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[PATCH v5] serial: support for 16550A serial ports on LP-8x4x

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  [PATCH v5] serial: support for 16550A serial ports on LP-8x4x Sergei Ianovich <ynvich@gmail.com> - 2015-12-15 22:10 +0100
    Re: [PATCH v5] serial: support for 16550A serial ports on LP-8x4x Arnd Bergmann <arnd@arndb.de> - 2015-12-15 23:00 +0100
      Re: [PATCH v5] serial: support for 16550A serial ports on LP-8x4x Sergei Ianovich <ynvich@gmail.com> - 2015-12-16 09:10 +0100
        Re: [PATCH v5] serial: support for 16550A serial ports on LP-8x4x Arnd Bergmann <arnd@arndb.de> - 2015-12-16 11:30 +0100
          Re: [PATCH v5] serial: support for 16550A serial ports on LP-8x4x Sergei Ianovich <ynvich@gmail.com> - 2015-12-19 09:20 +0100
      Re: [PATCH v5] serial: support for 16550A serial ports on LP-8x4x Sergei Ianovich <ynvich@gmail.com> - 2015-12-19 22:50 +0100
    Re: [PATCH v5] serial: support for 16550A serial ports on LP-8x4x Andy Shevchenko <andriy.shevchenko@linux.intel.com> - 2015-12-17 16:00 +0100

#1292545 — [PATCH v5] serial: support for 16550A serial ports on LP-8x4x

The patch adds support for 3 additional LP-8x4x built-in serial
ports.

The device can also host up to 8 extension cards with 4 serial ports
on each card for a total of 35 ports. However, I don't have
the hardware to test extension cards, so they are not supported, yet.

Signed-off-by: Sergei Ianovich <ynvich@gmail.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
CC: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
---
   v4..v5
   * constify struct of_device_id
   * drop .owner from struct platform_driver
   * rewrite set_termios() baud rate hadnling as suggested by Alan Cox

   v3..v4
   * move DTS bindings to a different patch (8/21) as suggested by
     Heikki Krogerus

   v2..v3
   * no changes (except number 10/16 -> 12/21)

   v0..v2
   * register platform driver instead of platform device
   * use device tree
   * use devm helpers where possible

 .../devicetree/bindings/serial/lp8x4x-serial.txt   |  35 +++++
 drivers/tty/serial/8250/8250_lp8x4x.c              | 168 +++++++++++++++++++++
 drivers/tty/serial/8250/Kconfig                    |  12 ++
 drivers/tty/serial/8250/Makefile                   |   1 +
 4 files changed, 216 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/serial/lp8x4x-serial.txt
 create mode 100644 drivers/tty/serial/8250/8250_lp8x4x.c

