diff mbox

[1/3] mfd: add Cypress FM33256B Processor Companion driver

Message ID 1461150471-23163-2-git-send-email-jlp@gomspace.com
State Changes Requested
Headers show

Commit Message

Jeppe Ledet-Pedersen April 20, 2016, 11:07 a.m. UTC
This patch adds support for the Cypress Semiconductor FM33256B processor
companion. The device contains a 256 kbit FRAM, an RTC, a supply voltage
monitor, and a watchdog timer.

Signed-off-by: Jeppe Ledet-Pedersen <jlp@gomspace.com>
---
 Documentation/devicetree/bindings/mfd/fm33256b.txt |  30 ++
 MAINTAINERS                                        |   6 +
 drivers/mfd/Kconfig                                |  16 +
 drivers/mfd/Makefile                               |   1 +
 drivers/mfd/fm33256b.c                             | 488 +++++++++++++++++++++
 include/linux/mfd/fm33256b.h                       |  76 ++++
 6 files changed, 617 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mfd/fm33256b.txt
 create mode 100644 drivers/mfd/fm33256b.c
 create mode 100644 include/linux/mfd/fm33256b.h

Comments

kernel test robot April 22, 2016, 12:47 a.m. UTC | #1
Hi,

[auto build test ERROR on ljones-mfd/for-mfd-next]
[also build test ERROR on v4.6-rc4 next-20160421]
[if your patch is applied to the wrong git tree, please drop us a note to help improving the system]

url:    https://github.com/0day-ci/linux/commits/Jeppe-Ledet-Pedersen/Cypress-FM33256B-processor-companion-support/20160420-193004
base:   https://git.kernel.org/pub/scm/linux/kernel/git/lee/mfd.git for-mfd-next
config: x86_64-randconfig-n0-04220648 (attached as .config)
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All error/warnings (new ones prefixed by >>):

warning: (BMP085_SPI && TOUCHSCREEN_TSC2005 && SERIAL_MAX310X && SERIAL_SC16IS7XX_SPI && MFD_FM33256B && MFD_DA9052_SPI && MFD_MC13XXX_SPI && MFD_TPS65912_SPI && MFD_ARIZONA_SPI && MFD_WM831X_SPI && SND_SOC && SND_SOC_ADAU1761_SPI && SND_SOC_ADAU1781_SPI && SND_SOC_ADAU1977_SPI && SND_SOC_CS4271_SPI && SND_SOC_PCM3168A_SPI && SND_SOC_PCM512x_SPI && SND_SOC_SSM2602_SPI && SND_SOC_WM8804_SPI && RTC_I2C_AND_SPI && RTC_DRV_DS1343 && RTC_DRV_RX6110 && BMC150_ACCEL_SPI && MMA7455_SPI && AD5380 && BMG160_SPI && AFE4403 && INV_MPU6050_SPI && SENSORS_HMC5843_SPI) selects REGMAP_SPI which has unmet direct dependencies (SPI)
   drivers/built-in.o: In function `regmap_spi_read':
>> regmap-spi.c:(.text+0x29e4c9): undefined reference to `spi_write_then_read'
   drivers/built-in.o: In function `regmap_spi_gather_write':
>> regmap-spi.c:(.text+0x29e5e9): undefined reference to `spi_sync'
   drivers/built-in.o: In function `regmap_spi_write':
   regmap-spi.c:(.text+0x29e6d9): undefined reference to `spi_sync'
   drivers/built-in.o: In function `regmap_spi_async_write':
>> regmap-spi.c:(.text+0x29e9eb): undefined reference to `spi_async'
   drivers/built-in.o: In function `fm33256b_probe':
>> fm33256b.c:(.text+0x35c975): undefined reference to `spi_setup'
   drivers/built-in.o: In function `fm33256b_io':
>> fm33256b.c:(.text+0x35cec6): undefined reference to `spi_sync'
   fm33256b.c:(.text+0x35cf53): undefined reference to `spi_sync'
   drivers/built-in.o: In function `fm33256b_spi_driver_init':
>> fm33256b.c:(.init.text+0x131e9): undefined reference to `__spi_register_driver'

