[PATCH v1] spi: master driver to enable RTC on ICPDAS LP-8841

[PATCH v1] spi: master driver to enable RTC on ICPDAS LP-8841

[Sergei Ianovich]

ICP DAS LP-8841 contains a DS-1302 RTC. This driver provides an SPI
master which makes the RTC usable. The driver is not supposed to work
with anything else.

The driver uses the standard MicroWire half-duplex transfer timing.
Master output is set on low clock and sensed by the RTC on the rising
edge. Master input is set by the RTC on the trailing edge and is sensed
by the master on low clock.

Signed-off-by: Sergei Ianovich <ynvich@gmail.com>
---
 .../devicetree/bindings/spi/spi-lp8841-rtc.txt     |  55 +++++
 drivers/spi/Kconfig                                |  10 +
 drivers/spi/Makefile                               |   1 +
 drivers/spi/spi-lp8841-rtc.c                       | 272 +++++++++++++++++++++
 4 files changed, 338 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/spi/spi-lp8841-rtc.txt
 create mode 100644 drivers/spi/spi-lp8841-rtc.c

diff --git a/Documentation/devicetree/bindings/spi/spi-lp8841-rtc.txt b/Documentation/devicetree/bindings/spi/spi-lp8841-rtc.txt
new file mode 100644
index 0000000..f191aef
--- /dev/null
+++ b/Documentation/devicetree/bindings/spi/spi-lp8841-rtc.txt
@@ -0,0 +1,55 @@
+* ICP DAS LP-8841 SPI Controller for RTC
+
+ICP DAS LP-8841 contains a DS-1302 RTC. This driver provides an SPI
+master which makes the RTC usable. The driver is not supposed to work
+with anything else.
+
+The driver uses the standard MicroWire half-duplex transfer timing.
+Master output is set on low clock and sensed by the RTC on the rising
+edge. Master input is set by the RTC on the trailing edge and is sensed
+by the master on low clock.
+
+Required properties:
+
+- #address-cells: should be 1
+
+- #size-cells: should be 0
+
+- compatible: should be "icpdas,spi-lp8841-rtc"
+
+- reg: should provide IO memory address
+
+Requirements to SPI slave nodes:
+
+- There can be only one slave device.
+
+- The spi slave node should claim the following flags which are
+  required by the spi controller.
+
+  - spi-3wire: The master itself has only 3 wire. It cannor work in
+    full duplex mode.
+
+  - spi-cs-high: DS-1302 has active high chip select line. The master
+    doesn't support active low.
+
+  - spi-lsb-first: DS-1302 requires least significant bit first
+    transfers. The master only support this type of bit ordering.
+
+
+Example:
+
+spi0@901c {
+	#address-cells = <1>;
+	#size-cells = <0>;
+	compatible = "icpdas,spi-lp8841-rtc";
+	reg = <0x901c 0x1>;
+
+	rtc@0 {
+		compatible = "maxim,rtc-ds1302";
+		reg = <0>;
+		spi-max-frequency = <500000>;
+		spi-3wire;
+		spi-lsb-first;
+		spi-cs-high;
+	};
+};
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 7706416..33908c1 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -271,6 +271,16 @@ config SPI_LM70_LLP
 	  which interfaces to an LM70 temperature sensor using
 	  a parallel port.
 
+config SPI_LP8841_RTC
+	tristate "ICP DAS LP-8841 SPI Controller for RTC"
+	depends on OF && (MACH_PXA27X_DT || COMPILE_TEST)
+	help
+	  This driver provides an SPI master device to drive Maxim
+	  DS-1302 real time clock.
+
+	  Say N here unless you plan to run the kernel on an ICP DAS
+	  LP-8x4x industrial computer.
+
 config SPI_MPC52xx
 	tristate "Freescale MPC52xx SPI (non-PSC) controller support"
 	depends on PPC_MPC52xx
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index 8991ffc..9d10ddc 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -46,6 +46,7 @@ obj-$(CONFIG_SPI_GPIO)			+= spi-gpio.o
 obj-$(CONFIG_SPI_IMG_SPFI)		+= spi-img-spfi.o
 obj-$(CONFIG_SPI_IMX)			+= spi-imx.o
 obj-$(CONFIG_SPI_LM70_LLP)		+= spi-lm70llp.o
+obj-$(CONFIG_SPI_LP8841_RTC)		+= spi-lp8841-rtc.o
 obj-$(CONFIG_SPI_MESON_SPIFC)		+= spi-meson-spifc.o
 obj-$(CONFIG_SPI_MPC512x_PSC)		+= spi-mpc512x-psc.o
 obj-$(CONFIG_SPI_MPC52xx_PSC)		+= spi-mpc52xx-psc.o
diff --git a/drivers/spi/spi-lp8841-rtc.c b/drivers/spi/spi-lp8841-rtc.c
new file mode 100644
index 0000000..bf6678e
--- /dev/null
+++ b/drivers/spi/spi-lp8841-rtc.c
@@ -0,0 +1,272 @@
+/*
+ * SPI master driver for ICP DAS LP-8841 RTC
+ *
+ * Copyright (C) 2016 Sergei Ianovich
+ *
+ * based on
+ *
+ * Dallas DS1302 RTC Support
+ * Copyright (C) 2002 David McCullough
+ * Copyright (C) 2003 - 2007 Paul Mundt
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+#include <linux/delay.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/spi/spi.h>
+
+#define SPI_LP8841_RTC_CE	0x01
+#define SPI_LP8841_RTC_CLK	0x02
+#define SPI_LP8841_RTC_nWE	0x04
+#define SPI_LP8841_RTC_MOSI	0x08
+#define SPI_LP8841_RTC_MISO	0x01
+
+/*
+ * REVISIT If there is support for SPI_3WIRE and SPI_LSB_FIRST in SPI
+ * GPIO driver, this SPI driver can be replaced by a simple GPIO driver
+ * providing 3 GPIO pins.
+ */
+
+struct spi_lp8841_rtc {
+	void		*iomem;
+	unsigned long	state;
+};
+
+#ifndef DRIVER_NAME
+#define DRIVER_NAME	"spi_lp8841_rtc"
+#endif
+
+static inline void
+setsck(struct spi_lp8841_rtc *data, int is_on)
+{
+	if (is_on)
+		data->state |= SPI_LP8841_RTC_CLK;
+	else
+		data->state &= ~SPI_LP8841_RTC_CLK;
+	writeb(data->state, data->iomem);
+}
+
+static inline void
+setmosi(struct spi_lp8841_rtc *data, int is_on)
+{
+	if (is_on)
+		data->state |= SPI_LP8841_RTC_MOSI;
+	else
+		data->state &= ~SPI_LP8841_RTC_MOSI;
+	writeb(data->state, data->iomem);
+}
+
+static inline int
+getmiso(struct spi_lp8841_rtc *data)
+{
+	return ioread8(data->iomem) & SPI_LP8841_RTC_MISO;
+}
+
+static inline void
+spidelay(unsigned usec)
+{
+	usleep_range(usec, usec + 1);
+}
+
+static inline u32
+bitbang_txrx_be_cpha0_lsb(struct spi_lp8841_rtc *data,
+		unsigned usecs, unsigned cpol, unsigned flags,
+		u32 word, u8 bits)
+{
+	/* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */
+
+	u32 shift = 32 - bits;
+	/* clock starts at inactive polarity */
+	for (; likely(bits); bits--) {
+
+		/* setup LSB (to slave) on leading edge */
+		if ((flags & SPI_MASTER_NO_TX) == 0)
+			setmosi(data, (word & 1));
+
+		spidelay(usecs);	/* T(setup) */
+
+		/* sample LSB (from slave) on trailing edge */
+		word >>= 1;
+		if ((flags & SPI_MASTER_NO_RX) == 0)
+			word |= (getmiso(data) << 31);
+
+		setsck(data, !cpol);
+		spidelay(usecs);
+
+		setsck(data, cpol);
+	}
+
+	word >>= shift;
+	return word;
+}
+
+static int
+spi_lp8841_rtc_transfer_one(struct spi_master *master,
+			    struct spi_device *spi,
+			    struct spi_transfer *t)
+{
+	struct spi_lp8841_rtc	*data = spi_master_get_devdata(master);
+	unsigned		count = t->len;
+	const u8		*tx = t->tx_buf;
+	u8			*rx = t->rx_buf;
+	u8			word = 0;
+	int			ret = 0;
+
+	if (tx) {
+		data->state &= ~SPI_LP8841_RTC_nWE;
+		writeb(data->state, data->iomem);
+		while (likely(count > 0)) {
+			word = *tx++;
+			bitbang_txrx_be_cpha0_lsb(data, 1, 0,
+					SPI_MASTER_NO_RX, word, 8);
+			count--;
+		}
+	} else if (rx) {
+		data->state |= SPI_LP8841_RTC_nWE;
+		writeb(data->state, data->iomem);
+		while (likely(count > 0)) {
+			word = bitbang_txrx_be_cpha0_lsb(data, 1, 0,
+					SPI_MASTER_NO_TX, word, 8);
+			*rx++ = word;
+			count--;
+		}
+	} else {
+		ret = -EINVAL;
+	}
+
+	spi_finalize_current_transfer(master);
+
+	return ret;
+}
+
+static void
+spi_lp8841_rtc_set_cs(struct spi_device *spi, bool enable)
+{
+	struct spi_lp8841_rtc *data = spi_master_get_devdata(spi->master);
+
+	data->state = 0;
+	writeb(data->state, data->iomem);
+	if (enable) {
+		spidelay(4);
+		data->state |= SPI_LP8841_RTC_CE;
+		writeb(data->state, data->iomem);
+		spidelay(4);
+	}
+}
+
+static int
+spi_lp8841_rtc_setup(struct spi_device *spi)
+{
+	if ((spi->mode & SPI_CS_HIGH) == 0) {
+		dev_err(&spi->dev, "unsupported active low chip select\n");
+		return -EINVAL;
+	}
+
+	if ((spi->mode & SPI_LSB_FIRST) == 0) {
+		dev_err(&spi->dev, "unsupported MSB first mode\n");
+		return -EINVAL;
+	}
+
+	if ((spi->mode & SPI_3WIRE) == 0) {
+		dev_err(&spi->dev, "unsupported wiring. 3 wires required\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void
+spi_lp8841_rtc_cleanup(struct spi_device *spi)
+{
+}
+
+static const struct of_device_id spi_lp8841_rtc_dt_ids[] = {
+	{ .compatible = "icpdas,spi-lp8841-rtc" },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(of, spi_lp8841_rtc_dt_ids);
+
+static int
+spi_lp8841_rtc_probe(struct platform_device *pdev)
+{
+	int				ret;
+	struct spi_master		*master;
+	struct spi_lp8841_rtc		*data;
+	void				*iomem;
+
+	master = spi_alloc_master(&pdev->dev, sizeof(*data));
+	if (!master)
+		return -ENOMEM;
+	platform_set_drvdata(pdev, master);
+
+	master->flags = SPI_MASTER_HALF_DUPLEX;
+	master->mode_bits = SPI_CS_HIGH | SPI_3WIRE | SPI_LSB_FIRST;
+
+	master->bus_num = pdev->id;
+	master->num_chipselect = 1;
+	master->setup = spi_lp8841_rtc_setup;
+	master->cleanup = spi_lp8841_rtc_cleanup;
+	master->set_cs = spi_lp8841_rtc_set_cs;
+	master->transfer_one = spi_lp8841_rtc_transfer_one;
+	master->bits_per_word_mask = SPI_BPW_MASK(8);
+	master->dev.of_node = pdev->dev.of_node;
+
+	data = spi_master_get_devdata(master);
+
+	iomem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	data->iomem =  devm_ioremap_resource(&pdev->dev, iomem);
+	if (IS_ERR(data->iomem)) {
+		dev_err(&pdev->dev, "failed to get IO address\n");
+		goto err_put_master;
+	}
+
+	/* register with the SPI framework */
+	ret = devm_spi_register_master(&pdev->dev, master);
+	if (ret) {
+		dev_err(&pdev->dev, "cannot register spi master\n");
+		goto err_put_master;
+	}
+
+	return ret;
+
+
+err_put_master:
+	spi_master_put(master);
+
+	return ret;
+}
+
+static int
+spi_lp8841_rtc_remove(struct platform_device *pdev)
+{
+	return 0;
+}
+
+MODULE_ALIAS("platform:" DRIVER_NAME);
+
+static struct platform_driver spi_lp8841_rtc_driver = {
+	.driver = {
+		.name	= DRIVER_NAME,
+		.of_match_table = of_match_ptr(spi_lp8841_rtc_dt_ids),
+	},
+	.probe		= spi_lp8841_rtc_probe,
+	.remove		= spi_lp8841_rtc_remove,
+};
+module_platform_driver(spi_lp8841_rtc_driver);
+
+MODULE_DESCRIPTION("SPI master driver for ICP DAS LP-8841 RTC");
+MODULE_AUTHOR("Sergei Ianovich");
+MODULE_LICENSE("GPL");
-- 
2.6.3

