target/linux/generic/pending-5.10/801-gpio-gpio-cascade-add-generic-GPIO-cascade.patch

   1 From fc23ea48ba52c24f201fe5ca0132ee1a3de5a70a Mon Sep 17 00:00:00 2001
   2 From: Mauri Sandberg <maukka@ext.kapsi.fi>
   3 Date: Thu, 25 Mar 2021 11:48:05 +0200
   4 Subject: [PATCH 2/2] gpio: gpio-cascade: add generic GPIO cascade
   5
   6 Adds support for building cascades of GPIO lines. That is, it allows
   7 setups when there is one upstream line and multiple cascaded lines, out
   8 of which one can be chosen at a time. The status of the upstream line
   9 can be conveyed to the selected cascaded line or, vice versa, the status
  10 of the cascaded line can be conveyed to the upstream line.
  11
  12 A multiplexer is being used to select, which cascaded GPIO line is being
  13 used at any given time.
  14
  15 At the moment only input direction is supported. In future it should be
  16 possible to add support for output direction, too.
  17
  18 Signed-off-by: Mauri Sandberg <maukka@ext.kapsi.fi>
  19 Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
  20 Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
  21 ---
  22 v7 -> v8:
  23  - rearrange members in struct gpio_cascade
  24  - cosmetic changes in file header and in one function declaration
  25  - added Reviewed-by tags by Linus and Andy
  26 v6 -> v7:
  27  - In Kconfig add info about module name
  28  - adhere to new convention that allows lines longer than 80 chars
  29  - use dev_probe_err with upstream gpio line too
  30  - refactor for cleaner exit of probe function.
  31 v5 -> v6:
  32  - In Kconfig, remove dependency to OF_GPIO and select only MULTIPLEXER
  33  - refactor code preferring one-liners
  34  - clean up prints, removing them from success-path.
  35  - don't explicitly set gpio_chip.of_node as it's done in the GPIO library
  36  - use devm_gpiochip_add_data instead of gpiochip_add
  37 v4 -> v5:
  38  - renamed gpio-mux-input -> gpio-cascade. refactored code accordingly
  39    here and there and changed to use new bindings and compatible string
  40    - ambigious and vague 'pin' was rename to 'upstream_line'
  41  - dropped Tested-by and Reviewed-by due to changes in bindings
  42  - dropped Reported-by suggested by an automatic bot as it was not really
  43    appropriate to begin with
  44  - functionally it's the same as v4
  45 v3 -> v4:
  46  - Changed author email
  47  - Included Tested-by and Reviewed-by from Drew
  48 v2 -> v3:
  49  - use managed device resources
  50  - update Kconfig description
  51 v1 -> v2:
  52  - removed .owner from platform_driver as per test bot's instruction
  53  - added MODULE_AUTHOR, MODULE_DESCRIPTION, MODULE_LICENSE
  54  - added gpio_mux_input_get_direction as it's recommended for all chips
  55  - removed because this is input only chip: gpio_mux_input_set_value
  56  - removed because they are not needed for input/output only chips:
  57      gpio_mux_input_direction_input
  58      gpio_mux_input_direction_output
  59  - fixed typo in an error message
  60  - added info message about successful registration
  61  - removed can_sleep flag as this does not sleep while getting GPIO value
  62    like I2C or SPI do
  63  - Updated description in Kconfig
  64 ---
  65  drivers/gpio/Kconfig        |  15 +++++
  66  drivers/gpio/Makefile       |   1 +
  67  drivers/gpio/gpio-cascade.c | 117 ++++++++++++++++++++++++++++++++++++
  68  3 files changed, 133 insertions(+)
  69  create mode 100644 drivers/gpio/gpio-cascade.c
  70
  71 --- a/drivers/gpio/Kconfig
  72 +++ b/drivers/gpio/Kconfig
  73 @@ -1617,4 +1617,19 @@ config GPIO_MOCKUP
  74           tools/testing/selftests/gpio/gpio-mockup.sh. Reference the usage in
  75           it.
  76
  77 +comment "Other GPIO expanders"
  78 +
  79 +config GPIO_CASCADE
  80 +       tristate "General GPIO cascade"
  81 +       select MULTIPLEXER
  82 +       help
  83 +         Say yes here to enable support for generic GPIO cascade.
  84 +
  85 +         This allows building one-to-many cascades of GPIO lines using
  86 +         different types of multiplexers readily available. At the
  87 +         moment only input lines are supported.
  88 +
  89 +         To build the driver as a module choose 'm' and the resulting module
  90 +         will be called 'gpio-cascade'.