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
Rob Herring April 22, 2016, 7:32 p.m. UTC | #2
On Wed, Apr 20, 2016 at 01:07:49PM +0200, Jeppe Ledet-Pedersen wrote:
> This patch adds support for the Cypress Semiconductor FM33256B processor
> companion. The device contains a 256 kbit FRAM, an RTC, a supply voltage
> monitor, and a watchdog timer.
> 
> Signed-off-by: Jeppe Ledet-Pedersen <jlp@gomspace.com>
> ---
>  Documentation/devicetree/bindings/mfd/fm33256b.txt |  30 ++
>  MAINTAINERS                                        |   6 +
>  drivers/mfd/Kconfig                                |  16 +
>  drivers/mfd/Makefile                               |   1 +
>  drivers/mfd/fm33256b.c                             | 488 +++++++++++++++++++++
>  include/linux/mfd/fm33256b.h                       |  76 ++++
>  6 files changed, 617 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mfd/fm33256b.txt
>  create mode 100644 drivers/mfd/fm33256b.c
>  create mode 100644 include/linux/mfd/fm33256b.h
> 
> diff --git a/Documentation/devicetree/bindings/mfd/fm33256b.txt b/Documentation/devicetree/bindings/mfd/fm33256b.txt
> new file mode 100644
> index 0000000..6591c94
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mfd/fm33256b.txt
> @@ -0,0 +1,30 @@
> +Device-tree bindings for Cypress Semiconductor FM33256B Processor Companion
> +---------------------------------------------------------------------------
> +
> +Required properties:
> +- compatible: must be "cypress,fm33256b".
> +- reg: SPI chip select
> +- spi-max-frequency: Max SPI frequency to use (< 16000000)
> +
> +Optional properties:
> +- cypress,charge-enabled: enable trickle charger

What does the driver do if charging is disabled? Would using 'status = 
"disabled"' be any different?
 
> +- cypress,charge-fast: enable fast (1 mA) charging

What does fast mean?

I think it is time for a common binding here. There's all sorts of 
variations on setting the charge current in bindings. Add something like 
"charge-current-microamp" in power_supply.txt and use it here. Then 
1000uA implies "fast charge".

> +
> +The MFD exposes two subdevices:
> +- The FRAM: "cypress,fm33256b-fram"
> +- The RTC: "cypress,fm33256b-rtc"
> +
> +Example:
> +
> +spi1: spi@f800800 {
> +	status = "okay";
> +	cs-gpios = <&pioC 25 0>;
> +
> +	fm33256b@0 {
> +		compatible = "cypress,fm33256b";
> +		spi-max-frequency = <10000000>;
> +		cypress,charge-enabled;
> +		cypress,charge-fast;
> +		reg = <0>;
> +	};

Where's the 2nd sub device?

> +};
Alexandre Belloni April 22, 2016, 8:11 p.m. UTC | #3
On 22/04/2016 at 14:32:32 -0500, Rob Herring wrote :
> On Wed, Apr 20, 2016 at 01:07:49PM +0200, Jeppe Ledet-Pedersen wrote:
> > This patch adds support for the Cypress Semiconductor FM33256B processor
> > companion. The device contains a 256 kbit FRAM, an RTC, a supply voltage
> > monitor, and a watchdog timer.
> > 
> > Signed-off-by: Jeppe Ledet-Pedersen <jlp@gomspace.com>
> > ---
> >  Documentation/devicetree/bindings/mfd/fm33256b.txt |  30 ++
> >  MAINTAINERS                                        |   6 +
> >  drivers/mfd/Kconfig                                |  16 +
> >  drivers/mfd/Makefile                               |   1 +
> >  drivers/mfd/fm33256b.c                             | 488 +++++++++++++++++++++
> >  include/linux/mfd/fm33256b.h                       |  76 ++++
> >  6 files changed, 617 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/mfd/fm33256b.txt
> >  create mode 100644 drivers/mfd/fm33256b.c
> >  create mode 100644 include/linux/mfd/fm33256b.h
> > 
> > diff --git a/Documentation/devicetree/bindings/mfd/fm33256b.txt b/Documentation/devicetree/bindings/mfd/fm33256b.txt
> > new file mode 100644
> > index 0000000..6591c94
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/mfd/fm33256b.txt
> > @@ -0,0 +1,30 @@
> > +Device-tree bindings for Cypress Semiconductor FM33256B Processor Companion
> > +---------------------------------------------------------------------------
> > +
> > +Required properties:
> > +- compatible: must be "cypress,fm33256b".
> > +- reg: SPI chip select
> > +- spi-max-frequency: Max SPI frequency to use (< 16000000)
> > +
> > +Optional properties:
> > +- cypress,charge-enabled: enable trickle charger
> 
> What does the driver do if charging is disabled? Would using 'status = 
> "disabled"' be any different?
>  

Good catch, I didn't look at this patch but it includes a lot of code
that should be going to the RTC driver.
If trickle charging is not enabled, I guess the RTC will not charge its
backup battery.

> > +- cypress,charge-fast: enable fast (1 mA) charging
> 
> What does fast mean?
> 
> I think it is time for a common binding here. There's all sorts of 
> variations on setting the charge current in bindings. Add something like 
> "charge-current-microamp" in power_supply.txt and use it here. Then 
> 1000uA implies "fast charge".

Well, this is not a power supply, it is an RTC.

I think both properties should got to the RTC subdevice and be parsed in
the RTC driver.

Note that for trickle charging, we currently have the following
properties:
 - trickle-resistor-ohms
 - trickle-diode-disable
 - abracon,tc-diode
 - abracon,tc-resistor

abracon,tc-resistor can be replaced by trickle-resistor-ohms, I'll make
a patch but abracon,tc-diode allows to select a diode type (and in
particular a voltage drop).

