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Date:   Fri, 16 Oct 2020 16:09:42 +0200
From:   Etienne Carriere <etienne.carriere@...aro.org>
To:     Cristian Marussi <cristian.marussi@....com>
Cc:     linux-kernel@...r.kernel.org,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        Sudeep Holla <sudeep.holla@....com>, lukasz.luba@....com,
        Jim Quinlan <james.quinlan@...adcom.com>,
        Jonathan.Cameron@...wei.com, broonie@...nel.org,
        Rob Herring <robh@...nel.org>, satyakim@....qualcomm.com,
        f.fainelli@...il.com, Vincent Guittot <vincent.guittot@...aro.org>,
        Souvik Chakravarty <souvik.chakravarty@....com>
Subject: Re: [PATCH v2 3/4] regulator: add SCMI driver

Hi Cristian,

Some minor comments...

Etienne


On Thu, 15 Oct 2020 at 17:40, Cristian Marussi <cristian.marussi@....com> wrote:
>
> Add a simple regulator based on SCMI Voltage Domain Protocol.
>
> Signed-off-by: Cristian Marussi <cristian.marussi@....com>
> ----
> v1 --> v2
> - removed duplicate regulator naming
> - removed redundant .get/set_voltage ops: only _sel variants implemented
> - removed condexpr on fail path to increase readability
>
> v0 --> v1
> - fixed init_data constraint parsing
> - fixes for v5.8 (linear_range.h)
> - fixed commit message content and subject line format
> - factored out SCMI core specific changes to distinct patch
> - reworked Kconfig and Makefile to keep proper alphabetic order
> - fixed SPDX comment style
> - removed unneeded inline functions
> - reworked conditionals for legibility
> - fixed some return paths to properly report SCMI original errors codes
> - added some more descriptive error messages when fw returns invalid ranges
> - removed unneeded explicit devm_regulator_unregister from .remove()
> ---
>  drivers/regulator/Kconfig          |   9 +
>  drivers/regulator/Makefile         |   1 +
>  drivers/regulator/scmi-regulator.c | 453 +++++++++++++++++++++++++++++
>  3 files changed, 463 insertions(+)
>  create mode 100644 drivers/regulator/scmi-regulator.c
>
> diff --git a/drivers/regulator/Kconfig b/drivers/regulator/Kconfig
> index de17ef7e18f0..6d3a10cb9833 100644
> --- a/drivers/regulator/Kconfig
> +++ b/drivers/regulator/Kconfig
> @@ -155,6 +155,15 @@ config REGULATOR_ARIZONA_MICSUPP
>           and Wolfson Microelectronic Arizona codecs
>           devices.
>
> +config REGULATOR_ARM_SCMI
> +       tristate "SCMI based regulator driver"
> +       depends on ARM_SCMI_PROTOCOL && OF
> +       help
> +         This adds the regulator driver support for ARM platforms using SCMI
> +         protocol for device voltage management.
> +         This driver uses SCMI Message Protocol driver to interact with the
> +         firmware providing the device Voltage functionality.
> +
>  config REGULATOR_AS3711
>         tristate "AS3711 PMIC"
>         depends on MFD_AS3711
> diff --git a/drivers/regulator/Makefile b/drivers/regulator/Makefile
> index d8d3ecf526a8..0532a7393d5d 100644
> --- a/drivers/regulator/Makefile
> +++ b/drivers/regulator/Makefile
> @@ -24,6 +24,7 @@ obj-$(CONFIG_REGULATOR_AD5398) += ad5398.o
>  obj-$(CONFIG_REGULATOR_ANATOP) += anatop-regulator.o
>  obj-$(CONFIG_REGULATOR_ARIZONA_LDO1) += arizona-ldo1.o
>  obj-$(CONFIG_REGULATOR_ARIZONA_MICSUPP) += arizona-micsupp.o
> +obj-$(CONFIG_REGULATOR_ARM_SCMI) += scmi-regulator.o
>  obj-$(CONFIG_REGULATOR_AS3711) += as3711-regulator.o
>  obj-$(CONFIG_REGULATOR_AS3722) += as3722-regulator.o
>  obj-$(CONFIG_REGULATOR_AXP20X) += axp20x-regulator.o
> diff --git a/drivers/regulator/scmi-regulator.c b/drivers/regulator/scmi-regulator.c
> new file mode 100644
> index 000000000000..e4e7d0345723
> --- /dev/null
> +++ b/drivers/regulator/scmi-regulator.c
> @@ -0,0 +1,453 @@
> +// SPDX-License-Identifier: GPL-2.0
> +//
> +// System Control and Management Interface (SCMI) based regulator driver
> +//
> +// Copyright (C) 2020 ARM Ltd.
> +//