diff --git a/Documentation/devicetree/bindings/serial/lp8x4x-serial.txt b/Documentation/devicetree/bindings/serial/lp8x4x-serial.txt
new file mode 100644
index 0000000..5f9a4c1
--- /dev/null
+++ b/Documentation/devicetree/bindings/serial/lp8x4x-serial.txt
@@ -0,0 +1,35 @@
+UART ports on ICP DAS LP-8x4x
+
+ICP DAS LP-8x4x contains three additional serial ports interfaced via
+Analog Devices ADM213EA chips in addition to 3 serial ports on PXA CPU.
+
+Required properties:
+- compatible : should be "icpdas,uart-lp8x4x"
+
+- reg : should provide 16 byte man IO memory region and 1 byte region for
+	termios
+
+- interrupts : should provide interrupt
+
+- interrupt-parent : should provide a link to interrupt controller either
+		     explicitly or implicitly from a parent node
+
+Examples (from pxa27x-lp8x4x.dts):
+
+		uart@9050 {
+			compatible = "icpdas,uart-lp8x4x";
+			reg = <0x9050 0x10
+			       0x9030 0x02>;
+			interrupt-parent = <&fpgairg>;
+			interrupts = <13>;
+			status = "okay";
+		};
+
+		uart@9060 {
+			compatible = "icpdas,uart-lp8x4x";
+			reg = <0x9060 0x10
+			       0x9032 0x02>;
+			interrupt-parent = <&fpgairg>;
+			interrupts = <14>;
+			status = "okay";
+		};
diff --git a/drivers/tty/serial/8250/8250_lp8x4x.c b/drivers/tty/serial/8250/8250_lp8x4x.c
new file mode 100644
index 0000000..0e07220
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_lp8x4x.c
@@ -0,0 +1,168 @@
+/*  linux/drivers/tty/serial/8250/8250_lp8x4x.c
+ *
+ *  Support for 16550A serial ports on ICP DAS LP-8x4x
+ *
+ *  Copyright (C) 2013 Sergei Ianovich <ynvich@gmail.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2 as
+ *  published by the Free Software Foundation.
+ */
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/irq.h>
+#include <linux/module.h>
+#include <linux/serial_8250.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+struct lp8x4x_serial_data {
+	int			line;
+	void			*ios_mem;
+};
+
+static void lp8x4x_serial_set_termios(struct uart_port *port,
+		struct ktermios *termios, struct ktermios *old)
+{
+	unsigned int len;
+	unsigned int baud;
+	struct lp8x4x_serial_data *data = port->private_data;
+
+	serial8250_do_set_termios(port, termios, old);
+
+	switch (termios->c_cflag & CSIZE) {
+	case CS5:
+		len = 7;
+		break;
+	case CS6:
+		len = 8;
+		break;
+	case CS7:
+		len = 9;
+		break;
+	default:
+	case CS8:
+		len = 10;
+		break;
+	}
+
+	if (termios->c_cflag & CSTOPB)
+		len++;
+	if (termios->c_cflag & PARENB)
+		len++;
+	if (!(termios->c_cflag & PARODD))
+		len++;
+#ifdef CMSPAR
+	if (termios->c_cflag & CMSPAR)
+		len++;
+#endif
+
+	len -= 9;
+	len &= 3;
+	len <<= 3;
+	/*
+	 * Ask the core to calculate the divisor for us.
+	 */
+	baud = tty_termios_baud_rate(termios);
+
+	switch (baud) {
+	case 115200:
+		len |= 7;
+		break;
+	case 57600:
+		len |= 6;
+		break;
+	case 38400:
+		len |= 5;
+		break;
+	case 19200:
+		len |= 4;
+		break;
+	case 9600:
+		len |= 3;
+		break;
+	case 4800:
+		len |= 2;
+		break;
+	case 2400:
+	default:
+		len |= 1;
+		break;
+	};
+	iowrite8(len, data->ios_mem);
+
+}
+
+static const struct of_device_id lp8x4x_serial_dt_ids[] = {
+	{ .compatible = "icpdas,uart-lp8x4x", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, lp8x4x_serial_dt_ids);
+
+static int lp8x4x_serial_probe(struct platform_device *pdev)
+{
+	struct uart_8250_port uart = {};
+	struct lp8x4x_serial_data *data;
+	struct resource *mmres, *mires, *irqres;
+	int ret;
+
+	mmres = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	mires = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+	irqres = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
+	if (!mmres || !mires || !irqres)
+		return -ENODEV;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->ios_mem = devm_ioremap_resource(&pdev->dev, mires);
+	if (!data->ios_mem)
+		return -EFAULT;
+
+	uart.port.iotype = UPIO_MEM;
+	uart.port.mapbase = mmres->start;
+	uart.port.iobase = mmres->start;
+	uart.port.regshift = 1;
+	uart.port.irq = irqres->start;
+	uart.port.flags = UPF_IOREMAP;
+	uart.port.dev = &pdev->dev;
+	uart.port.uartclk = 14745600;
+	uart.port.set_termios = lp8x4x_serial_set_termios;
+	uart.port.private_data = data;
+
+	ret = serial8250_register_8250_port(&uart);
+	if (ret < 0)
+		return ret;
+
+	data->line = ret;
+
+	platform_set_drvdata(pdev, data);
+
+	return 0;
+}
+
+static int lp8x4x_serial_remove(struct platform_device *pdev)
+{
+	struct lp8x4x_serial_data *data = platform_get_drvdata(pdev);
+
+	serial8250_unregister_port(data->line);
+
+	return 0;
+}
+
+static struct platform_driver lp8x4x_serial_driver = {
+	.probe          = lp8x4x_serial_probe,
+	.remove         = lp8x4x_serial_remove,
+
+	.driver		= {
+		.name	= "uart-lp8x4x",
+		.of_match_table = lp8x4x_serial_dt_ids,
+	},
+};
+
+module_platform_driver(lp8x4x_serial_driver);
+
+MODULE_AUTHOR("Sergei Ianovich");
+MODULE_DESCRIPTION("8250 serial port module for LP-8x4x");
+MODULE_LICENSE("GPL");
diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index 48b6253..00eb6b0 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -387,3 +387,15 @@ config SERIAL_8250_PXA
 	  can enable its onboard serial ports by enabling this option.
 