Re: [PATCH v1] spi: master driver to enable RTC on ICPDAS LP-8841

[Mark Brown]

[-- Attachment #1: Type: text/plain, Size: 1968 bytes --]

On Mon, Feb 22, 2016 at 04:47:06AM +0300, Sergei Ianovich wrote:
> ICP DAS LP-8841 contains a DS-1302 RTC. This driver provides an SPI
> master which makes the RTC usable. The driver is not supposed to work
> with anything else.

So this is something that is internal to a single chip or something?
I'm slightly unclear from the above if this is or is not a SPI
controller.  If it isn't generic the DT should probably just describe
the IP and let the driver create the SPI controller and device if that
is an expedient way of doing things.

> +spi0@901c {
> +	#address-cells = <1>;
> +	#size-cells = <0>;
> +	compatible = "icpdas,spi-lp8841-rtc";
> +	reg = <0x901c 0x1>;
> +
> +	rtc@0 {
> +		compatible = "maxim,rtc-ds1302";
> +		reg = <0>;
> +		spi-max-frequency = <500000>;
> +		spi-3wire;
> +		spi-lsb-first;
> +		spi-cs-high;
> +	};
> +};

This example makes it seem like an actual SPI controller but just one
that's broken/limited?

> +config SPI_LP8841_RTC
> +	tristate "ICP DAS LP-8841 SPI Controller for RTC"
> +	depends on OF && (MACH_PXA27X_DT || COMPILE_TEST)

Does this need a strict DT dependency or can it build without DT?

> +/*
> + * REVISIT If there is support for SPI_3WIRE and SPI_LSB_FIRST in SPI
> + * GPIO driver, this SPI driver can be replaced by a simple GPIO driver
> + * providing 3 GPIO pins.
> + */

What's the advantage of not doing that?  Overall the driver looks fairly
good but it does seem to just implement a straight bitbanging driver
with less flexibility.

> +#ifndef DRIVER_NAME
> +#define DRIVER_NAME	"spi_lp8841_rtc"
> +#endif

If you want to use a define for this just use a define for it, don't do
this ifdef stuff.

> +static inline void
> +spidelay(unsigned usec)
> +{
> +	usleep_range(usec, usec + 1);
> +}

Just use usleep_range() directly.

> +static void
> +spi_lp8841_rtc_cleanup(struct spi_device *spi)
> +{
> +}

Remove empty functions, if they can be empty the core will support
ignoring them if they are missing.

[-- Attachment #2: signature.asc --]
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Re: [PATCH v1] spi: master driver to enable RTC on ICPDAS LP-8841

[Sergei Ianovich]

On Mon, 2016-02-22 at 12:10 +0900, Mark Brown wrote:
> On Mon, Feb 22, 2016 at 04:47:06AM +0300, Sergei Ianovich wrote:
> > ICP DAS LP-8841 contains a DS-1302 RTC. This driver provides an SPI
> > master which makes the RTC usable. The driver is not supposed to
> > work
> > with anything else.
> 
> So this is something that is internal to a single chip or something?
> I'm slightly unclear from the above if this is or is not a SPI
> controller.  If it isn't generic the DT should probably just describe
> the IP and let the driver create the SPI controller and device if
> that
> is an expedient way of doing things.
> 
> > +spi0@901c {
> > +	#address-cells = <1>;
> > +	#size-cells = <0>;
> > +	compatible = "icpdas,spi-lp8841-rtc";
> > +	reg = <0x901c 0x1>;
> > +
> > +	rtc@0 {
> > +		compatible = "maxim,rtc-ds1302";
> > +		reg = <0>;
> > +		spi-max-frequency = <500000>;
> > +		spi-3wire;
> > +		spi-lsb-first;
> > +		spi-cs-high;
> > +	};
> > +};
> 
> This example makes it seem like an actual SPI controller but just one
> that's broken/limited?

