[PATCH V4 0/5] Add big-endian MMIO support to serial8250

[PATCH V4 0/5] Add big-endian MMIO support to serial8250

[Kevin Cernekee]

V3->V4:

Rebase on Linus' head of tree

Tweak documentation per Grant's request

Drop the of_earlycon patches in favor of Peter's series


Kevin Cernekee (5):
  of: Add helper function to check MMIO register endianness
  of/fdt: Add endianness helper function for early init code
  of: Document {little,big,native}-endian bindings
  serial: 8250: Add support for big-endian MMIO accesses
  serial: of_serial: Support big-endian register accesses

 .../devicetree/bindings/common-properties.txt      | 60 ++++++++++++++++++++++
 drivers/of/base.c                                  | 23 +++++++++
 drivers/of/fdt.c                                   | 19 +++++++
 drivers/tty/serial/8250/8250_core.c                | 20 ++++++++
 drivers/tty/serial/8250/8250_early.c               |  5 ++
 drivers/tty/serial/of_serial.c                     |  3 +-
 include/linux/of.h                                 |  6 +++
 include/linux/of_fdt.h                             |  2 +
 8 files changed, 137 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/devicetree/bindings/common-properties.txt

-- 
2.2.2

[PATCH V4 1/5] of: Add helper function to check MMIO register endianness

[Kevin Cernekee]

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.

Signed-off-by: Kevin Cernekee <cernekee-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 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 8f165b112e03..3a10d1ed37f8 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -568,6 +568,29 @@ 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 dfde07e77a63..a0cd62ef22db 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -305,6 +305,7 @@ 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);
@@ -466,6 +467,11 @@ 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)
-- 
2.2.2

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[PATCH V4 2/5] of/fdt: Add endianness helper function for early init code

[Kevin Cernekee]

Provide a libfdt-based equivalent for of_device_is_big_endian(), suitable
for use in the early_init_* functions.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
---
 drivers/of/fdt.c       | 19 +++++++++++++++++++
 include/linux/of_fdt.h |  2 ++
 2 files changed, 21 insertions(+)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 3a896c9aeb74..1ebd6194fe7f 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -109,6 +109,25 @@ int of_fdt_is_compatible(const void *blob,
 }
 
 /**
+ * of_fdt_is_big_endian - Return true if given node needs BE MMIO accesses
+ * @blob: A device tree blob
+ * @node: node to test
+ *
+ * Returns true if the node has a "big-endian" property, or if the kernel
+ * was compiled for BE *and* the node has a "native-endian" property.
+ * Returns false otherwise.
+ */
+bool of_fdt_is_big_endian(const void *blob, unsigned long node)
+{
+	if (fdt_getprop(blob, node, "big-endian", NULL))
+		return true;
+	if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN) &&
+	    fdt_getprop(blob, node, "native-endian", NULL))
+		return true;
+	return false;
+}
+
+/**
  * of_fdt_match - Return true if node matches a list of compatible values
  */
 int of_fdt_match(const void *blob, unsigned long node,
diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
index 0ff360d5b3b3..587ee507965d 100644
--- a/include/linux/of_fdt.h
+++ b/include/linux/of_fdt.h
@@ -33,6 +33,8 @@ extern void *of_fdt_get_property(const void *blob,
 extern int of_fdt_is_compatible(const void *blob,
 				unsigned long node,
 				const char *compat);
+extern bool of_fdt_is_big_endian(const void *blob,
+				 unsigned long node);
 extern int of_fdt_match(const void *blob, unsigned long node,
 			const char *const *compat);
 extern void of_fdt_unflatten_tree(unsigned long *blob,
-- 
2.2.2

[PATCH V4 3/5] of: Document {little,big,native}-endian bindings

[Kevin Cernekee]