 	  If you choose M here, the module name will be 8250_pxa.
+
+config SERIAL_8250_LP8X4X
+	tristate "Support 16550A ports on ICP DAS LP-8x4x"
+	depends on OF && SERIAL_8250 && SERIAL_8250_MANY_PORTS && ARCH_PXA
+	select LP8X4X_IRQ
+	help
+	  In addition to serial ports on PXA270 SoC, LP-8x4x has 1 dual
+	  RS232/RS485 port, 1 RS485 port and 1 RS232 port.
+
+	  Say N here, unless you plan to run this kernel on a LP-8x4x system.
+
+	  If you choose M here, the module name will be 8250_lp8x4x.
diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile
index 7e54413..8bdbf40 100644
--- a/drivers/tty/serial/8250/Makefile
+++ b/drivers/tty/serial/8250/Makefile
@@ -18,6 +18,7 @@ obj-$(CONFIG_SERIAL_8250_ACCENT)	+= 8250_accent.o
 obj-$(CONFIG_SERIAL_8250_BOCA)		+= 8250_boca.o
 obj-$(CONFIG_SERIAL_8250_EXAR_ST16C554)	+= 8250_exar_st16c554.o
 obj-$(CONFIG_SERIAL_8250_HUB6)		+= 8250_hub6.o
+obj-$(CONFIG_SERIAL_8250_LP8X4X)	+= 8250_lp8x4x.o
 obj-$(CONFIG_SERIAL_8250_FSL)		+= 8250_fsl.o
 obj-$(CONFIG_SERIAL_8250_DW)		+= 8250_dw.o
 obj-$(CONFIG_SERIAL_8250_EM)		+= 8250_em.o
-- 
2.6.2

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#1292579

On Wednesday 16 December 2015 00:04:45 Sergei Ianovich wrote:
> index 0000000..5f9a4c1
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/serial/lp8x4x-serial.txt
> @@ -0,0 +1,35 @@
> +UART ports on ICP DAS LP-8x4x
> +
> +ICP DAS LP-8x4x contains three additional serial ports interfaced via
> +Analog Devices ADM213EA chips in addition to 3 serial ports on PXA CPU.
> +
> +Required properties:
> +- compatible : should be "icpdas,uart-lp8x4x"

Compatible strings should not include a 'x' wildcard like this, better use
the specific chip name.

Also, it sounds like you named them after the board vendor, which sounds
wrong as the vendor part of the compatible string should be the whoever
made that part (analog?)

> +- reg : should provide 16 byte man IO memory region and 1 byte region for
> +       termios
> +
> +- interrupts : should provide interrupt
> +
> +- interrupt-parent : should provide a link to interrupt controller either
> +                    explicitly or implicitly from a parent node

interrupt-parent should be an optional property, or you can leave it out,
as this is a standard property that can always be there when there is 
interrupts.

> +Examples (from pxa27x-lp8x4x.dts):
> +
> +               uart@9050 {

By convention, the name should be 'serial', not 'uart'.

	Arnd.
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#1292812

On Tue, 2015-12-15 at 22:51 +0100, Arnd Bergmann wrote:
> On Wednesday 16 December 2015 00:04:45 Sergei Ianovich wrote:
> > index 0000000..5f9a4c1
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/serial/lp8x4x-serial.txt
> > @@ -0,0 +1,35 @@
> > +UART ports on ICP DAS LP-8x4x
> > +
> > +ICP DAS LP-8x4x contains three additional serial ports interfaced
> > via
> > +Analog Devices ADM213EA chips in addition to 3 serial ports on PXA
> > CPU.
> > +
> > +Required properties:
> > +- compatible : should be "icpdas,uart-lp8x4x"
> 
> Compatible strings should not include a 'x' wildcard like this, better
> use
> the specific chip name.
> 
> Also, it sounds like you named them after the board vendor, which
> sounds
> wrong as the vendor part of the compatible string should be the
> whoever
> made that part (analog?)

