Hi Saravana, On 04.03.2021 20:51, 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 <r...@kernel.org> > Cc: Ulf Hansson <ulf.hans...@linaro.org> > Cc: John Stultz <john.stu...@linaro.org> > Cc: Saravana Kannan <sarava...@google.com> > Cc: Linus Walleij <linus.wall...@linaro.org> > Cc: Sudeep Holla <sudeep.ho...@arm.com> > Cc: Nicolas Saenz Julienne <nsaenzjulie...@suse.de> > Cc: Geert Uytterhoeven <geert+rene...@glider.be> > Cc: Marek Szyprowski <m.szyprow...@samsung.com> > Cc: Russell King <li...@armlinux.org.uk> > Signed-off-by: Saravana Kannan <sarava...@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. > > Marek, > > Would you mind testing this? It looks okay with my limited testing.
It looks it works fine on my test systems. I've checked current linux-next and this patch. You can add: Tested-by: Marek Szyprowski <m.szyprow...@samsung.com> I've briefly scanned the code and I'm curious how does it work. Does it depend on the recently introduced "fw_devlink=on" feature? I don't see other mechanism, which would trigger matching amba device if pm domains, clocks or resets were not available on time to read pid/cid while adding a device... Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland
