Re: [RFC 02/13] driver core: Introduce MMIO configuration
From: Robin Murphy <robin.murphy@arm.com>
Date: 2021-03-02 12:04:31
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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?
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Signed-off-by: Nicolas Saenz Julienne <redacted> --- 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.
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+ 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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