Yes. This is an actual SPI controller with minimal required
functionality. I didn't implement anything I don't need.

> > +config SPI_LP8841_RTC
> > +	tristate "ICP DAS LP-8841 SPI Controller for RTC"
> > +	depends on OF && (MACH_PXA27X_DT || COMPILE_TEST)
> 
> Does this need a strict DT dependency or can it build without DT?

The driver can only be useful on a single industrial PC. That PC
requires DT, so I made this a strict dependency. The dependency can be
removed by using ifdefs, but I see no point why.

> > +/*
> > + * REVISIT If there is support for SPI_3WIRE and SPI_LSB_FIRST in
> > SPI
> > + * GPIO driver, this SPI driver can be replaced by a simple GPIO
> > driver
> > + * providing 3 GPIO pins.
> > + */
> 
> What's the advantage of not doing that?  Overall the driver looks
> fairly
> good but it does seem to just implement a straight bitbanging driver
> with less flexibility.

MicroWire (SPI_3WIRE) mode is slightly different from the modes
implemented in spi-bitbang-txrx.h. I was getting junk from device in
both Mode0 and Mode2 until I changed the implementation. The change is
documented in the patch.

There will also need to be changes in bitbang.c. SPI_LSB_FIRST will
require a new flasg in txrx_word(). To keep overhead low will require
to grow txrx_word[] from 4 to 16 or even 32. CPOL, CPHA, LSB_FIRST,
3_WIRE each requires an additional power of 2.

While this change could be benefitial to both spi-gpio and spi-bitbang, 
it is very big.

> > +#ifndef DRIVER_NAME
> > +#define DRIVER_NAME	"spi_lp8841_rtc"
> > +#endif
> 
> If you want to use a define for this just use a define for it, don't
> do
> this ifdef stuff.

Yes, I'll fix this. This has been blindly copied from spi-gpio.c.

> > +static inline void
> > +spidelay(unsigned usec)
> > +{
> > +	usleep_range(usec, usec + 1);
> > +}
> 
> Just use usleep_range() directly.

Yes, I will.

> > +static void
> > +spi_lp8841_rtc_cleanup(struct spi_device *spi)
> > +{
> > +}
> 
> Remove empty functions, if they can be empty the core will support
> ignoring them if they are missing.

Yes, I will.

Thanks for a lightning fast review.
> > 

[PATCH v2] spi: master driver to enable RTC on ICPDAS LP-8841

[Sergei Ianovich]

ICP DAS LP-8841 contains a DS-1302 RTC. This driver provides an SPI
master which makes the RTC usable. The driver is not supposed to work
with anything else.

The driver uses the standard MicroWire half-duplex transfer timing.
Master output is set on low clock and sensed by the RTC on the rising
edge. Master input is set by the RTC on the trailing edge and is sensed
by the master on low clock.

Signed-off-by: Sergei Ianovich <ynvich@gmail.com>
CC: Mark Brown <broonie@kernel.org>
---
   v1..v2 to fix Mark Brown review comments
   * drop ifdef around MODULE_NAME
   * use usleep_range directly
   * drop empty master->cleanup

 .../devicetree/bindings/spi/spi-lp8841-rtc.txt     |  55 +++++
 drivers/spi/Kconfig                                |  10 +
 drivers/spi/Makefile                               |   1 +
 drivers/spi/spi-lp8841-rtc.c                       | 258 +++++++++++++++++++++
 4 files changed, 324 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/spi/spi-lp8841-rtc.txt
 create mode 100644 drivers/spi/spi-lp8841-rtc.c

diff --git a/Documentation/devicetree/bindings/spi/spi-lp8841-rtc.txt b/Documentation/devicetree/bindings/spi/spi-lp8841-rtc.txt
new file mode 100644
index 0000000..f191aef
--- /dev/null
+++ b/Documentation/devicetree/bindings/spi/spi-lp8841-rtc.txt
@@ -0,0 +1,55 @@
+* ICP DAS LP-8841 SPI Controller for RTC
+
+ICP DAS LP-8841 contains a DS-1302 RTC. This driver provides an SPI
+master which makes the RTC usable. The driver is not supposed to work
+with anything else.
+
+The driver uses the standard MicroWire half-duplex transfer timing.
+Master output is set on low clock and sensed by the RTC on the rising
+edge. Master input is set by the RTC on the trailing edge and is sensed
+by the master on low clock.
+
+Required properties:
+
+- #address-cells: should be 1
+
+- #size-cells: should be 0
+
+- compatible: should be "icpdas,spi-lp8841-rtc"
+
+- reg: should provide IO memory address
+
+Requirements to SPI slave nodes:
+
+- There can be only one slave device.
+
+- The spi slave node should claim the following flags which are
+  required by the spi controller.
+
+  - spi-3wire: The master itself has only 3 wire. It cannor work in
+    full duplex mode.
+
+  - spi-cs-high: DS-1302 has active high chip select line. The master
+    doesn't support active low.
+
+  - spi-lsb-first: DS-1302 requires least significant bit first
+    transfers. The master only support this type of bit ordering.
+
+
+Example:
+
+spi0@901c {
+	#address-cells = <1>;
+	#size-cells = <0>;
+	compatible = "icpdas,spi-lp8841-rtc";
+	reg = <0x901c 0x1>;
+
+	rtc@0 {
+		compatible = "maxim,rtc-ds1302";
+		reg = <0>;
+		spi-max-frequency = <500000>;
+		spi-3wire;
+		spi-lsb-first;
+		spi-cs-high;
+	};
+};
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 7706416..33908c1 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -271,6 +271,16 @@ config SPI_LM70_LLP
 	  which interfaces to an LM70 temperature sensor using
 	  a parallel port.
 
