On Thu, 22 Dec 2016, "Wang, Elaine" <elaine.wang@xxxxxxxxx> wrote:
> Hi Jani, Ville,
>
> Any comment about the "PCH_NOP" vs "num_pipes == 0"?
>
> Thanks,
> Elaine
>> On Thu, 15 Dec 2016, Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> wrote:
>> > On Mon, Dec 12, 2016 at 02:57:44PM +0800, Wang Elaine wrote:
>> >> From: Elaine Wang <elaine.wang@xxxxxxxxx>
>> >>
>> >> Some platforms don't have display. To avoid accessing the
>> >> non-existent registers, check HAS_PCH_NOP before invoking display
>> >> IRQ install or reset function.
>> >>
>> >> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
>> >> Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
>> >> Signed-off-by: Elaine Wang <elaine.wang@xxxxxxxxx>
>> >> ---
>> >> drivers/gpu/drm/i915/i915_irq.c | 10 +++++++---
>> >> 1 file changed, 7 insertions(+), 3 deletions(-)
>> >>
>> >> diff --git a/drivers/gpu/drm/i915/i915_irq.c
>> >> b/drivers/gpu/drm/i915/i915_irq.c index 0b119b9..369a038 100644
>> >> --- a/drivers/gpu/drm/i915/i915_irq.c
>> >> +++ b/drivers/gpu/drm/i915/i915_irq.c
>> >> @@ -2990,8 +2990,10 @@ static void gen8_irq_reset(struct drm_device
>> *dev)
>> >>
>> POWER_DOMAIN_PIPE(pipe)))
>> >> GEN8_IRQ_RESET_NDX(DE_PIPE, pipe);
>> >>
>> >> - GEN5_IRQ_RESET(GEN8_DE_PORT_);
>> >> - GEN5_IRQ_RESET(GEN8_DE_MISC_);
>> >> + if (!HAS_PCH_NOP(dev_priv)) {
>> >> + GEN5_IRQ_RESET(GEN8_DE_PORT_);
>> >> + GEN5_IRQ_RESET(GEN8_DE_MISC_);
>> >> + }
>> >
>> > Hmm. These are north side registers so looking at PCH_NOP feels
>> > questionable.
>>
>> Indeed, num_pipes == 0 isn't exactly the same thing as HAS_PCH_NOP.
>>
>> Jani.
>
> I thought HAS_PCH_NOP had same meaning as num_pipes == 0 because I saw
> following code in i915_drv.c. Is there any exception?
>
> https://cgit.freedesktop.org/drm-intel/tree/drivers/gpu/drm/i915/i915_drv.c?h=drm-intel-nightly#n145
> static void intel_detect_pch(struct drm_i915_private *dev_priv) {
> struct pci_dev *pch = NULL;
>
> /* In all current cases, num_pipes is equivalent to the PCH_NOP setting
> * (which really amounts to a PCH but no South Display).
> */
The key is in this comment; "In all current cases", where "current" is
3½ years ago. IIRC this was written for some Xeons which did have a PCH
but no display. PCH_NOP is a kind of hack for those. Nowadays you don't
always have a PCH on gen 5+ (VLV, CHV, BXT, ...). You might have a PCH
but only need the North Display for some outputs. And I guess you might
still have a PCH but no display at all.
I'm just saying, we should not overload this hack to, say, cover
platforms that don't even have a PCH, or platforms that have a PCH but a
functioning North Display.
BR,
Jani.
> if (INTEL_INFO(dev_priv)->num_pipes == 0) {
> dev_priv->pch_type = PCH_NOP;
> return;
> }
>
> Thanks,
> Elaine
>>
>>
>> >
>> >> GEN5_IRQ_RESET(GEN8_PCU_);
>> >>
>> >> if (HAS_PCH_SPLIT(dev_priv))
>> >> @@ -3414,7 +3416,9 @@ static int gen8_irq_postinstall(struct
>> >> drm_device
>> *dev)
>> >> ibx_irq_pre_postinstall(dev);
>> >>
>> >> gen8_gt_irq_postinstall(dev_priv);
>> >> - gen8_de_irq_postinstall(dev_priv);
>> >> +
>> >> + if (!HAS_PCH_NOP(dev_priv))
>> >> + gen8_de_irq_postinstall(dev_priv);
>> >>
>> >> if (HAS_PCH_SPLIT(dev_priv))
>> >> ibx_irq_postinstall(dev);
>> >> --
>> >> 1.9.1
>>
>> --
>> Jani Nikula, Intel Open Source Technology Center
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--
Jani Nikula, Intel Open Source Technology Center
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