On Tue, Apr 4, 2023 at 6:48 PM AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx> wrote: > > Changes in v3: > - Added DPTX AUX block initialization before trying to communicate > to stop relying on the bootloader keeping it initialized before > booting Linux. > - Fixed commit description for patch [09/09] and removed commented > out code (that slipped from dev phase.. sorry!). > > This series adds "real" support for eDP in the mtk-dp DisplayPort driver. > > Explaining the "real": > Before this change, the DisplayPort driver did support eDP to some > extent, but it was treating it entirely like a regular DP interface > which is partially fine, after all, embedded DisplayPort *is* actually > DisplayPort, but there might be some differences to account for... and > this is for both small performance improvements and, more importantly, > for correct functionality in some systems. > > Functionality first: > > One of the common differences found in various boards implementing eDP > and machines using an eDP panel is that many times the HPD line is not > connected. This *must* be accounted for: at startup, this specific IP > will raise a HPD interrupt (which should maybe be ignored... as it does > not appear to be a "real" event...) that will make the eDP panel to be > detected and to actually work but, after a suspend-resume cycle, there > will be no HPD interrupt (as there's no HPD line in my case!) producing > a functionality issue - specifically, the DP Link Training fails because > the panel doesn't get powered up, then it stays black and won't work > until rebooting the machine (or removing and reinserting the module I > think, but I haven't tried that). > > Now for.. both: > eDP panels are *e*DP because they are *not* removable (in the sense that > you can't unplug the cable without disassembling the machine, in which > case, the machine shall be powered down..!): this (correct) assumption > makes us able to solve some issues and to also gain a little performance > during PM operations. > > What was done here is: > - Caching the EDID if the panel is eDP: we're always going to read the > same data everytime, so we can just cache that (as it's small enough) > shortening PM resume times for the eDP driver instance; > - Always return connector_status_connected if it's eDP: non-removable > means connector_status_disconnected can't happen during runtime... > this also saves us some time and even power, as we won't have to > perform yet another power cycle of the HW; > - Added aux-bus support! > This makes us able to rely on panel autodetection from the EDID, > avoiding to add more and more panel timings to panel-edp and, even > better, allowing to use one panel node in devicetrees for multiple > variants of the same machine since, at that point, it's not important > to "preventively know" what panel we have (eh, it's autodetected...!). > > This was tested on a MT8195 Cherry Tomato Chromebook (panel-edp on aux-bus) > > > P.S.: For your own testing commodity, here's a reference devicetree: > &edp_tx { > status = "okay"; > > pinctrl-names = "default"; > pinctrl-0 = <&edptx_pins_default>; > > ports { > #address-cells = <1>; > #size-cells = <0>; > > port@0 { > reg = <0>; > edp_in: endpoint { > remote-endpoint = <&dp_intf0_out>; > }; > }; > > port@1 { > reg = <1>; > edp_out: endpoint { > data-lanes = <0 1 2 3>; > remote-endpoint = <&panel_in>; > }; > }; > }; > > aux-bus { > panel: panel { > compatible = "edp-panel"; > power-supply = <&pp3300_disp_x>; > backlight = <&backlight_lcd0>; > port { > panel_in: endpoint { > remote-endpoint = <&edp_out>; > }; > }; > }; > }; > }; > > AngeloGioacchino Del Regno (9): > drm/mediatek: dp: Cache EDID for eDP panel > drm/mediatek: dp: Move AUX and panel poweron/off sequence to function > drm/mediatek: dp: Always return connected status for eDP in .detect() > drm/mediatek: dp: Always set cable_plugged_in at resume for eDP panel > drm/mediatek: dp: Change logging to dev for mtk_dp_aux_transfer() > drm/mediatek: dp: Enable event interrupt only when bridge attached > drm/mediatek: dp: Use devm variant of drm_bridge_add() > drm/mediatek: dp: Move AUX_P0 setting to > mtk_dp_initialize_aux_settings() > drm/mediatek: dp: Add support for embedded DisplayPort aux-bus Tested-by: Chen-Yu Tsai <wenst@xxxxxxxxxxxx> on MT8195 Tomato: eDP panel works if the display panel regulator is always on. External DP works. Maybe it has something to do with the driver not supporting .wait_hpd_asserted and not using a GPIO for HPD?