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14f4957313
Several memories have a write-protect pin, that when pulled high, it blocks the write operation. On some boards, this pin is connected to a GPIO and pulled high by default, which forces the user to manually change its state before writing. Instead of modifying all the memory drivers to check this pin, make the NVMEM subsystem check if the write-protect GPIO being passed through the nvmem_config or defined in the device tree and pull it low whenever writing to the memory. Add a new optional property to the device tree binding document, which allows to specify the GPIO line to which the write-protect pin is connected. Signed-off-by: Khouloud Touil <ktouil@baylibre.com> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Reviewed-by: Rob Herring <robh@kernel.org> Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
105 lines
2.5 KiB
YAML
105 lines
2.5 KiB
YAML
# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
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%YAML 1.2
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---
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$id: http://devicetree.org/schemas/nvmem/nvmem.yaml#
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$schema: http://devicetree.org/meta-schemas/core.yaml#
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title: NVMEM (Non Volatile Memory) Device Tree Bindings
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maintainers:
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- Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
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description: |
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This binding is intended to represent the location of hardware
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configuration data stored in NVMEMs like eeprom, efuses and so on.
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On a significant proportion of boards, the manufacturer has stored
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some data on NVMEM, for the OS to be able to retrieve these
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information and act upon it. Obviously, the OS has to know about
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where to retrieve these data from, and where they are stored on the
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storage device.
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properties:
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$nodename:
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pattern: "^(eeprom|efuse|nvram)(@.*|-[0-9a-f])*$"
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"#address-cells":
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const: 1
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"#size-cells":
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const: 1
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read-only:
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$ref: /schemas/types.yaml#/definitions/flag
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description:
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Mark the provider as read only.
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wp-gpios:
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description:
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GPIO to which the write-protect pin of the chip is connected.
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The write-protect GPIO is asserted, when it's driven high
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(logical '1') to block the write operation. It's deasserted,
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when it's driven low (logical '0') to allow writing.
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maxItems: 1
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patternProperties:
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"^.*@[0-9a-f]+$":
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type: object
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properties:
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reg:
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maxItems: 1
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description:
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Offset and size in bytes within the storage device.
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bits:
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maxItems: 1
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items:
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items:
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- minimum: 0
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maximum: 7
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description:
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Offset in bit within the address range specified by reg.
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- minimum: 1
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description:
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Size in bit within the address range specified by reg.
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required:
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- reg
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additionalProperties: false
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examples:
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- |
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#include <dt-bindings/gpio/gpio.h>
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qfprom: eeprom@700000 {
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#address-cells = <1>;
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#size-cells = <1>;
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wp-gpios = <&gpio1 3 GPIO_ACTIVE_HIGH>;
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/* ... */
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/* Data cells */
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tsens_calibration: calib@404 {
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reg = <0x404 0x10>;
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};
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tsens_calibration_bckp: calib_bckp@504 {
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reg = <0x504 0x11>;
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bits = <6 128>;
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};
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pvs_version: pvs-version@6 {
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reg = <0x6 0x2>;
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bits = <7 2>;
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};
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speed_bin: speed-bin@c{
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reg = <0xc 0x1>;
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bits = <2 3>;
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};
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};
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...
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