> +// Implements a regulator driver on top of the SCMI Voltage Protocol.
> +//
> +// The ARM SCMI Protocol aims in general to hide as much as possible all the
> +// underlying operational details while providing an abstracted interface for
> +// its users to operate upon: as a consequence the resulting operational
> +// capabilities and configurability of this regulator device are much more
> +// limited than the ones usually available on a standard physical regulator.
> +//
> +// The supported SCMI regulator ops are restricted to the bare minimum:
> +//
> +//  - 'status_ops': enable/disable/is_enabled
> +//  - 'voltage_ops': get_voltage_sel/set_voltage_sel
> +//                  list_voltage/map_voltage
> +//
> +// Each SCMI regulator instance is associated, through the means of a proper DT
> +// entry description, to a specific SCMI Voltage Domain.
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> +#include <linux/linear_range.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/regulator/driver.h>
> +#include <linux/regulator/machine.h>
> +#include <linux/regulator/of_regulator.h>
> +#include <linux/scmi_protocol.h>
> +#include <linux/slab.h>
> +#include <linux/types.h>
> +
> +struct scmi_regulator {
> +       u32 id;
> +       struct scmi_device *sdev;
> +       struct regulator_dev *rdev;
> +       struct device_node *of_node;
> +       struct regulator_desc desc;
> +       struct regulator_config conf;
> +};
> +
> +struct scmi_regulator_info {
> +       int num_doms;
> +       struct scmi_regulator **sregv;
> +};
> +
> +static int scmi_reg_enable(struct regulator_dev *rdev)
> +{
> +       struct scmi_regulator *sreg = rdev_get_drvdata(rdev);
> +       const struct scmi_handle *handle = sreg->sdev->handle;
> +
> +       return handle->voltage_ops->config_set(handle, sreg->id,
> +                                              SCMI_VOLTAGE_ARCH_STATE_ON);
> +}
> +
> +static int scmi_reg_disable(struct regulator_dev *rdev)
> +{
> +       struct scmi_regulator *sreg = rdev_get_drvdata(rdev);
> +       const struct scmi_handle *handle = sreg->sdev->handle;
> +
> +       return handle->voltage_ops->config_set(handle, sreg->id,
> +                                              SCMI_VOLTAGE_ARCH_STATE_OFF);
> +}
> +
> +static int scmi_reg_is_enabled(struct regulator_dev *rdev)
> +{
> +       int ret;
> +       u32 config;
> +       struct scmi_regulator *sreg = rdev_get_drvdata(rdev);
> +       const struct scmi_handle *handle = sreg->sdev->handle;
> +
> +       ret = handle->voltage_ops->config_get(handle, sreg->id,
> +                                             &config);
> +       if (ret) {
> +               dev_err(&sreg->sdev->dev,
> +                       "Error %d reading regulator %s status.\n",
> +                       ret, sreg->desc.name);
> +               return 0;
> +       }
> +
> +       return config & SCMI_VOLTAGE_ARCH_STATE_ON;
> +}
> +
> +static int scmi_reg_get_voltage_sel(struct regulator_dev *rdev)
> +{
> +       int ret;
> +       s32 volt_uV;
> +       struct scmi_regulator *sreg = rdev_get_drvdata(rdev);
> +       const struct scmi_handle *handle = sreg->sdev->handle;
> +
> +       ret = handle->voltage_ops->level_get(handle, sreg->id, &volt_uV);
> +       if (ret)
> +               return ret;
> +
> +       return sreg->desc.ops->map_voltage(rdev, volt_uV, volt_uV);
> +}
> +
> +static int scmi_reg_set_voltage_sel(struct regulator_dev *rdev,
> +                                   unsigned int selector)
> +{
> +       int ret;
> +       s32 volt_uV;
> +       struct scmi_regulator *sreg = rdev_get_drvdata(rdev);
> +       const struct scmi_handle *handle = sreg->sdev->handle;
> +
> +       volt_uV = sreg->desc.ops->list_voltage(rdev, selector);
> +       if (volt_uV <= 0)
> +               return -EINVAL;
> +
> +       ret = handle->voltage_ops->level_set(handle, sreg->id, 0x0, volt_uV);
> +       if (ret)
> +               return ret;
> +
> +       return ret;

