| Message ID | 20161121100148.24769-8-lorenzo.pieralisi@arm.com (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
Rafael, Mark, Suravee, On Mon, Nov 21, 2016 at 10:01:39AM +0000, Lorenzo Pieralisi wrote: > On DT based systems, the of_dma_configure() API implements DMA > configuration for a given device. On ACPI systems an API equivalent to > of_dma_configure() is missing which implies that it is currently not > possible to set-up DMA operations for devices through the ACPI generic > kernel layer. > > This patch fills the gap by introducing acpi_dma_configure/deconfigure() > calls that for now are just wrappers around arch_setup_dma_ops() and > arch_teardown_dma_ops() and also updates ACPI and PCI core code to use > the newly introduced acpi_dma_configure/acpi_dma_deconfigure functions. > > Since acpi_dma_configure() is used to configure DMA operations, the > function initializes the dma/coherent_dma masks to sane default values > if the current masks are uninitialized (also to keep the default values > consistent with DT systems) to make sure the device has a complete > default DMA set-up. I spotted a niggle that unfortunately was hard to spot (and should not be a problem per se but better safe than sorry) and I am not comfortable with it. Following commit d0562674838c ("ACPI / scan: Parse _CCA and setup device coherency") in acpi_bind_one() we check if the acpi_device associated with a device just added supports DMA, first it was done with acpi_check_dma() and then commit 1831eff876bd ("device property: ACPI: Make use of the new DMA Attribute APIs") changed it to acpi_get_dma_attr(). The subsequent check (attr != DEV_DMA_NOT_SUPPORTED) is always true on _any_ acpi device we pass to acpi_bind_one() on x86, which was fine because we used it to call arch_setup_dma_ops(), which is a nop on x86. On ARM64 a _CCA method is required to define if a device supports DMA so (attr != DEV_DMA_NOT_SUPPORTED) may well be false. Now, acpi_bind_one() is used to bind an acpi_device to its physical node also for pseudo-devices like cpus and memory nodes. For those objects, on x86, attr will always be != DEV_DMA_NOT_SUPPORTED. So far so good, because on x86 arch_setup_dma_ops() is empty code. With this patch, I use the (attr != DEV_DMA_NOT_SUPPORTED) check to call acpi_dma_configure() which is basically a nop on x86 except that it sets up the dma_mask/coherent_dma_mask to a sane default value (after all we are setting up DMA for the device so it makes sense to initialize the masks there if they were unset since we are configuring DMA for the device in question) for the given device. Problem is, as per the explanation above, we are also setting the default dma masks for pseudo-devices (eg CPUs) that were previously untouched, it should not be a problem per-se but I am not comfortable with that, honestly it does not make much sense. An easy "fix" would be to move the default dma masks initialization out of acpi_dma_configure() (as it was in previous patch versions of this series - I moved it to acpi_dma_configure() just a consolidation point for initializing the masks instead of scattering them in every acpi_dma_configure caller) I can send this as a fix-up patch to Joerg if we think that's the right thing to do (or I can send it to Rafael later when the code is in the merged depending on the timing) just let me know please. Thanks ! Lorenzo > The DMA range size passed to arch_setup_dma_ops() is sized according > to the device coherent_dma_mask (starting at address 0x0), mirroring the > DT probing path behaviour when a dma-ranges property is not provided > for the device being probed; this changes the current arch_setup_dma_ops() > call parameters in the ACPI probing case, but since arch_setup_dma_ops() > is a NOP on all architectures but ARM/ARM64 this patch does not change > the current kernel behaviour on them. > > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> > Acked-by: Bjorn Helgaas <bhelgaas@google.com> [pci] > Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > Reviewed-by: Tomasz Nowicki <tn@semihalf.com> > Tested-by: Hanjun Guo <hanjun.guo@linaro.org> > Tested-by: Tomasz Nowicki <tn@semihalf.com> > Cc: Bjorn Helgaas <bhelgaas@google.com> > Cc: Robin Murphy <robin.murphy@arm.com> > Cc: Tomasz Nowicki <tn@semihalf.com> > Cc: Joerg Roedel <joro@8bytes.org> > Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> > --- > drivers/acpi/glue.c | 4 ++-- > drivers/acpi/scan.c | 40 ++++++++++++++++++++++++++++++++++++++++ > drivers/pci/probe.c | 3 +-- > include/acpi/acpi_bus.h | 2 ++ > include/linux/acpi.h | 5 +++++ > 5 files changed, 50 insertions(+), 4 deletions(-) > > diff --git a/drivers/acpi/glue.c b/drivers/acpi/glue.c > index 5ea5dc2..f8d6564 100644 > --- a/drivers/acpi/glue.c > +++ b/drivers/acpi/glue.c > @@ -227,8 +227,7 @@ int