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

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Date:   Mon, 28 Sep 2020 16:10:22 -0700
From:   Matt Roper <matthew.d.roper@...el.com>
To:     Lucas De Marchi <lucas.demarchi@...el.com>
Cc:     Jani Nikula <jani.nikula@...ux.intel.com>,
        "Surendrakumar Upadhyay, TejaskumarX" 
        <tejaskumarx.surendrakumar.upadhyay@...el.com>,
        "Vivi, Rodrigo" <rodrigo.vivi@...el.com>,
        "airlied@...ux.ie" <airlied@...ux.ie>,
        "daniel@...ll.ch" <daniel@...ll.ch>,
        "intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Ausmus, James" <james.ausmus@...el.com>,
        "Souza, Jose" <jose.souza@...el.com>,
        "ville.syrjala@...ux.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, 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.


Matt

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

-- 
Matt Roper
Graphics Software Engineer
VTT-OSGC Platform Enablement
Intel Corporation
(916) 356-2795