The chips themselves are standard, they would work with 8250_core if
properly connected. However, they are not connected normally. Al least
some of their config pins are wired to a different address region. So
the driver is board-specific.

'x' wildcards in the name of the board seem important. There are devices
made by the same vendor without 8 or 4 in their name. Those devices
either are not shipped with linux or are base on a x86 platform.

Does this justify the choice of the compatible string?

> > +- reg : should provide 16 byte man IO memory region and 1 byte
> > region for
> > +       termios
> > +
> > +- interrupts : should provide interrupt
> > +
> > +- interrupt-parent : should provide a link to interrupt controller
> > either
> > +                    explicitly or implicitly from a parent node
> 
> interrupt-parent should be an optional property, or you can leave it
> out,
> as this is a standard property that can always be there when there is 
> interrupts.

ok

> > +Examples (from pxa27x-lp8x4x.dts):
> > +
> > +               uart@9050 {
> 
> By convention, the name should be 'serial', not 'uart'.

ok
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#1292871

On Wednesday 16 December 2015 11:04:57 Sergei Ianovich wrote:
> On Tue, 2015-12-15 at 22:51 +0100, Arnd Bergmann wrote:
> > On Wednesday 16 December 2015 00:04:45 Sergei Ianovich wrote:
> > > index 0000000..5f9a4c1
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/serial/lp8x4x-serial.txt
> > > @@ -0,0 +1,35 @@
> > > +UART ports on ICP DAS LP-8x4x
> > > +
> > > +ICP DAS LP-8x4x contains three additional serial ports interfaced
> > > via
> > > +Analog Devices ADM213EA chips in addition to 3 serial ports on PXA
> > > CPU.
> > > +
> > > +Required properties:
> > > +- compatible : should be "icpdas,uart-lp8x4x"
> > 
> > Compatible strings should not include a 'x' wildcard like this, better
> > use
> > the specific chip name.
> > 
> > Also, it sounds like you named them after the board vendor, which
> > sounds
> > wrong as the vendor part of the compatible string should be the
> > whoever
> > made that part (analog?)
> 
> The chips themselves are standard, they would work with 8250_core if
> properly connected. However, they are not connected normally. Al least
> some of their config pins are wired to a different address region. So
> the driver is board-specific.

Ok, I see.

> 'x' wildcards in the name of the board seem important. There are devices
> made by the same vendor without 8 or 4 in their name. Those devices
> either are not shipped with linux or are base on a x86 platform.
> 
> Does this justify the choice of the compatible string?

What I meant was that you should use the specific numbers of one machine,
precisely for the reason you list above.

If there is e.g. a LP-8040 and a LP-8141 today, and you use lp8x4x in
the compatible string to cover both, this will no longer work when the
vendor comes out with a LP8047 that is completely different.

Instead, what you should do is to use the compatible string to identify
one particular board (e.g. the first one that used this setup), and
then list the other ones as compatible with this. You can also add the
other board names in addition, e.g.

compatible = "icpdas,uart-lp8041", "icpdas,uart-lp8040";

for a lp8041 that is compatible with the lp8040. If it turns out later
that they are not entirely compatible, we can work around this in the
driver by checking for the lp8041 string that will be matched first, while
the lp8040 can be used by the driver to match the entire family of
compatible machines (no need to list every one in the driver).