acpi_bind_one(struct device *dev, struct acpi_device *acpi_dev) > > attr = acpi_get_dma_attr(acpi_dev); > if (attr != DEV_DMA_NOT_SUPPORTED) > - arch_setup_dma_ops(dev, 0, 0, NULL, > - attr == DEV_DMA_COHERENT); > + acpi_dma_configure(dev, attr); > > acpi_physnode_link_name(physical_node_name, node_id); > retval = sysfs_create_link(&acpi_dev->dev.kobj, &dev->kobj, > @@ -251,6 +250,7 @@ int acpi_bind_one(struct device *dev, struct acpi_device *acpi_dev) > return 0; > > err: > + acpi_dma_deconfigure(dev); > ACPI_COMPANION_SET(dev, NULL); > put_device(dev); > put_device(&acpi_dev->dev); > diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c > index 3d1856f..45b5710 100644 > --- a/drivers/acpi/scan.c > +++ b/drivers/acpi/scan.c > @@ -1370,6 +1370,46 @@ enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev) > return DEV_DMA_NON_COHERENT; > } > > +/** > + * acpi_dma_configure - Set-up DMA configuration for the device. > + * @dev: The pointer to the device > + * @attr: device dma attributes > + */ > +void acpi_dma_configure(struct device *dev, enum dev_dma_attr attr) > +{ > + /* > + * Set default coherent_dma_mask to 32 bit. Drivers are expected to > + * setup the correct supported mask. > + */ > + if (!dev->coherent_dma_mask) > + dev->coherent_dma_mask = DMA_BIT_MASK(32); > + > + /* > + * Set it to coherent_dma_mask by default if the architecture > + * code has not set it. > + */ > + if (!dev->dma_mask) > + dev->dma_mask = &dev->coherent_dma_mask; > + > + /* > + * Assume dma valid range starts at 0 and covers the whole > + * coherent_dma_mask. > + */ > + arch_setup_dma_ops(dev, 0, dev->coherent_dma_mask + 1, NULL, > + attr == DEV_DMA_COHERENT); > +} > +EXPORT_SYMBOL_GPL(acpi_dma_configure); > + > +/** > + * acpi_dma_deconfigure - Tear-down DMA configuration for the device. > + * @dev: The pointer to the device > + */ > +void acpi_dma_deconfigure(struct device *dev) > +{ > + arch_teardown_dma_ops(dev); > +} > +EXPORT_SYMBOL_GPL(acpi_dma_deconfigure); > + > static void acpi_init_coherency(struct acpi_device *adev) > { > unsigned long long cca = 0; > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index ab00267..c29e07a 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -1738,8 +1738,7 @@ static void pci_dma_configure(struct pci_dev *dev) > if (attr == DEV_DMA_NOT_SUPPORTED) > dev_warn(&dev->dev, "DMA not supported.\n"); > else > - arch_setup_dma_ops(&dev->dev, 0, 0, NULL, > - attr == DEV_DMA_COHERENT); > + acpi_dma_configure(&dev->dev, attr); > } > > pci_put_host_bridge_device(bridge); > diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h > index c1a524d..4242c31 100644 > --- a/include/acpi/acpi_bus.h > +++ b/include/acpi/acpi_bus.h > @@ -573,6 +573,8 @@ struct acpi_pci_root { > > bool acpi_dma_supported(struct acpi_device *adev); > enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev); > +void acpi_dma_configure(struct device *dev, enum dev_dma_attr attr); > +void acpi_dma_deconfigure(struct device *dev); > > struct acpi_device *acpi_find_child_device(struct acpi_device *parent, > u64 address, bool check_children); > diff --git a/include/linux/acpi.h b/include/linux/acpi.h > index 996a29c..8d15fc5 100644 > --- a/include/linux/acpi.h > +++ b/include/linux/acpi.h > @@ -765,6 +765,11 @@ static inline enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev) > return DEV_DMA_NOT_SUPPORTED; > } > > +static inline void acpi_dma_configure(struct device *dev, > + enum dev_dma_attr attr) { } > + > +static inline void acpi_dma_deconfigure(struct device *dev) { } > + > #define ACPI_PTR(_ptr) (NULL) > > static inline void acpi_device_set_enumerated(struct acpi_device *adev) > -- > 2.10.0 > -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, Dec 2, 2016 at 4:38 PM, Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> wrote: > Rafael, Mark, Suravee, > > On Mon, Nov 21, 2016 at 10:01:39AM +0000, Lorenzo Pieralisi wrote: >> On DT based systems, the of_dma_configure() API implements DMA >> configuration for a given device. On ACPI systems an API equivalent to >> of_dma_configure() is missing which implies that it is currently not >> possible to set-up DMA operations for devices through the ACPI generic >> kernel layer. >> >> This patch fills the gap by introducing acpi_dma_configure/deconfigure() >> calls that for now are just wrappers around arch_setup_dma_ops() and >> arch_teardown_dma_ops() and also updates ACPI and PCI core code to use >> the newly introduced acpi_dma_configure/acpi_dma_deconfigure functions. >> >> Since acpi_dma_configure() is used to configure DMA operations, the >> function initializes the dma/coherent_dma masks to sane default values >> if the current masks are uninitialized (also to keep the default values >> consistent with DT systems) to make sure the device has a complete >> default DMA set-up. > > I spotted