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kernel: 5.10: backport gpio-cascade and related symbols
The patch is under review at [1]. Signed-off-by: Mauri Sandberg <maukka@ext.kapsi.fi> [1] http://patchwork.ozlabs.org/project/linux-gpio/patch/20211026191506.3099-3-maukka@ext.kapsi.fi/
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target/linux/generic/pending-5.10/801-gpio-gpio-cascade-add-generic-GPIO-cascade.patch
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From fc23ea48ba52c24f201fe5ca0132ee1a3de5a70a Mon Sep 17 00:00:00 2001 | ||
From: Mauri Sandberg <maukka@ext.kapsi.fi> | ||
Date: Thu, 25 Mar 2021 11:48:05 +0200 | ||
Subject: [PATCH 2/2] gpio: gpio-cascade: add generic GPIO cascade | ||
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Adds support for building cascades of GPIO lines. That is, it allows | ||
setups when there is one upstream line and multiple cascaded lines, out | ||
of which one can be chosen at a time. The status of the upstream line | ||
can be conveyed to the selected cascaded line or, vice versa, the status | ||
of the cascaded line can be conveyed to the upstream line. | ||
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A multiplexer is being used to select, which cascaded GPIO line is being | ||
used at any given time. | ||
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At the moment only input direction is supported. In future it should be | ||
possible to add support for output direction, too. | ||
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Signed-off-by: Mauri Sandberg <maukka@ext.kapsi.fi> | ||
Reviewed-by: Linus Walleij <linus.walleij@linaro.org> | ||
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> | ||
--- | ||
v7 -> v8: | ||
- rearrange members in struct gpio_cascade | ||
- cosmetic changes in file header and in one function declaration | ||
- added Reviewed-by tags by Linus and Andy | ||
v6 -> v7: | ||
- In Kconfig add info about module name | ||
- adhere to new convention that allows lines longer than 80 chars | ||
- use dev_probe_err with upstream gpio line too | ||
- refactor for cleaner exit of probe function. | ||
v5 -> v6: | ||
- In Kconfig, remove dependency to OF_GPIO and select only MULTIPLEXER | ||
- refactor code preferring one-liners | ||
- clean up prints, removing them from success-path. | ||
- don't explicitly set gpio_chip.of_node as it's done in the GPIO library | ||
- use devm_gpiochip_add_data instead of gpiochip_add | ||
v4 -> v5: | ||
- renamed gpio-mux-input -> gpio-cascade. refactored code accordingly | ||
here and there and changed to use new bindings and compatible string | ||
- ambigious and vague 'pin' was rename to 'upstream_line' | ||
- dropped Tested-by and Reviewed-by due to changes in bindings | ||
- dropped Reported-by suggested by an automatic bot as it was not really | ||
appropriate to begin with | ||
- functionally it's the same as v4 | ||
v3 -> v4: | ||
- Changed author email | ||
- Included Tested-by and Reviewed-by from Drew | ||
v2 -> v3: | ||
- use managed device resources | ||
- update Kconfig description | ||
v1 -> v2: | ||
- removed .owner from platform_driver as per test bot's instruction | ||
