will cause mode_fixup() to be called with
>> an empty mode, failing that test.
>>
>> Removing the check seems to get things working fine for a short while,
>> but a later modeset invariably gets the VOP to hang (as reported by
>> [1]).
>>
>> Do you know why that check was put in place and what exactly could be
>> causing the hw to hang?
>>
>> [0]
>> https://cgit.freedesktop.org/xorg/app/intel-gpu-tools/tree/lib/igt_kms.c#n1616
>> [1]
>> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/drivers/gpu/drm/rockchip/rockchip_drm_vop.c#n873
>>
>> Thanks,
>>
>> Tomeu
>>
> Hi Tomeu
>
> Just thinking that "adjusted_mode->htotal == 0 || adjusted_mode->vtotal ==
> 0" is not a good mode for vop.

Ah, ok. Guess it should be removed then so we don't break userspace?

> And you said VOP hang, only WARN_ON error message? or system hang, die?

Sorry, the symptom was only the warning, I just went a bit too far and
assumed the VOP had stopped working at all.

> I think maybe crtc disable too fast, vblank is off, then no one can feed the
> wait_update_complete.
> Can you test it again with following patch?

Actually, in today's testing I don't see that happening any more,
sorry about that :/

What I have been looking at today is a related issue when running the
kms_flip_event_leak test from intel-gpu-tools. If I remove the check
mentioned above so CRTCs can be disabled with the SetCRTC IOCTL, I see
this page fault the second and subsequent times I run the test.

[   75.809031] rk_iommu ff930300.iommu: Page fault at 0x01000000 of type read
[   75.809035] rk_iommu ff930300.iommu: iova = 0x01000000: dte_index:
0x4 pte_index: 0x0 page_offset: 0x0
[   75.809040] rk_iommu ff930300.iommu: mmu_dte_addr: 0x2c258000
dte@...c258010: 0x2c561001 valid: 1 pte@...c561000: 0x2a000006 valid:
0 page@...0000000 flags: 0x0
[   76.951288] rk_iommu ff930300.iommu: Enable stall request timed
out, status: 0x00004b

I have written a smaller standalone test that is attached in case you
want to check it out, but I haven't been able to find out why it only
happens when the test is rerun.

Apparently the VOP is still trying to read a BO (0x01000000) right
when the kernel frees it, but from what I can see, it should be
scanning another BO at that point.

Do you have any ideas on what could be happening?

Thanks,

Tomeu

> drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> @@ -503,6 +503,8 @@ static void vop_crtc_disable(struct drm_crtc *crtc)
>         if (!vop->is_enabled)
>                 return;
>  +       vop_crtc_wait_for_update(crtc);
> +
>         drm_crtc_vblank_off(crtc);
>
> Thanks.
>
> --
> Ｍark Yao
>
>

View attachment "page_fault.c" of type "text/x-csrc" (3368 bytes)