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([2600:1700:2442:6db0:7c5a:aa57:ff5:df70]) by smtp.gmail.com with ESMTPSA id g2-20020a925202000000b002d5199dab1fsm1184668ilb.42.2022.06.16.09.45.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 16 Jun 2022 09:45:19 -0700 (PDT) Message-ID: Date: Thu, 16 Jun 2022 11:45:17 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: Re: Default async probing for DT based systems Content-Language: en-US To: Saravana Kannan , LKML , linux-arm-kernel , Marek Szyprowski , Geert Uytterhoeven , Kevin Hilman , Greg Kroah-Hartman , Marc Zyngier , Will Deacon , Rob Herring , "Rafael J. Wysocki" , Ulf Hansson , Linus Walleij , Sebastian Andrzej Siewior , Frank Rowand Cc: Android Kernel Team , Linux PM References: From: Frank Rowand In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Saravana, You failed to include me in the distribution. Adding myself now... -Frank On 6/15/22 23:24, Saravana Kannan wrote: > Hi, > > TL;DR: I want to improve boot times by enabling async probing by > default for DT based systems. Can you give it a shot please? > > Why do you think it might work when async probing has been a pain before? > ========================================================== > Since fw_devlink=on is the default behavior and fw_devlink understands > approximately 24 DT bindings, it should capture most of the device > dependencies and ensure proper probe ordering. For example, on a Pixel > 6, fw_devlink figures out 325 dependencies that it uses to enforce > probe ordering. > > You can find all the dependencies under /sys/class/devlink. > > Fine! What do you want me to try? > ========================== > With the patches that have landed in 5.19-rc1, we can now enable > default async probing for all built-in drivers by adding the following > to the kernel command line: > > driver_async_probe=* > > I'd really appreciate it if folks can try adding driver_async_probe=* > to their kernel command line and report any boot time > improvements/regression or boot/probe failures it causes. > > (* insert cat begging pic *) > Can I haz some reports pleez?! > > Tips: > ==== > One easy way to check for devices probe failures is to compare the > output of this command with/without the commandline changes: > > # find /sys/devices -name driver > > Btw, if you need to force sync probing for a few drivers so that your > rootfs mounts properly, you can set the flag in the driver, or you can > list them as exceptions following the * in the command line option. > For example: > driver_async_probe=*,my_flash_driver,my_sdio_driver > > Report these too. > > Known issues: > =========== > fw_devlink doesn't yet support phy-handle and mdio-parent DT bindings. > They have some tricky issues I need to resolve first and I need to add > both of them together -- I'm working on it. If there are other DT > bindings that are missing support, do let me know. Most of them are > easy to add. > > The driver_async_probe=* won't have any useful impact for modules > without adding .async_probe to the commandline or > async_probe as a module option when loading it. This is because > modules intentionally force sync before they exit. There's a patch for > a global flag for modules too [1], but it can never be set by default > for userspace reasons[2]. > > [1] - https://lore.kernel.org/lkml/20220604010101.719508-1-saravanak@google.com/ > [2] - https://lore.kernel.org/lkml/CA+55aFxV40V2WvNtJY3EC0F-B9wPk8CV2o1TTTyoF4CoWH7rhQ@mail.gmail.com/ > > Thanks, > Saravana > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel