diff mbox series

[v3,3/7] mfd: Add base driver for Netronix embedded controller

Message ID 20200924192455.2484005-4-j.neuschaefer@gmx.net
State New, archived
Headers show
Series Netronix embedded controller driver for Kobo and Tolino ebook readers | expand

Commit Message

Jonathan Neuschäfer Sept. 24, 2020, 7:24 p.m. UTC
The Netronix embedded controller is a microcontroller found in some
e-book readers designed by the ODM Netronix, Inc. It contains RTC,
battery monitoring, system power management, and PWM functionality.

This driver implements register access and version detection.

Third-party hardware documentation is available at:

  https://github.com/neuschaefer/linux/wiki/Netronix-MSP430-embedded-controller

The EC supports interrupts, but the driver doesn't make use of them so
far.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
---

v3:
- Add (EC) to CONFIG_MFD_NTXEC prompt
- Relicense as GPLv2 or later
- Add email address to copyright line
- remove empty lines in ntxec_poweroff and ntxec_restart functions
- Split long lines
- Remove 'Install ... handler' comments
- Make naming of struct i2c_client parameter consistent
- Remove struct ntxec_info
- Rework 'depends on' lines in Kconfig, hard-depend on I2C, select REGMAP_I2C and
  MFD_CORE
- Register subdevices via mfd_cells
- Move 8-bit register conversion to ntxec.h

v2:
- https://lore.kernel.org/lkml/20200905133230.1014581-4-j.neuschaefer@gmx.net/
- Add a description of the device to the patch text
- Unify spelling as 'Netronix embedded controller'.
  'Netronix' is the proper name of the manufacturer, but 'embedded controller'
  is just a label that I have assigned to the device.
- Switch to regmap, avoid regmap use in poweroff and reboot handlers.
  Inspired by cf84dc0bb40f4 ("mfd: rn5t618: Make restart handler atomic safe")
- Use a list of known-working firmware versions instead of checking for a
  known-incompatible version
- Prefix registers with NTXEC_REG_
- Define register values as constants
- Various style cleanups as suggested by Lee Jones
- Don't align = signs in struct initializers [Uwe Kleine-König]
- Don't use dev_dbg for an error message
- Explain sleep in poweroff handler
- Remove (struct ntxec).client
- Switch to .probe_new in i2c driver
- Add .remove callback
- Make CONFIG_MFD_NTXEC a tristate option
---
 drivers/mfd/Kconfig       |  10 ++
 drivers/mfd/Makefile      |   1 +
 drivers/mfd/ntxec.c       | 206 ++++++++++++++++++++++++++++++++++++++
 include/linux/mfd/ntxec.h |  31 ++++++
 4 files changed, 248 insertions(+)
 create mode 100644 drivers/mfd/ntxec.c
 create mode 100644 include/linux/mfd/ntxec.h

--
2.28.0

Comments

Andy Shevchenko Sept. 25, 2020, 9:29 a.m. UTC | #1
On Thu, Sep 24, 2020 at 10:26 PM Jonathan Neuschäfer
<j.neuschaefer@gmx.net> wrote:
>
> The Netronix embedded controller is a microcontroller found in some
> e-book readers designed by the ODM Netronix, Inc. It contains RTC,
> battery monitoring, system power management, and PWM functionality.
>
> This driver implements register access and version detection.
>
> Third-party hardware documentation is available at:
>
>   https://github.com/neuschaefer/linux/wiki/Netronix-MSP430-embedded-controller
>
> The EC supports interrupts, but the driver doesn't make use of them so
> far.

...

> +#include <asm/unaligned.h>

This usually goes after linux/*.h
(and actually not visible how it's being used, but see below first)

> +#include <linux/delay.h>
> +#include <linux/errno.h>
> +#include <linux/i2c.h>
> +#include <linux/mfd/core.h>
> +#include <linux/mfd/ntxec.h>
> +#include <linux/module.h>
> +#include <linux/pm.h>
> +#include <linux/reboot.h>
> +#include <linux/regmap.h>
> +#include <linux/types.h>

...

> +static void ntxec_poweroff(void)
> +{
> +       int res;
> +       u8 buf[] = {
> +               NTXEC_REG_POWEROFF,

> +               (NTXEC_POWEROFF_VALUE >> 8) & 0xff,
> +               NTXEC_POWEROFF_VALUE & 0xff,

'& 0xff' parts are redundant. *u8 implies that. Fix in all cases.
Also I would rather see something like

  buf[0] = _POWEROFF;
  put_unaligned_be16(_VALUE, &buf[1]);

to explicitly show the endianess of the register values.