	Arnd
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#1295325

On Wed, 2015-12-16 at 11:26 +0100, Arnd Bergmann wrote:
> On Wednesday 16 December 2015 11:04:57 Sergei Ianovich wrote:
> > On Tue, 2015-12-15 at 22:51 +0100, Arnd Bergmann wrote:
> > > 'x' wildcards in the name of the board seem important. There are
> > devices
> > made by the same vendor without 8 or 4 in their name. Those devices
> > either are not shipped with linux or are base on a x86 platform.
> > 
> > Does this justify the choice of the compatible string?
> 
> What I meant was that you should use the specific numbers of one
> machine,
> precisely for the reason you list above.
> 
> If there is e.g. a LP-8040 and a LP-8141 today, and you use lp8x4x in
> the compatible string to cover both, this will no longer work when the
> vendor comes out with a LP8047 that is completely different.
> 
> Instead, what you should do is to use the compatible string to
> identify
> one particular board (e.g. the first one that used this setup), and
> then list the other ones as compatible with this. You can also add the
> other board names in addition, e.g.
> 
> compatible = "icpdas,uart-lp8041", "icpdas,uart-lp8040";
> 
> for a lp8041 that is compatible with the lp8040. If it turns out later
> that they are not entirely compatible, we can work around this in the
> driver by checking for the lp8041 string that will be matched first,
> while
> the lp8040 can be used by the driver to match the entire family of
> compatible machines (no need to list every one in the driver).

I'll try to be more specific. This driver will support ports on LP-8081, 
LP-8141, LP-8441, LP-8841. Last time I checked the vendor was announcing
a series with 3 as the last digit. They use lp8x4x name, eg. in
documentation like `LP-8x4x_ChangeLog.txt`. They ship their proprietary
SDK in `lp8x4x_sdk_for_linux.tar`. All of this implies that it is a
single board.
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#1295477

On Tue, 2015-12-15 at 22:51 +0100, Arnd Bergmann wrote:
> On Wednesday 16 December 2015 00:04:45 Sergei Ianovich wrote:
> > +Examples (from pxa27x-lp8x4x.dts):
> > +
> > +               uart@9050 {
> 
> By convention, the name should be 'serial', not 'uart'.
> 

arch/arm/boot/dts/pxa2xx.dtsi uses 'uart'. Should I change the names in
the patch with dts file for LP-8xx?
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#1293953

On Wed, 2015-12-16 at 00:04 +0300, Sergei Ianovich wrote:
> The patch adds support for 3 additional LP-8x4x built-in serial
> ports.
> 
> The device can also host up to 8 extension cards with 4 serial ports
> on each card for a total of 35 ports. However, I don't have
> the hardware to test extension cards, so they are not supported, yet.
> 

Few nitpicks, though everything looks okay.