    return handle->voltage_ops->level_set(handle, sreg->id, 0x0, volt_uV);

> +}
> +
> +static const struct regulator_ops scmi_reg_fixed_ops = {
> +       .enable = scmi_reg_enable,
> +       .disable = scmi_reg_disable,
> +       .is_enabled = scmi_reg_is_enabled,
> +};
> +
> +static const struct regulator_ops scmi_reg_linear_ops = {
> +       .enable = scmi_reg_enable,
> +       .disable = scmi_reg_disable,
> +       .is_enabled = scmi_reg_is_enabled,
> +       .get_voltage_sel = scmi_reg_get_voltage_sel,
> +       .set_voltage_sel = scmi_reg_set_voltage_sel,
> +       .list_voltage = regulator_list_voltage_linear,
> +       .map_voltage = regulator_map_voltage_linear,
> +};
> +
> +static const struct regulator_ops scmi_reg_range_ops = {
> +       .enable = scmi_reg_enable,
> +       .disable = scmi_reg_disable,
> +       .is_enabled = scmi_reg_is_enabled,
> +       .get_voltage_sel = scmi_reg_get_voltage_sel,
> +       .set_voltage_sel = scmi_reg_set_voltage_sel,
> +       .list_voltage = regulator_list_voltage_linear_range,
> +       .map_voltage = regulator_map_voltage_linear_range,
> +};
> +
> +static const struct regulator_ops scmi_reg_discrete_ops = {
> +       .enable = scmi_reg_enable,
> +       .disable = scmi_reg_disable,
> +       .is_enabled = scmi_reg_is_enabled,
> +       .get_voltage_sel = scmi_reg_get_voltage_sel,
> +       .set_voltage_sel = scmi_reg_set_voltage_sel,
> +       .list_voltage = regulator_list_voltage_table,
> +       .map_voltage = regulator_map_voltage_iterate,
> +};
> +
> +static int
> +scmi_config_linear_regulator_mappings(struct scmi_regulator *sreg,
> +                                     const struct scmi_voltage_info *vinfo)
> +{
> +       /*
> +        * Note that SCMI voltage domains describable by linear ranges
> +        * (segments) {low, high, step} are guaranteed to come in triplets by
> +        * the SCMI Voltage Domain protocol support itself.
> +        */
> +       if (vinfo->num_levels == 3) {
> +               s32 delta_uV;
> +
> +               delta_uV = (vinfo->levels_uv[SCMI_VOLTAGE_SEGMENT_HIGH] -
> +                               vinfo->levels_uv[SCMI_VOLTAGE_SEGMENT_LOW]);
> +               /* Rule out buggy negative-intervals answers from fw */
> +               if (delta_uV < 0) {
> +                       dev_err(&sreg->sdev->dev,
> +                               "Invalid volt-range %d-%duV for domain %d\n",
> +                               vinfo->levels_uv[SCMI_VOLTAGE_SEGMENT_LOW],
> +                               vinfo->levels_uv[SCMI_VOLTAGE_SEGMENT_HIGH],
> +                               sreg->id);
> +                       return -EINVAL;
> +               }
> +
> +               if (!delta_uV) {
> +                       /* Just one fixed voltage exposed by SCMI */
> +                       sreg->desc.fixed_uV =
> +                               vinfo->levels_uv[SCMI_VOLTAGE_SEGMENT_LOW];
> +                       sreg->desc.n_voltages = 1;
> +                       sreg->desc.ops = &scmi_reg_fixed_ops;
> +               } else {
> +                       /* One simple linear mapping. */
> +                       sreg->desc.min_uV =
> +                               vinfo->levels_uv[SCMI_VOLTAGE_SEGMENT_LOW];
> +                       sreg->desc.uV_step =
> +                               vinfo->levels_uv[SCMI_VOLTAGE_SEGMENT_STEP];
> +                       sreg->desc.linear_min_sel = 0;
> +                       sreg->desc.n_voltages = delta_uV / sreg->desc.uV_step;
> +                       sreg->desc.ops = &scmi_reg_linear_ops;
> +               }
> +       } else {
> +               /* Multiple linear mappings. */