> +       };
> +       struct i2c_msg msgs[] = {
> +               {
> +                       .addr = poweroff_restart_client->addr,
> +                       .flags = 0,
> +                       .len = sizeof(buf),

> +                       .buf = buf

It's slightly better to keep trailing commas in cases like this.

> +               }
> +       };
> +
> +       res = i2c_transfer(poweroff_restart_client->adapter, msgs, ARRAY_SIZE(msgs));
> +       if (res < 0)

> +               dev_alert(&poweroff_restart_client->dev,
> +                         "Failed to power off (err = %d)\n", res);

alert? This needs to be explained.

> +       /*
> +        * The time from the register write until the host CPU is powered off
> +        * has been observed to be about 2.5 to 3 seconds. Sleep long enough to
> +        * safely avoid returning from the poweroff handler.
> +        */
> +       msleep(5000);
> +}
> +
> +static int ntxec_restart(struct notifier_block *nb,
> +                        unsigned long action, void *data)
> +{
> +       int res;
> +       /*
> +        * NOTE: The lower half of the reset value is not sent, because sending
> +        * it causes an error

Why? Any root cause? Perhaps you need to send 0xffff ?

> +        */
> +       u8 buf[] = {
> +               NTXEC_REG_RESET,

> +               (NTXEC_RESET_VALUE >> 8) & 0xff,

Here you may still use put_unaligned_be16() but move the comment to be
before len hardcoded to sizeof(buf) - 1.

> +       };
> +       struct i2c_msg msgs[] = {
> +               {
> +                       .addr = poweroff_restart_client->addr,
> +                       .flags = 0,
> +                       .len = sizeof(buf),
> +                       .buf = buf
> +               }
> +       };
> +
> +       res = i2c_transfer(poweroff_restart_client->adapter, msgs, ARRAY_SIZE(msgs));
> +       if (res < 0)
> +               dev_alert(&poweroff_restart_client->dev,
> +                         "Failed to restart (err = %d)\n", res);
> +
> +       return NOTIFY_DONE;
> +}

...

> +static int ntxec_probe(struct i2c_client *client)
> +{
> +       struct ntxec *ec;
> +       unsigned int version;
> +       int res;
> +
> +       ec = devm_kmalloc(&client->dev, sizeof(*ec), GFP_KERNEL);
> +       if (!ec)
> +               return -ENOMEM;
> +
> +       ec->dev = &client->dev;
> +
> +       ec->regmap = devm_regmap_init_i2c(client, &regmap_config);
> +       if (IS_ERR(ec->regmap)) {
> +               dev_err(ec->dev, "Failed to set up regmap for device\n");
> +               return res;
> +       }
> +
> +       /* Determine the firmware version */
> +       res = regmap_read(ec->regmap, NTXEC_REG_VERSION, &version);
> +       if (res < 0) {
> +               dev_err(ec->dev, "Failed to read firmware version number\n");
> +               return res;
> +       }

> +       dev_info(ec->dev,
> +                "Netronix embedded controller version %04x detected.\n",
> +                version);

This info level may confuse users if followed by an error path.

> +       /* Bail out if we encounter an unknown firmware version */
> +       switch (version) {
> +       case 0xd726: /* found in Kobo Aura */
> +               break;
> +       default:
> +               return -ENODEV;
> +       }
> +
> +       if (of_device_is_system_power_controller(ec->dev->of_node)) {
> +               /*
> +                * Set the 'powerkeep' bit. This is necessary on some boards
> +                * in order to keep the system running.
> +                */
> +               res = regmap_write(ec->regmap, NTXEC_REG_POWERKEEP,
> +                                  NTXEC_POWERKEEP_VALUE);
> +               if (res < 0)
> +                       return res;

> +               WARN_ON(poweroff_restart_client);

WARN_ON? All these alerts, WARNs, BUGs must be explained. Screaming to
the user is not good if it wasn't justified.