+config SPI_LP8841_RTC
+	tristate "ICP DAS LP-8841 SPI Controller for RTC"
+	depends on OF && (MACH_PXA27X_DT || COMPILE_TEST)
+	help
+	  This driver provides an SPI master device to drive Maxim
+	  DS-1302 real time clock.
+
+	  Say N here unless you plan to run the kernel on an ICP DAS
+	  LP-8x4x industrial computer.
+
 config SPI_MPC52xx
 	tristate "Freescale MPC52xx SPI (non-PSC) controller support"
 	depends on PPC_MPC52xx
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index 8991ffc..9d10ddc 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -46,6 +46,7 @@ obj-$(CONFIG_SPI_GPIO)			+= spi-gpio.o
 obj-$(CONFIG_SPI_IMG_SPFI)		+= spi-img-spfi.o
 obj-$(CONFIG_SPI_IMX)			+= spi-imx.o
 obj-$(CONFIG_SPI_LM70_LLP)		+= spi-lm70llp.o
+obj-$(CONFIG_SPI_LP8841_RTC)		+= spi-lp8841-rtc.o
 obj-$(CONFIG_SPI_MESON_SPIFC)		+= spi-meson-spifc.o
 obj-$(CONFIG_SPI_MPC512x_PSC)		+= spi-mpc512x-psc.o
 obj-$(CONFIG_SPI_MPC52xx_PSC)		+= spi-mpc52xx-psc.o
diff --git a/drivers/spi/spi-lp8841-rtc.c b/drivers/spi/spi-lp8841-rtc.c
new file mode 100644
index 0000000..042719b
--- /dev/null
+++ b/drivers/spi/spi-lp8841-rtc.c
@@ -0,0 +1,258 @@
+/*
+ * SPI master driver for ICP DAS LP-8841 RTC
+ *
+ * Copyright (C) 2016 Sergei Ianovich
+ *
+ * based on
+ *
+ * Dallas DS1302 RTC Support
+ * Copyright (C) 2002 David McCullough
+ * Copyright (C) 2003 - 2007 Paul Mundt
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+#include <linux/delay.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/spi/spi.h>
+
+#define DRIVER_NAME	"spi_lp8841_rtc"
+
+#define SPI_LP8841_RTC_CE	0x01
+#define SPI_LP8841_RTC_CLK	0x02
+#define SPI_LP8841_RTC_nWE	0x04
+#define SPI_LP8841_RTC_MOSI	0x08
+#define SPI_LP8841_RTC_MISO	0x01
+
+/*
+ * REVISIT If there is support for SPI_3WIRE and SPI_LSB_FIRST in SPI
+ * GPIO driver, this SPI driver can be replaced by a simple GPIO driver
+ * providing 3 GPIO pins.
+ */
+
+struct spi_lp8841_rtc {
+	void		*iomem;
+	unsigned long	state;
+};
+
+static inline void
+setsck(struct spi_lp8841_rtc *data, int is_on)
+{
+	if (is_on)
+		data->state |= SPI_LP8841_RTC_CLK;
+	else
+		data->state &= ~SPI_LP8841_RTC_CLK;
+	writeb(data->state, data->iomem);
+}
+
+static inline void
+setmosi(struct spi_lp8841_rtc *data, int is_on)
+{
+	if (is_on)
+		data->state |= SPI_LP8841_RTC_MOSI;
+	else
+		data->state &= ~SPI_LP8841_RTC_MOSI;
+	writeb(data->state, data->iomem);
+}
+
+static inline int
+getmiso(struct spi_lp8841_rtc *data)
+{
+	return ioread8(data->iomem) & SPI_LP8841_RTC_MISO;
+}
+
+static inline u32
+bitbang_txrx_be_cpha0_lsb(struct spi_lp8841_rtc *data,
+		unsigned usecs, unsigned cpol, unsigned flags,
+		u32 word, u8 bits)
+{
+	/* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */
+
+	u32 shift = 32 - bits;
+	/* clock starts at inactive polarity */
+	for (; likely(bits); bits--) {
+
+		/* setup LSB (to slave) on leading edge */
+		if ((flags & SPI_MASTER_NO_TX) == 0)
+			setmosi(data, (word & 1));
+
+		usleep_range(usecs, usecs + 1);	/* T(setup) */
+
+		/* sample LSB (from slave) on trailing edge */
+		word >>= 1;
+		if ((flags & SPI_MASTER_NO_RX) == 0)
+			word |= (getmiso(data) << 31);
+
+		setsck(data, !cpol);
+		usleep_range(usecs, usecs + 1);
+
+		setsck(data, cpol);
+	}
+
+	word >>= shift;
+	return word;
+}
+
+static int
+spi_lp8841_rtc_transfer_one(struct spi_master *master,
+			    struct spi_device *spi,
+			    struct spi_transfer *t)
+{
+	struct spi_lp8841_rtc	*data = spi_master_get_devdata(master);
+	unsigned		count = t->len;
+	const u8		*tx = t->tx_buf;
+	u8			*rx = t->rx_buf;
+	u8			word = 0;
+	int			ret = 0;
+
+	if (tx) {
+		data->state &= ~SPI_LP8841_RTC_nWE;
+		writeb(data->state, data->iomem);
+		while (likely(count > 0)) {
+			word = *tx++;
+			bitbang_txrx_be_cpha0_lsb(data, 1, 0,
+					SPI_MASTER_NO_RX, word, 8);
+			count--;
+		}
+	} else if (rx) {
+		data->state |= SPI_LP8841_RTC_nWE;
+		writeb(data->state, data->iomem);
+		while (likely(count > 0)) {
+			word = bitbang_txrx_be_cpha0_lsb(data, 1, 0,
+					SPI_MASTER_NO_TX, word, 8);
+			*rx++ = word;
+			count--;
+		}
+	} else {
+		ret = -EINVAL;
+	}
+
+	spi_finalize_current_transfer(master);
+
+	return ret;
+}
+
+static void
+spi_lp8841_rtc_set_cs(struct spi_device *spi, bool enable)
+{
+	struct spi_lp8841_rtc *data = spi_master_get_devdata(spi->master);
+
+	data->state = 0;
+	writeb(data->state, data->iomem);
+	if (enable) {
+		usleep_range(4, 5);
+		data->state |= SPI_LP8841_RTC_CE;
+		writeb(data->state, data->iomem);
+		usleep_range(4, 5);
+	}
+}
+
+static int
+spi_lp8841_rtc_setup(struct spi_device *spi)
+{
+	if ((spi->mode & SPI_CS_HIGH) == 0) {
+		dev_err(&spi->dev, "unsupported active low chip select\n");
+		return -EINVAL;
+	}
+
+	if ((spi->mode & SPI_LSB_FIRST) == 0) {
+		dev_err(&spi->dev, "unsupported MSB first mode\n");
+		return -EINVAL;
+	}
+
+	if ((spi->mode & SPI_3WIRE) == 0) {
+		dev_err(&spi->dev, "unsupported wiring. 3 wires required\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id spi_lp8841_rtc_dt_ids[] = {
+	{ .compatible = "icpdas,spi-lp8841-rtc" },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(of, spi_lp8841_rtc_dt_ids);
+
+static int
+spi_lp8841_rtc_probe(struct platform_device *pdev)
+{
+	int				ret;
+	struct spi_master		*master;
+	struct spi_lp8841_rtc		*data;
+	void				*iomem;
+
+	master = spi_alloc_master(&pdev->dev, sizeof(*data));
+	if (!master)
+		return -ENOMEM;
+	platform_set_drvdata(pdev, master);
+
+	master->flags = SPI_MASTER_HALF_DUPLEX;
+	master->mode_bits = SPI_CS_HIGH | SPI_3WIRE | SPI_LSB_FIRST;
+
+	master->bus_num = pdev->id;
+	master->num_chipselect = 1;
+	master->setup = spi_lp8841_rtc_setup;
+	master->set_cs = spi_lp8841_rtc_set_cs;
+	master->transfer_one = spi_lp8841_rtc_transfer_one;
+	master->bits_per_word_mask = SPI_BPW_MASK(8);
+	master->dev.of_node = pdev->dev.of_node;
+
+	data = spi_master_get_devdata(master);
+
+	iomem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	data->iomem =  devm_ioremap_resource(&pdev->dev, iomem);
+	if (IS_ERR(data->iomem)) {
+		dev_err(&pdev->dev, "failed to get IO address\n");
+		goto err_put_master;
+	}
+
+	/* register with the SPI framework */
+	ret = devm_spi_register_master(&pdev->dev, master);
+	if (ret) {
+		dev_err(&pdev->dev, "cannot register spi master\n");
+		goto err_put_master;
+	}
+
+	return ret;
+
+
+err_put_master:
+	spi_master_put(master);
+
+	return ret;
+}
+
+static int
+spi_lp8841_rtc_remove(struct platform_device *pdev)
+{
+	return 0;
+}
+
+MODULE_ALIAS("platform:" DRIVER_NAME);
+
+static struct platform_driver spi_lp8841_rtc_driver = {
+	.driver = {
+		.name	= DRIVER_NAME,
+		.of_match_table = of_match_ptr(spi_lp8841_rtc_dt_ids),
+	},
+	.probe		= spi_lp8841_rtc_probe,
+	.remove		= spi_lp8841_rtc_remove,
+};
+module_platform_driver(spi_lp8841_rtc_driver);
+
+MODULE_DESCRIPTION("SPI master driver for ICP DAS LP-8841 RTC");
+MODULE_AUTHOR("Sergei Ianovich");
+MODULE_LICENSE("GPL");
-- 
2.6.3

Re: [PATCH v2] spi: master driver to enable RTC on ICPDAS LP-8841

[Mark Brown]

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On Mon, Feb 22, 2016 at 12:40:54PM +0300, Sergei Ianovich wrote:

>    * drop empty master->cleanup

You still have an empty remove() function.

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Re: [PATCH v1] spi: master driver to enable RTC on ICPDAS LP-8841

[Mark Brown]

[-- Attachment #1: Type: text/plain, Size: 1906 bytes --]

On Mon, Feb 22, 2016 at 12:26:14PM +0300, Sergei Ianovich wrote:
> On Mon, 2016-02-22 at 12:10 +0900, Mark Brown wrote:
> > On Mon, Feb 22, 2016 at 04:47:06AM +0300, Sergei Ianovich wrote:

> > > +config SPI_LP8841_RTC
> > > +	tristate "ICP DAS LP-8841 SPI Controller for RTC"
> > > +	depends on OF && (MACH_PXA27X_DT || COMPILE_TEST)

> > Does this need a strict DT dependency or can it build without DT?

> The driver can only be useful on a single industrial PC. That PC
> requires DT, so I made this a strict dependency. The dependency can be
> removed by using ifdefs, but I see no point why.

