This is a note to let you know that I've just added the patch titled drm/i915: Avoid PPS HW/SW state mismatch due to rounding to the 4.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: drm-i915-avoid-pps-hw-sw-state-mismatch-due-to-rounding.patch and it can be found in the queue-4.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 5643205c6340b565a3be0fe0e7305dc4aa551c74 Mon Sep 17 00:00:00 2001 From: Imre Deak <imre.deak@xxxxxxxxx> Date: Wed, 29 Nov 2017 19:51:37 +0200 Subject: drm/i915: Avoid PPS HW/SW state mismatch due to rounding MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Imre Deak <imre.deak@xxxxxxxxx> commit 5643205c6340b565a3be0fe0e7305dc4aa551c74 upstream. We store a SW state of the t11_t12 timing in 100usec units but have to program it in 100msec as required by HW. The rounding used during programming means there will be a mismatch between the SW and HW states of this value triggering a "PPS state mismatch" error. Avoid this by storing the already rounded-up value in the SW state. Note that we still calculate panel_power_cycle_delay with the finer 100usec granularity to avoid any needless waits using that version of the delay. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103903 Cc: joks <joks@xxxxxxxx> Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx> Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/20171129175137.2889-1-imre.deak@xxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/gpu/drm/i915/intel_dp.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/drivers/gpu/drm/i915/intel_dp.c +++ b/drivers/gpu/drm/i915/intel_dp.c @@ -5336,6 +5336,12 @@ intel_dp_init_panel_power_sequencer(stru */ final->t8 = 1; final->t9 = 1; + + /* + * HW has only a 100msec granularity for t11_t12 so round it up + * accordingly. + */ + final->t11_t12 = roundup(final->t11_t12, 100 * 10); } static void Patches currently in stable-queue which might be from imre.deak@xxxxxxxxx are queue-4.15/drm-i915-avoid-pps-hw-sw-state-mismatch-due-to-rounding.patch