> +               poweroff_restart_client = client;
> +               if (pm_power_off)
> +                       dev_err(ec->dev, "pm_power_off already assigned\n");
> +               else
> +                       pm_power_off = ntxec_poweroff;
> +
> +               res = register_restart_handler(&ntxec_restart_handler);
> +               if (res)
> +                       dev_err(ec->dev,
> +                               "Failed to register restart handler: %d\n", res);
> +       }
> +
> +       i2c_set_clientdata(client, ec);
> +
> +       res = devm_mfd_add_devices(ec->dev, PLATFORM_DEVID_NONE, ntxec_subdevices,
> +                                  ARRAY_SIZE(ntxec_subdevices), NULL, 0, NULL);
> +       if (res)

> +               dev_warn(ec->dev, "Failed to add subdevices: %d\n", res);

'warn' is inconsistent with 'return err'. Either do not return an
error, or mark a message as an error one.

And above with the restart handler has the same issue.

> +       return res;
> +}
> +
> +static int ntxec_remove(struct i2c_client *client)
> +{

> +       if (client == poweroff_restart_client) {

When it's not the case?

> +               poweroff_restart_client = NULL;
> +               pm_power_off = NULL;
> +               unregister_restart_handler(&ntxec_restart_handler);
> +       }
> +
> +       return 0;
> +}

...

> +#include <linux/types.h>
> +

Missed

struct device;
struct regmap;

here.

> +struct ntxec {
> +       struct device *dev;
> +       struct regmap *regmap;
> +};

> +/*
> + * Some registers, such as the battery status register (0x41), are in
> + * big-endian, but others only have eight significant bits, which are in the
> + * first byte transmitted over I2C (the MSB of the big-endian value).
> + * This convenience function converts an 8-bit value to 16-bit for use in the
> + * second kind of register.
> + */
> +static inline u16 ntxec_reg8(u8 value)
> +{
> +       return value << 8;
> +}

I'm wondering why __be16 is not used as returned type.
Jonathan Neuschäfer Sept. 25, 2020, 9:32 p.m. UTC | #2
On Fri, Sep 25, 2020 at 12:29:45PM +0300, Andy Shevchenko wrote:
> On Thu, Sep 24, 2020 at 10:26 PM Jonathan Neuschäfer
> <j.neuschaefer@gmx.net> wrote:
> >
> > The Netronix embedded controller is a microcontroller found in some
> > e-book readers designed by the ODM Netronix, Inc. It contains RTC,
> > battery monitoring, system power management, and PWM functionality.
> >
> > This driver implements register access and version detection.
> >
> > Third-party hardware documentation is available at:
> >
> >   https://github.com/neuschaefer/linux/wiki/Netronix-MSP430-embedded-controller
> >
> > The EC supports interrupts, but the driver doesn't make use of them so
> > far.
> 
> ...
> 
> > +#include <asm/unaligned.h>
> 
> This usually goes after linux/*.h
> (and actually not visible how it's being used, but see below first)

I think it was a leftover from v1 before I used regmap for general
access to the registers. Will fix the ordering.

> > +#include <linux/delay.h>
> > +#include <linux/errno.h>
> > +#include <linux/i2c.h>
> > +#include <linux/mfd/core.h>
> > +#include <linux/mfd/ntxec.h>
> > +#include <linux/module.h>
> > +#include <linux/pm.h>
> > +#include <linux/reboot.h>
> > +#include <linux/regmap.h>
> > +#include <linux/types.h>
> 
> ...
> 
> > +static void ntxec_poweroff(void)
> > +{
> > +       int res;
> > +       u8 buf[] = {
> > +               NTXEC_REG_POWEROFF,
> 
> > +               (NTXEC_POWEROFF_VALUE >> 8) & 0xff,
> > +               NTXEC_POWEROFF_VALUE & 0xff,
> 
> '& 0xff' parts are redundant. *u8 implies that. Fix in all cases.
> Also I would rather see something like
> 
>   buf[0] = _POWEROFF;
>   put_unaligned_be16(_VALUE, &buf[1]);
> 
> to explicitly show the endianess of the register values.

Good idea.

> > +       };
> > +       struct i2c_msg msgs[] = {
> > +               {
> > +                       .addr = poweroff_restart_client->addr,
> > +                       .flags = 0,
> > +                       .len = sizeof(buf),
> 
> > +                       .buf = buf
> 
> It's slightly better to keep trailing commas in cases like this.

Ok.

> 
> > +               }
> > +       };
> > +
> > +       res = i2c_transfer(poweroff_restart_client->adapter, msgs, ARRAY_SIZE(msgs));
> > +       if (res < 0)
> 
> > +               dev_alert(&poweroff_restart_client->dev,
> > +                         "Failed to power off (err = %d)\n", res);
> 
> alert? This needs to be explained.

