Re: [PATCH v2 3/3] reset: Add the TI SCI reset driver

[Mathieu Poirier]

On 27 October 2016 at 15:49, Andrew F. Davis <afd@xxxxxx> wrote:
> Some TI Keystone family of SoCs contain a system controller (like the
> Power Management Micro Controller (PMMC) on K2G SoCs) that manage the
> low-level device control (like clocks, resets etc) for the various
> hardware modules present on the SoC. These device control operations
> are provided to the host processor OS through a communication protocol
> called the TI System Control Interface (TI SCI) protocol.
>
> This patch adds a reset driver that communicates to the system
> controller over the TI SCI protocol for performing reset management
> of various devices present on the SoC. Various reset functionalities
> are achieved by the means of different TI SCI device operations
> provided by the TI SCI framework.
>
> Signed-off-by: Andrew F. Davis <afd@xxxxxx>
> [s-anna@xxxxxx: documentation changes, revised commit message]
> Signed-off-by: Suman Anna <s-anna@xxxxxx>
> Signed-off-by: Nishanth Menon <nm@xxxxxx>
> ---
>  MAINTAINERS                  |   1 +
>  drivers/reset/Kconfig        |   9 ++
>  drivers/reset/Makefile       |   1 +
>  drivers/reset/reset-ti-sci.c | 262 +++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 273 insertions(+)
>  create mode 100644 drivers/reset/reset-ti-sci.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index accf991..b93d91a 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -11901,6 +11901,7 @@ F:      include/dt-bindings/clock/k2g.h
>  F:     drivers/clk/keystone/sci-clk.c
>  F:     Documentation/devicetree/bindings/reset/ti,sci-reset.txt
>  F:     include/dt-bindings/reset/k2g.h
> +F:     drivers/reset/reset-ti-sci.c
>
>  THANKO'S RAREMONO AM/FM/SW RADIO RECEIVER USB DRIVER
>  M:     Hans Verkuil <hverkuil@xxxxxxxxx>
> diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
> index 06d9fa2..4c21c9d 100644
> --- a/drivers/reset/Kconfig
> +++ b/drivers/reset/Kconfig
> @@ -66,6 +66,15 @@ config RESET_SUNXI
>         help
>           This enables the reset driver for Allwinner SoCs.
>
> +config RESET_TI_SCI
> +       tristate "TI System Control Interface (TI-SCI) reset driver"
> +       depends on RESET_CONTROLLER
> +       depends on TI_SCI_PROTOCOL
> +       help
> +         This enables the reset driver support over TI System Control Interface
> +         available on some new TI SoCs. If you wish to use reset resources
> +         managed by the TI System Controller, say Y here. Otherwise, say N.
> +
>  config TI_SYSCON_RESET
>         tristate "TI SYSCON Reset Driver"
>         depends on HAS_IOMEM
> diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
> index bbe7026..36321f2 100644
> --- a/drivers/reset/Makefile
> +++ b/drivers/reset/Makefile
> @@ -10,6 +10,7 @@ obj-$(CONFIG_RESET_PISTACHIO) += reset-pistachio.o
>  obj-$(CONFIG_RESET_SOCFPGA) += reset-socfpga.o
>  obj-$(CONFIG_RESET_STM32) += reset-stm32.o
>  obj-$(CONFIG_RESET_SUNXI) += reset-sunxi.o
> +obj-$(CONFIG_RESET_TI_SCI) += reset-ti-sci.o
>  obj-$(CONFIG_TI_SYSCON_RESET) += reset-ti-syscon.o
>  obj-$(CONFIG_RESET_UNIPHIER) += reset-uniphier.o
>  obj-$(CONFIG_RESET_ZYNQ) += reset-zynq.o
> diff --git a/drivers/reset/reset-ti-sci.c b/drivers/reset/reset-ti-sci.c
> new file mode 100644
> index 0000000..42ccf12
> --- /dev/null
> +++ b/drivers/reset/reset-ti-sci.c
> @@ -0,0 +1,262 @@
> +/*
> + * Texas Instrument's System Control Interface (TI-SCI) reset driver
> + *
> + * Copyright (C) 2015-2016 Texas Instruments Incorporated - http://www.ti.com/
> + *     Andrew F. Davis <afd@xxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed "as is" WITHOUT ANY WARRANTY of any
> + * kind, whether express or implied; without even the implied warranty
> + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/idr.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/reset-controller.h>
> +#include <linux/soc/ti/ti_sci_protocol.h>
> +
> +/**
> + * struct ti_sci_reset_control - reset control structure
> + * @dev_id: SoC-specific device identifier
> + * @reset_mask: reset mask to use for toggling reset
> + */
> +struct ti_sci_reset_control {
> +       u32 dev_id;
> +       u32 reset_mask;
> +};
> +
> +/**
> + * struct ti_sci_reset_data - reset controller information structure
> + * @rcdev: reset controller entity
> + * @dev: reset controller device pointer
> + * @sci: TI SCI handle used for communication with system controller
> + * @idr: idr structure for mapping ids to reset control structures
> + */
> +struct ti_sci_reset_data {
> +       struct reset_controller_dev rcdev;
> +       struct device *dev;
> +       const struct ti_sci_handle *sci;
> +       struct idr idr;
> +};
> +
> +#define to_ti_sci_reset_data(p)        \
> +       container_of((p), struct ti_sci_reset_data, rcdev)
> +
> +/**
> + * ti_sci_reset_set() - program a device's reset
> + * @rcdev: reset controller entity
> + * @id: ID of the reset to toggle
> + * @assert: boolean flag to indicate assert or deassert
> + *
> + * This is a common internal function used to assert or deassert a device's
> + * reset using the TI SCI protocol. The device's reset is asserted if the
> + * @assert argument is true, or deasserted if @assert argument is false.
> + * The mechanism itself is a read-modify-write procedure, the current device
> + * reset register is read using a TI SCI device operation, the new value is
> + * set or un-set using the reset's mask, and the new reset value written by
> + * using another TI SCI device operation.
> + *
> + * Return: 0 for successful request, else a corresponding error value
> + */
> +static int ti_sci_reset_set(struct reset_controller_dev *rcdev,
> +                           unsigned long id, bool assert)
> +{
> +       struct ti_sci_reset_data *data = to_ti_sci_reset_data(rcdev);
> +       const struct ti_sci_handle *sci = data->sci;
> +       const struct ti_sci_dev_ops *dev_ops = &sci->ops.dev_ops;
> +       struct ti_sci_reset_control *control;
