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  1. 05 Nov, 2017 3 commits
  3. 01 Nov, 2017 7 commits
  5. 30 Oct, 2017 8 commits
    • Claudio Foellmi's avatar
      i2c: omap: Trigger bus recovery in lockup case · 93367bfc
      Claudio Foellmi authored 
      A very conservative check for bus activity (to prevent interference
in multimaster setups) prevented the bus recovery methods from being
triggered in the case that SDA or SCL was stuck low.
This defeats the purpose of the recovery mechanism, which was introduced
for exactly this situation (a slave device keeping SDA pulled down).

Also added a check to make sure SDA is low before attempting recovery.
If SDA is not stuck low, recovery will not help, so we can skip it.

Note that bus lockups can persist across reboots. The only other options
are to reset or power cycle the offending slave device, and many i2c
slaves do not even have a reset pin.

If we see that one of the lines is low for the entire timeout duration,
we can actually be sure that there is no other master driving the bus.
It is therefore save for us to attempt a bus recovery.
Signed-off-by: default avatarClaudio Foellmi <claudio.foellmi@ergon.ch>
Tested-by: default avatarVignesh R <vigneshr@ti.com>
Reviewed-by: default avatarGrygorii Strashko <grygorii.strashko@ti.com>
[wsa: fixed one return code to -EBUSY]
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
      93367bfc
    • Linus Walleij's avatar
      i2c: gpio: Add support for named gpios in DT · 05c74778
      Linus Walleij authored 
      This adds support for using the "sda" and "scl" GPIOs in
device tree instead of anonymously using index 0 and 1 of
the "gpios" property.

We add a helper function to retrieve the GPIO descriptors
and some explicit error handling since the probe may have
to be deferred. At least this happened to me when moving
to using named "sda" and "scl" lines (all of a sudden this
started to probe before the GPIO driver) so we need to
gracefully defer probe when we ge -ENOENT in the error
pointer.
Suggested-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Tested-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
      05c74778
    • Geert Uytterhoeven's avatar
      dt-bindings: i2c: i2c-gpio: Add support for named gpios · 7d29f509
      Geert Uytterhoeven authored 
      The current i2c-gpio DT bindings use a single unnamed "gpios" property
to refer to the SDA and SCL signal lines by index.  This is error-prone
for the casual DT writer and reviewer, as one has to look up the order
in the DT bindings.

Fix this by amending the DT bindings to use two separate named gpios
properties, and deprecate the old unnamed variant.

Take this opportunity to clearly deprecate the "i2c-gpio,sda-open-drain"
and "i2c-gpio,scl-open-drain" flags as well. The commit describes
in detail what these flags actually mean, and why they should not be
used in new device trees.

Cc: devicetree@vger.kernel.org
Signed-off-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
[Augmented to what I and Rob would like]
Tested-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Acked-by: default avatarRob Herring <robh@kernel.org>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
      7d29f509
    • Linus Walleij's avatar
      i2c: gpio: Local vars in probe · b9ab0517
      Linus Walleij authored 
      By creating local variables for *dev and *np, the code become
much easier to read, in my opinion.
Tested-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
      b9ab0517
    • Linus Walleij's avatar
      i2c: gpio: Augment all boardfiles to use open drain · 4d0ce62c
      Linus Walleij authored 
      We now handle the open drain mode internally in the I2C GPIO
driver, but we will get warnings from the gpiolib that we
override the default mode of the line so it becomes open
drain.

We can fix all in-kernel users by simply passing the right
flag along in the descriptor table, and we already touched
all of these files in the series so let's just tidy it up.

