Messages in this thread | | | Subject | Re: [RFC 02/13] driver core: Introduce MMIO configuration | From | Robin Murphy <> | Date | Tue, 2 Mar 2021 11:29:10 +0000 |
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On 2021-02-26 14:02, Nicolas Saenz Julienne wrote: > Some devices might inadvertently sit on buses that don't support 64bit > MMIO access, and need a mechanism to query these limitations without > prejudice to other buses in the system (i.e. defaulting to 32bit access > system wide isn't an option). > > Introduce a new bus callback, 'mmio_configure(),' which will take care > of populating the relevant device properties based on the bus' > limitations.
Devil's advocate: there already exist workarounds for 8-bit and/or 16-bit accesses not working in various places, does it make sense for a 64-bit workaround to be so wildly different and disjoint?
> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de> > --- > arch/Kconfig | 8 ++++++++ > drivers/base/dd.c | 6 ++++++ > include/linux/device.h | 3 +++ > include/linux/device/bus.h | 3 +++ > 4 files changed, 20 insertions(+) > > diff --git a/arch/Kconfig b/arch/Kconfig > index 2bb30673d8e6..ba7f246b6b9d 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -1191,6 +1191,14 @@ config ARCH_SPLIT_ARG64 > config ARCH_HAS_ELFCORE_COMPAT > bool > > +config ARCH_HAS_64BIT_MMIO_BROKEN > + bool > + depends on 64BIT
As mentioned previously, 32-bit systems may not need the overrides for kernel I/O accessors, but they could still need the same workarounds for the memory-mapping implications (if this is to be a proper generic mechanism).
> + default n
Tip: it is always redundant to state that.
Robin.
> + help > + Arch might contain busses unable to perform 64bit mmio accessses on > + an otherwise 64bit system. > + > source "kernel/gcov/Kconfig" > > source "scripts/gcc-plugins/Kconfig" > diff --git a/drivers/base/dd.c b/drivers/base/dd.c > index 9179825ff646..8086ce8f17a6 100644 > --- a/drivers/base/dd.c > +++ b/drivers/base/dd.c > @@ -538,6 +538,12 @@ static int really_probe(struct device *dev, struct device_driver *drv) > goto probe_failed; > } > > + if (dev->bus->mmio_configure) { > + ret = dev->bus->mmio_configure(dev); > + if (ret) > + goto probe_failed; > + } > + > if (driver_sysfs_add(dev)) { > pr_err("%s: driver_sysfs_add(%s) failed\n", > __func__, dev_name(dev)); > diff --git a/include/linux/device.h b/include/linux/device.h > index ba660731bd25..bd94aa0cbd72 100644 > --- a/include/linux/device.h > +++ b/include/linux/device.h > @@ -553,6 +553,9 @@ struct device { > #ifdef CONFIG_DMA_OPS_BYPASS > bool dma_ops_bypass : 1; > #endif > +#if defined(CONFIG_ARCH_HAS_64BIT_MMIO_BROKEN) > + bool mmio_64bit_broken:1; > +#endif > }; > > /** > diff --git a/include/linux/device/bus.h b/include/linux/device/bus.h > index 1ea5e1d1545b..680dfc3b4744 100644 > --- a/include/linux/device/bus.h > +++ b/include/linux/device/bus.h > @@ -59,6 +59,8 @@ struct fwnode_handle; > * bus supports. > * @dma_configure: Called to setup DMA configuration on a device on > * this bus. > + * @mmio_configure: Called to setup MMIO configuration on a device on > + * this bus. > * @pm: Power management operations of this bus, callback the specific > * device driver's pm-ops. > * @iommu_ops: IOMMU specific operations for this bus, used to attach IOMMU > @@ -103,6 +105,7 @@ struct bus_type { > int (*num_vf)(struct device *dev); > > int (*dma_configure)(struct device *dev); > + int (*mmio_configure)(struct device *dev); > > const struct dev_pm_ops *pm; > >
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