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R. A. Prado wrote: > On Fri, Aug 09, 2024 at 12:13:25PM -0400, Nícolas F. R. A. Prado wrote: >> On Mon, Jul 29, 2024 at 05:08:48PM -0700, Saravana Kannan wrote: >>> On Mon, Jul 29, 2024 at 2:25 PM Nícolas F. R. A. Prado >>> wrote: >>>> >>>> On Tue, Jun 25, 2024 at 09:56:07AM -0400, Nícolas F. R. A. Prado wrote: >>>>> On Mon, Jun 24, 2024 at 04:53:30PM -0700, Saravana Kannan wrote: >>>>>> On Mon, Jun 24, 2024 at 8:21 AM Nícolas F. R. A. Prado >>>>>> wrote: >>>>>>> >>>>>>> Commit ac66c5bbb437 ("driver core: Allow only unprobed consumers for >>>>>>> SYNC_STATE_ONLY device links") introduced an early return in >>>>>>> device_link_add() to prevent useless links from being created. However >>>>>>> the calling function fw_devlink_create_devlink() unconditionally prints >>>>>>> an error if device_link_add() didn't create a link, even in this case >>>>>>> where it is intentionally skipping the link creation. >>>>>>> >>>>>>> Add a check to detect if the link wasn't created intentionally and in >>>>>>> that case don't log an error. >>>>>> >>>>>> Your point is somewhat valid, and I might Ack this. But this really >>>>>> shouldn't be happening a lot. Can you give more context on how you are >>>>>> hitting this? >>>>> >>>>> Of course. I'm seeing this on the mt8195-cherry-tomato-r2 platform. >>>>> >>>>> The following error is printed during boot: >>>>> >>>>> mediatek-drm-dp 1c500000.edp-tx: Failed to create device link (0x180) with backlight-lcd0 >>>>> >>>>> It doesn't happen with the upstream defconfig, but with the following config >>>>> change it does: >>>>> >>>>> -CONFIG_PWM_MTK_DISP=m >>>>> +CONFIG_PWM_MTK_DISP=y >>>>> >>>>> That probably changes the order in which the MTK DP and the backlight drivers >>>>> probe, resulting in the error. >>>>> >>>>> One peculiarity that comes to mind is that the DP driver calls >>>>> devm_of_dp_aux_populate_bus() to run a callback once the panel has finished >>>>> probing. I'm not sure if this could have something to do with the error. >>>>> >>>>> Full log at https://lava.collabora.dev/scheduler/job/14573149 >>>> >>>> Hi Saravana, >>>> >>>> With the given context for where this issue is happening, what do you think >>>> about this patch? >>> >>> Ah sorry, missed your earlier email. >>> >>> Couple of points: >>> 1. It looks like the link in question is "SYNC_STATE_ONLY" because >>> it's part of a cycle. Correct me if I'm wrong. You might want to use >>> the new "post-init-providers" property to help fw_devlink break the >>> cycle and enforce the right dependency between the edp-tx and your >>> backlight. And then this error should go away and your device ordering >>> is enforced a bit better. >> >> I don't see any cycle there. edp-tx points to backlight, but backlight doesn't >> point back (from mt8195-cherry.dtsi): >> >> &edp_tx { >> ... >> aux-bus { >> panel { >> compatible = "edp-panel"; >> power-supply = <&pp3300_disp_x>; >> backlight = <&backlight_lcd0>; >> >> >> backlight_lcd0: backlight-lcd0 { >> compatible = "pwm-backlight"; >> brightness-levels = <0 1023>; >> default-brightness-level = <576>; >> enable-gpios = <&pio 82 GPIO_ACTIVE_HIGH>; >> num-interpolated-steps = <1023>; >> pwms = <&disp_pwm0 0 500000>; >> power-supply = <&ppvar_sys>; >> }; >> >> And DL_FLAG_CYCLE is not set in the