I think we could add a trickle-current-microamp like you suggested and
trickle-diode-disable can be reused.
Jeppe Ledet-Pedersen April 26, 2016, 2:31 p.m. UTC | #4
On 22/04/16 22:11, Alexandre Belloni wrote:
> On 22/04/2016 at 14:32:32 -0500, Rob Herring wrote :
>> On Wed, Apr 20, 2016 at 01:07:49PM +0200, Jeppe Ledet-Pedersen wrote:
>>> This patch adds support for the Cypress Semiconductor FM33256B processor
>>> companion. The device contains a 256 kbit FRAM, an RTC, a supply voltage
>>> monitor, and a watchdog timer.
>>>
>>> Signed-off-by: Jeppe Ledet-Pedersen <jlp@gomspace.com>
>>> ---
>>>  Documentation/devicetree/bindings/mfd/fm33256b.txt |  30 ++
>>>  MAINTAINERS                                        |   6 +
>>>  drivers/mfd/Kconfig                                |  16 +
>>>  drivers/mfd/Makefile                               |   1 +
>>>  drivers/mfd/fm33256b.c                             | 488 +++++++++++++++++++++
>>>  include/linux/mfd/fm33256b.h                       |  76 ++++
>>>  6 files changed, 617 insertions(+)
>>>  create mode 100644 Documentation/devicetree/bindings/mfd/fm33256b.txt
>>>  create mode 100644 drivers/mfd/fm33256b.c
>>>  create mode 100644 include/linux/mfd/fm33256b.h
>>>
>>> diff --git a/Documentation/devicetree/bindings/mfd/fm33256b.txt b/Documentation/devicetree/bindings/mfd/fm33256b.txt
>>> new file mode 100644
>>> index 0000000..6591c94
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/mfd/fm33256b.txt
>>> @@ -0,0 +1,30 @@
>>> +Device-tree bindings for Cypress Semiconductor FM33256B Processor Companion
>>> +---------------------------------------------------------------------------
>>> +
>>> +Required properties:
>>> +- compatible: must be "cypress,fm33256b".
>>> +- reg: SPI chip select
>>> +- spi-max-frequency: Max SPI frequency to use (< 16000000)
>>> +
>>> +Optional properties:
>>> +- cypress,charge-enabled: enable trickle charger
>>
>> What does the driver do if charging is disabled? Would using 'status = 
>> "disabled"' be any different?
>>  
> 
> Good catch, I didn't look at this patch but it includes a lot of code
> that should be going to the RTC driver.
> If trickle charging is not enabled, I guess the RTC will not charge its
> backup battery.

Thank you for the comments.

Alexandre is correct. If the "cypress,charge-enabled" property is
present, the internal 80 uA trickle charger is enabled to charge a
backup capacitor on the VBAK pin.

Do you want more code than the trickle charger setup moved to the RTC
driver?

>>> +- cypress,charge-fast: enable fast (1 mA) charging
>>
>> What does fast mean?
>>

Fast charging means charging with 1 mA instead of 80 uA. The wording is
from the datasheet, but I agree it should be renamed to something that
better explains what the difference is.

>> I think it is time for a common binding here. There's all sorts of 
>> variations on setting the charge current in bindings. Add something like 
>> "charge-current-microamp" in power_supply.txt and use it here. Then 
>> 1000uA implies "fast charge".
> 
> Well, this is not a power supply, it is an RTC.
> 
> I think both properties should got to the RTC subdevice and be parsed in
> the RTC driver.

The backup capacitor is primarily used to supply current to the RTC, but
a couple of other registers are also battery-backed (watchdog reset
cause, event counter), so I put the charger setup in the main MFD file.

If you prefer, I can move them both to the RTC driver?

> Note that for trickle charging, we currently have the following
> properties:
>  - trickle-resistor-ohms
>  - trickle-diode-disable
>  - abracon,tc-diode
>  - abracon,tc-resistor
> 
> abracon,tc-resistor can be replaced by trickle-resistor-ohms, I'll make
> a patch but abracon,tc-diode allows to select a diode type (and in
> particular a voltage drop).
> 
> I think we could add a trickle-current-microamp like you suggested and
> trickle-diode-disable can be reused.

So replace "cypress,charge-enabled/charge-fast" with
"trickle-current-microamp" and a check for 0/80/1000 uA?

Thanks,

-Jeppe
Jeppe Ledet-Pedersen April 26, 2016, 2:42 p.m. UTC | #5
On 22/04/16 21:32, Rob Herring wrote:
> On Wed, Apr 20, 2016 at 01:07:49PM +0200, Jeppe Ledet-Pedersen wrote:
[snip]
>> +
>> +The MFD exposes two subdevices:
>> +- The FRAM: "cypress,fm33256b-fram"
>> +- The RTC: "cypress,fm33256b-rtc"
>> +
>> +Example:
>> +
>> +spi1: spi@f800800 {
>> +	status = "okay";
>> +	cs-gpios = <&pioC 25 0>;
>> +
>> +	fm33256b@0 {
>> +		compatible = "cypress,fm33256b";
>> +		spi-max-frequency = <10000000>;
>> +		cypress,charge-enabled;
>> +		cypress,charge-fast;
>> +		reg = <0>;
>> +	};
> 
> Where's the 2nd sub device?