a niggle that unfortunately was hard to spot (and should not > be a problem per se but better safe than sorry) and I am not comfortable > with it. > > Following commit d0562674838c ("ACPI / scan: Parse _CCA and setup > device coherency") in acpi_bind_one() we check if the acpi_device > associated with a device just added supports DMA, first it was > done with acpi_check_dma() and then commit 1831eff876bd ("device > property: ACPI: Make use of the new DMA Attribute APIs") changed > it to acpi_get_dma_attr(). > > The subsequent check (attr != DEV_DMA_NOT_SUPPORTED) is always true > on _any_ acpi device we pass to acpi_bind_one() on x86, which was > fine because we used it to call arch_setup_dma_ops(), which is a nop > on x86. On ARM64 a _CCA method is required to define if a device > supports DMA so (attr != DEV_DMA_NOT_SUPPORTED) may well be false. > > Now, acpi_bind_one() is used to bind an acpi_device to its physical > node also for pseudo-devices like cpus and memory nodes. For those > objects, on x86, attr will always be != DEV_DMA_NOT_SUPPORTED. > > So far so good, because on x86 arch_setup_dma_ops() is empty code. > > With this patch, I use the (attr != DEV_DMA_NOT_SUPPORTED) check > to call acpi_dma_configure() which is basically a nop on x86 except > that it sets up the dma_mask/coherent_dma_mask to a sane default value > (after all we are setting up DMA for the device so it makes sense to > initialize the masks there if they were unset since we are configuring > DMA for the device in question) for the given device. > > Problem is, as per the explanation above, we are also setting the > default dma masks for pseudo-devices (eg CPUs) that were previously > untouched, it should not be a problem per-se but I am not comfortable > with that, honestly it does not make much sense. > > An easy "fix" would be to move the default dma masks initialization out > of acpi_dma_configure() (as it was in previous patch versions of this > series - I moved it to acpi_dma_configure() just a consolidation point > for initializing the masks instead of scattering them in every > acpi_dma_configure caller) I can send this as a fix-up patch to Joerg if > we think that's the right thing to do (or I can send it to Rafael later > when the code is in the merged depending on the timing) just let me > know please. Why can't arch_setup_dma_ops() set those masks too? Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sat, Dec 03, 2016 at 03:11:09AM +0100, Rafael J. Wysocki wrote: > On Fri, Dec 2, 2016 at 4:38 PM, Lorenzo Pieralisi > <lorenzo.pieralisi@arm.com> wrote: > > Rafael, Mark, Suravee, > > > > On Mon, Nov 21, 2016 at 10:01:39AM +0000, Lorenzo Pieralisi wrote: > >> On DT based systems, the of_dma_configure() API implements DMA > >> configuration for a given device. On ACPI systems an API equivalent to > >> of_dma_configure() is missing which implies that it is currently not > >> possible to set-up DMA operations for devices through the ACPI generic > >> kernel layer. > >> > >> This patch fills the gap by introducing acpi_dma_configure/deconfigure() > >> calls that for now are just wrappers around arch_setup_dma_ops() and > >> arch_teardown_dma_ops() and also updates ACPI and PCI core code to use > >> the newly introduced acpi_dma_configure/acpi_dma_deconfigure functions. > >> > >> Since acpi_dma_configure() is used to configure DMA operations, the > >> function initializes the dma/coherent_dma masks to sane default values > >> if the current masks are uninitialized (also to keep the default values > >> consistent with DT systems) to make sure the device has a complete > >> default DMA set-up. > > > > I spotted a niggle that unfortunately was hard to spot (and should not > > be a problem per se but better safe than sorry) and I am not comfortable > > with it. > > > > Following commit d0562674838c ("ACPI / scan: Parse _CCA and setup > > device coherency") in acpi_bind_one() we check if the acpi_device > > associated with a device just added supports DMA, first it was > > done with acpi_check_dma() and then commit 1831eff876bd ("device > > property: ACPI: Make use of the new DMA Attribute APIs") changed > > it to acpi_get_dma_attr(). > > > > The subsequent check (attr != DEV_DMA_NOT_SUPPORTED) is always true > > on _any_ acpi device we pass to acpi_bind_one() on x86, which was > > fine because we used it to call arch_setup_dma_ops(), which is a nop > > on x86. On ARM64 a _CCA method is required to define if a device > > supports DMA so (attr != DEV_DMA_NOT_SUPPORTED) may well be false. > > > > Now, acpi_bind_one() is used to bind an acpi_device to its physical > > node also for pseudo-devices like cpus and memory nodes. For those > > objects, on x86, attr will always be != DEV_DMA_NOT_SUPPORTED. > > > > So far so good, because on x86 arch_setup_dma_ops() is