> +       u32 reset_state;
> +       int ret;
> +
> +       control = idr_find(&data->idr, id);
> +       if (!control)
> +               return -EINVAL;
> +
> +       ret = dev_ops->get_device_resets(sci, control->dev_id,
> +                                        &reset_state);
> +       if (ret)
> +               return ret;
> +
> +       if (assert)
> +               reset_state |= control->reset_mask;
> +       else
> +               reset_state &= ~control->reset_mask;
> +
> +       return dev_ops->set_device_resets(sci, control->dev_id,
> +                                         reset_state);
> +}
> +
> +/**
> + * ti_sci_reset_assert() - assert device reset
> + * @rcdev: reset controller entity
> + * @id: ID of the reset to be asserted
> + *
> + * This function implements the reset driver op to assert a device's reset
> + * using the TI SCI protocol. This invokes the function ti_sci_reset_set()
> + * with the corresponding parameters as passed in, but with the @assert
> + * argument set to true for asserting the reset.
> + *
> + * Return: 0 for successful request, else a corresponding error value
> + */
> +static int ti_sci_reset_assert(struct reset_controller_dev *rcdev,
> +                              unsigned long id)
> +{
> +       return ti_sci_reset_set(rcdev, id, true);
> +}
> +
> +/**
> + * ti_sci_reset_deassert() - deassert device reset
> + * @rcdev: reset controller entity
> + * @id: ID of the reset to be deasserted
> + *
> + * This function implements the reset driver op to deassert a device's reset
> + * using the TI SCI protocol. This invokes the function ti_sci_reset_set()
> + * with the corresponding parameters as passed in, but with the @assert
> + * argument set to false for deasserting the reset.
> + *
> + * Return: 0 for successful request, else a corresponding error value
> + */
> +static int ti_sci_reset_deassert(struct reset_controller_dev *rcdev,
> +                                unsigned long id)
> +{
> +       return ti_sci_reset_set(rcdev, id, false);
> +}
> +
> +/**
> + * ti_sci_reset_status() - check device reset status
> + * @rcdev: reset controller entity
> + * @id: ID of reset to be checked
> + *
> + * This function implements the reset driver op to return the status of a
> + * device's reset using the TI SCI protocol. The reset register value is read
> + * by invoking the TI SCI device opertation .get_device_resets(), and the
> + * status of the specific reset is extracted and returned using this reset's
> + * reset mask.
> + *
> + * Return: 0 if reset is deasserted, or a non-zero value if reset is asserted
> + */
> +static int ti_sci_reset_status(struct reset_controller_dev *rcdev,
> +                              unsigned long id)
> +{
> +       struct ti_sci_reset_data *data = to_ti_sci_reset_data(rcdev);
> +       const struct ti_sci_handle *sci = data->sci;
> +       const struct ti_sci_dev_ops *dev_ops = &sci->ops.dev_ops;
> +       struct ti_sci_reset_control *control;
> +       u32 reset_state;
> +       int ret;
> +
> +       control = idr_find(&data->idr, id);
> +       if (!control)
> +               return -EINVAL;
> +
> +       ret = dev_ops->get_device_resets(sci, control->dev_id,
> +                                        &reset_state);
> +       if (ret)
> +               return ret;
> +
> +       return reset_state & control->reset_mask;
> +}
> +
> +static struct reset_control_ops ti_sci_reset_ops = {
> +       .assert         = ti_sci_reset_assert,
> +       .deassert       = ti_sci_reset_deassert,
> +       .status         = ti_sci_reset_status,
> +};
> +
> +/**
> + * ti_sci_reset_of_xlate() - translate a set of OF arguments to a reset ID
> + * @rcdev: reset controller entity
> + * @reset_spec: OF reset argument specifier
> + *
> + * This function performs the translation of the reset argument specifier
> + * values defined in a reset consumer device node. The function allocates a
> + * reset control structure for that device reset, and will be used by the
> + * driver for performing any reset functions on that reset. An idr structure
> + * is allocated and used to map to the reset control structure. This idr
> + * is used by the driver to do reset lookups.
> + *
> + * Return: 0 for successful request, else a corresponding error value
> + */
> +static int ti_sci_reset_of_xlate(struct reset_controller_dev *rcdev,
> +                                const struct of_phandle_args *reset_spec)
> +{
> +       struct ti_sci_reset_data *data = to_ti_sci_reset_data(rcdev);
> +       struct ti_sci_reset_control *control;
> +
> +       if (WARN_ON(reset_spec->args_count != rcdev->of_reset_n_cells))
> +               return -EINVAL;
> +
> +       control = devm_kzalloc(data->dev, sizeof(*control), GFP_KERNEL);
> +       if (!control)
> +               return -ENOMEM;
> +
> +       control->dev_id = reset_spec->args[0];
> +       control->reset_mask = reset_spec->args[1];
> +
> +       return idr_alloc(&data->idr, control, 0, 0, GFP_KERNEL);
> +}
> +
> +static const struct of_device_id ti_sci_reset_of_match[] = {
> +       { .compatible = "ti,sci-reset", },
> +       { /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(of, ti_sci_reset_of_match);
> +
> +static int ti_sci_reset_probe(struct platform_device *pdev)
> +{
> +       struct ti_sci_reset_data *data;
> +
> +       if (!pdev->dev.of_node)
> +               return -ENODEV;
> +
> +       data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
> +       if (!data)
> +               return -ENOMEM;
> +
> +       data->sci = devm_ti_sci_get_handle(&pdev->dev);
> +       if (IS_ERR(data->sci))
> +               return PTR_ERR(data->sci);
> +
> +       data->rcdev.ops = &ti_sci_reset_ops;
> +       data->rcdev.owner = THIS_MODULE;
> +       data->rcdev.of_node = pdev->dev.of_node;
> +       data->rcdev.of_reset_n_cells = 2;
> +       data->rcdev.of_xlate = ti_sci_reset_of_xlate;
> +       data->dev = &pdev->dev;
> +       idr_init(&data->idr);