Hi Rob,

Right now I just add the two sub-devices using mfd_add_devices in the
fm33256b_probe function in my MFD driver. Would it be better to check
for compatible child nodes before adding each sub-device, like it's done
in drivers/mfd/tc3589x.c?

Thanks,

-Jeppe
Alexandre Belloni May 3, 2016, 8:14 a.m. UTC | #6
On 26/04/2016 at 16:31:46 +0200, Jeppe Ledet-Pedersen wrote :
> > Good catch, I didn't look at this patch but it includes a lot of code
> > that should be going to the RTC driver.
> > If trickle charging is not enabled, I guess the RTC will not charge its
> > backup battery.
> 
> Thank you for the comments.
> 
> Alexandre is correct. If the "cypress,charge-enabled" property is
> present, the internal 80 uA trickle charger is enabled to charge a
> backup capacitor on the VBAK pin.
> 
> Do you want more code than the trickle charger setup moved to the RTC
> driver?
> 

I guess the 32k oscillator could go in the rtc driver too.

> >>> +- cypress,charge-fast: enable fast (1 mA) charging
> >>
> >> What does fast mean?
> >>
> 
> Fast charging means charging with 1 mA instead of 80 uA. The wording is
> from the datasheet, but I agree it should be renamed to something that
> better explains what the difference is.
> 
> >> I think it is time for a common binding here. There's all sorts of 
> >> variations on setting the charge current in bindings. Add something like 
> >> "charge-current-microamp" in power_supply.txt and use it here. Then 
> >> 1000uA implies "fast charge".
> > 
> > Well, this is not a power supply, it is an RTC.
> > 
> > I think both properties should got to the RTC subdevice and be parsed in
> > the RTC driver.
> 
> The backup capacitor is primarily used to supply current to the RTC, but
> a couple of other registers are also battery-backed (watchdog reset
> cause, event counter), so I put the charger setup in the main MFD file.
> 
> If you prefer, I can move them both to the RTC driver?

I would prefer unless you think that many people are not using the RTC
while still using the watchdog (I'd say that is not the case).

> 
> > Note that for trickle charging, we currently have the following
> > properties:
> >  - trickle-resistor-ohms
> >  - trickle-diode-disable
> >  - abracon,tc-diode
> >  - abracon,tc-resistor
> > 
> > abracon,tc-resistor can be replaced by trickle-resistor-ohms, I'll make
> > a patch but abracon,tc-diode allows to select a diode type (and in
> > particular a voltage drop).
> > 
> > I think we could add a trickle-current-microamp like you suggested and
> > trickle-diode-disable can be reused.
> 
> So replace "cypress,charge-enabled/charge-fast" with
> "trickle-current-microamp" and a check for 0/80/1000 uA?
> 

Yeah, seems fine.
diff mbox

Patch

diff --git a/Documentation/devicetree/bindings/mfd/fm33256b.txt b/Documentation/devicetree/bindings/mfd/fm33256b.txt
new file mode 100644
index 0000000..6591c94
--- /dev/null
+++ b/Documentation/devicetree/bindings/mfd/fm33256b.txt
@@ -0,0 +1,30 @@ 
+Device-tree bindings for Cypress Semiconductor FM33256B Processor Companion
+---------------------------------------------------------------------------
+
+Required properties:
+- compatible: must be "cypress,fm33256b".
+- reg: SPI chip select
+- spi-max-frequency: Max SPI frequency to use (< 16000000)
+
+Optional properties:
+- cypress,charge-enabled: enable trickle charger
+- cypress,charge-fast: enable fast (1 mA) charging
+
+The MFD exposes two subdevices:
+- The FRAM: "cypress,fm33256b-fram"
+- The RTC: "cypress,fm33256b-rtc"
+
+Example:
+
+spi1: spi@f800800 {
+	status = "okay";
+	cs-gpios = <&pioC 25 0>;
+
+	fm33256b@0 {
+		compatible = "cypress,fm33256b";
+		spi-max-frequency = <10000000>;
+		cypress,charge-enabled;
+		cypress,charge-fast;
+		reg = <0>;
+	};
+};
diff --git a/MAINTAINERS b/MAINTAINERS
index 1d5b4be..87b5023 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3382,6 +3382,12 @@  T:	git git://linuxtv.org/anttip/media_tree.git
 S:	Maintained
 F:	drivers/media/common/cypress_firmware*
 
+CYPRESS FM33256B PROCESSOR COMPANION DRIVER
+M:	Jeppe Ledet-Pedersen <jlp@gomspace.com>
+S:	Maintained
+F:	include/linux/mfd/fm33256b.h
+F:	drivers/mfd/fm33256b.c
+
 CYTTSP TOUCHSCREEN DRIVER
 M:	Ferruh Yigit <fery@cypress.com>
 L:	linux-input@vger.kernel.org
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index eea61e3..3a0d3a3 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -93,6 +93,22 @@  config MFD_ATMEL_HLCDC
 	  additional drivers must be enabled in order to use the
 	  functionality of the device.
 
