On Mon, Jul 29, 2019 at 09:44:52AM +0200, Geert Uytterhoeven wrote: > Hi Eugniu, > > CC cpuidle people > > On Fri, Jul 26, 2019 at 11:47 AM Eugeniu Rosca <ero...@de.adit-jv.com> wrote: > > On Fri, Jul 26, 2019 at 11:13:29AM +0200, Rosca, Eugeniu (ADITG/ESM1) wrote: > > [..] > > > The culprit BSP commits are: > > > https://git.kernel.org/pub/scm/linux/kernel/git/horms/renesas-bsp.git/commit/?id=3c3b44c752c4ee > > > https://git.kernel.org/pub/scm/linux/kernel/git/horms/renesas-bsp.git/commit/?id=902ff7caa32dc71c > > > > > > Further narrowing it down, it turns out the CA57 cpuidle support is > > > not responsible for generating the issue. It's all about the CA53 idle > > > enablement. The reference target is H3-ES2.0-Salvator-X (the problem > > > originally emerged on M3-based customer HW). > > [..] > > > > Small amendment to the above (based on vanilla testing): > > > > Version Issue reproduced? > > (H3-ES2.0-Salvator-X) > > v5.3-rc1-96-g6789f873ed37 No > > v5.3-rc1-96-g6789f873ed37 + [1] No > > v5.3-rc1-96-g6789f873ed37 + [2] No > > v5.3-rc1-96-g6789f873ed37 + [1] + [2] Yes > > > > [1] https://patchwork.kernel.org/patch/10769701/ > > ("[v2,1/5] arm64: dts: r8a7795: Add cpuidle support for CA57 cores") > > > > [2] https://patchwork.kernel.org/patch/10769689/ > > ("[v2,2/5] arm64: dts: r8a7795: Add cpuidle support for CA53 cores") > > Thanks for your report and investigation! > > Unfortunately your original report didn't make it to lore.kernel.org, and > probably also not to the list, due to the large audio attachment. > > For the newly CCed people, the issue is about consistent dropouts > during audio playback using an in-house application, introduced by > adding cpuidle support to _both_ the big and LITTLE cores.
CPUidle entry/exit latencies are certainly bringing the issue about, I am not an audio expert but I suspect buffering should be tuned to cope with those _increased_ latencies or possibly idle states disabled for certain specific use cases - there is no silver bullet, entering deep idle states will increase latencies, there is no way around it. I am happy to help you debug the issue further. Lorenzo
