Messages in this thread | | | Date | Tue, 12 Jul 2022 22:35:24 +0800 | Subject | Re: [PATCH v4] amba: Remove deferred device addition | From | Kefeng Wang <> |
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On 2022/7/5 16:39, Saravana Kannan wrote: > The uevents generated for an amba device need PID and CID information > that's available only when the amba device is powered on, clocked and > out of reset. So, if those resources aren't available, the information > can't be read to generate the uevents. To workaround this requirement, > if the resources weren't available, the device addition was deferred and > retried periodically. > > However, this deferred addition retry isn't based on resources becoming > available. Instead, it's retried every 5 seconds and causes arbitrary > probe delays for amba devices and their consumers. > > Also, maintaining a separate deferred-probe like mechanism is > maintenance headache. > > With this commit, instead of deferring the device addition, we simply > defer the generation of uevents for the device and probing of the device > (because drivers needs PID and CID to match) until the PID and CID > information can be read. This allows us to delete all the amba specific > deferring code and also avoid the arbitrary probing delays. > > Cc: Rob Herring <robh@kernel.org> > Cc: Ulf Hansson <ulf.hansson@linaro.org> > Cc: John Stultz <john.stultz@linaro.org> > Cc: Saravana Kannan <saravanak@google.com> > Cc: Linus Walleij <linus.walleij@linaro.org> > Cc: Sudeep Holla <sudeep.holla@arm.com> > Cc: Nicolas Saenz Julienne <nsaenzjulienne@suse.de> > Cc: Geert Uytterhoeven <geert+renesas@glider.be> > Cc: Marek Szyprowski <m.szyprowski@samsung.com> > Cc: Kefeng Wang <wangkefeng.wang@huawei.com> > Cc: Russell King <linux@armlinux.org.uk> > Signed-off-by: Saravana Kannan <saravanak@google.com> > --- > > v1 -> v2: > - Dropped RFC tag > - Complete rewrite to not use stub devices. > > v2 -> v3: > - Flipped the if() condition for hard-coded periphids. > - Added a stub driver to handle the case where all amba drivers are > modules loaded by uevents. > - Cc Marek after I realized I forgot to add him. > > v3 -> v4: > - Finally figured out and fixed the issue reported by Kefeng (bus match > can't return an error other than -EPROBE_DEFER). > - I tested the patch on "V2P-CA15" on qemu > - Marek tested v3, but that was so long ago and the rebase wasn't clean, > so I didn't include the tested-by. > > Marek/Kefeng, > > Mind giving a Tested-by?
Hi Saravana, I tested on my qemu, and previous panic[1] disappeared, so
Tested-by: Kefeng Wang <wangkefeng.wang@huawei.com>
[1] https://lore.kernel.org/linux-arm-kernel/CAGETcx8RLor0JcboBuMrB96xUot14P1CAcqoen7ZHnYRi7KMEQ@mail.gmail.com/
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