Cc: Steven Miao <realmz6@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Acked-by: default avatarOlof Johansson <olof@lixom.net>
Acked-by: default avatarLee Jones <lee.jones@linaro.org>
Acked-by: default avatarRobert Jarzmik <robert.jarzmik@free.fr>
Acked-by: default avatarRalf Baechle <ralf@linux-mips.org>
Acked-by: default avatarWu, Aaron <Aaron.Wu@analog.com>
Acked-by: default avatarArnd Bergmann <arnd@arndb.de>
Tested-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
      4d0ce62c
    • Linus Walleij's avatar
      i2c: gpio: Enforce open drain through gpiolib · 7bb75029
      Linus Walleij authored 
      The I2C GPIO bitbang driver currently emulates open drain
behaviour by implementing what the gpiolib already does:
not actively driving the line high, instead setting it to
input.

This makes no sense. Use the new facility in gpiolib to
request the lines enforced into open drain mode, and let
the open drain emulation already present in the gpiolib
kick in and handle this.

As a bonus: if the GPIO driver in the back-end actually
supports open drain in hardware using the .set_config()
callback, it will be utilized. That's correct: we never
used that hardware feature before, instead relying on
emulating open drain even if the GPIO controller could
actually handle this for us.

Users will sometimes get messages like this:
gpio-485 (?): enforced open drain please flag it properly
  in DT/ACPI DSDT/board file
gpio-486 (?): enforced open drain please flag it properly
  in DT/ACPI DSDT/board file
i2c-gpio gpio-i2c: using lines 485 (SDA) and 486 (SCL)

Which is completely proper: since the line is used as
open drain, it should actually be flagged properly with
e.g.

gpios = <&gpio0 5 (GPIO_ACTIVE_HIGH|GPIO_OPEN_DRAIN)>,
        <&gpio0 6 (GPIO_ACTIVE_HIGH|GPIO_OPEN_DRAIN)>;

Or similar facilities in board file descriptor tables
or ACPI DSDT.
Tested-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
      7bb75029
    • Linus Walleij's avatar
      gpio: Make it possible for consumers to enforce open drain · f926dfc1
      Linus Walleij authored 
      Some busses, like I2C, strictly need to have the line handled
as open drain, i.e. not actively driven high. For this reason
the i2c-gpio.c bit-banged I2C driver is reimplementing open
drain handling outside of gpiolib.

This is not very optimal. Instead make it possible for a
consumer to explcitly express that the line must be handled
as open drain instead of allowing local hacks papering over
this issue.

The descriptor tables, whether DT, ACPI or board files, should
of course have flagged these lines as open drain. E.g.:
enum gpio_lookup_flags GPIO_OPEN_DRAIN for a board file, or
gpios = <&foo 42 GPIO_ACTIVE_HIGH|GPIO_OPEN_DRAIN>; in a
device tree using <dt-bindings/gpio/gpio.h>

But more often than not, these descriptors are wrong. So
we need to make it possible for consumers to enforce this
open drain behaviour.

We now have two new enumerated GPIO descriptor config flags:
GPIOD_OUT_LOW_OPEN_DRAIN and GPIOD_OUT_HIGH_OPEN_DRAIN
that will set up the lined enforced as open drain as output
low or high, using open drain (if the driver supports it)
or using open drain emulation (setting the line as input
to drive it high) from the gpiolib core.

Cc: linux-gpio@vger.kernel.org
Tested-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
      f926dfc1
    • Linus Walleij's avatar
      i2c: gpio: Convert to use descriptors · b2e63555
      Linus Walleij authored 
      This converts the GPIO-based I2C-driver to using GPIO
descriptors instead of the old global numberspace-based
GPIO interface. We:

- Convert the driver to unconditionally grab two GPIOs
  from the device by index 0 (SDA) and 1 (SCL) which
  will work fine with device tree and descriptor tables.
  The existing device trees will continue to work just
  like before, but without any roundtrip through the
  global numberspace.

- Brutally convert all boardfiles still passing global
  GPIOs by registering descriptor tables associated with
  the devices instead so this driver does not need to keep
  supporting passing any GPIO numbers as platform data.

There is no stepwise approach as elegant as this, I
strongly prefer this big hammer over any antsteps for this
conversion. This way the old GPIO numbers go away and
NEVER COME BACK.

