Message-ID: <CAAObsKBt-+syM+btLdRj64OYBzZNV96a7zpmRyn5nSoTuwQsVg@mail.gmail.com>
Date:	Mon, 21 Mar 2016 15:55:26 +0100
From:	Tomeu Vizoso <tomeu.vizoso@...labora.com>
To:	Mark yao <mark.yao@...k-chips.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] drm/rockchip: vop: Reset yrgb_mst when re-enabling

On 19 March 2016 at 02:15, Mark yao <mark.yao@...k-chips.com> wrote:
> On 2016年03月18日 19:22, Tomeu Vizoso wrote:
>>
>> When the VOP is re-enabled, it will start scanning right away the
>> framebuffers that were configured from the last time, even if those have
>> been destroyed already. To prevent the VOP from trying to access freed
>> memory, reset the registers that hold pointers to framebuffers right
>> after we can write to them, but before the VOP is awaken from standby.
>>
>> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@...labora.com>
>> Link:
>> http://lkml.kernel.org/g/CAAObsKAv+05ih5U+=4kic_NsjGMhfxYheHR8xXXmacZs+p5SHw@mail.gmail.com
>> ---
>>   drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 13 +++++++++++++
>>   1 file changed, 13 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>> b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>> index 5e57f5b2e4b0..0df91c28740b 100644
>> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>> @@ -429,6 +429,7 @@ static void vop_dsp_hold_valid_irq_disable(struct vop
>> *vop)
>>   static void vop_enable(struct drm_crtc *crtc)
>>   {
>>         struct vop *vop = to_vop(crtc);
>> +       int i;
>>         int ret;
>>         if (vop->is_enabled)
>> @@ -476,6 +477,18 @@ static void vop_enable(struct drm_crtc *crtc)
>>          */
>>         vop->is_enabled = true;
>>   +     /*
>> +        * Before turning the VOP completely on, unset the registers
>> +        * containing FB addresses to avoid the HW start scanning old FBs.
>> +        */
>> +       for (i = 0; i < vop->data->win_size; i++) {
>> +               struct vop_win *vop_win = &vop->win[i];
>> +               const struct vop_win_data *win = vop_win->data;
>> +
>> +               VOP_WIN_SET(vop, win, yrgb_mst, 0x0);
>> +               VOP_WIN_SET(vop, win, uv_mst, 0x0);
>> +       }
>> +
>
> Hi Tomeu
>
> Thanks for your fix.
>
> Set yrgb_mst and uv_mst is not a good idea, because 0x0 also is a memory
> buffer address, ddr will access the 0x0 buffer.
> I think you may enable DRM_FBDEV_EMULATION, the 0x0 address is iommu mmaped
> address for fbdev, so your test can works.
> but if DRM_FBDEV_EMULATION is not define, may be 0x0 address is unmmaped,
> would get the iommu crash.

I have checked with DRM_FBDEV_EMULATION disabled and seems to work equally well.

> I think we can use atomic disable function like this:
> for_each_plane_in_state(old_state, plane, old_plane_state, i) {
>     const struct drm_plane_helper_funcs *funcs;
>     funcs = plane->helper_private;
>     funcs->atomic_disable(plane, old_plane_state);
> }
>
> But I think we'd better find why we need do this hack here.
>
> Does the old FB address is ummaped when crtc disabling? why plane is not
> disabled?

Planes aren't being disabled because the CRTC is being disabled
already, see http://lxr.free-electrons.com/source/drivers/gpu/drm/drm_atomic_helper.c#L1306

Exynos is already disabling all planes when a crtc is disabled:

http://lxr.free-electrons.com/source/drivers/gpu/drm/exynos/exynos_drm_fimd.c#L782

I don't like it because there's state in the drm core and in the
drivers that is left inconsistent.

Regards,

Tomeu

> Thanks.
>
>>         spin_lock(&vop->reg_lock);
>>         VOP_CTRL_SET(vop, standby, 0);
>
>
>
> --
> Ｍark Yao
>
>
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