I copied the dev_alert from drivers/mfd/rn5t618.c.

Upon reconsideration, I'm not sure what the correct log level would be,
but _warn seems enough, or maybe _err is better

> > +       /*
> > +        * The time from the register write until the host CPU is powered off
> > +        * has been observed to be about 2.5 to 3 seconds. Sleep long enough to
> > +        * safely avoid returning from the poweroff handler.
> > +        */
> > +       msleep(5000);
> > +}
> > +
> > +static int ntxec_restart(struct notifier_block *nb,
> > +                        unsigned long action, void *data)
> > +{
> > +       int res;
> > +       /*
> > +        * NOTE: The lower half of the reset value is not sent, because sending
> > +        * it causes an error
> 
> Why? Any root cause? Perhaps you need to send 0xffff ?

Unknown, because I don't have the EC firmware for analysis. The vendor
kernel sends 0xff00 and gets an error.

Sending 0xffff doesn't help.

> > +        */
> > +       u8 buf[] = {
> > +               NTXEC_REG_RESET,
> 
> > +               (NTXEC_RESET_VALUE >> 8) & 0xff,
> 
> Here you may still use put_unaligned_be16() but move the comment to be
> before len hardcoded to sizeof(buf) - 1.

Okay, will do.

> 
> > +       };
> > +       struct i2c_msg msgs[] = {
> > +               {
> > +                       .addr = poweroff_restart_client->addr,
> > +                       .flags = 0,
> > +                       .len = sizeof(buf),
> > +                       .buf = buf
> > +               }
> > +       };
> > +
> > +       res = i2c_transfer(poweroff_restart_client->adapter, msgs, ARRAY_SIZE(msgs));
> > +       if (res < 0)
> > +               dev_alert(&poweroff_restart_client->dev,
> > +                         "Failed to restart (err = %d)\n", res);
> > +
> > +       return NOTIFY_DONE;
> > +}
> 
> ...

An error in the i2c transfer here is an abnormal situation that should
in my opinion be logged, but I don't see what else the code can do here
to handle the error.

> 
> > +static int ntxec_probe(struct i2c_client *client)
> > +{
> > +       struct ntxec *ec;
> > +       unsigned int version;
> > +       int res;
> > +
> > +       ec = devm_kmalloc(&client->dev, sizeof(*ec), GFP_KERNEL);
> > +       if (!ec)
> > +               return -ENOMEM;
> > +
> > +       ec->dev = &client->dev;
> > +
> > +       ec->regmap = devm_regmap_init_i2c(client, &regmap_config);
> > +       if (IS_ERR(ec->regmap)) {
> > +               dev_err(ec->dev, "Failed to set up regmap for device\n");
> > +               return res;
> > +       }
> > +
> > +       /* Determine the firmware version */
> > +       res = regmap_read(ec->regmap, NTXEC_REG_VERSION, &version);
> > +       if (res < 0) {
> > +               dev_err(ec->dev, "Failed to read firmware version number\n");
> > +               return res;
> > +       }
> 
> > +       dev_info(ec->dev,
> > +                "Netronix embedded controller version %04x detected.\n",
> > +                version);
> 
> This info level may confuse users if followed by an error path.

Right. I suppose printing incompatible versions is still useful, so how
about something like the following?


       /* Bail out if we encounter an unknown firmware version */
       switch (version) {
       case 0xd726: /* found in Kobo Aura */
	       dev_info(ec->dev,
			"Netronix embedded controller version %04x detected.\n",
			version);
               break;
       default:
	       dev_err(ec->dev,
			"Netronix embedded controller version %04x is not supported.\n",
			version);
               return -ENODEV;
       }

> > +
> > +       if (of_device_is_system_power_controller(ec->dev->of_node)) {
> > +               /*
> > +                * Set the 'powerkeep' bit. This is necessary on some boards
> > +                * in order to keep the system running.
> > +                */
> > +               res = regmap_write(ec->regmap, NTXEC_REG_POWERKEEP,
> > +                                  NTXEC_POWERKEEP_VALUE);
> > +               if (res < 0)
> > +                       return res;
> 
> > +               WARN_ON(poweroff_restart_client);
> 
> WARN_ON? All these alerts, WARNs, BUGs must be explained. Screaming to
> the user is not good if it wasn't justified.

poweroff_restart_client being already set is not a situation that should
happen (and would indicate a bug in this driver, AFAICT), but I guess
the log message could be better in that case...

