Re: [PATCH 01/14] drm/i915: Check for platform specific GPIO config

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 08 Feb 2017, "Shankar, Uma" <uma.shankar@intel.com> wrote:
>>-----Original Message-----
>>From: Intel-gfx [mailto:intel-gfx-bounces@lists.freedesktop.org] On Behalf Of
>>Jani Nikula
>>Sent: Wednesday, February 8, 2017 4:41 PM
>>To: Srinivas, Vidya <vidya.srinivas@intel.com>; intel-
>>gfx@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@intel.com> wrote:
>>>> -----Original Message-----
>>>> From: Jani Nikula [mailto:jani.nikula@linux.intel.com]
>>>> Sent: Wednesday, February 8, 2017 4:11 PM
>>>> To: Srinivas, Vidya <vidya.srinivas@intel.com>; intel-
>>>> gfx@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@intel.com> wrote:
>>>> >> -----Original Message-----
>>>> >> From: Jani Nikula [mailto:jani.nikula@linux.intel.com]
>>>> >> Sent: Monday, January 9, 2017 3:48 PM
>>>> >> To: Srinivas, Vidya <vidya.srinivas@intel.com>; intel-
>>>> >> gfx@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@intel.com> wrote:
>>>> >> > From: Uma Shankar <uma.shankar@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.


>
> Regards,
> Uma Shankar
>
>>BR,
>>Jani.
>>
>>
>>>>
>>>> BR,
>>>> Jani.
>>>>
>>>>
>>>>
>>>> >
>>>> > Regards
>>>> > Vidya
>>>> >>
>>>> >> BR,
>>>> >> Jani.
>>>> >>
>>>> >> >
>>>> >> > Signed-off-by: Uma Shankar <uma.shankar@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
>>_______________________________________________
>>Intel-gfx mailing list
>>Intel-gfx@lists.freedesktop.org
>>https://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Jani Nikula, Intel Open Source Technology Center
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