Date:	Thu, 17 Mar 2016 14:49:46 +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 16 March 2016 at 16:23, Tomeu Vizoso <tomeu@...euvizoso.net> wrote:
> 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?

Apparently, when the VOP is re-enabled, it will start scanning from
the framebuffer address that had been set last.

Because DMA addresses are recycled and there's going to be a low
number of framebuffers, this isn't going to be obvious unless we make
sure that there isn't a FB allocated at that DMA address any more.

The attached test case does just that.

Regards,

Tomeu

> 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" (3588 bytes)

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