target/linux/brcm2708/patches-4.19/950-0802-regulator-gpio-Allow-nonexclusive-GPIO-access.patch

   1 From f6d983b7bc9ae79d0eb4dea7bc30a1ad5ff428a7 Mon Sep 17 00:00:00 2001
   2 From: Linus Walleij <linus.walleij@linaro.org>
   3 Date: Fri, 12 Oct 2018 14:54:12 +0200
   4 Subject: [PATCH 802/806] regulator/gpio: Allow nonexclusive GPIO access
   5
   6 commit b0ce7b29bfcd090ddba476f45a75ec0a797b048a upstream.
   7
   8 [ This is a partial cherry-pick, omitting the regulator
   9 change which isn't required ]
  10
  11 This allows nonexclusive (simultaneous) access to a single
  12 GPIO line for the fixed regulator enable line. This happens
  13 when several regulators use the same GPIO for enabling and
  14 disabling a regulator, and all need a handle on their GPIO
  15 descriptor.
  16
  17 This solution with a special flag is not entirely elegant
  18 and should ideally be replaced by something more careful as
  19 this makes it possible for several consumers to
  20 enable/disable the same GPIO line to the left and right
  21 without any consistency. The current use inside the regulator
  22 core should however be fine as it takes special care to
  23 handle this.
  24
  25 For the state of the GPIO backend, this is still the
  26 lesser evil compared to going back to global GPIO
  27 numbers.
  28
  29 Cc: Marek Szyprowski <m.szyprowski@samsung.com>
  30 Cc: Jon Hunter <jonathanh@nvidia.com>
  31 Fixes: efdfeb079cc3 ("regulator: fixed: Convert to use GPIO descriptor only")
  32 Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
  33 Tested-by: Jon Hunter <jonathanh@nvidia.com>
  34 Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
  35 Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
  36 Signed-off-by: Mark Brown <broonie@kernel.org>
  37 ---
  38  drivers/gpio/gpiolib.c        | 19 +++++++++++++++++--
  39  include/linux/gpio/consumer.h |  1 +
  40  2 files changed, 18 insertions(+), 2 deletions(-)
  41
  42 --- a/drivers/gpio/gpiolib.c
  43 +++ b/drivers/gpio/gpiolib.c
  44 @@ -3959,8 +3959,23 @@ struct gpio_desc *__must_check gpiod_get
  45          * the device name as label
  46          */
  47         status = gpiod_request(desc, con_id ? con_id : devname);
  48 -       if (status < 0)
  49 -               return ERR_PTR(status);
  50 +       if (status < 0) {
  51 +               if (status == -EBUSY && flags & GPIOD_FLAGS_BIT_NONEXCLUSIVE) {
  52 +                       /*
  53 +                        * This happens when there are several consumers for
  54 +                        * the same GPIO line: we just return here without
  55 +                        * further initialization. It is a bit if a hack.
  56 +                        * This is necessary to support fixed regulators.
  57 +                        *
  58 +                        * FIXME: Make this more sane and safe.
  59 +                        */
  60 +                       dev_info(dev, "nonexclusive access to GPIO for %s\n",
  61 +                                con_id ? con_id : devname);
  62 +                       return desc;
  63 +               } else {
  64 +                       return ERR_PTR(status);
  65 +               }
  66 +       }
  67
  68         status = gpiod_configure_flags(desc, con_id, lookupflags, flags);
  69         if (status < 0) {
  70 --- a/include/linux/gpio/consumer.h
  71 +++ b/include/linux/gpio/consumer.h
  72 @@ -30,6 +30,7 @@ struct gpio_descs {
  73  #define GPIOD_FLAGS_BIT_DIR_OUT                BIT(1)
  74  #define GPIOD_FLAGS_BIT_DIR_VAL                BIT(2)
  75  #define GPIOD_FLAGS_BIT_OPEN_DRAIN     BIT(3)
  76 +#define GPIOD_FLAGS_BIT_NONEXCLUSIVE   BIT(4)
  77
  78  /**
  79   * Optional flags that can be passed to one of gpiod_* to configure direction