On Thu, 22 Dec 2016, "Wang, Elaine" <elaine.wang@xxxxxxxxx> wrote: >> >> 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. >> > I understand your point now. Thank you for explaining this. I'll update the patch and > Use num_pipes for checking whether display engine exists. Ville, how about adding something like: #define HAS_DISPLAY(dev_priv) (INTEL_INFO(dev_priv)->num_pipes == 0) and possibly #define HAS_SOUTH_DISPLAY(dev_priv) HAS_PCH_NOP(dev_priv) So we could clarify the code, and abstract the rules, so it'll perhaps be easier to change them later? Though I fear we may end up needing to add a finer granularity depending on which parts we do need to and must not touch, and that might not always map to low granularity north/south display. *shrug* BR, Jani. > Thanks, > Elaine >> >> > 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 >> > _______________________________________________ >> > Intel-gfx mailing list >> > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx >> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx >> >> -- >> Jani Nikula, Intel Open Source Technology Center -- Jani Nikula, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx