| Message ID | 1442844182-27787-23-git-send-email-tomeu.vizoso@collabora.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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@collabora.com> > --- > > 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. -Scott
On Wed, Oct 21, 2015 at 12:54 AM, Scott Wood <scottwood@freescale.com> 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@collabora.com> >> --- >> >> 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. Any plans to fix this and make PCI hosts hotplugable? For the scanning part, generally the host controller drivers are responsible for scanning their bus now. Rob
On Wed, 2015-10-21 at 08:44 -0500, Rob Herring wrote: > On Wed, Oct 21, 2015 at 12:54 AM, Scott Wood <scottwood@freescale.com> > 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@collabora.com> > > > --- > > > > > > 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. > Any plans to fix this and make PCI hosts hotplugable? For the scanning > part, generally the host controller drivers are responsible for > scanning their bus now. Scanning from the host controller driver seems like a reasonable goal, though it'd take a bit of digging to extract whatever other things fsl_pci may depend on from the common PPC PCI code, in particular the various things that pcibios_resource_survey() does after all PCI buses have been scanned. There's also check_swiotlb_enabled(), another subsys_initcall, which frees the swiotlb memory if ppc_swiotlb_enable hasn't been set. The PCI host controller probe sets ppc_swiotlb_enable if it wasn't able to create an inbound mapping for all RAM. Even if we were to change that to a later initcall, there's nothing later than late_initcall that we could use. -Scott
On Wed, 2015-10-21 at 00:54 -0500, Scott Wood 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@collabora.com> > > --- > > > > 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. Ah right. This is presumably why I'm not seeing any PCI devices on my p5020ds with linux-next. cheers
On 22 October 2015 at 00:51, Scott Wood <scottwood@freescale.com> 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@freescale.com> >> 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@collabora.com> >> > > --- >> > > >> > > 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, I don't see any reason why PPC wouldn't benefit from this series. Regards, Tomeu >> Any plans to fix this and make PCI hosts hotplugable? For the scanning >> part, generally the host controller drivers are responsible for >> scanning their bus now. > > Scanning from the host controller driver seems like a reasonable goal, though > > it'd take a bit of digging to extract whatever other things fsl_pci may > depend on from the common PPC PCI code, in particular the various things that > > pcibios_resource_survey() does after all PCI buses have been scanned. > > There's also check_swiotlb_enabled(), another subsys_initcall, which frees > the swiotlb memory if ppc_swiotlb_enable hasn't been set. The PCI host > controller probe sets ppc_swiotlb_enable if it wasn't able to create an > inbound mapping for all RAM. Even if we were to change that to a later > initcall, there's nothing later than late_initcall that we could use. > > -Scott > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
On Thu, 2015-10-22 at 15:04 +0200, Tomeu Vizoso wrote: > On 22 October 2015 at 00:51, Scott Wood <scottwood@freescale.com> 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@freescale.com> > > > 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@collabora.com> > > > > > --- > > > > > > > > > > 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. You limited it to OF because people complained that other things will break. Things still broke. 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? -Scott
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@freescale.com> 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@freescale.com> > > > > 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@collabora.com> > > > > > > --- > > > > > > > > > > > > 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
On 22 October 2015 at 23:27, Scott Wood <scottwood@freescale.com> wrote: > On Thu, 2015-10-22 at 15:04 +0200, Tomeu Vizoso wrote: >> On 22 October 2015 at 00:51, Scott Wood <scottwood@freescale.com> 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@freescale.com> >> > > 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@collabora.com> >> > > > > --- >> > > > > >> > > > > 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)? If the code in pcibios_init() depends on the PCI bus device having probed, then I would recommend making that dependency explicit by calling of_device_probe() on the OF node of the PCI controller when looking it up. >> 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? The problem is that a device that defers its probe is currently sent to the back of the queue, and that's undesired in some use cases in which there's a device that should be up as soon as possible during boot (and boot takes a long time). So the goal is to change the order in which devices with dependencies end up probing. > 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. You limited it to OF because people complained that other things > will break. Things still broke. 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? Yes, given the amount of breakage that's a sensible option. But in any case and even if this series is most likely to be dropped, I recommend to make explicit as many implicit dependencies as possible. Regards, Tomeu > -Scott > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
On Wed, Oct 28, 2015 at 9:40 AM, Tomeu Vizoso <tomeu.vizoso@collabora.com> wrote: > On 22 October 2015 at 23:27, Scott Wood <scottwood@freescale.com> wrote: >> On Thu, 2015-10-22 at 15:04 +0200, Tomeu Vizoso wrote: >>> On 22 October 2015 at 00:51, Scott Wood <scottwood@freescale.com> 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@freescale.com> >>> > > 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@collabora.com> >>> > > > > --- >>> > > > > >>> > > > > 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)? > > If the code in pcibios_init() depends on the PCI bus device having > probed, then I would recommend making that dependency explicit by > calling of_device_probe() on the OF node of the PCI controller when > looking it up. > >>> 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? > > The problem is that a device that defers its probe is currently sent > to the back of the queue, and that's undesired in some use cases in > which there's a device that should be up as soon as possible during > boot (and boot takes a long time). So the goal is to change the order > in which devices with dependencies end up probing. > >> 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. You limited it to OF because people complained that other things >> will break. Things still broke. 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? > > Yes, given the amount of breakage that's a sensible option. But in any > case and even if this series is most likely to be dropped, I recommend > to make explicit as many implicit dependencies as possible. It is dropped for now, but I expect much of this to still integrate with Rafael's proposal. However, it will need to be opt-in it seems. That is somewhat unfortunate because things like async probe are opt-in and seem to rarely get used. As to how we can make it opt-in, I think we can make of_platform_populate() callable multiple times at the root level. This will allow a platform to skip calling it and then a late call to it can register the devices after drivers have registered. This late call will then be a nop for platforms that don't opt-in and call of_platform_populate themselves. Rob
On Wed, 2015-10-28 at 15:40 +0100, Tomeu Vizoso wrote: > On 22 October 2015 at 23:27, Scott Wood <scottwood@freescale.com> wrote: > > On Thu, 2015-10-22 at 15:04 +0200, Tomeu Vizoso wrote: > > > On 22 October 2015 at 00:51, Scott Wood <scottwood@freescale.com> 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@freescale.com> > > > > > 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@collabora.com> > > > > > > > --- > > > > > > > > > > > > > > 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)? > > If the code in pcibios_init() depends on the PCI bus device having > probed, then I would recommend making that dependency explicit by > calling of_device_probe() on the OF node of the PCI controller when > looking it up. "when looking it up"? pcibios_init() doesn't do anything with the OF node or know any details about the particular PCI bus host implementation. > > > 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? > > The problem is that a device that defers its probe is currently sent > to the back of the queue, and that's undesired in some use cases in > which there's a device that should be up as soon as possible during > boot (and boot takes a long time). So the goal is to change the order > in which devices with dependencies end up probing. That doesn't answer my question about where the time is being spent. Did you profile? -Scott
diff --git a/drivers/of/platform.c b/drivers/of/platform.c index 408d89f1d124..7b33e0369374 100644 --- a/drivers/of/platform.c +++ b/drivers/of/platform.c @@ -164,7 +164,8 @@ static struct platform_device *of_platform_device_create_pdata( struct device_node *np, const char *bus_id, void *platform_data, - struct device *parent) + struct device *parent, + bool probe_late) { struct platform_device *dev; @@ -178,6 +179,7 @@ static struct platform_device *of_platform_device_create_pdata( dev->dev.bus = &platform_bus_type; dev->dev.platform_data = platform_data; + dev->dev.probe_late = probe_late; of_dma_configure(&dev->dev, dev->dev.of_node); of_msi_configure(&dev->dev, dev->dev.of_node); @@ -209,7 +211,8 @@ struct platform_device *of_platform_device_create(struct device_node *np, const char *bus_id, struct device *parent) { - return of_platform_device_create_pdata(np, bus_id, NULL, parent); + return of_platform_device_create_pdata(np, bus_id, NULL, parent, + false); } EXPORT_SYMBOL(of_platform_device_create); @@ -240,6 +243,7 @@ static struct amba_device *of_amba_device_create(struct device_node *node, dev->dev.of_node = of_node_get(node); dev->dev.parent = parent ? : &platform_bus; dev->dev.platform_data = platform_data; + dev->dev.probe_late = true; if (bus_id) dev_set_name(&dev->dev, "%s", bus_id); else @@ -358,7 +362,8 @@ static int of_platform_bus_create(struct device_node *bus, return 0; } - dev = of_platform_device_create_pdata(bus, bus_id, platform_data, parent); + dev = of_platform_device_create_pdata(bus, bus_id, platform_data, + parent, true); if (!dev || !of_match_node(matches, bus)) return 0;
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@collabora.com> --- 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(-)