[Intel-gfx] [PATCH 01/14] drm/i915: Check for platform specific GPIO config

[Shankar, Uma]

>-----Original Message-----
>From: Jani Nikula [mailto:jani.nikula at linux.intel.com]
>Sent: Wednesday, February 8, 2017 5:58 PM
>To: Shankar, Uma <uma.shankar at intel.com>; Srinivas, Vidya
><vidya.srinivas at intel.com>; intel-gfx at lists.freedesktop.org
>Subject: RE: [Intel-gfx] [PATCH 01/14] drm/i915: Check for platform specific
>GPIO config
>
>On Wed, 08 Feb 2017, "Shankar, Uma" <uma.shankar at intel.com> wrote:
>>>-----Original Message-----
>>>From: Intel-gfx [mailto:intel-gfx-bounces at lists.freedesktop.org] On
>>>Behalf Of Jani Nikula
>>>Sent: Wednesday, February 8, 2017 4:41 PM
>>>To: Srinivas, Vidya <vidya.srinivas at intel.com>; intel-
>>>gfx at lists.freedesktop.org
>>>Subject: Re: [Intel-gfx] [PATCH 01/14] drm/i915: Check for platform
>>>specific GPIO config
>>>
>>>On Wed, 08 Feb 2017, "Srinivas, Vidya" <vidya.srinivas at intel.com> wrote:
>>>>> -----Original Message-----
>>>>> From: Jani Nikula [mailto:jani.nikula at linux.intel.com]
>>>>> Sent: Wednesday, February 8, 2017 4:11 PM
>>>>> To: Srinivas, Vidya <vidya.srinivas at intel.com>; intel-
>>>>> gfx at lists.freedesktop.org
>>>>> Subject: RE: [Intel-gfx] [PATCH 01/14] drm/i915: Check for platform
>>>>> specific GPIO config
>>>>>
>>>>> On Wed, 08 Feb 2017, "Srinivas, Vidya" <vidya.srinivas at intel.com>
>wrote:
>>>>> >> -----Original Message-----
>>>>> >> From: Jani Nikula [mailto:jani.nikula at linux.intel.com]
>>>>> >> Sent: Monday, January 9, 2017 3:48 PM
>>>>> >> To: Srinivas, Vidya <vidya.srinivas at intel.com>; intel-
>>>>> >> gfx at lists.freedesktop.org
>>>>> >> Subject: Re: [Intel-gfx] [PATCH 01/14] drm/i915: Check for
>>>>> >> platform specific GPIO config
>>>>> >>
>>>>> >> On Mon, 09 Jan 2017, Vidya Srinivas <vidya.srinivas at intel.com>
>wrote:
>>>>> >> > From: Uma Shankar <uma.shankar at intel.com>
>>>>> >> >
>>>>> >> > Panel GPIO control should be done based on platform. Add a
>>>>> >> > check to restrict VLV and CHT specific GPIO confirguration, so
>>>>> >> > that they dont apply to other platforms.
>>>>> >>
>>>>> >> There are no code paths that would have
>>>>> >> dev_priv->vbt.dsi.config->pwm_blc == PPS_BLC_PMIC on platforms
>>>>> >> other than VLV/CVH.
>>>>> > This particular field is by default 0 which triggers a redundant
>>>>> > gpio get operation for BXT. Hence limiting this to BYT/CHT platforms.
>>>>>
>>>>> What do you mean by default 0? Are you saying that you have
>>>>> machines that have a VBT which indicate they have PMIC backlight
>>>>> control when they in fact don't?
>>>>
>>>> Sorry, what I meant is PPS_BLC_PMIC is 0. So even if the VBT field
>>>> is not changed it will still become true causing the condition to pass.
>>>
>>>In other words, the VBT contains PPS_BLC_PMIC for a machine that
>>>should not use PMIC. In yet other words, the VBT contains incorrect
>information.
>>>Right?
>>>
>>
>> Hi Jani,
>> In this case,  I guess the design for this value itself is wrong. A
>> value of 0 is a valid value from driver/vbt perspective (basically
>> signifies some logical entity). Thus if we don't touch this field in
>> VBT, it will still have 0 as a value (un-initialized).  Driver will consider it to be
>right and will go ahead with GPIO get calls. Ideally this should start from index
>as 1 or a default value of -1 was needed.
>>
>> In BYT/CHT, most platforms will be using that hence things were fine.
>> If a board design needed other value, VBT field would have been
>> updated. But this is not at all needed for platforms beyond BYT/CHT, hence
>this change was limited to those platforms.
>
>I filed a bug against the spec. That's where this info should be.
>
>BR,
>Jani.
Thanks Jani for filing this. Can you please point to the bug link ?

Regards,
Uma Shankar

>>>>> >> >
>>>>> >> > Signed-off-by: Uma Shankar <uma.shankar at intel.com>
>>>>> >> > ---
>>>>> >> >  drivers/gpu/drm/i915/intel_dsi.c | 3 ++-
>>>>> >> >  1 file changed, 2 insertions(+), 1 deletion(-)
>>>>> >> >
>>>>> >> > diff --git a/drivers/gpu/drm/i915/intel_dsi.c
>>>>> >> > b/drivers/gpu/drm/i915/intel_dsi.c
>>>>> >> > index 16732e7..27d8f95 100644
>>>>> >> > --- a/drivers/gpu/drm/i915/intel_dsi.c
>>>>> >> > +++ b/drivers/gpu/drm/i915/intel_dsi.c
>>>>> >> > @@ -1560,7 +1560,8 @@ void intel_dsi_init(struct
>>>>> >> > drm_i915_private
>>>>> >> *dev_priv)
>>>>> >> >  	 * In case of BYT with CRC PMIC, we need to use GPIO for
>>>>> >> >  	 * Panel control.
>>>>> >> >  	 */
>>>>> >> > -	if (dev_priv->vbt.dsi.config->pwm_blc == PPS_BLC_PMIC) {
>>>>> >> > +	if ((IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv))
>>>&&
>>>>> >> > +		(dev_priv->vbt.dsi.config->pwm_blc ==
>>>PPS_BLC_PMIC)) {
>>>>> >> >  		intel_dsi->gpio_panel =
>>>>> >> >  			gpiod_get(dev->dev, "panel",
>>>GPIOD_OUT_HIGH);
>>>>> >>
>>>>> >> --
>>>>> >> Jani Nikula, Intel Open Source Technology Center