[PATCH 1/4] drm/i915/bxt: Avoid early timeout during PLL enable

Imre Deak
2016-06-28T10:37:37Z

Since wait_for_atomic doesn't re-check the wait-for condition after
expiry of the timeout it can fail when called from non-atomic context
even if the condition is set correctly before the expiry. Fix this by
using the non-atomic wait_for instead.

I noticed this via the PLL locking timing out incorrectly, with this fix
I couldn't reproduce the problem.

Fixes: 0351b93992aa ("drm/i915: Do not lie about atomic timeout granularity")
CC: Chris Wilson <chris@chris-wilson.co.uk>
CC: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
---
drivers/gpu/drm/i915/intel_dpll_mgr.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dpll_mgr.c b/drivers/gpu/drm/i915/intel_dpll_mgr.c
index c0eff15..e130c3e 100644
--- a/drivers/gpu/drm/i915/intel_dpll_mgr.c
+++ b/drivers/gpu/drm/i915/intel_dpll_mgr.c
@@ -1374,8 +1374,8 @@ static void bxt_ddi_pll_enable(struct drm_i915_private *dev_priv,
I915_WRITE(BXT_PORT_PLL_ENABLE(port), temp);
POSTING_READ(BXT_PORT_PLL_ENABLE(port));

- if (wait_for_atomic_us((I915_READ(BXT_PORT_PLL_ENABLE(port)) &
- PORT_PLL_LOCK), 200))
+ if (wait_for_us((I915_READ(BXT_PORT_PLL_ENABLE(port)) & PORT_PLL_LOCK),
+ 200))
DRM_ERROR("PLL %d not locked\n", port);

/*
--
2.5.0