It makes it easier for anyone doing generic work on the kernel to build
test, one could make exactly the same argument about the dependency on
the PXA27x machine.

> > > +/*
> > > + * REVISIT If there is support for SPI_3WIRE and SPI_LSB_FIRST in
> > > SPI
> > > + * GPIO driver, this SPI driver can be replaced by a simple GPIO
> > > driver
> > > + * providing 3 GPIO pins.
> > > + */

> > What's the advantage of not doing that?  Overall the driver looks
> > fairly
> > good but it does seem to just implement a straight bitbanging driver
> > with less flexibility.

> MicroWire (SPI_3WIRE) mode is slightly different from the modes
> implemented in spi-bitbang-txrx.h. I was getting junk from device in
> both Mode0 and Mode2 until I changed the implementation. The change is
> documented in the patch.

> There will also need to be changes in bitbang.c. SPI_LSB_FIRST will
> require a new flasg in txrx_word(). To keep overhead low will require
> to grow txrx_word[] from 4 to 16 or even 32. CPOL, CPHA, LSB_FIRST,
> 3_WIRE each requires an additional power of 2.

> While this change could be benefitial to both spi-gpio and spi-bitbang, 
> it is very big.

OK, the number of users is probably small enough that it's not worth
worryinng about duplication.

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[PATCH v3] spi: master driver to enable RTC on ICPDAS LP-8841

[Sergei Ianovich]

ICP DAS LP-8841 contains a DS-1302 RTC. This driver provides an SPI
master which makes the RTC usable. The driver is not supposed to work
with anything else.

The driver uses the standard MicroWire half-duplex transfer timing.
Master output is set on low clock and sensed by the RTC on the rising
edge. Master input is set by the RTC on the trailing edge and is sensed
by the master on low clock.

Signed-off-by: Sergei Ianovich <ynvich@gmail.com>
CC: Mark Brown <broonie@kernel.org>
---
   v2..v3 to fix Mark Brown review comments
   * drop dependencies in Kconfig
   * use #ifdef CONFIG_OF to allow build without DT
   * drop empty driver->remove

   v1..v2 to fix Mark Brown review comments
   * drop ifdef around MODULE_NAME
   * use usleep_range directly
   * drop empty master->cleanup

 .../devicetree/bindings/spi/spi-lp8841-rtc.txt     |  55 +++++
 drivers/spi/Kconfig                                |   9 +
 drivers/spi/Makefile                               |   1 +
 drivers/spi/spi-lp8841-rtc.c                       | 255 +++++++++++++++++++++
 4 files changed, 320 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/spi/spi-lp8841-rtc.txt
 create mode 100644 drivers/spi/spi-lp8841-rtc.c

diff --git a/Documentation/devicetree/bindings/spi/spi-lp8841-rtc.txt b/Documentation/devicetree/bindings/spi/spi-lp8841-rtc.txt
new file mode 100644
index 0000000..f191aef
--- /dev/null
+++ b/Documentation/devicetree/bindings/spi/spi-lp8841-rtc.txt
@@ -0,0 +1,55 @@
+* ICP DAS LP-8841 SPI Controller for RTC
+
+ICP DAS LP-8841 contains a DS-1302 RTC. This driver provides an SPI
+master which makes the RTC usable. The driver is not supposed to work
+with anything else.
+
+The driver uses the standard MicroWire half-duplex transfer timing.
+Master output is set on low clock and sensed by the RTC on the rising
+edge. Master input is set by the RTC on the trailing edge and is sensed
+by the master on low clock.
+
+Required properties:
+
+- #address-cells: should be 1
+
+- #size-cells: should be 0
+
+- compatible: should be "icpdas,spi-lp8841-rtc"
+
+- reg: should provide IO memory address
+
+Requirements to SPI slave nodes:
+
+- There can be only one slave device.
+
+- The spi slave node should claim the following flags which are
+  required by the spi controller.
+
+  - spi-3wire: The master itself has only 3 wire. It cannor work in
+    full duplex mode.
+
+  - spi-cs-high: DS-1302 has active high chip select line. The master
+    doesn't support active low.
+
+  - spi-lsb-first: DS-1302 requires least significant bit first
+    transfers. The master only support this type of bit ordering.
+
+
+Example:
+
+spi0@901c {
+	#address-cells = <1>;
+	#size-cells = <0>;
+	compatible = "icpdas,spi-lp8841-rtc";
+	reg = <0x901c 0x1>;
+
+	rtc@0 {
+		compatible = "maxim,rtc-ds1302";
+		reg = <0>;
+		spi-max-frequency = <500000>;
+		spi-3wire;
+		spi-lsb-first;
+		spi-cs-high;
+	};
+};
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 7706416..6a6626a 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -271,6 +271,15 @@ config SPI_LM70_LLP
 	  which interfaces to an LM70 temperature sensor using
 	  a parallel port.
 
