A fix was committed upstream and backported to the stable kernels: The commit in Linux 5.4 stable (v5.4.53): https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-5.4.y&id=e93ab4628452e0869c24204ac495e558b4163149
The commit in Linux 5.7 stable (v5.7.10): https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-5.7.y&id=996b680d729c4e5aa7087080cc9e469a4f7b86d7 This bug can be closed once Ubuntu's kernel contains these upstream changes. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1876449 Title: Apple external Trackpad event timestamps are jittery Status in linux package in Ubuntu: Confirmed Bug description: Using a vanilla installation of Ubuntu 20.04, the timestamps of input events from my Apple "Magic Trackpad" - 1st generation, connected over Bluetooth - are jittery. This is a regression, the timestamps were fine when using Ubuntu 19.10. I bisected the bug. - The problem starts with upstream kernel commit 3b51c44bd693 ("Input: allow drivers specify timestamp for input events"). After that commit, the same timestamp is always emitted. - This was partially fixed in commit 4370b231d100 ("Input: reset device timestamp on sync"), however ever since then the timestamps are jittery. The problem still exists in the current upstream 'master' (commit c45e8bccecaf). The following patch fixes the bug, however this is obviously a hack. It effectively reverts commit 3b51c44bd693: diff --git a/drivers/input/input.c b/drivers/input/input.c index 3cfd2c18eebd..8890195547d6 100644 --- a/drivers/input/input.c +++ b/drivers/input/input.c @@ -1958,7 +1958,7 @@ ktime_t *input_get_timestamp(struct input_dev *dev) { const ktime_t invalid_timestamp = ktime_set(0, 0); - if (!ktime_compare(dev->timestamp[INPUT_CLK_MONO], invalid_timestamp)) + // if (!ktime_compare(dev->timestamp[INPUT_CLK_MONO], invalid_timestamp)) input_set_timestamp(dev, ktime_get()); return dev->timestamp; Steps to reproduce ------------------ I used the following script as a reproducer. It relies on libinput- debug-events. This script measures the time delta between consecutive input events, then prints a "histogram" of these deltas. #!/bin/bash # log file name logFile=${1:-~/Downloads/`uname -r`} echo logFile=$logFile if [[ "$1" == '' ]]; then echo record # log some events sudo libinput debug-events | grep POINTER | tee $logFile fi # process the results lastN=0 for f in `cat $logFile | awk '{print $3}' | sed "s/s//g" | sed "s/+//g"`; do echo "$f-$lastN" | bc; lastN=$f; done | sort | uniq -c 1. Pair an external Apple Trackpad over Blutooth. 2. Run the above script 3. Move your finger in circles on the touchpad for a few seconds 4. Press ctrl+c An example output of this script before the regression ------------------------------------------------------ 2 .010 371 .011 127 .012 1 .876 The above output means that: 2 times the delta was 10ms, 371 times 11ms, 127 times 12ms and 1 time 876ms. This corresponds well with the Trackpad's ~90Hz polling rate. An example output of this script after the regression ----------------------------------------------------- 3 .003 12 .004 16 .005 14 .006 21 .007 16 .008 20 .009 13 .010 359 .011 47 .012 20 .013 17 .014 21 .015 14 .016 16 .017 15 .018 2 .019 1 .020 38 .022 21 .023 1 1.060 I suspect that other input devices might be affected as well. ProblemType: Bug DistroRelease: Ubuntu 20.04 Package: linux-image-5.4.0-28-generic 5.4.0-28.32 ProcVersionSignature: Ubuntu 5.4.0-28.32-generic 5.4.30 Uname: Linux 5.4.0-28-generic x86_64 ApportVersion: 2.20.11-0ubuntu27 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: yariv 1783 F.... pulseaudio CasperMD5CheckResult: skip Date: Sat May 2 13:58:34 2020 InstallationDate: Installed on 2019-07-13 (293 days ago) InstallationMedia: Ubuntu 19.04 "Disco Dingo" - Release amd64 (20190416) MachineType: Gigabyte Technology Co., Ltd. Z170X-UD5 TH ProcFB: 0 i915drmfb ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-5.4.0-28-generic root=UUID=6deee348-bb50-4b88-837b-108413e4d8f2 ro quiet splash btusb.enable_autosuspend=0 vt.handoff=7 RelatedPackageVersions: linux-restricted-modules-5.4.0-28-generic N/A linux-backports-modules-5.4.0-28-generic N/A linux-firmware 1.187 RfKill: 0: hci0: Bluetooth Soft blocked: no Hard blocked: no SourcePackage: linux UpgradeStatus: Upgraded to focal on 2020-04-28 (3 days ago) dmi.bios.date: 03/09/2018 dmi.bios.vendor: American Megatrends Inc. dmi.bios.version: F22g dmi.board.asset.tag: Default string dmi.board.name: Z170X-UD5 TH-CF dmi.board.vendor: Gigabyte Technology Co., Ltd. dmi.board.version: x.x dmi.chassis.asset.tag: Default string dmi.chassis.type: 3 dmi.chassis.vendor: Default string dmi.chassis.version: Default string dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrF22g:bd03/09/2018:svnGigabyteTechnologyCo.,Ltd.:pnZ170X-UD5TH:pvrDefaultstring:rvnGigabyteTechnologyCo.,Ltd.:rnZ170X-UD5TH-CF:rvrx.x:cvnDefaultstring:ct3:cvrDefaultstring: dmi.product.family: Default string dmi.product.name: Z170X-UD5 TH dmi.product.sku: Default string dmi.product.version: Default string dmi.sys.vendor: Gigabyte Technology Co., Ltd. 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