[Intel-gfx] [PATCH] CHROMIUM: i915: Select non-alternate SSC frequency for some systems

[Jesse Barnes]

On Fri, 14 Oct 2011 13:33:35 -0700
Bryan Freed <bfreed at chromium.org> wrote:

> On Thu, Oct 6, 2011 at 8:09 AM, Jesse Barnes <jbarnes at virtuousgeek.org>wrote:
> 
> > On Wed, 5 Oct 2011 22:45:55 -0700
> > Simon Que <sque at chromium.org> wrote:
> >
> > > Hi,
> > >
> > > Here's a patch to introduce a DMI-based SSC frequency selection in
> > > intel_bios.c.  Instead of always selecting the "alternate" SSC
> > > frequency as default during initialization, this patch lets some
> > > systems have the non-alternate frequency by default.
> > >
> > > Thanks,
> > > Simon
> > > =====================================================
> > > drivers: i915: Select non-alternate SSC frequency for some systems
> > >
> > > When initializing VBT default values, the alternate BIOS SSC frequency
> > > is selected.  This patch allows the non-alternate frequency to be
> > > selected as a default, for specified systems.  There is a DMI match list
> > > for systems that are to use the non-alternate frequency.  Currently,
> > > only Lumpy is on the list.
> > >
> > > Signed-off-by: Simon Que <sque at chromium.org>
> > > ---
> > >  drivers/gpu/drm/i915/intel_bios.c |   17 ++++++++++++++++-
> > >  1 files changed, 16 insertions(+), 1 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/intel_bios.c
> > > b/drivers/gpu/drm/i915/intel_bios.c
> > > index 927442a..ec75f15 100644
> > > --- a/drivers/gpu/drm/i915/intel_bios.c
> > > +++ b/drivers/gpu/drm/i915/intel_bios.c
> > > @@ -25,6 +25,7 @@
> > >   *
> > >   */
> > >  #include <drm/drm_dp_helper.h>
> > > +#include <linux/dmi.h>
> > >  #include "drmP.h"
> > >  #include "drm.h"
> > >  #include "i915_drm.h"
> > > @@ -565,6 +566,17 @@ parse_device_mapping(struct drm_i915_private
> > *dev_priv,
> > >       return;
> > >  }
> > >
> > > +static const struct dmi_system_id lvds_do_not_use_alternate_frequency[]
> > = {
> > > +     {
> > > +             .callback = NULL,
> > > +             .ident = "Lumpy",
> > > +             .matches = {
> > > +                     DMI_MATCH(DMI_PRODUCT_NAME, "Lumpy"),
> > > +             }
> > > +     },
> > > +     { }
> > > +};
> > > +
> > >  static void
> > >  init_vbt_defaults(struct drm_i915_private *dev_priv)
> > >  {
> > > @@ -585,7 +597,10 @@ init_vbt_defaults(struct drm_i915_private *dev_priv)
> > >
> > >       /* Default to using SSC */
> > >       dev_priv->lvds_use_ssc = 1;
> > > -     dev_priv->lvds_ssc_freq = intel_bios_ssc_frequency(dev, 1);
> > > +     if (dmi_check_system(lvds_do_not_use_alternate_frequency))
> > > +             dev_priv->lvds_ssc_freq = intel_bios_ssc_frequency(dev, 0);
> > > +     else
> > > +             dev_priv->lvds_ssc_freq = intel_bios_ssc_frequency(dev, 1);
> > >       DRM_DEBUG("Set default to SSC at %dMHz\n",
> > dev_priv->lvds_ssc_freq);
> > >
> > >       /* eDP data */
> >
> > Do you expect to have other settings that you won't get from a VBIOS VBT
> > (e.g. video timings, dual refresh info)?
> >
> > If so, it might make more sense to have an alternate init path for the
> > non-VBT values to replace all the VBT parsing.  I.e. if your DMI match
> > happens, call into something other than our init_bios routine to set up
> > defaults for the platform.
> >
> > --
> > Jesse Barnes, Intel Open Source Technology Center
> >
> 
> Hi Jesse.
> 
> Thanks for the response.
> Let me try to get this thread going again.
> 
> We do expect to have more settings trickle in as we develop new boards, but
> no additional settings are expected for this board.
> 
> Our BIOS boots in two different modes: dev mode which turns on the display
> and provides VBT to the kernel, and normal mode which does not turn on the
> screen or provide VBT.  When we get VBT from the BIOS, we want to honor it.
> 
> When we do not get VBT from BIOS, we want the i915 driver to give us usable
> settings.  Indeed, about a year ago we added init_vbt_defaults() to do this
> for us.
> 
> Now we want to differentiate these defaults (really just the lvds_ssc_freq
> setting for now) for different systems, and the proposed solution is to
> use dmi_check_system() for this.
> When our next board comes along, it too may need the "non-alternate" ssc
> frequency.  So making this a list of matches seems to make sense.
> 
> So we still want to call intel_parse_bios(), setup our defaults, then let
> VBT processing proceed or fail as the case may be.

Ok that's fine.  This patch has my acked-by for now.  We can look at
abstracting things better as you add more boards here.

-- 
Jesse Barnes, Intel Open Source Technology Center
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