Hello Andrew,

For my own education, is there a specific reason to use a struct idr
as opposed to keeping a pointer to a struct ti_sci_reset_control in
truct ti_sci_reset_data?   I'm not opposed to the way you've done
things but simply keeping a pointer sound more intuitive to me.

Thanks,
Mathieu

> +
> +       platform_set_drvdata(pdev, data);
> +
> +       return reset_controller_register(&data->rcdev);
> +}
> +
> +static int ti_sci_reset_remove(struct platform_device *pdev)
> +{
> +       struct ti_sci_reset_data *data = platform_get_drvdata(pdev);
> +
> +       reset_controller_unregister(&data->rcdev);
> +
> +       idr_destroy(&data->idr);
> +
> +       return 0;
> +}
> +
> +static struct platform_driver ti_sci_reset_driver = {
> +       .probe = ti_sci_reset_probe,
> +       .remove = ti_sci_reset_remove,
> +       .driver = {
> +               .name = "ti-sci-reset",
> +               .of_match_table = ti_sci_reset_of_match,
> +       },
> +};
> +module_platform_driver(ti_sci_reset_driver);
> +
> +MODULE_AUTHOR("Andrew F. Davis <afd@xxxxxx>");
> +MODULE_DESCRIPTION("TI System Control Interface (TI SCI) Reset driver");
> +MODULE_LICENSE("GPL v2");
> --
> 2.10.1
>