+config MFD_FM33256B
+	tristate "Cypress FM33256 Processor Companion support"
+	select MFD_CORE
+	select REGMAP_SPI
+	depends on OF
+	help
+	  If you say yes here you get support for the Cypress FM33256B
+	  Processor Companion device.
+
+	  This driver provides common support for accessing the device,
+	  additional drivers must be enabled in order to use the
+	  functionality of the device.
+
+	  This driver can also be built as a module. If so the module
+	  will be called fm33256b.
+
 config MFD_BCM590XX
 	tristate "Broadcom BCM590xx PMUs"
 	select MFD_CORE
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index 5eaa6465d..a13728d 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -203,3 +203,4 @@  intel-soc-pmic-objs		:= intel_soc_pmic_core.o intel_soc_pmic_crc.o
 intel-soc-pmic-$(CONFIG_INTEL_PMC_IPC)	+= intel_soc_pmic_bxtwc.o
 obj-$(CONFIG_INTEL_SOC_PMIC)	+= intel-soc-pmic.o
 obj-$(CONFIG_MFD_MT6397)	+= mt6397-core.o
+obj-$(CONFIG_MFD_FM33256B)	+= fm33256b.o
diff --git a/drivers/mfd/fm33256b.c b/drivers/mfd/fm33256b.c
new file mode 100644
index 0000000..880ccdd
--- /dev/null
+++ b/drivers/mfd/fm33256b.c
@@ -0,0 +1,488 @@ 
+/*
+ * Cypress FM33256B Processor Companion Driver
+ *
+ * Copyright (C) 2016 GomSpace ApS
+ *
+ * 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.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/mfd/fm33256b.h>
+#include <linux/mfd/core.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/spi/spi.h>
+#include <linux/device.h>
+#include <linux/of.h>
+
+static const struct mfd_cell fm33256b_cells[] = {
+	{
+		.name = "fm33256b-rtc",
+		.of_compatible = "cypress,fm33256b-rtc",
+	},
+	{
+		.name = "fm33256b-fram",
+		.of_compatible = "cypress,fm33256b-fram",
+	},
+};
+
+static int fm33256b_io(struct spi_device *spi, bool write_enable,
+		       uint8_t *out, uint8_t *in, size_t len)
+{
+	struct spi_message m;
+	struct fm33256b *fm33256b = dev_get_drvdata(&spi->dev);
+
+	uint8_t write_out[1] = {FM33256B_OP_WREN};
+
+	/* Payload transfer */
+	struct spi_transfer t = {
+		.tx_buf = out,
+		.rx_buf = in,
+		.len = len,
+	};
+
+	mutex_lock(&fm33256b->lock);
+
+	/* CS must go high for the write enable latch to be enabled,
+	 * so we have to split this in two transfers.
+	 */
+	if (write_enable)
+		spi_write(spi, write_out, 1);
+
+	spi_message_init(&m);
+	spi_message_add_tail(&t, &m);
+	spi_sync(spi, &m);
+
+	mutex_unlock(&fm33256b->lock);
+
+	return 0;
+}
+
+static int fm33256b_read_status(struct spi_device *spi, uint8_t *status)
+{
+	int ret;
+	uint8_t out[2] = {FM33256B_OP_RDSR, 0xff};
+	uint8_t in[2];
+
+	ret = fm33256b_io(spi, false, out, in, 2);
+	if (ret < 0)
+		return ret;
+
+	*status = in[1];
+
+	return 0;
+}
+
+static int fm33256b_write_status(struct spi_device *spi, uint8_t status)
+{
+	uint8_t out[2] = {FM33256B_OP_WRSR, status};
+	uint8_t in[2];
+
+	return fm33256b_io(spi, true, out, in, 2);
+}
+
+static int fm33256b_write_fram(struct spi_device *spi, uint16_t addr,
+			       const uint8_t *data, size_t len)
+{
+	int ret;
+	uint8_t *out = NULL, *in = NULL;
+
+	out = devm_kzalloc(&spi->dev, 3 + len, GFP_KERNEL);
+	in = devm_kzalloc(&spi->dev, 3 + len, GFP_KERNEL);
+	if (!out || !in) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	out[0] = FM33256B_OP_WRITE;
+	out[1] = (addr >> 8) & 0xff;
+	out[2] = addr & 0xff;
+	memcpy(&out[3], data, len);
+
+	ret = fm33256b_io(spi, true, out, in, 3 + len);
+
+out:
+	devm_kfree(&spi->dev, out);
+	devm_kfree(&spi->dev, in);
+
+	return ret;
+}
+
+static int fm33256b_read_fram(struct spi_device *spi, uint16_t addr,
