Message-ID: <b1d686cd-6a85-2097-823f-d01564d31554@ti.com>
Date:   Fri, 28 Oct 2016 13:30:14 -0500
From:   "Andrew F. Davis" <afd@...com>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
CC:     Nishanth Menon <nm@...com>, Tero Kristo <t-kristo@...com>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Suman Anna <s-anna@...com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] reset: Add the TI SCI reset driver

On 10/28/2016 12:43 PM, Mathieu Poirier wrote:
> On 27 October 2016 at 15:49, Andrew F. Davis <afd@...com> 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@...com>
>> [s-anna@...com: documentation changes, revised commit message]
>> Signed-off-by: Suman Anna <s-anna@...com>
>> Signed-off-by: Nishanth Menon <nm@...com>
>> ---
>>  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@...all.nl>
>> 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@...com>
>> + *
>> + * 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
> 

Hi Mathieu,

There is one ti_sci_reset_data per reset controller, and each reset
controller can have many resets (each described by a
ti_sci_reset_control instance). When a consumer requests a reset we need
to both generate a unique ID to give back to the consumer to reference
this reset and then internally map this ID to a new ti_sci_reset_control
instance for later look-up when the consumer uses this reset, IDR does
both of these for us.

Thanks,
Andrew

>> +
>> +       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@...com>");
>> +MODULE_DESCRIPTION("TI System Control Interface (TI SCI) Reset driver");
>> +MODULE_LICENSE("GPL v2");
>> --
>> 2.10.1
>>

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