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

[Mark yao <mark.yao@rock-chips.com>]

On 2016年03月14日 21:35, Tomeu Vizoso wrote:
> On 2 December 2014 at 10:15, Mark Yao <mark.yao@rock-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.

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

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?
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