empty code. > > > > With this patch, I use the (attr != DEV_DMA_NOT_SUPPORTED) check > > to call acpi_dma_configure() which is basically a nop on x86 except > > that it sets up the dma_mask/coherent_dma_mask to a sane default value > > (after all we are setting up DMA for the device so it makes sense to > > initialize the masks there if they were unset since we are configuring > > DMA for the device in question) for the given device. > > > > Problem is, as per the explanation above, we are also setting the > > default dma masks for pseudo-devices (eg CPUs) that were previously > > untouched, it should not be a problem per-se but I am not comfortable > > with that, honestly it does not make much sense. > > > > An easy "fix" would be to move the default dma masks initialization out > > of acpi_dma_configure() (as it was in previous patch versions of this > > series - I moved it to acpi_dma_configure() just a consolidation point > > for initializing the masks instead of scattering them in every > > acpi_dma_configure caller) I can send this as a fix-up patch to Joerg if > > we think that's the right thing to do (or I can send it to Rafael later > > when the code is in the merged depending on the timing) just let me > > know please. > > Why can't arch_setup_dma_ops() set those masks too? Because the dma masks set-up is done by the caller (see of_dma_configure()) according to firmware configuration or platform data knowledge. I wanted to replicate the of_dma_configure() interface on ACPI for obvious reasons (on ARM systems), I stopped short of adding ACPI code to mirror of_dma_get_range() equivalent (through the _DMA object) but I am really really nervous about changing the code path on x86 because in theory all is fine, in practice even just setting the masks to sane values can have unexpected consequences, I just can't know (that's why I wasn't doing it in the first iterations of this series). Side note: DT with of_dma_configure() and ACPI with acpi_create_platform_device() set the default dma mask for all platform devices already _regardless_ of what they really are, though arguably acpi_bind_one() touches ways more devices. I really think that removing the default dma masks settings from acpi_dma_configure() is the safer thing to do for the time being (or moving acpi_dma_configure() to acpi_create_platform_device(), where the DMA masks are set-up by default by core ACPI. Mark, Suravee, what was the rationale behind calling arch_setup_dma_ops() in acpi_bind_one() ?) Please let me know, fix-up is trivial however we decide to proceed. Thank you ! Lorenzo -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sat, Dec 3, 2016 at 11:39 AM, Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> wrote: > On Sat, Dec 03, 2016 at 03:11:09AM +0100, Rafael J. Wysocki wrote: >> On Fri, Dec 2, 2016 at 4:38 PM, Lorenzo Pieralisi >> <lorenzo.pieralisi@arm.com> wrote: >> > Rafael, Mark, Suravee, >> > >> > On Mon, Nov 21, 2016 at 10:01:39AM +0000, Lorenzo Pieralisi wrote: >> >> On DT based systems, the of_dma_configure() API implements DMA >> >> configuration for a given device. On ACPI systems an API equivalent to >> >> of_dma_configure() is missing which implies that it is currently not >> >> possible to set-up DMA operations for devices through the ACPI generic >> >> kernel layer. >> >> >> >> This patch fills the gap by introducing acpi_dma_configure/deconfigure() >> >> calls that for now are just wrappers around arch_setup_dma_ops() and >> >> arch_teardown_dma_ops() and also updates ACPI and PCI core code to use >> >> the newly introduced acpi_dma_configure/acpi_dma_deconfigure functions. >> >> >> >> Since acpi_dma_configure() is used to configure DMA operations, the >> >> function initializes the dma/coherent_dma masks to sane default values >> >> if the current masks are uninitialized (also to keep the default values >> >> consistent with DT systems) to make sure the device has a complete >> >> default DMA set-up. >> > >> > I spotted a niggle that unfortunately was hard to spot (and should not >> > be a problem per se but better safe than sorry) and I am not comfortable >> > with it. >> > >> > Following commit d0562674838c ("ACPI / scan: Parse _CCA and setup >> > device coherency") in acpi_bind_one() we check if the acpi_device >> > associated with a device just added supports DMA, first it was >> > done with acpi_check_dma() and then commit 1831eff876bd ("device >> > property: ACPI: Make use of the new DMA Attribute APIs") changed >> > it to acpi_get_dma_attr(). >> > >> > The subsequent check (attr != DEV_DMA_NOT_SUPPORTED) is always true >> > on _any_ acpi device we pass to acpi_bind_one() on x86, which was >> > fine because we used it to call arch_setup_dma_ops(), which is a nop >> > on x86. On ARM64 a _CCA method is required to define if a