Message-ID: <6c5a77b0-fc1f-33c8-ff1d-83e198e4acda@ti.com>
Date:   Thu, 3 Nov 2016 12:50:34 -0500
From:   "Andrew F. Davis" <afd@...com>
To:     Philipp Zabel <p.zabel@...gutronix.de>
CC:     Nishanth Menon <nm@...com>, Tero Kristo <t-kristo@...com>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Suman Anna <s-anna@...com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...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 04:36 AM, Philipp Zabel wrote:
> Hi Andrew,
> 
> is there (going to be) as stable branch I can base these on, or should I
> just wait until the prerequisite patches appear in arm-soc/for-next?
> 
> Am Donnerstag, den 27.10.2016, 16:49 -0500 schrieb Andrew F. Davis:
>> 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);
> 
> Without any locking? Maybe the read-modify-write could just be moved one
> level down with an update_bits type of callback in the ti_sci_dev_ops.
> 

That may be useful to add at some point, for now I want to work with the
existing framework, it can always be moved later. I'll add some
per-control locks for v3.

Thanks,
Andrew

>> +}
>> +
>> +/**
>> + * 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);
>> +
>> +	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");
> 
> regards
> Philipp
> 

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