  91 +
  92  endif
  93 --- a/drivers/gpio/Makefile
  94 +++ b/drivers/gpio/Makefile
  95 @@ -44,6 +44,7 @@ obj-$(CONFIG_GPIO_BD9571MWV)          += gpio-bd
  96  obj-$(CONFIG_GPIO_BRCMSTB)             += gpio-brcmstb.o
  97  obj-$(CONFIG_GPIO_BT8XX)               += gpio-bt8xx.o
  98  obj-$(CONFIG_GPIO_CADENCE)             += gpio-cadence.o
  99 +obj-$(CONFIG_GPIO_CASCADE)             += gpio-cascade.o
 100  obj-$(CONFIG_GPIO_CLPS711X)            += gpio-clps711x.o
 101  obj-$(CONFIG_GPIO_SNPS_CREG)           += gpio-creg-snps.o
 102  obj-$(CONFIG_GPIO_CRYSTAL_COVE)                += gpio-crystalcove.o
 103 --- /dev/null
 104 +++ b/drivers/gpio/gpio-cascade.c
 105 @@ -0,0 +1,117 @@
 106 +// SPDX-License-Identifier: GPL-2.0-only
 107 +/*
 108 + *  A generic GPIO cascade driver
 109 + *
 110 + *  Copyright (C) 2021 Mauri Sandberg <maukka@ext.kapsi.fi>
 111 + *
 112 + * This allows building cascades of GPIO lines in a manner illustrated
 113 + * below:
 114 + *
 115 + *                 /|---- Cascaded GPIO line 0
 116 + *  Upstream      | |---- Cascaded GPIO line 1
 117 + *  GPIO line ----+ | .
 118 + *                | | .
 119 + *                 \|---- Cascaded GPIO line n
 120 + *
 121 + * A multiplexer is being used to select, which cascaded line is being
 122 + * addressed at any given time.
 123 + *
 124 + * At the moment only input mode is supported due to lack of means for
 125 + * testing output functionality. At least theoretically output should be
 126 + * possible with open drain constructions.
 127 + */
 128 +
 129 +#include <linux/module.h>
 130 +#include <linux/slab.h>
 131 +#include <linux/platform_device.h>
 132 +#include <linux/mux/consumer.h>
 133 +
 134 +#include <linux/gpio/consumer.h>
 135 +#include <linux/gpio/driver.h>
 136 +
 137 +struct gpio_cascade {
 138 +       struct gpio_chip        gpio_chip;
 139 +       struct device           *parent;
 140 +       struct mux_control      *mux_control;
 141 +       struct gpio_desc        *upstream_line;
 142 +};
 143 +
 144 +static struct gpio_cascade *chip_to_cascade(struct gpio_chip *gc)
 145 +{
 146 +       return container_of(gc, struct gpio_cascade, gpio_chip);
 147 +}
 148 +
 149 +static int gpio_cascade_get_direction(struct gpio_chip *gc, unsigned int offset)
 150 +{
 151 +       return GPIO_LINE_DIRECTION_IN;
 152 +}
 153 +
 154 +static int gpio_cascade_get_value(struct gpio_chip *gc, unsigned int offset)
 155 +{
 156 +       struct gpio_cascade *cas = chip_to_cascade(gc);
 157 +       int ret;
 158 +
 159 +       ret = mux_control_select(cas->mux_control, offset);
 160 +       if (ret)
 161 +               return ret;
 162 +
 163 +       ret = gpiod_get_value(cas->upstream_line);
 164 +       mux_control_deselect(cas->mux_control);
 165 +       return ret;
 166 +}
 167 +
 168 +static int gpio_cascade_probe(struct platform_device *pdev)
 169 +{
 170 +       struct device *dev = &pdev->dev;
 171 +       struct gpio_cascade *cas;
 172 +       struct mux_control *mc;
 173 +       struct gpio_desc *upstream;
 174 +       struct gpio_chip *gc;
 175 +
 176 +       cas = devm_kzalloc(dev, sizeof(*cas), GFP_KERNEL);
 177 +       if (!cas)
 178 +               return -ENOMEM;
 179 +
 180 +       mc = devm_mux_control_get(dev, NULL);
 181 +       if (IS_ERR(mc))
 182 +               return dev_err_probe(dev, PTR_ERR(mc), "unable to get mux-control\n");
 183 +
 184 +       cas->mux_control = mc;
 185 +       upstream = devm_gpiod_get(dev, "upstream",  GPIOD_IN);
 186 +       if (IS_ERR(upstream))
 187 +               return dev_err_probe(dev, PTR_ERR(upstream), "unable to claim upstream GPIO line\n");
 188 +
 189 +       cas->upstream_line = upstream;
 190 +       cas->parent = dev;
 191 +
 192 +       gc = &cas->gpio_chip;
 193 +       gc->get = gpio_cascade_get_value;
 194 +       gc->get_direction = gpio_cascade_get_direction;
 195 +       gc->base = -1;
 196 +       gc->ngpio = mux_control_states(mc);
 197 +       gc->label = dev_name(cas->parent);
 198 +       gc->parent = cas->parent;
 199 +       gc->owner = THIS_MODULE;
 200 +
 201 +       platform_set_drvdata(pdev, cas);
 202 +       return devm_gpiochip_add_data(dev, &cas->gpio_chip, NULL);
 203 +}
 204 +
 205 +static const struct of_device_id gpio_cascade_id[] = {
 206 +       { .compatible = "gpio-cascade" },
 207 +       { /* sentinel */ }
 208 +};
 209 +MODULE_DEVICE_TABLE(of, gpio_cascade_id);
 210 +
 211 +static struct platform_driver gpio_cascade_driver = {
 212 +       .driver = {
 213 +               .name           = "gpio-cascade",
 214 +               .of_match_table = gpio_cascade_id,
 215 +       },
 216 +       .probe  = gpio_cascade_probe,
 217 +};
 218 +module_platform_driver(gpio_cascade_driver);
 219 +
 220 +MODULE_AUTHOR("Mauri Sandberg <maukka@ext.kapsi.fi>");
 221 +MODULE_DESCRIPTION("Generic GPIO cascade");
 222 +MODULE_LICENSE("GPL");