Hi, On Wed, Jul 5, 2023 at 12:51 AM Bert Karwatzki <spasswolf@xxxxxx> wrote: > > The fairphone-fp3 has a drm_panel attached to a dsi bridge. This are added to > the bridge_chain in struct drm_encoder in the order dsi, panel. When the > drm_atomic_bridge_chain_pre_enable these get enabled in the order panel, dsi > because of the list_for_each_entry_reverse. But the drm_panel of the fairphone- > fp3 is enabled using mipi_dsi_dcs_write_buffer which only works if the dsi is > enabled before the panel. > To work around this one can revert > > commit 9e15123eca7942caa8a3e1f58ec0df7d088df149 > Author: Douglas Anderson <dianders@xxxxxxxxxxxx> > Date: Tue Jan 31 14:18:25 2023 -0800 > > drm/msm/dsi: Stop unconditionally powering up DSI hosts at modeset > > This leads to a working panel on startup. But when suspending one runs again > into a similar problem. When the bridges are disabled the dsi is disabled first > which leads to a failure in disabling the panel again because > mipi_dsi_dcs_write_buffer fails when the dsi is already switched of. > As a simple workarund for both problems I have found it works to exchange the > order of the bridge chain in drm_endcoder: > > diff --git a/drivers/gpu/drm/msm/dsi/dsi_manager.c > b/drivers/gpu/drm/msm/dsi/dsi_manager.c > index 28b8012a21f2..990f7c68a27c 100644 > --- a/drivers/gpu/drm/msm/dsi/dsi_manager.c > +++ b/drivers/gpu/drm/msm/dsi/dsi_manager.c > @@ -550,6 +555,8 @@ int msm_dsi_manager_ext_bridge_init(u8 id) > if (ret < 0) > return ret; > } > + /* swap bridges in list */ > + list_swap(&encoder->bridge_chain, encoder->bridge_chain.next); > > /* The pipeline is ready, ping encoders if necessary */ > msm_dsi_manager_set_split_display(id); > > But this does not look like a portable solution so I wonder if there is a better > way to do this. > > The linux kernel used here is a linux-next-20220630, with several out-of-tree > patches which are needed for the msm8953 gpu and the display used in the > fairphone-fp3 located here: https://github.com/spasswolf/msm8953-linux.git in > branch msm8953_iommu_rebase_v2_wlan_modem_ipa_cpufreq_display_debug. Any chance that "pre_enable_prev_first" works for you? For the best summary I'm aware of this issue, see: https://lore.kernel.org/r/CAD=FV=X_xonf1Dz0BsNTKm4-zBm+ccKvPO+wEWFVMUVY_2=h3Q@xxxxxxxxxxxxxx -Doug
