From: Paulo Zanoni <paulo.r.zanoni at intel.com>
And rely on the fact that it's 0 to assume that machines without a PCH
will have PCH_NONE as dev_priv->pch_type.
Just today I finally realized that HAS_PCH_IBX is true for machines
without a PCH. IMHO this is totally counter-intuitive and I don't
think it's a good idea to assume that we're going to check for
HAS_PCH_IBX only after we check for HAS_PCH_SPLIT.
I believe that in the future we'll have more PCH types and checks
like:
if (HAS_PCH_IBX(dev) || HAS_PCH_CPT(dev))
will become more and more common. There's a good chance that we may
break non-PCH machines by adding these checks in code that runs on all
machines. I also believe that the HAS_PCH_SPLIT check will become less
common as we add more and more different PCH types. We'll probably
start replacing checks like:
if (HAS_PCH_SPLIT(dev))
foo();
else
bar();
with:
if (HAS_PCH_NEW(dev))
baz();
else if (HAS_PCH_OLD(dev) || HAS_PCH_IBX(dev))
foo();
else
bar();
and this may break gen 2/3/4.
As far as we have investigated, this patch will affect the behavior of
intel_hdmi_dpms and intel_dp_link_down on gen 4. In both functions the
code inside the HAS_PCH_IBX check is for IBX-specific workarounds, so
we should be safe. If we start bisecting gen 2/3/4 bugs to this commit
we should consider replacing the HAS_PCH_IBX checks with something
else.
V2: Improve commit message, list possible side effects and solution.
Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
---
drivers/gpu/drm/i915/i915_drv.h | 1 +
1 file changed, 1 insertion(+)
Another alternative would have been to change HAS_PCH_IBX to also
check for HAS_PCH_SPLIT, but I'm not exactly in favor of adding more
conditionals...
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index b7a1eaa..b12e79a 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -333,6 +333,7 @@ enum no_fbc_reason {
};
enum intel_pch {
+ PCH_NONE = 0, /* No PCH present */
PCH_IBX, /* Ibexpeak PCH */
PCH_CPT, /* Cougarpoint PCH */
PCH_LPT, /* Lynxpoint PCH */
--
1.7.10.2