> > +               poweroff_restart_client = client;
> > +               if (pm_power_off)
> > +                       dev_err(ec->dev, "pm_power_off already assigned\n");
> > +               else
> > +                       pm_power_off = ntxec_poweroff;
> > +
> > +               res = register_restart_handler(&ntxec_restart_handler);
> > +               if (res)
> > +                       dev_err(ec->dev,
> > +                               "Failed to register restart handler: %d\n", res);
> > +       }
> > +
> > +       i2c_set_clientdata(client, ec);
> > +
> > +       res = devm_mfd_add_devices(ec->dev, PLATFORM_DEVID_NONE, ntxec_subdevices,
> > +                                  ARRAY_SIZE(ntxec_subdevices), NULL, 0, NULL);
> > +       if (res)
> 
> > +               dev_warn(ec->dev, "Failed to add subdevices: %d\n", res);
> 
> 'warn' is inconsistent with 'return err'. Either do not return an
> error, or mark a message as an error one.

Okay, I'll change it to dev_err.

> 
> And above with the restart handler has the same issue.
> 
> > +       return res;
> > +}
> > +
> > +static int ntxec_remove(struct i2c_client *client)
> > +{
> 
> > +       if (client == poweroff_restart_client) {
> 
> When it's not the case?

The EC doesn't always need to provide poweroff/restart functionality,
and AFAIK, in some systems it doesn't. In those systems, ntxec_remove
would run with poweroff_restart_client == NULL.

In theory, there might also be two of it in the same system, of which
only one controls system poweroff/restart, but I'm not sure if that is
actually the case on any existing board design.

> > +               poweroff_restart_client = NULL;
> > +               pm_power_off = NULL;
> > +               unregister_restart_handler(&ntxec_restart_handler);
> > +       }
> > +
> > +       return 0;
> > +}
> 
> ...
> 
> > +#include <linux/types.h>
> > +
> 
> Missed
> 
> struct device;
> struct regmap;
> 
> here.

I'll add them.

> > +struct ntxec {
> > +       struct device *dev;
> > +       struct regmap *regmap;
> > +};
> 
> > +/*
> > + * Some registers, such as the battery status register (0x41), are in
> > + * big-endian, but others only have eight significant bits, which are in the
> > + * first byte transmitted over I2C (the MSB of the big-endian value).
> > + * This convenience function converts an 8-bit value to 16-bit for use in the
> > + * second kind of register.
> > + */
> > +static inline u16 ntxec_reg8(u8 value)
> > +{
> > +       return value << 8;
> > +}
> 
> I'm wondering why __be16 is not used as returned type.

I didn't think of it, but it's a good idea. Will do.


Thanks,
Jonathan Neuschäfer
Andy Shevchenko Sept. 29, 2020, 4:37 p.m. UTC | #3
On Sat, Sep 26, 2020 at 12:32 AM Jonathan Neuschäfer
<j.neuschaefer@gmx.net> wrote:
> On Fri, Sep 25, 2020 at 12:29:45PM +0300, Andy Shevchenko wrote:
> > On Thu, Sep 24, 2020 at 10:26 PM Jonathan Neuschäfer
> > <j.neuschaefer@gmx.net> wrote:

...

> > > +               dev_alert(&poweroff_restart_client->dev,
> > > +                         "Failed to power off (err = %d)\n", res);
> >
> > alert? This needs to be explained.
>
> I copied the dev_alert from drivers/mfd/rn5t618.c.
>
> Upon reconsideration, I'm not sure what the correct log level would be,
> but _warn seems enough, or maybe _err is better

It's up to you to decide, but crit/alert and similar has to be
justified (commit message / comment in the code).

...

> > > +       /*
> > > +        * NOTE: The lower half of the reset value is not sent, because sending
> > > +        * it causes an error
> >
> > Why? Any root cause? Perhaps you need to send 0xffff ?
>
> Unknown, because I don't have the EC firmware for analysis. The vendor
> kernel sends 0xff00 and gets an error.
>
> Sending 0xffff doesn't help.

Maybe a slightly elaborated comment that it's copied from the vendor
kernel (which is?).

> > > +        */

...

