On Wed, 12 Nov 2014 12:54:02 -0800 , Kevin Cernekee <[email protected]> wrote: > SoC peripherals can come in several different flavors: > > - little-endian: registers always need to be accessed in LE mode (so the > kernel should perform a swap if the CPU is running BE) > > - big-endian: registers always need to be accessed in BE mode (so the > kernel should perform a swap if the CPU is running LE) > > - native-endian: the bus will automatically swap accesses, so the kernel > should never swap > Introduce a function that checks an OF device node to see whether it > contains a "big-endian" or "native-endian" property. For the former case, > always return true. For the latter case, return true iff the kernel was > built for BE (implying that the BE MMIO accessors do not perform a swap). > Otherwise return false, assuming LE registers. > > LE registers are assumed by default because most existing drivers (libahci, > serial8250, usb) always use readl/writel in the absence of instructions > to the contrary, so that will be our fallback.
This is proposing a new binding, or at least a common pattern to be used by other bindings. It should be documented under Documentation/devicetree/bindings/. I suggest creating a new file under bindings/common-properties.txt Otherwise looks fine to me. We'll give it a week to see if there are any other comments, but I think this looks fine. g. > > Signed-off-by: Kevin Cernekee <[email protected]> > --- > drivers/of/base.c | 23 +++++++++++++++++++++++ > include/linux/of.h | 6 ++++++ > 2 files changed, 29 insertions(+) > > diff --git a/drivers/of/base.c b/drivers/of/base.c > index 81c095f..35d95a1 100644 > --- a/drivers/of/base.c > +++ b/drivers/of/base.c > @@ -552,6 +552,29 @@ bool of_device_is_available(const struct device_node > *device) > EXPORT_SYMBOL(of_device_is_available); > > /** > + * of_device_is_big_endian - check if a device has BE registers > + * > + * @device: Node to check for endianness > + * > + * Returns true if the device has a "big-endian" property, or if the kernel > + * was compiled for BE *and* the device has a "native-endian" property. > + * Returns false otherwise. > + * > + * Callers would nominally use ioread32be/iowrite32be if > + * of_device_is_big_endian() == true, or readl/writel otherwise. > + */ > +bool of_device_is_big_endian(const struct device_node *device) > +{ > + if (of_property_read_bool(device, "big-endian")) > + return true; > + if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN) && > + of_property_read_bool(device, "native-endian")) > + return true; > + return false; > +} > +EXPORT_SYMBOL(of_device_is_big_endian); > + > +/** > * of_get_parent - Get a node's parent if any > * @node: Node to get parent > * > diff --git a/include/linux/of.h b/include/linux/of.h > index 7aaaa59..fc70b01 100644 > --- a/include/linux/of.h > +++ b/include/linux/of.h > @@ -276,6 +276,7 @@ extern int of_property_read_string_helper(struct > device_node *np, > extern int of_device_is_compatible(const struct device_node *device, > const char *); > extern bool of_device_is_available(const struct device_node *device); > +extern bool of_device_is_big_endian(const struct device_node *device); > extern const void *of_get_property(const struct device_node *node, > const char *name, > int *lenp); > @@ -431,6 +432,11 @@ static inline bool of_device_is_available(const struct > device_node *device) > return false; > } > > +static inline bool of_device_is_big_endian(const struct device_node *device) > +{ > + return false; > +} > + > static inline struct property *of_find_property(const struct device_node *np, > const char *name, > int *lenp) > -- > 2.1.1 > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