+			      uint8_t *data, size_t len)
+{
+	int ret;
+	uint8_t *out = NULL, *in = NULL;
+
+	out = devm_kzalloc(&spi->dev, 3 + len, GFP_KERNEL);
+	in = devm_kzalloc(&spi->dev, 3 + len, GFP_KERNEL);
+	if (!out || !in) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	out[0] = FM33256B_OP_READ;
+	out[1] = (addr >> 8) & 0xff;
+	out[2] = addr & 0xff;
+	memset(&out[3], 0xff, len);
+
+	ret = fm33256b_io(spi, false, out, in, 3 + len);
+	if (ret == 0)
+		memcpy(data, &in[3], len);
+
+out:
+	devm_kfree(&spi->dev, out);
+	devm_kfree(&spi->dev, in);
+
+	return ret;
+}
+
+static int fm33256b_write_pc(struct spi_device *spi, uint8_t reg,
+			     const uint8_t *data, size_t len)
+{
+	int ret;
+	uint8_t *out = NULL, *in = NULL;
+
+	out = devm_kzalloc(&spi->dev, 2 + len, GFP_KERNEL);
+	in = devm_kzalloc(&spi->dev, 2 + len, GFP_KERNEL);
+	if (!out || !in) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	out[0] = FM33256B_OP_WRPC;
+	out[1] = reg;
+	memcpy(&out[2], data, len);
+
+	ret = fm33256b_io(spi, true, out, in, 2 + len);
+
+out:
+	devm_kfree(&spi->dev, out);
+	devm_kfree(&spi->dev, in);
+
+	return ret;
+}
+
+static int fm33256b_read_pc(struct spi_device *spi, uint8_t reg,
+			    uint8_t *data, size_t len)
+{
+	int ret;
+	uint8_t *out = NULL, *in = NULL;
+
+	out = devm_kzalloc(&spi->dev, 2 + len, GFP_KERNEL);
+	in = devm_kzalloc(&spi->dev, 2 + len, GFP_KERNEL);
+	if (!out || !in) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	out[0] = FM33256B_OP_RDPC;
+	out[1] = reg;
+	memset(&out[2], 0xff, len);
+
+	ret = fm33256b_io(spi, false, out, in, 2 + len);
+	if (ret == 0)
+		memcpy(data, &in[2], len);
+
+out:
+	devm_kfree(&spi->dev, out);
+	devm_kfree(&spi->dev, in);
+
+	return ret;
+}
+
+static int fm33256b_pc_regmap_read(void *context, const void *reg,
+				   size_t reg_size, void *val,
+				   size_t val_size)
+{
+	struct device *dev = context;
+	struct spi_device *spi = to_spi_device(dev);
+
+	if (reg_size != 1)
+		return -ENOTSUPP;
+
+	return fm33256b_read_pc(spi, *(uint8_t *)reg, val, val_size);
+}
+
+static int fm33256b_pc_regmap_write(void *context, const void *data,
+				    size_t count)
+{
+	struct device *dev = context;
+	struct spi_device *spi = to_spi_device(dev);
+
+	const uint8_t *out = data;
+	const uint8_t *val = &out[1];
+
+	uint8_t reg = out[0];
+
+	return fm33256b_write_pc(spi, reg, val, count - sizeof(reg));
+}
+
+static int fm33256b_fram_regmap_read(void *context, const void *reg,
+				     size_t reg_size, void *val,
+				     size_t val_size)
+{
+	struct device *dev = context;
+	struct spi_device *spi = to_spi_device(dev);
+
+	const uint8_t *addrp = reg;
+
+	uint16_t addr = ((uint16_t)addrp[0] << 8) | addrp[1];
+
+	if (reg_size != 2)
+		return -ENOTSUPP;
+
+	return fm33256b_read_fram(spi, addr, val, val_size);
+}
+
+static int fm33256b_fram_regmap_write(void *context, const void *data,
+				      size_t count)
+{
+	struct device *dev = context;
+	struct spi_device *spi = to_spi_device(dev);
+
+	const uint8_t *out = data;
+	const uint8_t *val = &out[2];
+
+	uint16_t addr = ((uint16_t)out[0] << 8) | out[1];
+
+	return fm33256b_write_fram(spi, addr, val, count - sizeof(addr));
+}
+
+static ssize_t fm33256b_bp_show(struct device *dev,
+				struct device_attribute *attr,
+				char *buf)
+{
+	struct spi_device *spi = to_spi_device(dev);
+	int ret;
+	uint8_t status, bp;
+
+	ret = fm33256b_read_status(spi, &status);
+	if (ret < 0)
+		return ret;
+
+	bp = (status & 0x0c) >> 2;
+
+	return snprintf(buf, PAGE_SIZE, "%hhu\n", bp);
+}
+
+static ssize_t fm33256b_bp_store(struct device *dev,
+				 struct device_attribute *attr,
+				 const char *buf, size_t count)
+{
+	struct spi_device *spi = to_spi_device(dev);
+	int ret;
+	uint8_t status, bp;
+	unsigned long input;
+
+	ret = kstrtoul(buf, 10, &input);
+	if (ret < 0)
+		return ret;
+
+	if (input > 3)
+		return -EINVAL;
+
+	bp = (uint8_t)input << 2;
+
+	ret = fm33256b_read_status(spi, &status);
+	if (ret < 0)
+		return ret;
+
+	status = (status & 0xf3) | bp;
+
+	ret = fm33256b_write_status(spi, status);
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+static ssize_t fm33256b_serial_show(struct device *dev,
+				    struct device_attribute *attr,
+				    char *buf)
+{
+	struct spi_device *spi = to_spi_device(dev);
+	char serial[9];
+	int ret;
+
+	ret = fm33256b_read_pc(spi, FM33256B_SERIAL_BYTE0_REG, serial, 8);
+	if (ret < 0)
+		return ret;
+
+	serial[8] = '\0';
+
+	return snprintf(buf, PAGE_SIZE, "%-8s\n", serial);
+}
+
+static ssize_t fm33256b_serial_store(struct device *dev,
+				     struct device_attribute *attr,
+				     const char *buf, size_t count)
+{
+	struct spi_device *spi = to_spi_device(dev);
+	char serial[9];
+	int ret;
+
+	if (sscanf(buf, "%8s", serial) != 1)
+		return -EINVAL;
+
+	ret = fm33256b_write_pc(spi, FM33256B_SERIAL_BYTE0_REG, serial, 8);
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+DEVICE_ATTR(bp, S_IWUSR | S_IRUGO,
+	    fm33256b_bp_show, fm33256b_bp_store);
+DEVICE_ATTR(serial, S_IWUSR | S_IRUGO,
+	    fm33256b_serial_show, fm33256b_serial_store);
+
+/* Processor Companion Register Map */
+static const struct regmap_config fm33256b_pc_regmap_conf = {
+	.name = "pc",
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = FM33256B_MAX_REGISTER,
+};
+
+static struct regmap_bus fm33256b_pc_regmap_bus = {
+	.write = fm33256b_pc_regmap_write,
+	.read = fm33256b_pc_regmap_read,
+};
+
+/* FRAM Register Map */
+static const struct regmap_config fm33256b_fram_regmap_conf = {
+	.name = "fram",
+	.reg_bits = 16,
+	.val_bits = 8,
+	.max_register = FM33256B_MAX_FRAM,
+};
+
+static struct regmap_bus fm33256b_fram_regmap_bus = {
+	.write = fm33256b_fram_regmap_write,
+	.read = fm33256b_fram_regmap_read,
+};
+
+static int fm33256b_setup(struct spi_device *spi, struct fm33256b *fm33256b)
+{
+	int ret;
+	uint8_t companion_ctl = FM33256B_ALSW, rtc_alarm_ctl = 0;
+
+	/* Setup charger control from DT */
+	if (of_get_property(spi->dev.of_node, "cypress,charge-enabled", NULL))
+		companion_ctl |= FM33256B_VBC;
+
+	if (of_get_property(spi->dev.of_node, "cypress,charge-fast", NULL))
+		companion_ctl |= FM33256B_FC;
+
+	/* Setup charging if enabled */
+	ret = regmap_write(fm33256b->regmap_pc,
+			   FM33256B_COMPANION_CONTROL_REG,
+			   companion_ctl);
+	if (ret < 0)
+		return ret;
+
+	/* Enable 32 kHz oscillator */
+	ret = regmap_write(fm33256b->regmap_pc,
+			   FM33256B_RTC_ALARM_CONTROL_REG,
+			   rtc_alarm_ctl);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+static int fm33256b_probe(struct spi_device *spi)
+{
+	int ret;
+	struct device *dev = &spi->dev;
+	struct fm33256b *fm33256b;
+
+	fm33256b = devm_kzalloc(dev, sizeof(*fm33256b), GFP_KERNEL);
+	if (!fm33256b)
+		return -ENOMEM;
+
+	mutex_init(&fm33256b->lock);
+
+	spi->mode = SPI_MODE_0;
+	spi->max_speed_hz = spi->max_speed_hz ? : 8000000;
+
+	ret = spi_setup(spi);
+	if (ret < 0)
+		return ret;
+
+	/* Setup processor companion regmap */
+	fm33256b->regmap_pc =
+		devm_regmap_init(dev, &fm33256b_pc_regmap_bus,
+				 dev, &fm33256b_pc_regmap_conf);
+	if (IS_ERR(fm33256b->regmap_pc))
