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drm/i915/gen9: fix the WaWmMemoryReadLatency implementation
Bspec says: "The mailbox response data may not account for memory read latency. If the mailbox response data for level 0 is 0us, add 2 microseconds to the result for each valid level." This means we should only do the +2 in case wm[0] == 0, not always. So split the sanitizing implementation from the WA implementation and fix the WA implementation. v2: Add Fixes tag (Maarten). Fixes:367294be7c
("drm/i915/gen9: Add 2us read latency to WM level") Cc: stable@vger.kernel.org Cc: Vandana Kannan <vandana.kannan@intel.com> Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/1474578035-424-5-git-send-email-paulo.r.zanoni@intel.com (cherry picked from commit0727e40a48
) Signed-off-by: Jani Nikula <jani.nikula@intel.com>
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@ -2126,33 +2126,35 @@ static void intel_read_wm_latency(struct drm_device *dev, uint16_t wm[8])
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wm[7] = (val >> GEN9_MEM_LATENCY_LEVEL_3_7_SHIFT) &
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GEN9_MEM_LATENCY_LEVEL_MASK;
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/*
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* If a level n (n > 1) has a 0us latency, all levels m (m >= n)
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* need to be disabled. We make sure to sanitize the values out
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* of the punit to satisfy this requirement.
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*/
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for (level = 1; level <= max_level; level++) {
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if (wm[level] == 0) {
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for (i = level + 1; i <= max_level; i++)
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wm[i] = 0;
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break;
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}
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}
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/*
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* WaWmMemoryReadLatency:skl
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*
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* punit doesn't take into account the read latency so we need
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* to add 2us to the various latency levels we retrieve from
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* the punit.
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* - W0 is a bit special in that it's the only level that
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* can't be disabled if we want to have display working, so
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* we always add 2us there.
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* - For levels >=1, punit returns 0us latency when they are
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* disabled, so we respect that and don't add 2us then
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*
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* Additionally, if a level n (n > 1) has a 0us latency, all
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* levels m (m >= n) need to be disabled. We make sure to
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* sanitize the values out of the punit to satisfy this
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* requirement.
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* to add 2us to the various latency levels we retrieve from the
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* punit when level 0 response data us 0us.
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*/
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wm[0] += 2;
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for (level = 1; level <= max_level; level++)
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if (wm[level] != 0)
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if (wm[0] == 0) {
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wm[0] += 2;
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for (level = 1; level <= max_level; level++) {
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if (wm[level] == 0)
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break;
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wm[level] += 2;
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else {
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for (i = level + 1; i <= max_level; i++)
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wm[i] = 0;
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break;
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}
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}
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} else if (IS_HASWELL(dev) || IS_BROADWELL(dev)) {
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uint64_t sskpd = I915_READ64(MCH_SSKPD);
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