On Tue, Mar 23, 2021 at 11:39:09AM +0100, Hans de Goede wrote: > Hi, > > On 3/2/21 3:51 PM, Ville Syrjälä wrote: > > On Tue, Mar 02, 2021 at 01:00:40PM +0100, Hans de Goede wrote: > >> As explained by a long comment block, on VLV intel_setup_outputs() > >> sometimes thinks there might be an eDP panel connected while there is none. > >> In this case intel_setup_outputs() will call intel_dp_init() to check. > >> > >> In this scenario vlv_find_free_pps() ends up selecting pipe A for the pps, > >> even though this might be in use for non DP purposes. When this is the case > >> then the assert_pipe() in vlv_force_pll_on() will fail when called from > >> vlv_power_sequencer_kick(). > > > > The idea is that you *can* select a PPS from a pipe used for a non-DP > > port since those don't care about the PPS stuff. So this doesn't seem > > correct. > > They may not care about the PPS stuff, but as the WARN / backtrace > shows if the DPLL_VCO_ENABLE bit is not already set for the pipe, while > the pipe is "otherwise" in use then vlv_force_pll_on() becomes unhappy > triggering the WARN. > > > a) I would like to see the VBT for this machine > > https://fedorapeople.org/~jwrdegoede/voyo-winpad-a15-vbt > > > b) I wonder if the DSI PLL is sufficient for getting the PPS going? > > I have no idea, I just noticed the WARN / backtrace and this seemed > like a reasonably way to deal with it. With that said I'm fine with fixing > this a different way. > > > c) If we do need the normal DPLL is there any harm to DSI in enabling it? > > I would assume this increases power-consumption and DSI panels are almost > always used in battery powered devices. This is just used while probing the panel, so power consumption is not a concern. > > Also this would impact all BYT/CHT devices, possible triggering unwanted > side-effects. Where as the proposed fix below is much more narrowly targeted > at the problem. It might not be the most pretty fix but AFAICT it has a low > risk of causing regressions. It rather significantly changes the logic of the workaround, potentially causing us to not find a free PPS at all. Eg. if you were to boot with a VLV with pipe A -> eDP B + eDP C inactive + pipe B -> VGA then your change would cause us to not find the free pipe B PPS for probing eDP C, and in the end we'd get a WARN and fall back to pipe A PPS which would clobber the actually in use pipe A PPS. -- Ville Syrjälä Intel _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
