On Fri, Dec 11, 2020 at 8:34 AM Robin Murphy <robin.murphy@xxxxxxx> wrote: > > On 2020-12-11 14:11, Qian Cai wrote: > > On Fri, 2020-11-20 at 18:02 -0800, Saravana Kannan wrote: > >> The current implementation of fw_devlink is very inefficient because it > >> tries to get away without creating fwnode links in the name of saving > >> memory usage. Past attempts to optimize runtime at the cost of memory > >> usage were blocked with request for data showing that the optimization > >> made significant improvement for real world scenarios. > >> > >> We have those scenarios now. There have been several reports of boot > >> time increase in the order of seconds in this thread [1]. Several OEMs > >> and SoC manufacturers have also privately reported significant > >> (350-400ms) increase in boot time due to all the parsing done by > >> fw_devlink. > >> > >> So this patch uses all the setup done by the previous patches in this > >> series to refactor fw_devlink to be more efficient. Most of the code has > >> been moved out of firmware specific (DT mostly) code into driver core. > >> > >> This brings the following benefits: > >> - Instead of parsing the device tree multiple times during bootup, > >> fw_devlink parses each fwnode node/property only once and creates > >> fwnode links. The rest of the fw_devlink code then just looks at these > >> fwnode links to do rest of the work. > >> > >> - Makes it much easier to debug probe issue due to fw_devlink in the > >> future. fw_devlink=on blocks the probing of devices if they depend on > >> a device that hasn't been added yet. With this refactor, it'll be very > >> easy to tell what that device is because we now have a reference to > >> the fwnode of the device. > >> > >> - Much easier to add fw_devlink support to ACPI and other firmware > >> types. A refactor to move the common bits from DT specific code to > >> driver core was in my TODO list as a prerequisite to adding ACPI > >> support to fw_devlink. This series gets that done. > >> > >> [1] - https://lore.kernel.org/linux-omap/ea02f57e-871d-cd16-4418-c1da4bbc4696@xxxxxx/ > >> Signed-off-by: Saravana Kannan <saravanak@xxxxxxxxxx> > >> Tested-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> > >> Tested-by: Grygorii Strashko <grygorii.strashko@xxxxxx> > > > > Reverting this commit and its dependency: > > > > 2d09e6eb4a6f driver core: Delete pointless parameter in fwnode_operations.add_links > > > > from today's linux-next fixed a boot crash on an arm64 Thunder X2 server. > > Since the call stack implicates the platform-device-wrangling we do in > IORT code I took a quick look; AFAICS my guess would be it's blowing up > trying to walk a zeroed list head since "driver core: Add fwnode_init()" > missed acpi_alloc_fwnode_static(). Thanks Robin. I'm pretty sure this is the reason. I thought I fixed all ACPI cases, but clearly I missed this one. I'll send out a patch for this today. If you think there are any other places I missed please let me know. I'll try some git grep foo to see if I missed any other instances of fwnode ops being set. -Saravana