I don't see this multi-linear mapping in the v3.0 beta of the spec.
Is it something planned?

> +               int i, num_ranges, last_max = -1;
> +               struct linear_range *lr;
> +
> +               num_ranges = vinfo->num_levels / 3;
> +               lr = devm_kcalloc(&sreg->sdev->dev, num_ranges,
> +                                 sizeof(*lr), GFP_KERNEL);
> +               if (!lr)
> +                       return -ENOMEM;
> +
> +               sreg->desc.n_linear_ranges = num_ranges;
> +               sreg->desc.linear_ranges = lr;
> +               for (i = 0; num_ranges; num_ranges--, i += 3, lr++) {
> +                       s32 delta_uV;
> +
> +                       lr->min =
> +                               vinfo->levels_uv[i + SCMI_VOLTAGE_SEGMENT_LOW];
> +                       lr->step =
> +                               vinfo->levels_uv[i + SCMI_VOLTAGE_SEGMENT_STEP];
> +                       delta_uV =
> +                           vinfo->levels_uv[i + SCMI_VOLTAGE_SEGMENT_HIGH] -
> +                           lr->min;
> +                       if (delta_uV <= 0 || !(delta_uV / lr->step)) {
> +                               dev_err(&sreg->sdev->dev,
> +                                       "Invalid volt-range %d-%duV for domain %d\n",
> +                                    vinfo->levels_uv[SCMI_VOLTAGE_SEGMENT_LOW],
> +                                   vinfo->levels_uv[SCMI_VOLTAGE_SEGMENT_HIGH],
> +                                                                     sreg->id);
> +                               return -EINVAL;
> +                       }
> +                       lr->max_sel = delta_uV / lr->step - 1;
> +                       lr->min_sel = last_max + 1;
> +                       last_max = lr->max_sel;
> +               }
> +               sreg->desc.n_voltages = last_max + 1;
> +               sreg->desc.ops = &scmi_reg_range_ops;
> +       }
> +
> +       return 0;
> +}
> +
> +static int
> +scmi_config_discrete_regulator_mappings(struct scmi_regulator *sreg,
> +                                       const struct scmi_voltage_info *vinfo)
> +{
> +       /* Discrete non linear levels are mapped to volt_table */
> +       sreg->desc.n_voltages = vinfo->num_levels;
> +       if (sreg->desc.n_voltages > 1) {
> +               sreg->desc.volt_table = (const unsigned int *)vinfo->levels_uv;
> +               sreg->desc.ops = &scmi_reg_discrete_ops;
> +       } else {
> +               sreg->desc.fixed_uV = vinfo->levels_uv[0];
> +               sreg->desc.ops = &scmi_reg_fixed_ops;
> +       }
> +
> +       return 0;
> +}
> +
> +static int scmi_regulator_common_init(struct scmi_regulator *sreg)
> +{
> +       int ret;
> +       const struct scmi_handle *handle = sreg->sdev->handle;
> +       struct device *dev = &sreg->sdev->dev;