> > > +       dev_info(ec->dev,
> > > +                "Netronix embedded controller version %04x detected.\n",
> > > +                version);
> >
> > This info level may confuse users if followed by an error path.
>
> Right. I suppose printing incompatible versions is still useful, so how
> about something like the following?
>
>
>        /* Bail out if we encounter an unknown firmware version */
>        switch (version) {
>        case 0xd726: /* found in Kobo Aura */
>                dev_info(ec->dev,
>                         "Netronix embedded controller version %04x detected.\n",
>                         version);
>                break;
>        default:
>                dev_err(ec->dev,
>                         "Netronix embedded controller version %04x is not supported.\n",
>                         version);
>                return -ENODEV;
>        }

This is better.

...

> > > +               WARN_ON(poweroff_restart_client);
> >
> > WARN_ON? All these alerts, WARNs, BUGs must be explained. Screaming to
> > the user is not good if it wasn't justified.
>
> poweroff_restart_client being already set is not a situation that should
> happen (and would indicate a bug in this driver, AFAICT), but I guess
> the log message could be better in that case...

As per above.
Jonathan Neuschäfer Oct. 2, 2020, 10:54 p.m. UTC | #4
On Tue, Sep 29, 2020 at 07:37:21PM +0300, Andy Shevchenko wrote:
> On Sat, Sep 26, 2020 at 12:32 AM Jonathan Neuschäfer
> <j.neuschaefer@gmx.net> wrote:
> > On Fri, Sep 25, 2020 at 12:29:45PM +0300, Andy Shevchenko wrote:
> > > On Thu, Sep 24, 2020 at 10:26 PM Jonathan Neuschäfer
> > > <j.neuschaefer@gmx.net> wrote:
> 
> ...
> 
> > > > +               dev_alert(&poweroff_restart_client->dev,
> > > > +                         "Failed to power off (err = %d)\n", res);
> > >
> > > alert? This needs to be explained.
> >
> > I copied the dev_alert from drivers/mfd/rn5t618.c.
> >
> > Upon reconsideration, I'm not sure what the correct log level would be,
> > but _warn seems enough, or maybe _err is better
> 
> It's up to you to decide, but crit/alert and similar has to be
> justified (commit message / comment in the code).

Alright, thanks for explaining.

> > > > +       /*
> > > > +        * NOTE: The lower half of the reset value is not sent, because sending
> > > > +        * it causes an error
> > >
> > > Why? Any root cause? Perhaps you need to send 0xffff ?
> >
> > Unknown, because I don't have the EC firmware for analysis. The vendor
> > kernel sends 0xff00 and gets an error.
> >
> > Sending 0xffff doesn't help.
> 
> Maybe a slightly elaborated comment that it's copied from the vendor
> kernel (which is?).

Good idea, I'll do that.

> ...
> 
> > > > +       dev_info(ec->dev,
> > > > +                "Netronix embedded controller version %04x detected.\n",
> > > > +                version);
> > >
> > > This info level may confuse users if followed by an error path.
> >
> > Right. I suppose printing incompatible versions is still useful, so how
> > about something like the following?
> >
> >
> >        /* Bail out if we encounter an unknown firmware version */
> >        switch (version) {
> >        case 0xd726: /* found in Kobo Aura */
> >                dev_info(ec->dev,
> >                         "Netronix embedded controller version %04x detected.\n",
> >                         version);
> >                break;
> >        default:
> >                dev_err(ec->dev,
> >                         "Netronix embedded controller version %04x is not supported.\n",
> >                         version);
> >                return -ENODEV;
> >        }
> 
> This is better.
> 
> ...
> 
> > > > +               WARN_ON(poweroff_restart_client);
> > >
> > > WARN_ON? All these alerts, WARNs, BUGs must be explained. Screaming to
> > > the user is not good if it wasn't justified.
> >
> > poweroff_restart_client being already set is not a situation that should
> > happen (and would indicate a bug in this driver, AFAICT), but I guess
> > the log message could be better in that case...
> 
> As per above.

Okay, I'll rework the dev_alert/WARN_ON parts.



Thanks,
Jonathan Neuschäfer
diff mbox series

Patch

diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 33df0837ab415..b313103151508 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -978,6 +978,16 @@  config MFD_VIPERBOARD
 	  You need to select the mfd cell drivers separately.
 	  The drivers do not support all features the board exposes.