These apply to newly converted drivers, like serial8250/libahci/...
The examples were adapted from the regmap bindings document.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
---
 .../devicetree/bindings/common-properties.txt      | 60 ++++++++++++++++++++++
 1 file changed, 60 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/common-properties.txt

diff --git a/Documentation/devicetree/bindings/common-properties.txt b/Documentation/devicetree/bindings/common-properties.txt
new file mode 100644
index 000000000000..3193979b1d05
--- /dev/null
+++ b/Documentation/devicetree/bindings/common-properties.txt
@@ -0,0 +1,60 @@
+Common properties
+
+The ePAPR specification does not define any properties related to hardware
+byteswapping, but endianness issues show up frequently in porting Linux to
+different machine types.  This document attempts to provide a consistent
+way of handling byteswapping across drivers.
+
+Optional properties:
+ - big-endian: Boolean; force big endian register accesses
+   unconditionally (e.g. ioread32be/iowrite32be).  Use this if you
+   know the peripheral always needs to be accessed in BE mode.
+ - little-endian: Boolean; force little endian register accesses
+   unconditionally (e.g. readl/writel).  Use this if you know the
+   peripheral always needs to be accessed in LE mode.
+ - native-endian: Boolean; always use register accesses matched to the
+   endianness of the kernel binary (e.g. LE vmlinux -> readl/writel,
+   BE vmlinux -> ioread32be/iowrite32be).  In this case no byteswaps
+   will ever be performed.  Use this if the hardware "self-adjusts"
+   register endianness based on the CPU's configured endianness.
+
+If a binding supports these properties, then the binding should also
+specify the default behavior if none of these properties are present.
+In such cases, little-endian is the preferred default, but it is not
+a requirement.  The of_device_is_big_endian() and of_fdt_is_big_endian()
+helper functions do assume that little-endian is the default, because
+most existing (PCI-based) drivers implicitly default to LE by using
+readl/writel for MMIO accesses.
+
+Examples:
+Scenario 1 : CPU in LE mode & device in LE mode.
+dev: dev@40031000 {
+	      compatible = "name";
+	      reg = <0x40031000 0x1000>;
+	      ...
+	      native-endian;
+};
+
+Scenario 2 : CPU in LE mode & device in BE mode.
+dev: dev@40031000 {
+	      compatible = "name";
+	      reg = <0x40031000 0x1000>;
+	      ...
+	      big-endian;
+};
+
+Scenario 3 : CPU in BE mode & device in BE mode.
+dev: dev@40031000 {
+	      compatible = "name";
+	      reg = <0x40031000 0x1000>;
+	      ...
+	      native-endian;
+};
+
+Scenario 4 : CPU in BE mode & device in LE mode.
+dev: dev@40031000 {
+	      compatible = "name";
+	      reg = <0x40031000 0x1000>;
+	      ...
+	      little-endian;
+};
-- 
2.2.2

[PATCH V4 4/5] serial: 8250: Add support for big-endian MMIO accesses

[Kevin Cernekee]

Add cases for UPIO_MEM32BE wherever there are currently cases handling
UPIO_MEM32.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
---
 drivers/tty/serial/8250/8250_core.c  | 20 ++++++++++++++++++++
 drivers/tty/serial/8250/8250_early.c |  5 +++++
 2 files changed, 25 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index deae122c9c4b..0bffa735eaa1 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -439,6 +439,18 @@ static unsigned int mem32_serial_in(struct uart_port *p, int offset)
 	return readl(p->membase + offset);
 }
 
+static void mem32be_serial_out(struct uart_port *p, int offset, int value)
+{
+	offset = offset << p->regshift;
+	iowrite32be(value, p->membase + offset);
+}
+
+static unsigned int mem32be_serial_in(struct uart_port *p, int offset)
+{
+	offset = offset << p->regshift;
+	return ioread32be(p->membase + offset);
+}
+
 static unsigned int io_serial_in(struct uart_port *p, int offset)
 {
 	offset = offset << p->regshift;
@@ -477,6 +489,11 @@ static void set_io_from_upio(struct uart_port *p)
 		p->serial_out = mem32_serial_out;
 		break;
 