> +       const struct scmi_voltage_info *vinfo;
> +
> +       vinfo = handle->voltage_ops->info_get(handle, sreg->id);
> +       if (!vinfo)
> +               return -ENODEV;
> +
> +       if (!vinfo->num_levels)
> +               return -EINVAL;
> +
> +       /*
> +        * Regulator framework does not fully support negative voltages
> +        * so we discard any voltage domain reported as supporting negative
> +        * voltages: as a consequence each levels_uv entry is guaranteed to
> +        * be non-negative from here on.
> +        */
> +       if (vinfo->negative_volts_allowed) {
> +               dev_warn(dev, "Negative voltages NOT supported...skip %s\n",
> +                        sreg->of_node->full_name);
> +               return -EOPNOTSUPP;
> +       }
> +
> +       sreg->desc.name = devm_kasprintf(dev, GFP_KERNEL, "%s", vinfo->name);
> +       if (!sreg->desc.name)
> +               return -ENOMEM;
> +
> +       sreg->desc.id = sreg->id;
> +       sreg->desc.type = REGULATOR_VOLTAGE;
> +       sreg->desc.owner = THIS_MODULE;
> +       sreg->desc.of_match = sreg->of_node->name;
> +       sreg->desc.regulators_node = "regulators";
> +       if (vinfo->segmented)
> +               ret = scmi_config_linear_regulator_mappings(sreg, vinfo);
> +       else
> +               ret = scmi_config_discrete_regulator_mappings(sreg, vinfo);
> +       if (ret)
> +               return ret;
> +
> +       sreg->conf.dev = dev;
> +       sreg->conf.driver_data = sreg;
> +
> +       return 0;
> +}
> +
> +static int process_scmi_regulator_of_node(struct scmi_device *sdev,
> +                                         struct device_node *np,
> +                                         struct scmi_regulator_info *rinfo)
> +{
> +       u32 dom, ret;
> +
> +       ret = of_property_read_u32(np, "reg", &dom);
> +       if (ret)
> +               return ret;
> +
> +       if (dom >= rinfo->num_doms)
> +               return -ENODEV;
> +
> +       if (rinfo->sregv[dom]) {
> +               dev_err(&sdev->dev,
> +                       "SCMI Voltage Domain %d already in use. Skipping: %s\n",
> +                       dom, np->full_name);
> +               return -EINVAL;
> +       }
> +
> +       rinfo->sregv[dom] = devm_kzalloc(&sdev->dev,
> +                                        sizeof(struct scmi_regulator),
> +                                        GFP_KERNEL);
> +       if (!rinfo->sregv[dom])
> +               return -ENOMEM;
> +
> +       rinfo->sregv[dom]->id = dom;
> +       rinfo->sregv[dom]->sdev = sdev;
> +       /* get hold of good nodes */
> +       of_node_get(np);
> +       rinfo->sregv[dom]->of_node = np;
> +       dev_info(&sdev->dev,
> +                "Found valid SCMI Regulator -- OF node [%d] -> %s\n",
> +                dom, np->full_name);
> +
> +       return ret;

suggest return 0; here.