+config MFD_NTXEC
+	tristate "Netronix embedded controller (EC)"
+	depends on OF || COMPILE_TEST
+	depends on I2C
+	select REGMAP_I2C
+	select MFD_CORE
+	help
+	  Say yes here if you want to support the embedded controller found in
+	  certain e-book readers designed by the ODM Netronix.
+
 config MFD_RETU
 	tristate "Nokia Retu and Tahvo multi-function device"
 	select MFD_CORE
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index a60e5f835283e..236a8acd917a0 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -217,6 +217,7 @@  obj-$(CONFIG_MFD_INTEL_MSIC)	+= intel_msic.o
 obj-$(CONFIG_MFD_INTEL_PMC_BXT)	+= intel_pmc_bxt.o
 obj-$(CONFIG_MFD_PALMAS)	+= palmas.o
 obj-$(CONFIG_MFD_VIPERBOARD)    += viperboard.o
+obj-$(CONFIG_MFD_NTXEC)		+= ntxec.o
 obj-$(CONFIG_MFD_RC5T583)	+= rc5t583.o rc5t583-irq.o
 obj-$(CONFIG_MFD_RK808)		+= rk808.o
 obj-$(CONFIG_MFD_RN5T618)	+= rn5t618.o
diff --git a/drivers/mfd/ntxec.c b/drivers/mfd/ntxec.c
new file mode 100644
index 0000000000000..93611b85a32e0
--- /dev/null
+++ b/drivers/mfd/ntxec.c
@@ -0,0 +1,206 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * The Netronix embedded controller is a microcontroller found in some
+ * e-book readers designed by the ODM Netronix, Inc. It contains RTC,
+ * battery monitoring, system power management, and PWM functionality.
+ *
+ * This driver implements register access, version detection, and system
+ * power-off/reset.
+ *
+ * Copyright 2020 Jonathan Neuschäfer <j.neuschaefer@gmx.net>
+ */
+
+#include <asm/unaligned.h>
+#include <linux/delay.h>
+#include <linux/errno.h>
+#include <linux/i2c.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/ntxec.h>
+#include <linux/module.h>
+#include <linux/pm.h>
+#include <linux/reboot.h>
+#include <linux/regmap.h>
+#include <linux/types.h>
+
+#define NTXEC_REG_VERSION	0x00
+#define NTXEC_REG_POWEROFF	0x50
+#define NTXEC_REG_POWERKEEP	0x70
+#define NTXEC_REG_RESET		0x90
+
+#define NTXEC_POWEROFF_VALUE	0x0100
+#define NTXEC_POWERKEEP_VALUE	0x0800
+#define NTXEC_RESET_VALUE	0xff00
+
+static struct i2c_client *poweroff_restart_client;
+
+static void ntxec_poweroff(void)
+{
+	int res;
+	u8 buf[] = {
+		NTXEC_REG_POWEROFF,
+		(NTXEC_POWEROFF_VALUE >> 8) & 0xff,
+		NTXEC_POWEROFF_VALUE & 0xff,
+	};
+	struct i2c_msg msgs[] = {
+		{
+			.addr = poweroff_restart_client->addr,
+			.flags = 0,
+			.len = sizeof(buf),
+			.buf = buf
+		}
+	};
+
+	res = i2c_transfer(poweroff_restart_client->adapter, msgs, ARRAY_SIZE(msgs));
+	if (res < 0)
+		dev_alert(&poweroff_restart_client->dev,
+			  "Failed to power off (err = %d)\n", res);
+
+	/*
+	 * The time from the register write until the host CPU is powered off
+	 * has been observed to be about 2.5 to 3 seconds. Sleep long enough to
+	 * safely avoid returning from the poweroff handler.
+	 */
+	msleep(5000);
+}
+
+static int ntxec_restart(struct notifier_block *nb,
+			 unsigned long action, void *data)
+{
+	int res;
+	/*
+	 * NOTE: The lower half of the reset value is not sent, because sending
+	 * it causes an error
+	 */
+	u8 buf[] = {
+		NTXEC_REG_RESET,
+		(NTXEC_RESET_VALUE >> 8) & 0xff,
+	};
+	struct i2c_msg msgs[] = {
+		{
+			.addr = poweroff_restart_client->addr,
+			.flags = 0,
+			.len = sizeof(buf),
+			.buf = buf
+		}
+	};
+
+	res = i2c_transfer(poweroff_restart_client->adapter, msgs, ARRAY_SIZE(msgs));
+	if (res < 0)
+		dev_alert(&poweroff_restart_client->dev,
+			  "Failed to restart (err = %d)\n", res);
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block ntxec_restart_handler = {
+	.notifier_call = ntxec_restart,
+	.priority = 128