device >> > supports DMA so (attr != DEV_DMA_NOT_SUPPORTED) may well be false. >> > >> > Now, acpi_bind_one() is used to bind an acpi_device to its physical >> > node also for pseudo-devices like cpus and memory nodes. For those >> > objects, on x86, attr will always be != DEV_DMA_NOT_SUPPORTED. >> > >> > So far so good, because on x86 arch_setup_dma_ops() is empty code. >> > >> > With this patch, I use the (attr != DEV_DMA_NOT_SUPPORTED) check >> > to call acpi_dma_configure() which is basically a nop on x86 except >> > that it sets up the dma_mask/coherent_dma_mask to a sane default value >> > (after all we are setting up DMA for the device so it makes sense to >> > initialize the masks there if they were unset since we are configuring >> > DMA for the device in question) for the given device. >> > >> > Problem is, as per the explanation above, we are also setting the >> > default dma masks for pseudo-devices (eg CPUs) that were previously >> > untouched, it should not be a problem per-se but I am not comfortable >> > with that, honestly it does not make much sense. >> > >> > An easy "fix" would be to move the default dma masks initialization out >> > of acpi_dma_configure() (as it was in previous patch versions of this >> > series - I moved it to acpi_dma_configure() just a consolidation point >> > for initializing the masks instead of scattering them in every >> > acpi_dma_configure caller) I can send this as a fix-up patch to Joerg if >> > we think that's the right thing to do (or I can send it to Rafael later >> > when the code is in the merged depending on the timing) just let me >> > know please. >> >> Why can't arch_setup_dma_ops() set those masks too? > > Because the dma masks set-up is done by the caller (see > of_dma_configure()) according to firmware configuration or > platform data knowledge. I wanted to replicate the of_dma_configure() > interface on ACPI for obvious reasons (on ARM systems), I stopped > short of adding ACPI code to mirror of_dma_get_range() equivalent > (through the _DMA object) but I am really really nervous about changing > the code path on x86 because in theory all is fine, in practice even > just setting the masks to sane values can have unexpected consequences, > I just can't know (that's why I wasn't doing it in the first iterations > of this series). > > Side note: DT with of_dma_configure() and ACPI with > acpi_create_platform_device() set the default dma mask for all > platform devices already _regardless_ of what they really are, though > arguably acpi_bind_one() touches ways more devices. > > I really think that removing the default dma masks settings from > acpi_dma_configure() is the safer thing to do for the time being (or > moving acpi_dma_configure() to acpi_create_platform_device(), where the > DMA masks are set-up by default by core ACPI. Mark, Suravee, what was > the rationale behind calling arch_setup_dma_ops() in acpi_bind_one() ?) Alternatively, you can add one more arch wrapper that will be a no-op on x86 and that will set up the default masks and call arch_setup_dma_ops() on ARM. Then, you can invoke that from acpi_dma_configure(). Or make the definition of acpi_dma_configure() itself depend on the architecture. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Lorenzo, > >On Sat, Dec 3, 2016 at 11:39 AM, Lorenzo Pieralisi ><lorenzo.pieralisi@arm.com> wrote: >> On Sat, Dec 03, 2016 at 03:11:09AM +0100, Rafael J. Wysocki wrote: >>> On Fri, Dec 2, 2016 at 4:38 PM, Lorenzo Pieralisi >>> <lorenzo.pieralisi@arm.com> wrote: >>> > Rafael, Mark, Suravee, >>> > >>> > On Mon, Nov 21, 2016 at 10:01:39AM +0000, Lorenzo Pieralisi wrote: >>> >> On DT based systems, the of_dma_configure() API implements DMA >>> >> configuration for a given device. On ACPI systems an API equivalent to >>> >> of_dma_configure() is missing which implies that it is currently not >>> >> possible to set-up DMA operations for devices through the ACPI generic >>> >> kernel layer. >>> >> >>> >> This patch fills the gap by introducing acpi_dma_configure/deconfigure() >>> >> calls that for now are just wrappers around arch_setup_dma_ops() and >>> >> arch_teardown_dma_ops() and also updates ACPI and PCI core code to use >>> >> the newly introduced acpi_dma_configure/acpi_dma_deconfigure functions. >>> >> >>> >> Since acpi_dma_configure() is used to configure DMA operations, the >>> >> function initializes the dma/coherent_dma masks to sane default values >>> >> if the current masks are uninitialized (also to keep the default values >>> >> consistent with DT systems) to make sure the device has a complete >>> >> default DMA set-up. >>> > >>> > I spotted a niggle that unfortunately was hard to spot (and should not >>> > be a problem per se but better safe than sorry) and I am not comfortable >>> > with it. >>> > >>> > Following