> Signed-off-by: Sergei Ianovich <ynvich@gmail.com>
> Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> CC: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
> ---
>    v4..v5
>    * constify struct of_device_id
>    * drop .owner from struct platform_driver
>    * rewrite set_termios() baud rate hadnling as suggested by Alan
> Cox
> 
>    v3..v4
>    * move DTS bindings to a different patch (8/21) as suggested by
>      Heikki Krogerus
> 
>    v2..v3
>    * no changes (except number 10/16 -> 12/21)
> 
>    v0..v2
>    * register platform driver instead of platform device
>    * use device tree
>    * use devm helpers where possible
> 
>  .../devicetree/bindings/serial/lp8x4x-serial.txt   |  35 +++++
>  drivers/tty/serial/8250/8250_lp8x4x.c              | 168
> +++++++++++++++++++++
>  drivers/tty/serial/8250/Kconfig                    |  12 ++
>  drivers/tty/serial/8250/Makefile                   |   1 +
>  4 files changed, 216 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/serial/lp8x4x-
> serial.txt
>  create mode 100644 drivers/tty/serial/8250/8250_lp8x4x.c
> 
> diff --git a/Documentation/devicetree/bindings/serial/lp8x4x-
> serial.txt b/Documentation/devicetree/bindings/serial/lp8x4x-
> serial.txt
> new file mode 100644
> index 0000000..5f9a4c1
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/serial/lp8x4x-serial.txt
> @@ -0,0 +1,35 @@
> +UART ports on ICP DAS LP-8x4x
> +
> +ICP DAS LP-8x4x contains three additional serial ports interfaced
> via
> +Analog Devices ADM213EA chips in addition to 3 serial ports on PXA
> CPU.
> +
> +Required properties:
> +- compatible : should be "icpdas,uart-lp8x4x"
> +
> +- reg : should provide 16 byte man IO memory region and 1 byte
> region for
> +	termios
> +
> +- interrupts : should provide interrupt
> +
> +- interrupt-parent : should provide a link to interrupt controller
> either
> +		     explicitly or implicitly from a parent node
> +
> +Examples (from pxa27x-lp8x4x.dts):
> +
> +		uart@9050 {
> +			compatible = "icpdas,uart-lp8x4x";
> +			reg = <0x9050 0x10
> +			       0x9030 0x02>;
> +			interrupt-parent = <&fpgairg>;
> +			interrupts = <13>;
> +			status = "okay";
> +		};
> +
> +		uart@9060 {
> +			compatible = "icpdas,uart-lp8x4x";
> +			reg = <0x9060 0x10
> +			       0x9032 0x02>;
> +			interrupt-parent = <&fpgairg>;
> +			interrupts = <14>;
> +			status = "okay";
> +		};
> diff --git a/drivers/tty/serial/8250/8250_lp8x4x.c
> b/drivers/tty/serial/8250/8250_lp8x4x.c
> new file mode 100644
> index 0000000..0e07220
> --- /dev/null
> +++ b/drivers/tty/serial/8250/8250_lp8x4x.c
> @@ -0,0 +1,168 @@
> +/*  linux/drivers/tty/serial/8250/8250_lp8x4x.c
> + *
> + *  Support for 16550A serial ports on ICP DAS LP-8x4x
> + *
> + *  Copyright (C) 2013 Sergei Ianovich <ynvich@gmail.com>
> + *
> + *  This program is free software; you can redistribute it and/or
> modify
> + *  it under the terms of the GNU General Public License version 2
> as
> + *  published by the Free Software Foundation.
> + */
> +#include <linux/init.h>
> +#include <linux/io.h>
> +#include <linux/irq.h>
> +#include <linux/module.h>
> +#include <linux/serial_8250.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +
> +struct lp8x4x_serial_data {
> +	int			line;
> +	void			*ios_mem;
> +};
> +
> +static void lp8x4x_serial_set_termios(struct uart_port *port,
> +		struct ktermios *termios, struct ktermios *old)
> +{
> +	unsigned int len;
> +	unsigned int baud;
> +	struct lp8x4x_serial_data *data = port->private_data;
> +
> +	serial8250_do_set_termios(port, termios, old);
> +
> +	switch (termios->c_cflag & CSIZE) {
> +	case CS5:
> +		len = 7;
> +		break;
> +	case CS6:
> +		len = 8;
> +		break;
> +	case CS7:
> +		len = 9;
> +		break;

> +	default:
> +	case CS8:

I would suggest to exchange those lines.

> +		len = 10;
> +		break;
> +	}
> +
> +	if (termios->c_cflag & CSTOPB)
> +		len++;
> +	if (termios->c_cflag & PARENB)
> +		len++;
> +	if (!(termios->c_cflag & PARODD))
> +		len++;
> +#ifdef CMSPAR
> +	if (termios->c_cflag & CMSPAR)
> +		len++;
> +#endif
> +
> +	len -= 9;
> +	len &= 3;
> +	len <<= 3;

> +	/*
> +	 * Ask the core to calculate the divisor for us.
> +	 */

Can it be one line?

> +	baud = tty_termios_baud_rate(termios);
> +
> +	switch (baud) {
> +	case 115200:
> +		len |= 7;
> +		break;
> +	case 57600:
> +		len |= 6;
> +		break;
> +	case 38400:
> +		len |= 5;
> +		break;
> +	case 19200:
> +		len |= 4;
> +		break;
> +	case 9600:
> +		len |= 3;
> +		break;
> +	case 4800:
> +		len |= 2;
> +		break;
> +	case 2400:
> +	default:
> +		len |= 1;
> +		break;
> +	};
> +	iowrite8(len, data->ios_mem);

writeb() ?

