linux-kernel - Re: [PATCH] drm/rockchip: vop: power off until vop standby take effect

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Message-ID: <54D19868.8000906@rock-chips.com>
Date:	Wed, 04 Feb 2015 11:56:24 +0800
From:	Mark yao <mark.yao@...k-chips.com>
To:	Daniel Kurtz <djkurtz@...omium.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	David Airlie <airlied@...ux.ie>,
	Rob Clark <robdclark@...il.com>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>
Subject: Re: [PATCH] drm/rockchip: vop: power off until vop standby take effect

On 2015年02月04日 11:48, Daniel Kurtz wrote:
> On Feb 4, 2015 11:38 AM, "Mark yao" <mark.yao@...k-chips.com> wrote:
>> On 2015年02月02日 15:53, Daniel Vetter wrote:
>>> On Mon, Feb 02, 2015 at 10:30:09AM +0800, Mark yao wrote:
>>>> On 2015年02月02日 10:07, Daniel Kurtz wrote:
>>>>> Hi Mark, Heiko,
>>>>>
>>>>> On Sat, Jan 31, 2015 at 4:41 PM, Mark Yao <mark.yao@...k-chips.com> wrote:
>>>>>> Vop standby will take effect end of current frame,
>>>>>> if dsp_hold_valid_irq happen, it means vop standby complete.
>>>>>>
>>>>>> we must wait standby complete when we want to disable aclk,
>>>>>> if not, memory bus maybe dead.
>>>>>>
>>>>>> Signed-off-by: Mark Yao <mark.yao@...k-chips.com>
>>>>>> ---
>>>>>>    drivers/gpu/drm/rockchip/rockchip_drm_vop.c |   76 ++++++++++++++++++++++-----
>>>>>>    1 file changed, 63 insertions(+), 13 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>>>>>> index fb25836..47ea61f 100644
>>>>>> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>>>>>> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>>>>>> @@ -89,6 +89,7 @@ struct vop {
>>>>>>           /* mutex vsync_ work */
>>>>>>           struct mutex vsync_mutex;
>>>>>>           bool vsync_work_pending;
>>>>>> +       struct completion dsp_hold_completion;
>>>>>>
>>>>>>           const struct vop_data *data;
>>>>>>
>>>>>> @@ -382,6 +383,34 @@ static bool is_alpha_support(uint32_t format)
>>>>>>           }
>>>>>>    }
>>>>>>
>>>>>> +static void vop_dsp_hold_valid_irq_enable(struct vop *vop)
>>>>>> +{
>>>>>> +       unsigned long flags;
>>>>>> +
>>>>>> +       BUG_ON(!vop->is_enabled);
>>>>> Re: Heiko "use a WARN_ON":
>>>>>
>>>>> If the VOP clock is off, then the system will just hang when trying to
>>>>> write the VOP register so in this case, BUG_ON gives a more reliable
>>>>> crash dump than the hang.
>>>>     In this way, you are right, if vop clocks is disabled, write vop register
>>>> will hang system, and the WARN_ON
>>> if (WARN_ON(cond))
>>>          return;
>>>
>>> is what we commonly use in i915. Because it's really not any good to use
>>> BUG_ON in drm drivers, at least if you expect anyone to use fbcon on top
>>> of it (i.e. anything even remotely resembling a normal distro): Then the
>>> intial modeset is all done under console_lock, which means that _none_ of
>>> your BUG_ON will ever get out over serial console.
>>>
>>> The problem is fbcon locking, but no fool yet signed up to fix it (it's
>>> horrible, I looked ...).
>>> -Daniel
>> I know this problem, if fbcon locking, and BUG_ON, we can't get any log from serial console, Trouble
>> me many times. So know, if no drm log output, the first thing I do is remove the fbcon lock, and then
>> we can see the crash dump.
>>
>> But here, I expect to use BUG_ON, because if BUG happen, vop register will hang system, and WARN_ON
>> may be have no chance to output.
> Yeah, but danvet is suggesting we just return immediately on the
> WARN_ON condition, to avoid accessing the vop registers and hanging.
>
> Thus, the WARN_ON will have a chance to put out (unless the early
> return path goes off and finds some other unprotected path goes to
> access unlocked registers).
>
> -Dan
All right, I got it.
>> Mark
>>
>
>


-- 
Ｍark Yao 姚智情

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E-mail:mark.yao@...k-chips.com


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