> +}
> +
> +static int scmi_regulator_probe(struct scmi_device *sdev)
> +{
> +       int d, ret, num_doms;
> +       struct device_node *np, *child;
> +       const struct scmi_handle *handle = sdev->handle;
> +       struct scmi_regulator_info *rinfo;
> +
> +       if (!handle || !handle->voltage_ops)
> +               return -ENODEV;
> +
> +       num_doms = handle->voltage_ops->num_domains_get(handle);
> +       if (num_doms <= 0) {
> +               if (!num_doms) {
> +                       dev_err(&sdev->dev,
> +                               "number of voltage domains invalid\n");
> +                       num_doms = -EINVAL;
> +               } else {
> +                       dev_err(&sdev->dev,
> +                               "failed to get voltage domains - err:%d\n",
> +                               num_doms);
> +               }
> +
> +               return num_doms;
> +       }
> +
> +       rinfo = devm_kzalloc(&sdev->dev, sizeof(*rinfo), GFP_KERNEL);
> +       if (!rinfo)
> +               return -ENOMEM;
> +
> +       /* Allocate pointers' array for all possible domains */
> +       rinfo->sregv = devm_kcalloc(&sdev->dev, num_doms,
> +                                   sizeof(rinfo->sregv), GFP_KERNEL);
> +       if (!rinfo->sregv)
> +               return -ENOMEM;
> +
> +       rinfo->num_doms = num_doms;
> +       /*
> +        * Start collecting into rinfo->sregv possibly good SCMI Regulators as
> +        * described by a well-formed DT entry and associated with an existing
> +        * plausible SCMI Voltage Domain number, all belonging to this SCMI
> +        * platform instance node (handle->dev->of_node).
> +        */
> +       np = of_find_node_by_name(handle->dev->of_node, "regulators");
> +       for_each_child_of_node(np, child) {
> +               ret = process_scmi_regulator_of_node(sdev, child, rinfo);
> +               /* abort on any mem issue */
> +               if (ret == -ENOMEM)
> +                       return ret;
> +       }
> +
> +       /*
> +        * Register a regulator for each valid regulator-DT-entry that we
> +        * can successfully reach via SCMI
> +        */
> +       for (d = 0; d < num_doms; d++) {
> +               struct scmi_regulator *sreg = rinfo->sregv[d];
> +
> +               if (!sreg)
> +                       continue;
> +               ret = scmi_regulator_common_init(sreg);
> +               if (ret)
> +                       continue;
> +               sreg->rdev = devm_regulator_register(&sdev->dev, &sreg->desc,
> +                                                    &sreg->conf);
> +               if (IS_ERR(sreg->rdev)) {
> +                       sreg->rdev = NULL;
> +                       continue;
> +               }
> +
> +               dev_info(&sdev->dev,
> +                        "Regulator %s registered for domain [%d](%s)\n",
> +                        sreg->desc.name, sreg->id, sreg->desc.name);

Maybe not display sreg->desc.name twice.

> +       }
> +
> +       dev_set_drvdata(&sdev->dev, rinfo);
> +
> +       return 0;
> +}
> +
> +static void scmi_regulator_remove(struct scmi_device *sdev)
> +{
> +       int d;
> +       struct scmi_regulator_info *rinfo;
> +
> +       rinfo = dev_get_drvdata(&sdev->dev);
> +       if (!rinfo)
> +               return;
> +
> +       for (d = 0; d < rinfo->num_doms; d++) {
> +               if (!rinfo->sregv[d])
> +                       continue;
> +               of_node_put(rinfo->sregv[d]->of_node);
> +       }
> +}
> +
> +static const struct scmi_device_id scmi_regulator_id_table[] = {
> +       { SCMI_PROTOCOL_VOLTAGE,  "regulator" },
> +       { },
> +};
> +MODULE_DEVICE_TABLE(scmi, scmi_regulator_id_table);
> +
> +static struct scmi_driver scmi_drv = {
> +       .name           = "scmi-regulator",
> +       .probe          = scmi_regulator_probe,
> +       .remove         = scmi_regulator_remove,
> +       .id_table       = scmi_regulator_id_table,
> +};
> +
> +module_scmi_driver(scmi_drv);
> +
> +MODULE_AUTHOR("Cristian Marussi <cristian.marussi@....com>");
> +MODULE_DESCRIPTION("ARM SCMI regulator driver");
> +MODULE_LICENSE("GPL v2");
> --
> 2.17.1
>

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