- added MODULE_AUTHOR, MODULE_DESCRIPTION, MODULE_LICENSE | ||
- added gpio_mux_input_get_direction as it's recommended for all chips | ||
- removed because this is input only chip: gpio_mux_input_set_value | ||
- removed because they are not needed for input/output only chips: | ||
gpio_mux_input_direction_input | ||
gpio_mux_input_direction_output | ||
- fixed typo in an error message | ||
- added info message about successful registration | ||
- removed can_sleep flag as this does not sleep while getting GPIO value | ||
like I2C or SPI do | ||
- Updated description in Kconfig | ||
--- | ||
drivers/gpio/Kconfig | 15 +++++ | ||
drivers/gpio/Makefile | 1 + | ||
drivers/gpio/gpio-cascade.c | 117 ++++++++++++++++++++++++++++++++++++ | ||
3 files changed, 133 insertions(+) | ||
create mode 100644 drivers/gpio/gpio-cascade.c | ||
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diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig | ||
index 37a6f77c86fe..e69457144459 100644 | ||
--- a/drivers/gpio/Kconfig | ||
+++ b/drivers/gpio/Kconfig | ||
@@ -1694,4 +1694,19 @@ config GPIO_VIRTIO | ||
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endmenu | ||
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+comment "Other GPIO expanders" | ||
+ | ||
+config GPIO_CASCADE | ||
+ tristate "General GPIO cascade" | ||
+ select MULTIPLEXER | ||
+ help | ||
+ Say yes here to enable support for generic GPIO cascade. | ||
+ | ||
+ This allows building one-to-many cascades of GPIO lines using | ||
+ different types of multiplexers readily available. At the | ||
+ moment only input lines are supported. | ||
+ | ||
+ To build the driver as a module choose 'm' and the resulting module | ||
+ will be called 'gpio-cascade'. | ||
+ | ||
endif | ||
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile | ||
index 71ee9fc2ff83..e8945456e7ea 100644 | ||
--- a/drivers/gpio/Makefile | ||
+++ b/drivers/gpio/Makefile | ||
@@ -45,6 +45,7 @@ obj-$(CONFIG_GPIO_BD9571MWV) += gpio-bd9571mwv.o | ||
obj-$(CONFIG_GPIO_BRCMSTB) += gpio-brcmstb.o | ||
obj-$(CONFIG_GPIO_BT8XX) += gpio-bt8xx.o | ||
obj-$(CONFIG_GPIO_CADENCE) += gpio-cadence.o | ||
+obj-$(CONFIG_GPIO_CASCADE) += gpio-cascade.o | ||
obj-$(CONFIG_GPIO_CLPS711X) += gpio-clps711x.o | ||
obj-$(CONFIG_GPIO_SNPS_CREG) += gpio-creg-snps.o | ||
obj-$(CONFIG_GPIO_CRYSTAL_COVE) += gpio-crystalcove.o | ||
diff --git a/drivers/gpio/gpio-cascade.c b/drivers/gpio/gpio-cascade.c | ||
new file mode 100644 | ||
index 000000000000..5cbda882d79a | ||
--- /dev/null | ||
+++ b/drivers/gpio/gpio-cascade.c | ||
@@ -0,0 +1,117 @@ | ||
+// SPDX-License-Identifier: GPL-2.0-only | ||
+/* | ||
+ * A generic GPIO cascade driver | ||
+ * | ||
+ * Copyright (C) 2021 Mauri Sandberg <maukka@ext.kapsi.fi> | ||
+ * | ||
+ * This allows building cascades of GPIO lines in a manner illustrated | ||
+ * below: | ||
+ * | ||
+ * /|---- Cascaded GPIO line 0 | ||
+ * Upstream | |---- Cascaded GPIO line 1 | ||
+ * GPIO line ----+ | . | ||
+ * | | . | ||
+ * \|---- Cascaded GPIO line n | ||
+ * | ||
+ * A multiplexer is being used to select, which cascaded line is being | ||
+ * addressed at any given time. | ||
+ * | ||
+ * At the moment only input mode is supported due to lack of means for | ||
