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@xxxxxxx>
---
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;
