On Fri, Aug 3, 2018 at 12:20 AM, Sodagudi Prasad <psoda...@codeaurora.org> wrote: >> From: RAFAEL J. WYSOCKI <raf...@kernel.org> >> Date: Wed, Aug 1, 2018 at 2:21 PM >> Subject: Re: [PATCH] dd: Invoke one probe retry cycle after every >> initcall level >> To: Rishabh Bhatnagar <risha...@codeaurora.org> >> Cc: "Rafael J. Wysocki" <raf...@kernel.org>, Greg Kroah-Hartman >> <gre...@linuxfoundation.org>, Linux Kernel Mailing List >> <linux-kernel@vger.kernel.org>, ckad...@codeaurora.org, >> ts...@codeaurora.org, Vikram Mulukutla <mark...@codeaurora.org> >> >> >> On Wed, Aug 1, 2018 at 11:18 PM, <risha...@codeaurora.org> wrote: >>> >>> On 2018-07-24 01:24, Rafael J. Wysocki wrote: >>>> >>>> >>>> On Mon, Jul 23, 2018 at 10:22 PM, <risha...@codeaurora.org> wrote: >>>>> >>>>> >>>>> On 2018-07-23 04:17, Rafael J. Wysocki wrote: >>>>>> >>>>>> >>>>>> >>>>>> On Thu, Jul 19, 2018 at 11:24 PM, Rishabh Bhatnagar >>>>>> <risha...@codeaurora.org> wrote: >>>>>>> >>>>>>> >>>>>>> >>>>>>> Drivers that are registered at an initcall level may have to >>>>>>> wait until late_init before the probe deferral mechanism can >>>>>>> retry their probe functions. It is possible that their >>>>>>> dependencies were resolved much earlier, in some cases even >>>>>>> before the next initcall level. Invoke one probe retry cycle >>>>>>> at every _sync initcall level, allowing these drivers to be >>>>>>> probed earlier. >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> Can you please say something about the actual use case this is >>>>>> expected to address? >>>>> >>>>> >>>>> >>>>> We have a display driver that depends 3 other devices to be >>>>> probed so that it can bring-up the display. Because of >> >> dependencies >>>>> >>>>> not being met the deferral mechanism defers the probes for a later >> >> time, >>>>> >>>>> even though the dependencies might be met earlier. With this >> >> change >>>>> >>>>> display can be brought up much earlier. >>>> >>>> >>>> >>>> OK >>>> >>>> What runlevel brings up the display after the change? >>>> >>>> Thanks, >>>> Rafael >>> >>> After the change the display can come up after device_initcall level >>> itself. >>> The above mentioned 3 devices are probed at 0.503253, 0.505210 and >> >> 0.523264 >>> >>> secs. >>> Only the first device is probed successfully. With the current >>> deferral mechanism the devices get probed again after late_initcall >>> at 9.19 and 9.35 secs. So display can only come up after 9.35 secs. >>> With this change the devices are re-probed successfully at 0.60 and >>> 0.613 secs. Therefore display can come just after 0.613 secs. >> >> >> OK, so why do you touch the initcall levels earlier than device_? > > 1) re-probe probing devices in the active list on every level help to > avoid circular dependency pending list. > 2) There are so many devices which gets deferred in earlier init call > levels, so we wanted to reprobe them at every successive init call level.
Do you have specific examples of devices for which that helps? >> >>> This change helps in overall android bootup as well. >> >> >> How exactly? > > We have seen less no of re-probes at late_init and most of the driver's > dependency met earlier than late_init call level. It helped display and > couple of other drivers by executing the re probe work at every init level. So I can believe that walking the deferred list on device_initcall and maybe on device_initcall_sync may help, but I'm not quite convinced that it matters for the earlier initcall levels.