+};
+
+static const struct regmap_config regmap_config = {
+	.name = "ntxec",
+	.reg_bits = 8,
+	.val_bits = 16,
+	.cache_type = REGCACHE_NONE,
+	.val_format_endian = REGMAP_ENDIAN_BIG,
+};
+
+static const struct mfd_cell ntxec_subdevices[] = {
+	{ .name = "ntxec-rtc" },
+	{ .name = "ntxec-pwm" },
+};
+
+static int ntxec_probe(struct i2c_client *client)
+{
+	struct ntxec *ec;
+	unsigned int version;
+	int res;
+
+	ec = devm_kmalloc(&client->dev, sizeof(*ec), GFP_KERNEL);
+	if (!ec)
+		return -ENOMEM;
+
+	ec->dev = &client->dev;
+
+	ec->regmap = devm_regmap_init_i2c(client, &regmap_config);
+	if (IS_ERR(ec->regmap)) {
+		dev_err(ec->dev, "Failed to set up regmap for device\n");
+		return res;
+	}
+
+	/* Determine the firmware version */
+	res = regmap_read(ec->regmap, NTXEC_REG_VERSION, &version);
+	if (res < 0) {
+		dev_err(ec->dev, "Failed to read firmware version number\n");
+		return res;
+	}
+	dev_info(ec->dev,
+		 "Netronix embedded controller version %04x detected.\n",
+		 version);
+
+	/* Bail out if we encounter an unknown firmware version */
+	switch (version) {
+	case 0xd726: /* found in Kobo Aura */
+		break;
+	default:
+		return -ENODEV;
+	}
+
+	if (of_device_is_system_power_controller(ec->dev->of_node)) {
+		/*
+		 * Set the 'powerkeep' bit. This is necessary on some boards
+		 * in order to keep the system running.
+		 */
+		res = regmap_write(ec->regmap, NTXEC_REG_POWERKEEP,
+				   NTXEC_POWERKEEP_VALUE);
+		if (res < 0)
+			return res;
+
+		WARN_ON(poweroff_restart_client);
+		poweroff_restart_client = client;
+		if (pm_power_off)
+			dev_err(ec->dev, "pm_power_off already assigned\n");
+		else
+			pm_power_off = ntxec_poweroff;
+
+		res = register_restart_handler(&ntxec_restart_handler);
+		if (res)
+			dev_err(ec->dev,
+				"Failed to register restart handler: %d\n", res);
+	}
+
+	i2c_set_clientdata(client, ec);
+
+	res = devm_mfd_add_devices(ec->dev, PLATFORM_DEVID_NONE, ntxec_subdevices,
+				   ARRAY_SIZE(ntxec_subdevices), NULL, 0, NULL);
+	if (res)
+		dev_warn(ec->dev, "Failed to add subdevices: %d\n", res);
+
+	return res;
+}
+
+static int ntxec_remove(struct i2c_client *client)
+{
+	if (client == poweroff_restart_client) {
+		poweroff_restart_client = NULL;
+		pm_power_off = NULL;
+		unregister_restart_handler(&ntxec_restart_handler);
+	}
+
+	return 0;
+}
+
+static const struct of_device_id of_ntxec_match_table[] = {
+	{ .compatible = "netronix,ntxec", },
+	{}
+};
+
+static struct i2c_driver ntxec_driver = {
+	.driver = {
+		.name = "ntxec",
+		.of_match_table = of_ntxec_match_table,
+	},
+	.probe_new = ntxec_probe,
+	.remove = ntxec_remove,
+};
+module_i2c_driver(ntxec_driver);
diff --git a/include/linux/mfd/ntxec.h b/include/linux/mfd/ntxec.h
new file mode 100644
index 0000000000000..a39c85978f61b
--- /dev/null
+++ b/include/linux/mfd/ntxec.h
@@ -0,0 +1,31 @@ 
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright 2020 Jonathan Neuschäfer
+ *
+ * Register access and version information for the Netronix embedded
+ * controller.
+ */
+
+#ifndef NTXEC_H
+#define NTXEC_H
+
+#include <linux/types.h>
+
+struct ntxec {
+	struct device *dev;
+	struct regmap *regmap;
+};
+
+/*
+ * Some registers, such as the battery status register (0x41), are in
+ * big-endian, but others only have eight significant bits, which are in the
+ * first byte transmitted over I2C (the MSB of the big-endian value).
+ * This convenience function converts an 8-bit value to 16-bit for use in the
+ * second kind of register.
+ */
+static inline u16 ntxec_reg8(u8 value)
+{
+	return value << 8;
+}
+
+#endif