> +
> +}
> +
> +static const struct of_device_id lp8x4x_serial_dt_ids[] = {
> +	{ .compatible = "icpdas,uart-lp8x4x", },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, lp8x4x_serial_dt_ids);
> +
> +static int lp8x4x_serial_probe(struct platform_device *pdev)
> +{
> +	struct uart_8250_port uart = {};
> +	struct lp8x4x_serial_data *data;
> +	struct resource *mmres, *mires, *irqres;
> +	int ret;
> +
> +	mmres = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	mires = platform_get_resource(pdev, IORESOURCE_MEM, 1);
> +	irqres = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
> +	if (!mmres || !mires || !irqres)
> +		return -ENODEV;
> +
> +	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	data->ios_mem = devm_ioremap_resource(&pdev->dev, mires);
> +	if (!data->ios_mem)
> +		return -EFAULT;
> +
> +	uart.port.iotype = UPIO_MEM;
> +	uart.port.mapbase = mmres->start;
> +	uart.port.iobase = mmres->start;
> +	uart.port.regshift = 1;
> +	uart.port.irq = irqres->start;
> +	uart.port.flags = UPF_IOREMAP;
> +	uart.port.dev = &pdev->dev;
> +	uart.port.uartclk = 14745600;
> +	uart.port.set_termios = lp8x4x_serial_set_termios;
> +	uart.port.private_data = data;
> +
> +	ret = serial8250_register_8250_port(&uart);
> +	if (ret < 0)
> +		return ret;
> +
> +	data->line = ret;
> +
> +	platform_set_drvdata(pdev, data);
> +
> +	return 0;
> +}
> +
> +static int lp8x4x_serial_remove(struct platform_device *pdev)
> +{
> +	struct lp8x4x_serial_data *data =
> platform_get_drvdata(pdev);
> +
> +	serial8250_unregister_port(data->line);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver lp8x4x_serial_driver = {
> +	.probe          = lp8x4x_serial_probe,
> +	.remove         = lp8x4x_serial_remove,
> +
> +	.driver		= {
> +		.name	= "uart-lp8x4x",
> +		.of_match_table = lp8x4x_serial_dt_ids,
> +	},
> +};
> +
> +module_platform_driver(lp8x4x_serial_driver);
> +
> +MODULE_AUTHOR("Sergei Ianovich");
> +MODULE_DESCRIPTION("8250 serial port module for LP-8x4x");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/tty/serial/8250/Kconfig
> b/drivers/tty/serial/8250/Kconfig
> index 48b6253..00eb6b0 100644
> --- a/drivers/tty/serial/8250/Kconfig
> +++ b/drivers/tty/serial/8250/Kconfig
> @@ -387,3 +387,15 @@ config SERIAL_8250_PXA
>  	  can enable its onboard serial ports by enabling this
> option.
>  
>  	  If you choose M here, the module name will be 8250_pxa.
> +
> +config SERIAL_8250_LP8X4X
> +	tristate "Support 16550A ports on ICP DAS LP-8x4x"
> +	depends on OF && SERIAL_8250 && SERIAL_8250_MANY_PORTS &&
> ARCH_PXA
> +	select LP8X4X_IRQ
> +	help
> +	  In addition to serial ports on PXA270 SoC, LP-8x4x has 1
> dual
> +	  RS232/RS485 port, 1 RS485 port and 1 RS232 port.
> +
> +	  Say N here, unless you plan to run this kernel on a LP-
> 8x4x system.
> +
> +	  If you choose M here, the module name will be 8250_lp8x4x.
> diff --git a/drivers/tty/serial/8250/Makefile
> b/drivers/tty/serial/8250/Makefile
> index 7e54413..8bdbf40 100644
> --- a/drivers/tty/serial/8250/Makefile
> +++ b/drivers/tty/serial/8250/Makefile
> @@ -18,6 +18,7 @@ obj-$(CONFIG_SERIAL_8250_ACCENT)	+=
> 8250_accent.o
>  obj-$(CONFIG_SERIAL_8250_BOCA)		+= 8250_boca.o
>  obj-$(CONFIG_SERIAL_8250_EXAR_ST16C554)	+=
> 8250_exar_st16c554.o
>  obj-$(CONFIG_SERIAL_8250_HUB6)		+= 8250_hub6.o
> +obj-$(CONFIG_SERIAL_8250_LP8X4X)	+= 8250_lp8x4x.o
>  obj-$(CONFIG_SERIAL_8250_FSL)		+= 8250_fsl.o
>  obj-$(CONFIG_SERIAL_8250_DW)		+= 8250_dw.o
>  obj-$(CONFIG_SERIAL_8250_EM)		+= 8250_em.o

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy

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