1. 30 Oct, 2017 1 commit
    • 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
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