On Wed, Aug 30, 2017 at 7:58 PM, Pandiyan, Dhinakaran
<dhinakaran.pandiyan@xxxxxxxxx> wrote:
> On Wed, 2017-08-30 at 20:32 +0100, Chris Wilson wrote:
>> Quoting Pandiyan, Dhinakaran (2017-08-30 20:12:52)
>> > On Wed, 2017-08-16 at 17:54 -0700, Rodrigo Vivi wrote:
>> > > Let's make it easier to add platforms that supports 2 pixel per
>> > > clock.
>> > >
>> > > With spread checks per platform it was easy to miss one or
>> > > another spot leading to loose some time on debug.
>> > >
>> > > Hopefully this check would save some cases in the future.
>> > >
>> > > No functional change.
>> > >
>> > > Cc: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx>
>> > > Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx>
>> > > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>> > > Signed-off-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
>> > > ---
>> > > drivers/gpu/drm/i915/i915_drv.h | 4 ++++
>> > > drivers/gpu/drm/i915/i915_pci.c | 2 ++
>> > > drivers/gpu/drm/i915/intel_cdclk.c | 8 ++++----
>> > > drivers/gpu/drm/i915/intel_pm.c | 3 +--
>> > > 4 files changed, 11 insertions(+), 6 deletions(-)
>> > >
>> > > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>> > > index 6c25c8520c87..94f5e6522e5e 100644
>> > > --- a/drivers/gpu/drm/i915/i915_drv.h
>> > > +++ b/drivers/gpu/drm/i915/i915_drv.h
>> > > @@ -748,6 +748,7 @@ struct intel_csr {
>> > > func(is_lp); \
>> > > func(is_alpha_support); \
>> > > /* Keep has_* in alphabetical order */ \
>> > > + func(has_2ppc); \
>> > > func(has_64bit_reloc); \
>> > > func(has_aliasing_ppgtt); \
>> > > func(has_csr); \
>> > > @@ -3025,6 +3026,9 @@ intel_info(const struct drm_i915_private *dev_priv)
>> > > #define NEEDS_WaRsDisableCoarsePowerGating(dev_priv) \
>> > > (IS_SKL_GT3(dev_priv) || IS_SKL_GT4(dev_priv))
>> > >
>> > > +/* Supports 2 pixel per clock */
>> > > +#define HAS_2PPC(dev_priv) ((dev_priv)->info.has_2ppc)
>> > > +
>> >
>> > How about
>> > #define HAS_2PPC(dev_priv) (IS_GEMINILAKE(dev_priv) ||
>> > INTEL_GEN(dev_priv) >= 10) ?
>> >
>> > I am not clear on what qualifies for a place in device_info, but
>> > defining it this way let's me go to the definition and quickly check
>> > which platform has 2 pixels per clock.
One thing I always wanted was to avoid 2 places to declare features &
capabilities.
Here or on the platform.
>>
>> A couple of rules of thumb for starting with:
>>
>> Use device_info if:
>>
>> - it fundamentally changes how the device operates, such that knowing
>> about it in debug logs is a key means of triage
I think on this one 2ppc qualifies
>>
>> - number of branches x callsites > 8
2 * 5 > 8 in this case?
or I'm getting the number of "branches" incorrectly?
What I was trying to save as well is the addition of any next platform.
When adding the feature it would be easier to search for HAS_2PPC instead of
searching for glk or cnl and analising that individually to see if it
is 2pp before
see if it applies to that platform.
But the reason that I put this patch on top is that I don't have
strong opinion here so
t would be fine for me to move on without ht.
Thanks,
Rodrigo.
>> (some estimate of the cost of inclusion inside device_info vs
>> savings in object code, for a more realistic estimate a branch will
>> ~12 bytes (depending on the phase of the moon) and cost for device
>> info will be the addition of a few strings, and a couple of calls
>> to use those string, so at a guess 100 bytes.)
>
> That's an interesting back-of-the-envelope calculation. I suppose the
> compiler is also more likely to load device_info->gen into a register
> than device_info->has_2ppc.
>
>
>>
>> -Chris
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--
Rodrigo Vivi
Blog: http://blog.vivi.eng.br
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