linux-kernel - Re: [Intel-gfx] [PATCH 2/2] drm/i915/edp/jsl: Update vswing table for HBR and HBR2

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Date:   Tue, 29 Sep 2020 10:30:25 +0300
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     Matt Roper <matthew.d.roper@...el.com>,
        Lucas De Marchi <lucas.demarchi@...el.com>
Cc:     "Surendrakumar Upadhyay\, TejaskumarX" 
        <tejaskumarx.surendrakumar.upadhyay@...el.com>,
        "Vivi\, Rodrigo" <rodrigo.vivi@...el.com>,
        "airlied\@linux.ie" <airlied@...ux.ie>,
        "daniel\@ffwll.ch" <daniel@...ll.ch>,
        "intel-gfx\@lists.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
        "dri-devel\@lists.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        "Ausmus\, James" <james.ausmus@...el.com>,
        "Souza\, Jose" <jose.souza@...el.com>,
        "ville.syrjala\@linux.intel.com" <ville.syrjala@...ux.intel.com>,
        "Pandey\, Hariom" <hariom.pandey@...el.com>
Subject: Re: [Intel-gfx] [PATCH 2/2] drm/i915/edp/jsl: Update vswing table for HBR and HBR2

On Mon, 28 Sep 2020, Matt Roper <matthew.d.roper@...el.com> wrote:
> On Mon, Sep 28, 2020 at 04:07:39PM -0700, Lucas De Marchi wrote:
>> On Mon, Sep 28, 2020 at 08:15:29PM +0300, Jani Nikula wrote:
>> > On Mon, 28 Sep 2020, "Surendrakumar Upadhyay, TejaskumarX"	<tejaskumarx.surendrakumar.upadhyay@...el.com> wrote:
>> > > This is a good example of a potential trap that having
>> > > IS_ELKHARTLAKE() cover both ELK and JSP creates. An unsuspecting coder
>> > > might change the if ladder to have IS_ELKHARTLAKE() first, and the
>> > > subsequent IS_JASPERLAKE() branch would never be taken.
>> > > 
>> > > BR,
>> > > Jani.
>> > > 
>> > > Tejas : In that case I will put attention note in comment about
>> > > platform checks such that ladder distrubance can be avoided. What you
>> > > suggest?
>> 
>> > The solution is to make IS_ELKHARTLAKE() mean ELK and only ELK.
>> 
>> Since we are talking about the TLA for JSL in the other patch, for
>> elkhartlake it is EHL, not ELK. ELK is something else, but I'm not sure
>> what:
>> 
>> $ git grep -w ELK -- drivers/gpu/drm/
>> drivers/gpu/drm/i915/gem/i915_gem_stolen.c:             IS_GM45(i915) ? "CTG" : "ELK", reg_val);
>> drivers/gpu/drm/i915/gem/i915_gem_stolen.c:      * Whether ILK really reuses the ELK register for this is unclear.
>> drivers/gpu/drm/i915/intel_pm.c:         * Not 100% sure which way ELK should go here as the
>> drivers/gpu/drm/i915/intel_pm.c:         * assume ELK doesn't need this.
>
> Yeah, ELK = Eagle Lake, CTG = Cantiga.  Both are old gen5 platforms IIRC.

Yeah, I know, my bad.

BR,
Jani.


>
>
> Matt
>
>> 
>> Lucas De Marchi
>> 
>> > 
>> > BR,
>> > Jani.
>> > 
>> > 
>> > -- 
>> > Jani Nikula, Intel Open Source Graphics Center

-- 
Jani Nikula, Intel Open Source Graphics Center