flags in the error log: 0x180. (Let me know >> if there's something else that I should be looking at to detect a cycle) > > Hi Saravana, > > Here are some debug logs to help contextualize the issue: > > [ 0.198518] device: 'backlight-lcd0': device_add > [ 0.198655] platform 1c500000.edp-tx: Linked as a sync state only consumer to backlight-lcd0 > > [ 34.971653] platform backlight-lcd0: error -EPROBE_DEFER: supplier 1100e000.pwm not ready > > [ 35.115480] mediatek-drm-dp 1c500000.edp-tx: driver: 'mediatek-drm-dp': driver_bound: bound to device > [ 35.160115] mediatek-drm-dp 1c500000.edp-tx: Dropping the link to backlight-lcd0 > > [ 53.910433] pwm-backlight backlight-lcd0: driver: 'pwm-backlight': driver_bound: bound to device > [ 53.919213] mediatek-drm-dp 1c500000.edp-tx: Failed to create device link (0x180) with backlight-lcd0 > > So a SYNC_STATE_ONLY device link is created from backlight-lcd0 to edp-tx. When > the edp-tx probes, the link is dropped, since it is SYNC_STATE_ONLY. When the > backlight-lcd0 probes a new devlink is attempted to the consumer edp-tx and > fails, since it is useless, printing the warning. > > You mentioned a cycle before. The only cycle I see is between the edp-tx and the > panel, but doesn't involve the backlight: > > [ 0.198104] ----- cycle: start ----- > [ 0.198105] /soc/edp-tx@1c500000/aux-bus/panel: cycle: depends on /soc/edp-tx@1c500000 > [ 0.198112] ----- cycle: start ----- > [ 0.198113] /soc/edp-tx@1c500000/aux-bus/panel: cycle: child of /soc/edp-tx@1c500000 > [ 0.198119] /soc/edp-tx@1c500000: cycle: depends on /soc/edp-tx@1c500000/aux-bus/panel > [ 0.198125] ----- cycle: end ----- > [ 0.198126] platform 1c500000.edp-tx: Fixed dependency cycle(s) with /soc/edp-tx@1c500000/aux-bus/panel > > Just in case I tried using post-init-providers: > > diff --git a/arch/arm64/boot/dts/mediatek/mt8195-cherry.dtsi b/arch/arm64/boot/dts/mediatek/mt8195-cherry.dtsi > index 75d56b2d5a3d..19df138ef043 100644 > --- a/arch/arm64/boot/dts/mediatek/mt8195-cherry.dtsi > +++ b/arch/arm64/boot/dts/mediatek/mt8195-cherry.dtsi > @@ -322,6 +322,7 @@ &edp_tx { > > pinctrl-names = "default"; > pinctrl-0 = <&edptx_pins_default>; > + post-init-providers = <&panel>; > > ports { > #address-cells = <1>; > @@ -344,7 +345,7 @@ edp_out: endpoint { > }; > > aux-bus { > - panel { > + panel: panel { > compatible = "edp-panel"; > power-supply = <&pp3300_disp_x>; > backlight = <&backlight_lcd0>; > > It broke the cycle, as I no longer see it in the logs, but the failed device > link warning is still there as expected. > > It seems to me that the issue comes form the device link being SYNC_STATE_ONLY > in the first place. I see that comes from the 'else' path in > > if (con->fwnode == link->consumer) > flags = fw_devlink_get_flags(link->flags); > else > flags = FW_DEVLINK_FLAGS_PERMISSIVE; > > and the value on each side of the comparison is: > > con->fwnode: /soc/edp-tx@1c500000 > link->consumer: /soc/edp-tx@1c500000/aux-bus/panel > > Could you help me understand what (if anything) is wrong here? > > (I also noticed that as per the DT the consumer for backlight-lcd0 should be the > panel, but the devlink has it instead as the edp-tx, I'm guessing that's another > symptom of the same issue) I did not seen any update on this. It would be great to get this fixed. Thanks Jon -- nvpublic