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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
This commit is contained in:
Paulo Zanoni 2016-09-22 18:00:30 -03:00
parent 6e3100ec21
commit 0727e40a48
1 changed files with 22 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

42
drivers/gpu/drm/i915/intel_pm.c
View File

@ -2126,33 +2126,35 @@ static void intel_read_wm_latency(struct drm_device *dev, uint16_t wm[8])
wm[7] = (val >> GEN9_MEM_LATENCY_LEVEL_3_7_SHIFT) &
GEN9_MEM_LATENCY_LEVEL_MASK;
/*
* If a level n (n > 1) has a 0us latency, all levels m (m >= n)
* need to be disabled. We make sure to sanitize the values out
* of the punit to satisfy this requirement.
*/
for (level = 1; level <= max_level; level++) {
if (wm[level] == 0) {
for (i = level + 1; i <= max_level; i++)
wm[i] = 0;
break;
}
}
/*
* WaWmMemoryReadLatency:skl
*
* punit doesn't take into account the read latency so we need
* to add 2us to the various latency levels we retrieve from
* the punit.
* - W0 is a bit special in that it's the only level that
* can't be disabled if we want to have display working, so
* we always add 2us there.
* - For levels >=1, punit returns 0us latency when they are
* disabled, so we respect that and don't add 2us then
*
* Additionally, if a level n (n > 1) has a 0us latency, all
* levels m (m >= n) need to be disabled. We make sure to
* sanitize the values out of the punit to satisfy this
* requirement.
* to add 2us to the various latency levels we retrieve from the
* punit when level 0 response data us 0us.
*/
wm[0] += 2;
for (level = 1; level <= max_level; level++)
if (wm[level] != 0)
if (wm[0] == 0) {
wm[0] += 2;
for (level = 1; level <= max_level; level++) {
if (wm[level] == 0)
break;
wm[level] += 2;
else {
for (i = level + 1; i <= max_level; i++)
wm[i] = 0;
break;
}
}
} else if (IS_HASWELL(dev) || IS_BROADWELL(dev)) {
uint64_t sskpd = I915_READ64(MCH_SSKPD);