+	case UPIO_MEM32BE:
+		p->serial_in = mem32be_serial_in;
+		p->serial_out = mem32be_serial_out;
+		break;
+
 #if defined(CONFIG_MIPS_ALCHEMY) || defined(CONFIG_SERIAL_8250_RT288X)
 	case UPIO_AU:
 		p->serial_in = au_serial_in;
@@ -502,6 +519,7 @@ serial_port_out_sync(struct uart_port *p, int offset, int value)
 	switch (p->iotype) {
 	case UPIO_MEM:
 	case UPIO_MEM32:
+	case UPIO_MEM32BE:
 	case UPIO_AU:
 		p->serial_out(p, offset, value);
 		p->serial_in(p, UART_LCR);	/* safe, no side-effects */
@@ -2743,6 +2761,7 @@ static int serial8250_request_std_resource(struct uart_8250_port *up)
 	case UPIO_AU:
 	case UPIO_TSI:
 	case UPIO_MEM32:
+	case UPIO_MEM32BE:
 	case UPIO_MEM:
 		if (!port->mapbase)
 			break;
@@ -2779,6 +2798,7 @@ static void serial8250_release_std_resource(struct uart_8250_port *up)
 	case UPIO_AU:
 	case UPIO_TSI:
 	case UPIO_MEM32:
+	case UPIO_MEM32BE:
 	case UPIO_MEM:
 		if (!port->mapbase)
 			break;
diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c
index c31a22b4f845..84f6d11bbeed 100644
--- a/drivers/tty/serial/8250/8250_early.c
+++ b/drivers/tty/serial/8250/8250_early.c
@@ -45,6 +45,8 @@ unsigned int __weak __init serial8250_early_in(struct uart_port *port, int offse
 		return readb(port->membase + offset);
 	case UPIO_MEM32:
 		return readl(port->membase + (offset << 2));
+	case UPIO_MEM32BE:
+		return ioread32be(port->membase + (offset << 2));
 	case UPIO_PORT:
 		return inb(port->iobase + offset);
 	default:
@@ -61,6 +63,9 @@ void __weak __init serial8250_early_out(struct uart_port *port, int offset, int
 	case UPIO_MEM32:
 		writel(value, port->membase + (offset << 2));
 		break;
+	case UPIO_MEM32BE:
+		iowrite32be(value, port->membase + (offset << 2));
+		break;
 	case UPIO_PORT:
 		outb(value, port->iobase + offset);
 		break;
-- 
2.2.2

[PATCH V4 5/5] serial: of_serial: Support big-endian register accesses

[Kevin Cernekee]

If the device node has a "big-endian" property and 32-bit registers, tell
the serial driver to use UPIO_MEM32BE instead of UPIO_MEM32.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
---
 drivers/tty/serial/of_serial.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/of_serial.c b/drivers/tty/serial/of_serial.c
index 33fb94f78967..e15c443b2a3c 100644
--- a/drivers/tty/serial/of_serial.c
+++ b/drivers/tty/serial/of_serial.c
@@ -115,7 +115,8 @@ static int of_platform_serial_setup(struct platform_device *ofdev,
 			port->iotype = UPIO_MEM;
 			break;
 		case 4:
-			port->iotype = UPIO_MEM32;
+			port->iotype = of_device_is_big_endian(np) ?
+				       UPIO_MEM32BE : UPIO_MEM32;
 			break;
 		default:
 			dev_warn(&ofdev->dev, "unsupported reg-io-width (%d)\n",
-- 
2.2.2

Re: [PATCH V4 0/5] Add big-endian MMIO support to serial8250

[Rob Herring]

On Thu, Apr 9, 2015 at 3:05 PM, Kevin Cernekee <cernekee@gmail.com> wrote:
> V3->V4:
>
> Rebase on Linus' head of tree
>
> Tweak documentation per Grant's request
>
> Drop the of_earlycon patches in favor of Peter's series

Are there conflicts with Peter's stuff? The series looks good to me.
So either I can take it with Greg's ack or Greg can take it.