+		return PTR_ERR(fm33256b->regmap_pc);
+
+	/* Setup FRAM regmap */
+	fm33256b->regmap_fram =
+		devm_regmap_init(dev, &fm33256b_fram_regmap_bus,
+				 dev, &fm33256b_fram_regmap_conf);
+	if (IS_ERR(fm33256b->regmap_fram))
+		return PTR_ERR(fm33256b->regmap_fram);
+
+	dev_set_drvdata(dev, fm33256b);
+
+	ret = fm33256b_setup(spi, fm33256b);
+	if (ret < 0)
+		return ret;
+
+	/* Create sysfs entries */
+	ret = device_create_file(&spi->dev, &dev_attr_bp);
+	if (ret < 0)
+		return ret;
+
+	ret = device_create_file(&spi->dev, &dev_attr_serial);
+	if (ret < 0) {
+		device_remove_file(&spi->dev, &dev_attr_bp);
+		return ret;
+	}
+
+	return mfd_add_devices(dev, -1, fm33256b_cells,
+			       ARRAY_SIZE(fm33256b_cells),
+			       NULL, 0, NULL);
+}
+
+static int fm33256b_remove(struct spi_device *spi)
+{
+	mfd_remove_devices(&spi->dev);
+	device_remove_file(&spi->dev, &dev_attr_serial);
+	device_remove_file(&spi->dev, &dev_attr_bp);
+
+	return 0;
+}
+
+static const struct of_device_id fm33256b_dt_ids[] = {
+	{ .compatible = "cypress,fm33256b" },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, fm33256b_dt_ids);
+
+static struct spi_driver fm33256b_spi_driver = {
+	.driver = {
+		.name = "fm33256b",
+		.owner = THIS_MODULE,
+		.of_match_table = fm33256b_dt_ids,
+	},
+	.probe = fm33256b_probe,
+	.remove = fm33256b_remove,
+};
+module_spi_driver(fm33256b_spi_driver);
+
+MODULE_ALIAS("spi:fm33256b");
+MODULE_DESCRIPTION("Cypress FM33256B Processor Companion Driver");
+MODULE_AUTHOR("Jeppe Ledet-Pedersen <jlp@gomspace.com>");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/mfd/fm33256b.h b/include/linux/mfd/fm33256b.h
new file mode 100644
index 0000000..cd1e37a
--- /dev/null
+++ b/include/linux/mfd/fm33256b.h
@@ -0,0 +1,76 @@ 
+/*
+ * Cypress FM33256B Processor Companion Driver
+ *
+ * Copyright (C) 2016 GomSpace ApS
+ *
+ * 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.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __LINUX_MFD_FM33256B_H
+#define __LINUX_MFD_FM33256B_H
+
+#include <linux/mutex.h>
+#include <linux/regmap.h>
+#include <linux/spi/spi.h>
+
+/* Opcodes */
+#define FM33256B_OP_WREN		0x06
+#define FM33256B_OP_WRDI		0x04
+#define FM33256B_OP_RDSR		0x05
+#define FM33256B_OP_WRSR		0x01
+#define FM33256B_OP_READ		0x03
+#define FM33256B_OP_WRITE		0x02
+#define FM33256B_OP_RDPC		0x13
+#define FM33256B_OP_WRPC		0x12
+
+/* RTC/Processor Companion Register Map */
+#define FM33256B_ALARM_MONTH		0x1D
+#define FM33256B_COMPANION_CONTROL_REG	0x18
+#define FM33256B_SERIAL_BYTE0_REG	0x10
+#define FM33256B_YEARS_REG		0x08
+#define FM33256B_MONTH_REG		0x07
+#define FM33256B_DATE_REG		0x06
+#define FM33256B_DAY_REG		0x05
+#define FM33256B_HOURS_REG		0x04
+#define FM33256B_MINUTES_REG		0x03
+#define FM33256B_SECONDS_REG		0x02
+#define FM33256B_CAL_CONTROL_REG	0x01
+#define FM33256B_RTC_ALARM_CONTROL_REG	0x00
+
+/* Companion Control bits */
+#define FM33256B_ALSW			BIT(6)
+#define FM33256B_VBC			BIT(3)
+#define FM33256B_FC			BIT(2)
+
+/* RTC/Alarm Control bits */
+#define FM33256B_R			BIT(0)
+#define FM33256B_W			BIT(1)
+#define FM33256B_CAL			BIT(2)
+#define FM33256B_OSCEN			BIT(7)
+
+/* Limits */
+#define FM33256B_MAX_REGISTER		FM33256B_ALARM_MONTH
+#define FM33256B_MAX_FRAM		(32 * 1024) /* 256 kb */
+
+/**
+ * Structure shared by the MFD device and its subdevices.
+ *
+ * @regmap: register map used to access registers
+ */
+struct fm33256b {
+	struct mutex lock;
+	struct regmap *regmap_pc;
+	struct regmap *regmap_fram;
+};
+
+#endif /* __LINUX_MFD_FM33256B_H */