Special conversion for the different boards utilizing
I2C-GPIO:

- EP93xx (arch/arm/mach-ep93xx): pretty straight forward as
  all boards were using the same two GPIO lines, just define
  these two in a lookup table for "i2c-gpio" and register
  these along with the device. None of them define any
  other platform data so just pass NULL as platform data.
  This platform selects GPIOLIB so all should be smooth.
  The pins appear on a gpiochip for bank "G" as pins 1 (SDA)
  and 0 (SCL).

- IXP4 (arch/arm/mach-ixp4): descriptor tables have to
  be registered for each board separately. They all use
  "IXP4XX_GPIO_CHIP" so it is pretty straight forward.
  Most board define no other platform data than SCL/SDA
  so they can drop the #include of <linux/i2c-gpio.h> and
  assign NULL to platform data.

  The "goramo_mlr" (Goramo Multilink Router) board is a bit
  worrisome: it implements its own I2C bit-banging in the
  board file, and optionally registers an I2C serial port,
  but claims the same GPIO lines for itself in the board file.
  This is not going to work: there will be competition for the
  GPIO lines, so delete the optional extra I2C bus instead, no
  I2C devices are registered on it anyway, there are just hints
  that it may contain an EEPROM that may be accessed from
  userspace. This needs to be fixed up properly by the serial
  clock using I2C emulation so drop a note in the code.

- KS8695 board acs5k (arch/arm/mach-ks8695/board-acs5.c)
  has some platform data in addition to the pins so it needs to
  be kept around sans GPIO lines. Its GPIO chip is named
  "KS8695" and the arch selects GPIOLIB.

- PXA boards (arch/arm/mach-pxa/*) use some of the platform
  data so it needs to be preserved here. The viper board even
  registers two GPIO I2Cs. The gpiochip is named "gpio-pxa" and
  the arch selects GPIOLIB.

- SA1100 Simpad (arch/arm/mach-sa1100/simpad.c) defines a GPIO
  I2C bus, and the arch selects GPIOLIB.

- Blackfin boards (arch/blackfin/bf533 etc) for these I assume
  their I2C GPIOs refer to the local gpiochip defined in
  arch/blackfin/kernel/bfin_gpio.c names "BFIN-GPIO".
  The arch selects GPIOLIB. The boards get spiked with
  IF_ENABLED(I2C_GPIO) but that is a side effect of it
  being like that already (I would just have Kconfig select
  I2C_GPIO and get rid of them all.) I also delete any
  platform data set to 0 as it will get that value anyway
  from static declartions of platform data.

- The MIPS selects GPIOLIB and the Alchemy machine is using
  two local GPIO chips, one of them has a GPIO I2C. We need
  to adjust the local offset from the global number space here.
  The ATH79 has a proper GPIO driver in drivers/gpio/gpio-ath79.c
  and AFAICT the chip is named "ath79-gpio" and the PB44
  PCF857x expander spawns from this on GPIO 1 and 0. The latter
  board only use the platform data to specify pins so it can be
  cut altogether after this.

- The MFD Silicon Motion SM501 is a special case. It dynamically
  spawns an I2C bus off the MFD using sm501_create_subdev().
  We use an approach to dynamically create a machine descriptor
  table and attach this to the "SM501-LOW" or "SM501-HIGH"
  gpiochip. We use chip-local offsets to grab the right lines.
  We can get rid of two local static inline helpers as part
  of this refactoring.

Cc: Steven Miao <realmz6@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Magnus Damm <magnus.damm@gmail.com>
Cc: Ben Dooks <ben.dooks@codethink.co.uk>
Cc: Heiko Schocher <hs@denx.de>
Acked-by: default avatarWu, Aaron <Aaron.Wu@analog.com>
Acked-by: default avatarOlof Johansson <olof@lixom.net>
Acked-by: default avatarLee Jones <lee.jones@linaro.org>
Acked-by: default avatarRalf Baechle <ralf@linux-mips.org>
Tested-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
      b2e63555
  7. 28 Oct, 2017 16 commits
  9. 27 Oct, 2017 6 commits
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