+config SPI_LP8841_RTC
+	tristate "ICP DAS LP-8841 SPI Controller for RTC"
+	help
+	  This driver provides an SPI master device to drive Maxim
+	  DS-1302 real time clock.
+
+	  Say N here unless you plan to run the kernel on an ICP DAS
+	  LP-8x4x industrial computer.
+
 config SPI_MPC52xx
 	tristate "Freescale MPC52xx SPI (non-PSC) controller support"
 	depends on PPC_MPC52xx
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index 8991ffc..9d10ddc 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -46,6 +46,7 @@ obj-$(CONFIG_SPI_GPIO)			+= spi-gpio.o
 obj-$(CONFIG_SPI_IMG_SPFI)		+= spi-img-spfi.o
 obj-$(CONFIG_SPI_IMX)			+= spi-imx.o
 obj-$(CONFIG_SPI_LM70_LLP)		+= spi-lm70llp.o
+obj-$(CONFIG_SPI_LP8841_RTC)		+= spi-lp8841-rtc.o
 obj-$(CONFIG_SPI_MESON_SPIFC)		+= spi-meson-spifc.o
 obj-$(CONFIG_SPI_MPC512x_PSC)		+= spi-mpc512x-psc.o
 obj-$(CONFIG_SPI_MPC52xx_PSC)		+= spi-mpc52xx-psc.o
diff --git a/drivers/spi/spi-lp8841-rtc.c b/drivers/spi/spi-lp8841-rtc.c
new file mode 100644
index 0000000..ae177bc
--- /dev/null
+++ b/drivers/spi/spi-lp8841-rtc.c
@@ -0,0 +1,255 @@
+/*
+ * SPI master driver for ICP DAS LP-8841 RTC
+ *
+ * Copyright (C) 2016 Sergei Ianovich
+ *
+ * based on
+ *
+ * Dallas DS1302 RTC Support
+ * Copyright (C) 2002 David McCullough
+ * Copyright (C) 2003 - 2007 Paul Mundt
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+#include <linux/delay.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/spi/spi.h>
+
+#define DRIVER_NAME	"spi_lp8841_rtc"
+
+#define SPI_LP8841_RTC_CE	0x01
+#define SPI_LP8841_RTC_CLK	0x02
+#define SPI_LP8841_RTC_nWE	0x04
+#define SPI_LP8841_RTC_MOSI	0x08
+#define SPI_LP8841_RTC_MISO	0x01
+
+/*
+ * REVISIT If there is support for SPI_3WIRE and SPI_LSB_FIRST in SPI
+ * GPIO driver, this SPI driver can be replaced by a simple GPIO driver
+ * providing 3 GPIO pins.
+ */
+
+struct spi_lp8841_rtc {
+	void		*iomem;
+	unsigned long	state;
+};
+
+static inline void
+setsck(struct spi_lp8841_rtc *data, int is_on)
+{
+	if (is_on)
+		data->state |= SPI_LP8841_RTC_CLK;
+	else
+		data->state &= ~SPI_LP8841_RTC_CLK;
+	writeb(data->state, data->iomem);
+}
+
+static inline void
+setmosi(struct spi_lp8841_rtc *data, int is_on)
+{
+	if (is_on)
+		data->state |= SPI_LP8841_RTC_MOSI;
+	else
+		data->state &= ~SPI_LP8841_RTC_MOSI;
+	writeb(data->state, data->iomem);
+}
+
+static inline int
+getmiso(struct spi_lp8841_rtc *data)
+{
+	return ioread8(data->iomem) & SPI_LP8841_RTC_MISO;
+}
+
+static inline u32
+bitbang_txrx_be_cpha0_lsb(struct spi_lp8841_rtc *data,
+		unsigned usecs, unsigned cpol, unsigned flags,
+		u32 word, u8 bits)
+{
+	/* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */
+
+	u32 shift = 32 - bits;
+	/* clock starts at inactive polarity */
+	for (; likely(bits); bits--) {
+
+		/* setup LSB (to slave) on leading edge */
+		if ((flags & SPI_MASTER_NO_TX) == 0)
+			setmosi(data, (word & 1));
+
+		usleep_range(usecs, usecs + 1);	/* T(setup) */
+
+		/* sample LSB (from slave) on trailing edge */
+		word >>= 1;
+		if ((flags & SPI_MASTER_NO_RX) == 0)
+			word |= (getmiso(data) << 31);
+
+		setsck(data, !cpol);
+		usleep_range(usecs, usecs + 1);
+
+		setsck(data, cpol);
+	}
+
+	word >>= shift;
+	return word;
+}
+
+static int
+spi_lp8841_rtc_transfer_one(struct spi_master *master,
+			    struct spi_device *spi,
+			    struct spi_transfer *t)
+{
+	struct spi_lp8841_rtc	*data = spi_master_get_devdata(master);
+	unsigned		count = t->len;
+	const u8		*tx = t->tx_buf;
+	u8			*rx = t->rx_buf;
+	u8			word = 0;
+	int			ret = 0;
+
+	if (tx) {
+		data->state &= ~SPI_LP8841_RTC_nWE;
+		writeb(data->state, data->iomem);
+		while (likely(count > 0)) {
+			word = *tx++;
+			bitbang_txrx_be_cpha0_lsb(data, 1, 0,
+					SPI_MASTER_NO_RX, word, 8);
+			count--;
+		}
+	} else if (rx) {
+		data->state |= SPI_LP8841_RTC_nWE;
+		writeb(data->state, data->iomem);
+		while (likely(count > 0)) {
+			word = bitbang_txrx_be_cpha0_lsb(data, 1, 0,
+					SPI_MASTER_NO_TX, word, 8);
+			*rx++ = word;
+			count--;
+		}
+	} else {
+		ret = -EINVAL;
+	}
+
+	spi_finalize_current_transfer(master);
+
+	return ret;
+}
+
+static void
+spi_lp8841_rtc_set_cs(struct spi_device *spi, bool enable)
+{
+	struct spi_lp8841_rtc *data = spi_master_get_devdata(spi->master);
+
+	data->state = 0;
+	writeb(data->state, data->iomem);
+	if (enable) {
+		usleep_range(4, 5);
+		data->state |= SPI_LP8841_RTC_CE;
+		writeb(data->state, data->iomem);
+		usleep_range(4, 5);
+	}
+}
+
+static int
+spi_lp8841_rtc_setup(struct spi_device *spi)
+{
+	if ((spi->mode & SPI_CS_HIGH) == 0) {
+		dev_err(&spi->dev, "unsupported active low chip select\n");
+		return -EINVAL;
+	}
+
+	if ((spi->mode & SPI_LSB_FIRST) == 0) {
+		dev_err(&spi->dev, "unsupported MSB first mode\n");
+		return -EINVAL;
+	}
+
+	if ((spi->mode & SPI_3WIRE) == 0) {
+		dev_err(&spi->dev, "unsupported wiring. 3 wires required\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id spi_lp8841_rtc_dt_ids[] = {
+	{ .compatible = "icpdas,spi-lp8841-rtc" },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(of, spi_lp8841_rtc_dt_ids);
+#endif
+
+static int
+spi_lp8841_rtc_probe(struct platform_device *pdev)
+{
+	int				ret;
+	struct spi_master		*master;
+	struct spi_lp8841_rtc		*data;
+	void				*iomem;
+
+	master = spi_alloc_master(&pdev->dev, sizeof(*data));
+	if (!master)
+		return -ENOMEM;
+	platform_set_drvdata(pdev, master);
+
+	master->flags = SPI_MASTER_HALF_DUPLEX;
+	master->mode_bits = SPI_CS_HIGH | SPI_3WIRE | SPI_LSB_FIRST;
+
+	master->bus_num = pdev->id;
+	master->num_chipselect = 1;
+	master->setup = spi_lp8841_rtc_setup;
+	master->set_cs = spi_lp8841_rtc_set_cs;
+	master->transfer_one = spi_lp8841_rtc_transfer_one;
+	master->bits_per_word_mask = SPI_BPW_MASK(8);
+#ifdef CONFIG_OF
+	master->dev.of_node = pdev->dev.of_node;
+#endif
+
+	data = spi_master_get_devdata(master);
+
+	iomem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	data->iomem =  devm_ioremap_resource(&pdev->dev, iomem);
+	if (IS_ERR(data->iomem)) {
+		dev_err(&pdev->dev, "failed to get IO address\n");
+		goto err_put_master;
+	}
+
+	/* register with the SPI framework */
+	ret = devm_spi_register_master(&pdev->dev, master);
+	if (ret) {
+		dev_err(&pdev->dev, "cannot register spi master\n");
+		goto err_put_master;
+	}
+
+	return ret;
+
+
+err_put_master:
+	spi_master_put(master);
+
+	return ret;
+}
+
+MODULE_ALIAS("platform:" DRIVER_NAME);
+
+static struct platform_driver spi_lp8841_rtc_driver = {
+	.driver = {
+		.name	= DRIVER_NAME,
+		.of_match_table = of_match_ptr(spi_lp8841_rtc_dt_ids),
+	},
+	.probe		= spi_lp8841_rtc_probe,
+};
+module_platform_driver(spi_lp8841_rtc_driver);
+
+MODULE_DESCRIPTION("SPI master driver for ICP DAS LP-8841 RTC");
+MODULE_AUTHOR("Sergei Ianovich");
+MODULE_LICENSE("GPL");
-- 
2.6.3

Re: [PATCH v1] spi: master driver to enable RTC on ICPDAS LP-8841

[Rob Herring]

On Mon, Feb 22, 2016 at 04:47:06AM +0300, Sergei Ianovich wrote:
> ICP DAS LP-8841 contains a DS-1302 RTC. This driver provides an SPI
> master which makes the RTC usable. The driver is not supposed to work
> with anything else.
> 
> The driver uses the standard MicroWire half-duplex transfer timing.
> Master output is set on low clock and sensed by the RTC on the rising
> edge. Master input is set by the RTC on the trailing edge and is sensed
> by the master on low clock.
> 
> Signed-off-by: Sergei Ianovich <ynvich@gmail.com>
> ---
>  .../devicetree/bindings/spi/spi-lp8841-rtc.txt     |  55 +++++
>  drivers/spi/Kconfig                                |  10 +
>  drivers/spi/Makefile                               |   1 +
>  drivers/spi/spi-lp8841-rtc.c                       | 272 +++++++++++++++++++++
>  4 files changed, 338 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/spi/spi-lp8841-rtc.txt
>  create mode 100644 drivers/spi/spi-lp8841-rtc.c
> 
> diff --git a/Documentation/devicetree/bindings/spi/spi-lp8841-rtc.txt b/Documentation/devicetree/bindings/spi/spi-lp8841-rtc.txt
> new file mode 100644
> index 0000000..f191aef
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/spi/spi-lp8841-rtc.txt
> @@ -0,0 +1,55 @@
> +* ICP DAS LP-8841 SPI Controller for RTC
> +
> +ICP DAS LP-8841 contains a DS-1302 RTC. This driver provides an SPI
> +master which makes the RTC usable. The driver is not supposed to work
> +with anything else.

Bindings describe h/w not drivers.

> +The driver uses the standard MicroWire half-duplex transfer timing.
> +Master output is set on low clock and sensed by the RTC on the rising
> +edge. Master input is set by the RTC on the trailing edge and is sensed
> +by the master on low clock.
> +
> +Required properties:
> +
> +- #address-cells: should be 1
> +
> +- #size-cells: should be 0
> +
> +- compatible: should be "icpdas,spi-lp8841-rtc"

icpdas,lp8841-spi-rtc would be more inline with naming conventions.

