4.8-stable review patch. If anyone has any objections, please let me know.
------------------ From: Paulo Zanoni <paulo.r.zan...@intel.com> commit 4e4d3814a9bb4d71cd3ff0701d8d7041edefd8f0 upstream. 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: 367294be7c25 ("drm/i915/gen9: Add 2us read latency to WM level") Cc: Vandana Kannan <vandana.kan...@intel.com> Reviewed-by: Maarten Lankhorst <maarten.lankho...@linux.intel.com> Signed-off-by: Paulo Zanoni <paulo.r.zan...@intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/1474578035-424-5-git-send-email-paulo.r.zan...@intel.com (cherry picked from commit 0727e40a48a1d08cf54ce2c01e120864b92e59bf) Signed-off-by: Jani Nikula <jani.nik...@intel.com> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- drivers/gpu/drm/i915/intel_pm.c | 42 ++++++++++++++++++++-------------------- 1 file changed, 22 insertions(+), 20 deletions(-) --- a/drivers/gpu/drm/i915/intel_pm.c +++ b/drivers/gpu/drm/i915/intel_pm.c @@ -2119,32 +2119,34 @@ static void intel_read_wm_latency(struct 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);