Acked-by: Rob Herring <robh@kernel.org>

Rob

>
>
> Kevin Cernekee (5):
>   of: Add helper function to check MMIO register endianness
>   of/fdt: Add endianness helper function for early init code
>   of: Document {little,big,native}-endian bindings
>   serial: 8250: Add support for big-endian MMIO accesses
>   serial: of_serial: Support big-endian register accesses
>
>  .../devicetree/bindings/common-properties.txt      | 60 ++++++++++++++++++++++
>  drivers/of/base.c                                  | 23 +++++++++
>  drivers/of/fdt.c                                   | 19 +++++++
>  drivers/tty/serial/8250/8250_core.c                | 20 ++++++++
>  drivers/tty/serial/8250/8250_early.c               |  5 ++
>  drivers/tty/serial/of_serial.c                     |  3 +-
>  include/linux/of.h                                 |  6 +++
>  include/linux/of_fdt.h                             |  2 +
>  8 files changed, 137 insertions(+), 1 deletion(-)
>  create mode 100644 Documentation/devicetree/bindings/common-properties.txt
>
> --
> 2.2.2
>

Re: [PATCH V4 0/5] Add big-endian MMIO support to serial8250

[Peter Hurley]

On 04/10/2015 09:52 AM, Rob Herring wrote:
> On Thu, Apr 9, 2015 at 3:05 PM, Kevin Cernekee <cernekee-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>> V3->V4:
>>
>> Rebase on Linus' head of tree
>>
>> Tweak documentation per Grant's request
>>
>> Drop the of_earlycon patches in favor of Peter's series
> 
> Are there conflicts with Peter's stuff?

No.

It adds the required pieces so that a trivial patch on top of 
both series will enable mmio32be for earlycon.

> The series looks good to me.

Same.

Reviewed-by: Peter Hurley <peter-WaGBZJeGNqdsbIuE7sb01tBPR1lH4CV8@public.gmane.org>

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Re: [PATCH V4 0/5] Add big-endian MMIO support to serial8250

[Greg Kroah-Hartman]

On Fri, Apr 10, 2015 at 10:28:55AM -0400, Peter Hurley wrote:
> On 04/10/2015 09:52 AM, Rob Herring wrote:
> > On Thu, Apr 9, 2015 at 3:05 PM, Kevin Cernekee <cernekee@gmail.com> wrote:
> >> V3->V4:
> >>
> >> Rebase on Linus' head of tree
> >>
> >> Tweak documentation per Grant's request
> >>
> >> Drop the of_earlycon patches in favor of Peter's series
> > 
> > Are there conflicts with Peter's stuff?
> 
> No.
> 
> It adds the required pieces so that a trivial patch on top of 
> both series will enable mmio32be for earlycon.
> 
> > The series looks good to me.
> 
> Same.
> 
> Reviewed-by: Peter Hurley <peter@hurleysoftware.com>

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Re: [PATCH V4 0/5] Add big-endian MMIO support to serial8250

[Rob Herring]

On Mon, Apr 13, 2015 at 12:09 PM, Greg Kroah-Hartman
<gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org> wrote:
> On Fri, Apr 10, 2015 at 10:28:55AM -0400, Peter Hurley wrote:
>> On 04/10/2015 09:52 AM, Rob Herring wrote:
>> > On Thu, Apr 9, 2015 at 3:05 PM, Kevin Cernekee <cernekee-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>> >> V3->V4:
>> >>
>> >> Rebase on Linus' head of tree
>> >>
>> >> Tweak documentation per Grant's request
>> >>
>> >> Drop the of_earlycon patches in favor of Peter's series
>> >
>> > Are there conflicts with Peter's stuff?
>>
>> No.
>>
>> It adds the required pieces so that a trivial patch on top of
>> both series will enable mmio32be for earlycon.
>>
>> > The series looks good to me.
>>
>> Same.
>>
>> Reviewed-by: Peter Hurley <peter-WaGBZJeGNqdsbIuE7sb01tBPR1lH4CV8@public.gmane.org>
>
> Acked-by: Greg Kroah-Hartman <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>

I've applied the series for 4.1. I took it since it got dropped last time.

Rob
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