> +
> +- reg: should provide IO memory address
> +
> +Requirements to SPI slave nodes:
> +
> +- There can be only one slave device.
> +
> +- The spi slave node should claim the following flags which are
> +  required by the spi controller.
> +
> +  - spi-3wire: The master itself has only 3 wire. It cannor work in

s/cannor/cannot/

> +    full duplex mode.
> +
> +  - spi-cs-high: DS-1302 has active high chip select line. The master
> +    doesn't support active low.
> +
> +  - spi-lsb-first: DS-1302 requires least significant bit first
> +    transfers. The master only support this type of bit ordering.
> +
> +
> +Example:
> +
> +spi0@901c {

spi@901c

> +	#address-cells = <1>;
> +	#size-cells = <0>;
> +	compatible = "icpdas,spi-lp8841-rtc";
> +	reg = <0x901c 0x1>;
> +
> +	rtc@0 {
> +		compatible = "maxim,rtc-ds1302";
> +		reg = <0>;
> +		spi-max-frequency = <500000>;
> +		spi-3wire;
> +		spi-lsb-first;
> +		spi-cs-high;
> +	};
> +};

Re: [PATCH v3] spi: master driver to enable RTC on ICPDAS LP-8841

[Mark Brown]

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On Mon, Feb 22, 2016 at 02:57:42PM +0300, Sergei Ianovich wrote:

Please don't send new patches in the middle of old threads, it makes it
hard to find what the current versions of things are.

>    v2..v3 to fix Mark Brown review comments
>    * drop dependencies in Kconfig

No, what I was asking you to do was to change where the || COMPILE_TEST
was grouped.  It is good to hide things from users where they clearly
can't use the driver, that's what COMPILE_TEST is for.

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[PATCH v4] spi: master driver to enable RTC on ICPDAS LP-8841

[Sergei Ianovich]

ICP DAS LP-8841 contains a DS-1302 RTC. This driver provides an SPI
master which makes the RTC usable. The driver is not supposed to work
with anything else.

The driver uses the standard MicroWire half-duplex transfer timing.
Master output is set on low clock and sensed by the RTC on the rising
edge. Master input is set by the RTC on the trailing edge and is sensed
by the master on low clock.

Signed-off-by: Sergei Ianovich <ynvich@gmail.com>
CC: Mark Brown <broonie@kernel.org>
CC: Rob Herring <robh@kernel.org>

   v3..v4
   fix Mark Brown review comments
   * fix dependencies in Kconfig

   fix Rob Herring review comments
   * rewrite binding description
   * change binding and doc file names
   * fix typo

   v2..v3 to fix Mark Brown review comments
   * drop dependencies in Kconfig
   * use #ifdef CONFIG_OF to allow build without DT
   * drop empty driver->remove

   v1..v2 to fix Mark Brown review comments
   * drop ifdef around MODULE_NAME
   * use usleep_range directly
   * drop empty master->cleanup
---
 .../bindings/spi/icpdas-lp8841-spi-rtc.txt         |  54 +++++
 drivers/spi/Kconfig                                |  10 +
 drivers/spi/Makefile                               |   1 +
 drivers/spi/spi-lp8841-rtc.c                       | 255 +++++++++++++++++++++
 4 files changed, 320 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/spi/icpdas-lp8841-spi-rtc.txt
 create mode 100644 drivers/spi/spi-lp8841-rtc.c

diff --git a/Documentation/devicetree/bindings/spi/icpdas-lp8841-spi-rtc.txt b/Documentation/devicetree/bindings/spi/icpdas-lp8841-spi-rtc.txt
new file mode 100644
index 0000000..852b651
--- /dev/null
+++ b/Documentation/devicetree/bindings/spi/icpdas-lp8841-spi-rtc.txt
@@ -0,0 +1,54 @@
+* ICP DAS LP-8841 SPI Controller for RTC
+
+ICP DAS LP-8841 contains a DS-1302 RTC. RTC is connected to an IO
+memory register, which acts as an SPI master device.
+
+The device uses the standard MicroWire half-duplex transfer timing.
+Master output is set on low clock and sensed by the RTC on the rising
+edge. Master input is set by the RTC on the trailing edge and is sensed
+by the master on low clock.
+
+Required properties:
+
+- #address-cells: should be 1
+
+- #size-cells: should be 0
+
+- compatible: should be "icpdas,lp8841-spi-rtc"
+
+- reg: should provide IO memory address
+
+Requirements to SPI slave nodes:
+
+- There can be only one slave device.
+
+- The spi slave node should claim the following flags which are
+  required by the spi controller.
+
+  - spi-3wire: The master itself has only 3 wire. It cannor work in
+    full duplex mode.
+
+  - spi-cs-high: DS-1302 has active high chip select line. The master
+    doesn't support active low.
+
+  - spi-lsb-first: DS-1302 requires least significant bit first
+    transfers. The master only support this type of bit ordering.
+
+
+Example:
+
+spi@901c {
+	#address-cells = <1>;
+	#size-cells = <0>;
+	compatible = "icpdas,lp8841-spi-rtc";
+	reg = <0x901c 0x1>;
+
+	rtc@0 {
+		compatible = "maxim,ds1302";
+		reg = <0>;
+		spi-max-frequency = <500000>;
+		spi-3wire;
+		spi-lsb-first;
+		spi-cs-high;
+	};
+};
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 7706416..1206a66 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -271,6 +271,16 @@ config SPI_LM70_LLP
 	  which interfaces to an LM70 temperature sensor using
 	  a parallel port.
 
