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

[Shankar, Uma]

>-----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.

Regards,
Uma Shankar

>BR,
>Jani.
>
>
>>>
>>> BR,
>>> Jani.
>>>
>>>
>>>
>>> >
>>> > Regards
>>> > Vidya
>>> >>
>>> >> BR,
>>> >> Jani.
>>> >>
>>> >> >
>>> >> > 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
>>>
>>> --
>>> Jani Nikula, Intel Open Source Technology Center
>
>--
>Jani Nikula, Intel Open Source Technology Center
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