Re: [PATCH resend 13/15] drm/i915/dsi: Execute MIPI_SEQ_TEAR_OFF from intel_dsi_post_disable

From: Jani Nikula <jani.nikula@linux.intel.com>
To: Hans de Goede <hdegoede@redhat.com>, Bob Paauwe <bob.j.paauwe@intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>,
	intel-gfx <intel-gfx@lists.freedesktop.org>
Subject: Re: [PATCH resend 13/15] drm/i915/dsi: Execute MIPI_SEQ_TEAR_OFF from intel_dsi_post_disable
Date: Mon, 27 Feb 2017 19:47:28 +0200	[thread overview]
Message-ID: <87lgsrv83z.fsf@intel.com> (raw)
In-Reply-To: <7825eb9a-56b9-7b10-ed99-eab984e3e302@redhat.com>

On Sat, 25 Feb 2017, Hans de Goede <hdegoede@redhat.com> wrote:
> Hi,
>
> On 24-02-17 18:02, Bob Paauwe wrote:
>> On Mon, 20 Feb 2017 15:08:43 +0100
>> Hans de Goede <hdegoede@redhat.com> wrote:
>>
>>> For v3 VBTs we should call MIPI_SEQ_TEAR_OFF before
>>> MIPI_SEQ_DISPLAY_OFF, for non v3 VBTs this is a nop.
>>
>> Isn't this only for command mode?  Or is there conflicting information
>> on this?
>
> In my (limited) set of test hardware vidmode panel VBTs simply
> do not define a MIPI_SEQ_TEAR_ON/OFF sequence. But it would probably
> be a good idea to guard this with a "if (is_cmd_mode(intel_dsi))"
> assuming we only want this for commandmode, which I think we do,
> but it would be good to have this confirmed.

Logically you wouldn't do tear on/off on video mode panels. But that's
really not the point. I wouldn't be surprised if there were setups where
someone noticed that this particular sequence gets run at an appropriate
time on Windows, and shoved some other stuff there, completely unrelated
to tear on/off.

BR,
Jani.

>
> I'll add the guard when I send out a v2 after we've clarified
> some of the other review questions.
>
> Regards,
>
> Hans
>
>
>
>>
>>>
>>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>>> ---
>>>  drivers/gpu/drm/i915/intel_dsi.c | 1 +
>>>  1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
>>> index 1914311..90263d6 100644
>>> --- a/drivers/gpu/drm/i915/intel_dsi.c
>>> +++ b/drivers/gpu/drm/i915/intel_dsi.c
>>> @@ -772,6 +772,7 @@ static void intel_dsi_post_disable(struct intel_encoder *encoder,
>>>  	 * XXX spec specifies SHUTDOWN before MIPI_SEQ_DISPLAY_OFF for
>>>  	 * v3 VBTs, but not for v2 VBTs?
>>>  	 */
>>> +	intel_dsi_exec_vbt_sequence(intel_dsi, MIPI_SEQ_TEAR_OFF);
>>>  	intel_dsi_exec_vbt_sequence(intel_dsi, MIPI_SEQ_DISPLAY_OFF);
>>>
>>>  	/* Transition to LP-00 */
>>
>>
>>

-- 
Jani Nikula, Intel Open Source Technology Center
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