commit d0562674838c ("ACPI / scan: Parse _CCA and setup >>> > device coherency") in acpi_bind_one() we check if the acpi_device >>> > associated with a device just added supports DMA, first it was >>> > done with acpi_check_dma() and then commit 1831eff876bd ("device >>> > property: ACPI: Make use of the new DMA Attribute APIs") changed >>> > it to acpi_get_dma_attr(). >>> > >>> > The subsequent check (attr != DEV_DMA_NOT_SUPPORTED) is always true >>> > on _any_ acpi device we pass to acpi_bind_one() on x86, which was >>> > fine because we used it to call arch_setup_dma_ops(), which is a nop >>> > on x86. On ARM64 a _CCA method is required to define if a device >>> > supports DMA so (attr != DEV_DMA_NOT_SUPPORTED) may well be false. >>> > >>> > Now, acpi_bind_one() is used to bind an acpi_device to its physical >>> > node also for pseudo-devices like cpus and memory nodes. For those >>> > objects, on x86, attr will always be != DEV_DMA_NOT_SUPPORTED. >>> > >>> > So far so good, because on x86 arch_setup_dma_ops() is empty code. >>> > >>> > With this patch, I use the (attr != DEV_DMA_NOT_SUPPORTED) check >>> > to call acpi_dma_configure() which is basically a nop on x86 except >>> > that it sets up the dma_mask/coherent_dma_mask to a sane default value >>> > (after all we are setting up DMA for the device so it makes sense to >>> > initialize the masks there if they were unset since we are configuring >>> > DMA for the device in question) for the given device. >>> > >>> > Problem is, as per the explanation above, we are also setting the >>> > default dma masks for pseudo-devices (eg CPUs) that were previously >>> > untouched, it should not be a problem per-se but I am not comfortable >>> > with that, honestly it does not make much sense. >>> > >>> > An easy "fix" would be to move the default dma masks initialization out >>> > of acpi_dma_configure() (as it was in previous patch versions of this >>> > series - I moved it to acpi_dma_configure() just a consolidation point >>> > for initializing the masks instead of scattering them in every >>> > acpi_dma_configure caller) I can send this as a fix-up patch to Joerg if >>> > we think that's the right thing to do (or I can send it to Rafael later >>> > when the code is in the merged depending on the timing) just let me >>> > know please. >>> >>> Why can't arch_setup_dma_ops() set those masks too? >> >> Because the dma masks set-up is done by the caller (see >> of_dma_configure()) according to firmware configuration or >> platform data knowledge. I wanted to replicate the of_dma_configure() >> interface on ACPI for obvious reasons (on ARM systems), I stopped >> short of adding ACPI code to mirror of_dma_get_range() equivalent >> (through the _DMA object) but I am really really nervous about changing >> the code path on x86 because in theory all is fine, in practice even >> just setting the masks to sane values can have unexpected consequences, >> I just can't know (that's why I wasn't doing it in the first iterations >> of this series). >> >> Side note: DT with of_dma_configure() and ACPI with >> acpi_create_platform_device() set the default dma mask for all >> platform devices already _regardless_ of what they really are, though >> arguably acpi_bind_one() touches ways more devices. >> >> I really think that removing the default dma masks settings from >> acpi_dma_configure() is the safer thing to do for the time being (or >> moving acpi_dma_configure() to acpi_create_platform_device(), where the >> DMA masks are set-up by default by core ACPI. Mark, Suravee, what was >> the rationale behind calling arch_setup_dma_ops() in acpi_bind_one() ?) > >Alternatively, you can add one more arch wrapper that will be a no-op >on x86 and that will set up the default masks and call >arch_setup_dma_ops() on ARM. Then, you can invoke that from >acpi_dma_configure(). > >Or make the definition of acpi_dma_configure() itself depend on the >architecture. > So is it better that either removing the masks from acpi_dma_configure (or) creating the wrapper as Rafael mentioned, than moving acpi_dma_configure itself , because with something like iommu probe deferral that is tried, acpi_dma_configure is getting invoked from a device's really_probe, a different path again ? Regards, Sricharan -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, Dec 05, 2016 at 03:22:02PM +0530, Sricharan wrote: > Hi Lorenzo, > > > > >On Sat, Dec 3, 2016 at 11:39 AM, Lorenzo Pieralisi > ><lorenzo.pieralisi@arm.com> wrote: > >> On Sat, Dec 03, 2016 at 03:11:09AM +0100, Rafael J. Wysocki wrote: > >>> On Fri, Dec 2, 2016 at 4:38 PM, Lorenzo Pieralisi > >>> <lorenzo.pieralisi@arm.com> wrote: > >>> > Rafael, Mark, Suravee, > >>> > > >>> > On Mon, Nov 21, 2016 at 10:01:39AM +0000, Lorenzo Pieralisi wrote: > >>> >> On DT based systems, the