On Thursday, October 22, 2015 04:27:10 PM Scott Wood wrote: > On Thu, 2015-10-22 at 15:04 +0200, Tomeu Vizoso wrote: > > On 22 October 2015 at 00:51, Scott Wood <scottwood@xxxxxxxxxxxxx> wrote: > > > On Wed, 2015-10-21 at 08:44 -0500, Rob Herring wrote: > > > > On Wed, Oct 21, 2015 at 12:54 AM, Scott Wood <scottwood@xxxxxxxxxxxxx> > > > > wrote: > > > > > On Mon, 2015-09-21 at 16:03 +0200, Tomeu Vizoso wrote: > > > > > > Instead of trying to match and probe platform and AMBA devices right > > > > > > after each is registered, delay their probes until > > > > > > device_initcall_sync. > > > > > > > > > > > > This means that devices will start probing once all built-in drivers > > > > > > have registered, and after all platform and AMBA devices from the DT > > > > > > have been registered already. > > > > > > > > > > > > This allows us to prevent deferred probes by probing dependencies on > > > > > > demand. > > > > > > > > > > > > Signed-off-by: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx> > > > > > > --- > > > > > > > > > > > > Changes in v4: > > > > > > - Also defer probes of AMBA devices registered from the DT as they > > > > > > can > > > > > > also request resources. > > > > > > > > > > > > drivers/of/platform.c | 11 ++++++++--- > > > > > > 1 file changed, 8 insertions(+), 3 deletions(-) > > > > > > > > > > This breaks arch/powerpc/sysdev/fsl_pci.c. The PCI bus is an OF > > > > > platform > > > > > device, and it must be probed before pcibios_init() which is a > > > > > subsys_initcall(), or else the PCI bus never gets scanned. > > > > > > > > Thanks for the report. This is probably getting dropped, but it could > > > > be disabled for PPC. > > > > > > I don't think that adding another arbitrary arch difference would be the > > > right solution. > > > > I think Rob meant temporarily disable it while things get fixed. At > > least, > > So, what is the permanent fix for the swiotlb issue (or more generally, the > inability to have a late_initcall that runs after non-module, non-hotplug > platform devices have been probed)? > > > I don't see any reason why PPC wouldn't benefit from this > > series. > > It's not clear to me what the benefit of this is at all, much less for PPC. > What is the fundamental problem with deferred probes? In the cover letter > you say this change saves 2.3 seconds, but where is that time being consumed? > Are the drivers taking too long in their probe function trying to initialize > and then deferring, rather than checking for dependencies up front? Or are > there really so many devices and such a pessimal ordering that most of the > time is spent iterating through and reordering the list, with each defer > happening quickly? > > Even if something different does need to be done at this level, forcing all > OF platform devices to be probed at the late_initcall level seems quite > intrusive. Totally agreed. > You limited it to OF because people complained that other things > will break. Right. And I'm not sure why that was regarded as a good enough reason to do it. > Things still broke. Yes, they did. > Surely there's a better way to address the > problem. Can't the delay be requested by drivers that might otherwise need > to defer (which could be done incrementally, focusing on the worst > performance problems), rather than enabling it for everything? Well, I was suggesting to use an opt-in flag there, but I'm not sure if Tomeu took that into consideration. In any case, probing is just one aspect of a deeper issue, which is that we have no way to represent functional dependencies between devices. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