+config SPI_LP8841_RTC
+	tristate "ICP DAS LP-8841 SPI Controller for RTC"
+	depends on MACH_PXA27X_DT || COMPILE_TEST
+	help
+	  This driver provides an SPI master device to drive Maxim
+	  DS-1302 real time clock.
+
+	  Say N here unless you plan to run the kernel on an ICP DAS
+	  LP-8x4x industrial computer.
+
 config SPI_MPC52xx
 	tristate "Freescale MPC52xx SPI (non-PSC) controller support"
 	depends on PPC_MPC52xx
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index 8991ffc..9d10ddc 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -46,6 +46,7 @@ obj-$(CONFIG_SPI_GPIO)			+= spi-gpio.o
 obj-$(CONFIG_SPI_IMG_SPFI)		+= spi-img-spfi.o
 obj-$(CONFIG_SPI_IMX)			+= spi-imx.o
 obj-$(CONFIG_SPI_LM70_LLP)		+= spi-lm70llp.o
+obj-$(CONFIG_SPI_LP8841_RTC)		+= spi-lp8841-rtc.o
 obj-$(CONFIG_SPI_MESON_SPIFC)		+= spi-meson-spifc.o
 obj-$(CONFIG_SPI_MPC512x_PSC)		+= spi-mpc512x-psc.o
 obj-$(CONFIG_SPI_MPC52xx_PSC)		+= spi-mpc52xx-psc.o
diff --git a/drivers/spi/spi-lp8841-rtc.c b/drivers/spi/spi-lp8841-rtc.c
new file mode 100644
index 0000000..44bb69c
--- /dev/null
+++ b/drivers/spi/spi-lp8841-rtc.c
@@ -0,0 +1,255 @@
+/*
+ * SPI master driver for ICP DAS LP-8841 RTC
+ *
+ * Copyright (C) 2016 Sergei Ianovich
+ *
+ * based on
+ *
+ * Dallas DS1302 RTC Support
+ * Copyright (C) 2002 David McCullough
+ * Copyright (C) 2003 - 2007 Paul Mundt
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+#include <linux/delay.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/spi/spi.h>
+
+#define DRIVER_NAME	"spi_lp8841_rtc"
+
+#define SPI_LP8841_RTC_CE	0x01
+#define SPI_LP8841_RTC_CLK	0x02
+#define SPI_LP8841_RTC_nWE	0x04
+#define SPI_LP8841_RTC_MOSI	0x08
+#define SPI_LP8841_RTC_MISO	0x01
+
+/*
+ * REVISIT If there is support for SPI_3WIRE and SPI_LSB_FIRST in SPI
+ * GPIO driver, this SPI driver can be replaced by a simple GPIO driver
+ * providing 3 GPIO pins.
+ */
+
+struct spi_lp8841_rtc {
+	void		*iomem;
+	unsigned long	state;
+};
+
+static inline void
+setsck(struct spi_lp8841_rtc *data, int is_on)
+{
+	if (is_on)
+		data->state |= SPI_LP8841_RTC_CLK;
+	else
+		data->state &= ~SPI_LP8841_RTC_CLK;
+	writeb(data->state, data->iomem);
+}
+
+static inline void
+setmosi(struct spi_lp8841_rtc *data, int is_on)
+{
+	if (is_on)
+		data->state |= SPI_LP8841_RTC_MOSI;
+	else
+		data->state &= ~SPI_LP8841_RTC_MOSI;
+	writeb(data->state, data->iomem);
+}
+
+static inline int
+getmiso(struct spi_lp8841_rtc *data)
+{
+	return ioread8(data->iomem) & SPI_LP8841_RTC_MISO;
+}
+
+static inline u32
+bitbang_txrx_be_cpha0_lsb(struct spi_lp8841_rtc *data,
+		unsigned usecs, unsigned cpol, unsigned flags,
+		u32 word, u8 bits)
+{
+	/* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */
+
+	u32 shift = 32 - bits;
+	/* clock starts at inactive polarity */
+	for (; likely(bits); bits--) {
+
+		/* setup LSB (to slave) on leading edge */
+		if ((flags & SPI_MASTER_NO_TX) == 0)
+			setmosi(data, (word & 1));
+
+		usleep_range(usecs, usecs + 1);	/* T(setup) */
+
+		/* sample LSB (from slave) on trailing edge */
+		word >>= 1;
+		if ((flags & SPI_MASTER_NO_RX) == 0)
+			word |= (getmiso(data) << 31);
+
+		setsck(data, !cpol);
+		usleep_range(usecs, usecs + 1);
+
+		setsck(data, cpol);
+	}
+
+	word >>= shift;
+	return word;
+}
+
+static int
+spi_lp8841_rtc_transfer_one(struct spi_master *master,
+			    struct spi_device *spi,
+			    struct spi_transfer *t)
+{
+	struct spi_lp8841_rtc	*data = spi_master_get_devdata(master);
+	unsigned		count = t->len;
+	const u8		*tx = t->tx_buf;
+	u8			*rx = t->rx_buf;
+	u8			word = 0;
+	int			ret = 0;
+
+	if (tx) {
+		data->state &= ~SPI_LP8841_RTC_nWE;
+		writeb(data->state, data->iomem);
+		while (likely(count > 0)) {
+			word = *tx++;
+			bitbang_txrx_be_cpha0_lsb(data, 1, 0,
+					SPI_MASTER_NO_RX, word, 8);
+			count--;
+		}
+	} else if (rx) {
+		data->state |= SPI_LP8841_RTC_nWE;
+		writeb(data->state, data->iomem);
+		while (likely(count > 0)) {
+			word = bitbang_txrx_be_cpha0_lsb(data, 1, 0,
+					SPI_MASTER_NO_TX, word, 8);
+			*rx++ = word;
+			count--;
+		}
+	} else {
+		ret = -EINVAL;
+	}
+
+	spi_finalize_current_transfer(master);
+
+	return ret;
+}
+
+static void
+spi_lp8841_rtc_set_cs(struct spi_device *spi, bool enable)
+{
+	struct spi_lp8841_rtc *data = spi_master_get_devdata(spi->master);
+
+	data->state = 0;
+	writeb(data->state, data->iomem);
+	if (enable) {
+		usleep_range(4, 5);
+		data->state |= SPI_LP8841_RTC_CE;
+		writeb(data->state, data->iomem);
+		usleep_range(4, 5);
+	}
+}
+
+static int
+spi_lp8841_rtc_setup(struct spi_device *spi)
+{
+	if ((spi->mode & SPI_CS_HIGH) == 0) {
+		dev_err(&spi->dev, "unsupported active low chip select\n");
+		return -EINVAL;
+	}
+
+	if ((spi->mode & SPI_LSB_FIRST) == 0) {
+		dev_err(&spi->dev, "unsupported MSB first mode\n");
+		return -EINVAL;
+	}
+
+	if ((spi->mode & SPI_3WIRE) == 0) {
+		dev_err(&spi->dev, "unsupported wiring. 3 wires required\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id spi_lp8841_rtc_dt_ids[] = {
+	{ .compatible = "icpdas,lp8841-spi-rtc" },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(of, spi_lp8841_rtc_dt_ids);
+#endif
+
+static int
+spi_lp8841_rtc_probe(struct platform_device *pdev)
+{
+	int				ret;
+	struct spi_master		*master;
+	struct spi_lp8841_rtc		*data;
+	void				*iomem;
+
+	master = spi_alloc_master(&pdev->dev, sizeof(*data));
+	if (!master)
+		return -ENOMEM;
+	platform_set_drvdata(pdev, master);
+
+	master->flags = SPI_MASTER_HALF_DUPLEX;
+	master->mode_bits = SPI_CS_HIGH | SPI_3WIRE | SPI_LSB_FIRST;
+
+	master->bus_num = pdev->id;
+	master->num_chipselect = 1;
+	master->setup = spi_lp8841_rtc_setup;
+	master->set_cs = spi_lp8841_rtc_set_cs;
+	master->transfer_one = spi_lp8841_rtc_transfer_one;
+	master->bits_per_word_mask = SPI_BPW_MASK(8);
+#ifdef CONFIG_OF
+	master->dev.of_node = pdev->dev.of_node;
+#endif
+
+	data = spi_master_get_devdata(master);
+
+	iomem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	data->iomem =  devm_ioremap_resource(&pdev->dev, iomem);
+	if (IS_ERR(data->iomem)) {
+		dev_err(&pdev->dev, "failed to get IO address\n");
+		goto err_put_master;
+	}
+
+	/* register with the SPI framework */
+	ret = devm_spi_register_master(&pdev->dev, master);
+	if (ret) {
+		dev_err(&pdev->dev, "cannot register spi master\n");
+		goto err_put_master;
+	}
+
+	return ret;
+
+
+err_put_master:
+	spi_master_put(master);
+
+	return ret;
+}
+
+MODULE_ALIAS("platform:" DRIVER_NAME);
+
+static struct platform_driver spi_lp8841_rtc_driver = {
+	.driver = {
+		.name	= DRIVER_NAME,
+		.of_match_table = of_match_ptr(spi_lp8841_rtc_dt_ids),
+	},
+	.probe		= spi_lp8841_rtc_probe,
+};
+module_platform_driver(spi_lp8841_rtc_driver);
+
+MODULE_DESCRIPTION("SPI master driver for ICP DAS LP-8841 RTC");
+MODULE_AUTHOR("Sergei Ianovich");
+MODULE_LICENSE("GPL");
-- 
2.7.0

Re: [PATCH v4] spi: master driver to enable RTC on ICPDAS LP-8841

[Rob Herring]

On Tue, Feb 23, 2016 at 01:44:28PM +0300, Sergei Ianovich wrote:
> ICP DAS LP-8841 contains a DS-1302 RTC. This driver provides an SPI
> master which makes the RTC usable. The driver is not supposed to work
> with anything else.
> 
> The driver uses the standard MicroWire half-duplex transfer timing.
> Master output is set on low clock and sensed by the RTC on the rising
> edge. Master input is set by the RTC on the trailing edge and is sensed
> by the master on low clock.
> 
> Signed-off-by: Sergei Ianovich <ynvich@gmail.com>
> CC: Mark Brown <broonie@kernel.org>
> CC: Rob Herring <robh@kernel.org>
> 
>    v3..v4
>    fix Mark Brown review comments
>    * fix dependencies in Kconfig
> 
>    fix Rob Herring review comments
>    * rewrite binding description
>    * change binding and doc file names
>    * fix typo
> 
>    v2..v3 to fix Mark Brown review comments
>    * drop dependencies in Kconfig
>    * use #ifdef CONFIG_OF to allow build without DT
>    * drop empty driver->remove
> 
>    v1..v2 to fix Mark Brown review comments
>    * drop ifdef around MODULE_NAME
>    * use usleep_range directly
>    * drop empty master->cleanup
> ---
>  .../bindings/spi/icpdas-lp8841-spi-rtc.txt         |  54 +++++

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

Re: [PATCH v4] spi: master driver to enable RTC on ICPDAS LP-8841

[Mark Brown]

[-- Attachment #1: Type: text/plain, Size: 368 bytes --]

On Tue, Feb 23, 2016 at 01:44:28PM +0300, Sergei Ianovich wrote:

> CC: Mark Brown <broonie@kernel.org>
> CC: Rob Herring <robh@kernel.org>
> 
>    v3..v4
>    fix Mark Brown review comments
>    * fix dependencies in Kconfig

> ---

As covered in SubmittingPatches please put inter-version changelogs
after the --- so they get stripped out when applied.

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