of_dma_configure() API implements DMA > >>> >> configuration for a given device. On ACPI systems an API equivalent to > >>> >> of_dma_configure() is missing which implies that it is currently not > >>> >> possible to set-up DMA operations for devices through the ACPI generic > >>> >> kernel layer. > >>> >> > >>> >> This patch fills the gap by introducing acpi_dma_configure/deconfigure() > >>> >> calls that for now are just wrappers around arch_setup_dma_ops() and > >>> >> arch_teardown_dma_ops() and also updates ACPI and PCI core code to use > >>> >> the newly introduced acpi_dma_configure/acpi_dma_deconfigure functions. > >>> >> > >>> >> Since acpi_dma_configure() is used to configure DMA operations, the > >>> >> function initializes the dma/coherent_dma masks to sane default values > >>> >> if the current masks are uninitialized (also to keep the default values > >>> >> consistent with DT systems) to make sure the device has a complete > >>> >> default DMA set-up. > >>> > > >>> > I spotted a niggle that unfortunately was hard to spot (and should not > >>> > be a problem per se but better safe than sorry) and I am not comfortable > >>> > with it. > >>> > > >>> > Following commit d0562674838c ("ACPI / scan: Parse _CCA and setup > >>> > device coherency") in acpi_bind_one() we check if the acpi_device > >>> > associated with a device just added supports DMA, first it was > >>> > done with acpi_check_dma() and then commit 1831eff876bd ("device > >>> > property: ACPI: Make use of the new DMA Attribute APIs") changed > >>> > it to acpi_get_dma_attr(). > >>> > > >>> > The subsequent check (attr != DEV_DMA_NOT_SUPPORTED) is always true > >>> > on _any_ acpi device we pass to acpi_bind_one() on x86, which was > >>> > fine because we used it to call arch_setup_dma_ops(), which is a nop > >>> > on x86. On ARM64 a _CCA method is required to define if a device > >>> > supports DMA so (attr != DEV_DMA_NOT_SUPPORTED) may well be false. > >>> > > >>> > Now, acpi_bind_one() is used to bind an acpi_device to its physical > >>> > node also for pseudo-devices like cpus and memory nodes. For those > >>> > objects, on x86, attr will always be != DEV_DMA_NOT_SUPPORTED. > >>> > > >>> > So far so good, because on x86 arch_setup_dma_ops() is empty code. > >>> > > >>> > With this patch, I use the (attr != DEV_DMA_NOT_SUPPORTED) check > >>> > to call acpi_dma_configure() which is basically a nop on x86 except > >>> > that it sets up the dma_mask/coherent_dma_mask to a sane default value > >>> > (after all we are setting up DMA for the device so it makes sense to > >>> > initialize the masks there if they were unset since we are configuring > >>> > DMA for the device in question) for the given device. > >>> > > >>> > Problem is, as per the explanation above, we are also setting the > >>> > default dma masks for pseudo-devices (eg CPUs) that were previously > >>> > untouched, it should not be a problem per-se but I am not comfortable > >>> > with that, honestly it does not make much sense. > >>> > > >>> > An easy "fix" would be to move the default dma masks initialization out > >>> > of acpi_dma_configure() (as it was in previous patch versions of this > >>> > series - I moved it to acpi_dma_configure() just a consolidation point > >>> > for initializing the masks instead of scattering them in every > >>> > acpi_dma_configure caller) I can send this as a fix-up patch to Joerg if > >>> > we think that's the right thing to do (or I can send it to Rafael later > >>> > when the code is in the merged depending on the timing) just let me > >>> > know please. > >>> > >>> Why can't arch_setup_dma_ops() set those masks too? > >> > >> Because the dma masks set-up is done by the caller (see > >> of_dma_configure()) according to firmware configuration or > >> platform data knowledge. I wanted to replicate the of_dma_configure() > >> interface on ACPI for obvious reasons (on ARM systems), I stopped > >> short of adding ACPI code to mirror of_dma_get_range() equivalent > >> (through the _DMA object) but I am really really nervous about changing > >> the code path on x86 because in theory all is fine, in practice even > >> just setting the masks to sane values can have unexpected consequences, > >> I just can't know (that's why I wasn't doing it in the first iterations > >> of this series). > >> > >> Side note: DT with of_dma_configure() and ACPI with > >> acpi_create_platform_device() set the default dma mask for all > >> platform devices already _regardless_ of what they really are, though > >> arguably acpi_bind_one() touches ways more devices. > >> > >> I really think that removing the default dma masks settings from > >> acpi_dma_configure() is the safer thing to do for the time being (or > >> moving acpi_dma_configure() to acpi_create_platform_device(), where the > >> DMA masks are set-up by default by core ACPI. Mark, Suravee, what was > >> the rationale behind calling arch_setup_dma_ops() in acpi_bind_one() ?) > > > >Alternatively, you can add one more arch wrapper that will be a no-op > >on x86 and that will set up the default masks and call > >arch_setup_dma_ops() on ARM. Then, you can invoke that from > >acpi_dma_configure(). > > > >Or make the definition of acpi_dma_configure() itself depend on the > >architecture. > > > > So is it better that either removing the masks from acpi_dma_configure > (or) creating the wrapper as Rafael mentioned, than moving > acpi_dma_configure itself , because with something like iommu probe > deferral that is tried, acpi_dma_configure is getting invoked from a > device's really_probe, a different path again ? Yes, I thought about that too. Given what I said above (ie I would like to extend the mask set-up with _DMA object - that is generic ACPI but can affect legacy x86 - and if that does not work through IORT specific bindings), as per Rafael suggestion I added an iort_set_dma_mask wrapper that is a NOP on x86, leaving acpi_dma_configure() unchanged for ARM64. Patch coming, thanks everyone. Lorenzo -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/acpi/glue.c b/drivers/acpi/glue.c index 5ea5dc2..f8d6564 100644 --- a/drivers/acpi/glue.c +++ b/drivers/acpi/glue.c @@ -227,8 +227,7 @@ int acpi_bind_one(struct device *dev, struct acpi_device *acpi_dev) attr = acpi_get_dma_attr(acpi_dev); if (attr != DEV_DMA_NOT_SUPPORTED) - arch_setup_dma_ops(dev, 0, 0, NULL, - attr == DEV_DMA_COHERENT); + acpi_dma_configure(dev, attr); acpi_physnode_link_name(physical_node_name, node_id); retval = sysfs_create_link(&acpi_dev->dev.kobj, &dev->kobj, @@ -251,6 +250,7 @@ int acpi_bind_one(struct device *dev, struct acpi_device *acpi_dev) return 0; err: + acpi_dma_deconfigure(dev); ACPI_COMPANION_SET(dev, NULL); put_device(dev); put_device(&acpi_dev->dev); diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c index 3d1856f..45b5710 100644 --- a/drivers/acpi/scan.c +++ b/drivers/acpi/scan.c @@ -1370,6 +1370,46 @@ enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev) return DEV_DMA_NON_COHERENT; } +/** + * acpi_dma_configure - Set-up DMA configuration for the device. + * @dev: The pointer to the device + * @attr: device dma attributes + */ +void acpi_dma_configure(struct device *dev, enum dev_dma_attr attr) +{ + /* + * Set default coherent_dma_mask to 32 bit. Drivers are expected to + * setup the correct supported mask. + */ + if (!dev->coherent_dma_mask) + dev->coherent_dma_mask = DMA_BIT_MASK(32); + + /* + * Set it to coherent_dma_mask by default if the architecture + * code has not set it. + */ + if (!dev->dma_mask) + dev->dma_mask = &dev->coherent_dma_mask; + + /* + * Assume dma valid range starts at 0 and covers the whole + * coherent_dma_mask. + */ + arch_setup_dma_ops(dev, 0, dev->coherent_dma_mask + 1, NULL, + attr == DEV_DMA_COHERENT); +} +EXPORT_SYMBOL_GPL(acpi_dma_configure); + +/** + * acpi_dma_deconfigure - Tear-down DMA configuration for the device. + * @dev: The pointer to the device + */ +void acpi_dma_deconfigure(struct device *dev) +{ + arch_teardown_dma_ops(dev); +} +EXPORT_SYMBOL_GPL(acpi_dma_deconfigure); + static void acpi_init_coherency(struct acpi_device *adev) { unsigned long long cca = 0; diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index ab00267..c29e07a 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -1738,8 +1738,7 @@ static void pci_dma_configure(struct pci_dev *dev) if (attr == DEV_DMA_NOT_SUPPORTED) dev_warn(&dev->dev, "DMA not supported.\n"); else - arch_setup_dma_ops(&dev->dev, 0, 0, NULL, - attr == DEV_DMA_COHERENT); + acpi_dma_configure(&dev->dev, attr); } pci_put_host_bridge_device(bridge); diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h index c1a524d..4242c31 100644 --- a/include/acpi/acpi_bus.h +++ b/include/acpi/acpi_bus.h @@ -573,6 +573,8 @@ struct acpi_pci_root { bool acpi_dma_supported(struct acpi_device *adev); enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev); +void acpi_dma_configure(struct device *dev, enum dev_dma_attr attr); +void acpi_dma_deconfigure(struct device *dev); struct acpi_device *acpi_find_child_device(struct acpi_device *parent, u64 address, bool check_children); diff --git a/include/linux/acpi.h b/include/linux/acpi.h index 996a29c..8d15fc5 100644 --- a/include/linux/acpi.h +++ b/include/linux/acpi.h @@ -765,6 +765,11 @@ static inline enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev) return DEV_DMA_NOT_SUPPORTED; } +static inline void acpi_dma_configure(struct device *dev, + enum dev_dma_attr attr) { } + +static inline void acpi_dma_deconfigure(struct device *dev) { } + #define ACPI_PTR(_ptr) (NULL) static inline void acpi_device_set_enumerated(struct acpi_device *adev)