+ * testing output functionality. At least theoretically output should be | ||
+ * possible with open drain constructions. | ||
+ */ | ||
+ | ||
+#include <linux/module.h> | ||
+#include <linux/slab.h> | ||
+#include <linux/platform_device.h> | ||
+#include <linux/mux/consumer.h> | ||
+ | ||
+#include <linux/gpio/consumer.h> | ||
+#include <linux/gpio/driver.h> | ||
+ | ||
+struct gpio_cascade { | ||
+ struct gpio_chip gpio_chip; | ||
+ struct device *parent; | ||
+ struct mux_control *mux_control; | ||
+ struct gpio_desc *upstream_line; | ||
+}; | ||
+ | ||
+static struct gpio_cascade *chip_to_cascade(struct gpio_chip *gc) | ||
+{ | ||
+ return container_of(gc, struct gpio_cascade, gpio_chip); | ||
+} | ||
+ | ||
+static int gpio_cascade_get_direction(struct gpio_chip *gc, unsigned int offset) | ||
+{ | ||
+ return GPIO_LINE_DIRECTION_IN; | ||
+} | ||
+ | ||
+static int gpio_cascade_get_value(struct gpio_chip *gc, unsigned int offset) | ||
+{ | ||
+ struct gpio_cascade *cas = chip_to_cascade(gc); | ||
+ int ret; | ||
+ | ||
+ ret = mux_control_select(cas->mux_control, offset); | ||
+ if (ret) | ||
+ return ret; | ||
+ | ||
+ ret = gpiod_get_value(cas->upstream_line); | ||
+ mux_control_deselect(cas->mux_control); | ||
+ return ret; | ||
+} | ||
+ | ||
+static int gpio_cascade_probe(struct platform_device *pdev) | ||
+{ | ||
+ struct device *dev = &pdev->dev; | ||
+ struct gpio_cascade *cas; | ||
+ struct mux_control *mc; | ||
+ struct gpio_desc *upstream; | ||
+ struct gpio_chip *gc; | ||
+ | ||
+ cas = devm_kzalloc(dev, sizeof(*cas), GFP_KERNEL); | ||
+ if (!cas) | ||
+ return -ENOMEM; | ||
+ | ||
+ mc = devm_mux_control_get(dev, NULL); | ||
+ if (IS_ERR(mc)) | ||
+ return dev_err_probe(dev, PTR_ERR(mc), "unable to get mux-control\n"); | ||
+ | ||
+ cas->mux_control = mc; | ||
+ upstream = devm_gpiod_get(dev, "upstream", GPIOD_IN); | ||
+ if (IS_ERR(upstream)) | ||
+ return dev_err_probe(dev, PTR_ERR(upstream), "unable to claim upstream GPIO line\n"); | ||
+ | ||
+ cas->upstream_line = upstream; | ||
+ cas->parent = dev; | ||
+ | ||
+ gc = &cas->gpio_chip; | ||
+ gc->get = gpio_cascade_get_value; | ||
+ gc->get_direction = gpio_cascade_get_direction; | ||
+ gc->base = -1; | ||
+ gc->ngpio = mux_control_states(mc); | ||
+ gc->label = dev_name(cas->parent); | ||
+ gc->parent = cas->parent; | ||
+ gc->owner = THIS_MODULE; | ||
+ | ||
+ platform_set_drvdata(pdev, cas); | ||
+ return devm_gpiochip_add_data(dev, &cas->gpio_chip, NULL); | ||
+} | ||
+ | ||
+static const struct of_device_id gpio_cascade_id[] = { | ||
+ { .compatible = "gpio-cascade" }, | ||
+ { /* sentinel */ } | ||
+}; | ||
+MODULE_DEVICE_TABLE(of, gpio_cascade_id); | ||
+ | ||
+static struct platform_driver gpio_cascade_driver = { | ||
+ .driver = { | ||
+ .name = "gpio-cascade", | ||
+ .of_match_table = gpio_cascade_id, | ||
+ }, | ||
+ .probe = gpio_cascade_probe, | ||
+}; | ||
+module_platform_driver(gpio_cascade_driver); | ||
+ | ||
+MODULE_AUTHOR("Mauri Sandberg <maukka@ext.kapsi.fi>"); | ||
+MODULE_DESCRIPTION("Generic GPIO cascade"); | ||
+MODULE_LICENSE("GPL"); | ||
-- | ||
2.25.1 | ||
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