Date:   Thu, 30 Jun 2022 16:20:19 +0000
From:   <Conor.Dooley@...rochip.com>
To:     <p.zabel@...gutronix.de>, <mturquette@...libre.com>,
        <sboyd@...nel.org>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <davem@...emloft.net>,
        <edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
        <palmer@...belt.com>, <Nicolas.Ferre@...rochip.com>,
        <Claudiu.Beznea@...rochip.com>, <Daire.McNamara@...rochip.com>
CC:     <paul.walmsley@...ive.com>, <aou@...s.berkeley.edu>,
        <linux-clk@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
        <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH v1 04/14] reset: add polarfire soc reset support

On 30/06/2022 10:12, Philipp Zabel wrote:

(This came to me oddly quoted, so I have fixed it myself)

>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>> 
>> Hi Conor,
>> 
>> On Do, 2022-06-30 at 09:05 +0100, Conor Dooley wrote:
>> Add support for the resets on Microchip's PolarFire SoC (MPFS).
>> Reset control is a single register, wedged in between registers for
>> clock control. To fit with existed DT etc, the reset controller is
>> 
> existing                     ^
>> 
>> created using the aux device framework & set up in the clock driver.
>> 
>> Signed-off-by: Conor Dooley <conor.dooley@...rochip.com>
>> ---
>>  drivers/reset/Kconfig      |   9 +++
>>  drivers/reset/Makefile     |   2 +-
>>  drivers/reset/reset-mpfs.c | 145 +++++++++++++++++++++++++++++++++++++
>>  3 files changed, 155 insertions(+), 1 deletion(-)
>>  create mode 100644 drivers/reset/reset-mpfs.c
>> 
>> diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
>> index 93c8d07ee328..edf48951f763 100644
>> --- a/drivers/reset/Kconfig
>> +++ b/drivers/reset/Kconfig
>> @@ -122,6 +122,15 @@ config RESET_MCHP_SPARX5
>>         help
>>           This driver supports switch core reset for the Microchip Sparx5 SoC.
>> 
>> 
>> +config RESET_POLARFIRE_SOC
>> +       bool "Microchip PolarFire SoC (MPFS) Reset Driver"
>> +       depends on AUXILIARY_BUS && MCHP_CLK_MPFS
>> +       default MCHP_CLK_MPFS
>> +       help
>> +         This driver supports peripheral reset for the Microchip PolarFire SoC
>> +
>> +         CONFIG_RESET_MPFS
>> 
>This doesn't look intentional.

Correct. I fixed it when rebasing on -next and forgot to re-fix it
when I had to reset back to -rc2...

>> 
>> +
>>  config RESET_MESON
>>         tristate "Meson Reset Driver"
>>         depends on ARCH_MESON || COMPILE_TEST
>> diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
>> index a80a9c4008a7..5fac3a753858 100644
>> --- a/drivers/reset/Makefile
>> +++ b/drivers/reset/Makefile
>> @@ -17,6 +17,7 @@ obj-$(CONFIG_RESET_K210) += reset-k210.o
>>  obj-$(CONFIG_RESET_LANTIQ) += reset-lantiq.o
>>  obj-$(CONFIG_RESET_LPC18XX) += reset-lpc18xx.o
>>  obj-$(CONFIG_RESET_MCHP_SPARX5) += reset-microchip-sparx5.o
>> +obj-$(CONFIG_RESET_POLARFIRE_SOC) += reset-mpfs.o
>>  obj-$(CONFIG_RESET_MESON) += reset-meson.o
>>  obj-$(CONFIG_RESET_MESON_AUDIO_ARB) += reset-meson-audio-arb.o
>>  obj-$(CONFIG_RESET_NPCM) += reset-npcm.o
>> @@ -38,4 +39,3 @@ obj-$(CONFIG_RESET_UNIPHIER) += reset-uniphier.o
>>  obj-$(CONFIG_RESET_UNIPHIER_GLUE) += reset-uniphier-glue.o
>>  obj-$(CONFIG_RESET_ZYNQ) += reset-zynq.o
>>  obj-$(CONFIG_ARCH_ZYNQMP) += reset-zynqmp.o
>> -
>> diff --git a/drivers/reset/reset-mpfs.c b/drivers/reset/reset-mpfs.c
>> new file mode 100644
>> index 000000000000..49c47a3e6c70
>> --- /dev/null
>> +++ b/drivers/reset/reset-mpfs.c
>> @@ -0,0 +1,145 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * PolarFire SoC (MPFS) Peripheral Clock Reset Controller
>> + *
>> + * Author: Conor Dooley <conor.dooley@...rochip.com>
>> + * Copyright (c) 2022 Microchip Technology Inc. and its subsidiaries.
>> + *
>> + */
>> +#include <linux/auxiliary_bus.h>
>> +#include <linux/delay.h>
>> +#include <linux/module.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/reset-controller.h>
>> +#include <dt-bindings/clock/microchip,mpfs-clock.h>
>> +#include <soc/microchip/mpfs.h>
>> +
>> +/*
>> + * The ENVM reset is the lowest bit in the register & I am using the CLK_FOO
>> + * defines in the dt to make things easier to configure - so this is accounting
>> + * for the offset of 3 there.
>> + */
>> +#define MPFS_PERIPH_OFFSET     CLK_ENVM
>> +#define MPFS_NUM_RESETS                30u
>> +#define MPFS_SLEEP_MIN_US      100
>> +#define MPFS_SLEEP_MAX_US      200
>> +
>> +/*
>> + * Peripheral clock resets
>> + */
>> +
>> +static int mpfs_assert(struct reset_controller_dev *rcdev, unsigned long id)
>> +{
>> +       u32 reg;
>> +
>> +       reg = mpfs_reset_read(rcdev->dev);
>> +       reg |= (1u << id);
>> +       mpfs_reset_write(rcdev->dev, reg);
> 
> This is missing a spinlock to protect against concurrent read-modify-
> writes.
>> 
>> +
>> +       return 0;
>> +}
>> +
>> +static int mpfs_deassert(struct reset_controller_dev *rcdev, unsigned long id)
>> +{
>> +       u32 reg, val;
>> +
>> +       reg = mpfs_reset_read(rcdev->dev);
>> +       val = reg & ~(1u << id);
> 
> You could use BIT(id) instead of (1u << id).
> 
>> +       mpfs_reset_write(rcdev->dev, val);
>> +
>> +       return 0;
>> +}
>> +
>> +static int mpfs_status(struct reset_controller_dev *rcdev, unsigned long id)
>> +{
>> +       u32 reg = mpfs_reset_read(rcdev->dev);
>> +
>> +       return (reg & (1u << id));
> 
> Side note, this works because MPFS_NUM_RESETS makes sure the sign bit
> is never hit.

I can add a comment to that effect if you want?

>> 
>> +}
>> +
>> +static int mpfs_reset(struct reset_controller_dev *rcdev, unsigned long id)
>> +{
>> +       mpfs_assert(rcdev, id);
>> +
>> +       usleep_range(MPFS_SLEEP_MIN_US, MPFS_SLEEP_MAX_US);
>> +
>> +       mpfs_deassert(rcdev, id);
>> +
>> +       return 0;
>> +}
>> +
>> +static const struct reset_control_ops mpfs_reset_ops = {
>> +       .reset = mpfs_reset,
>> +       .assert = mpfs_assert,
>> +       .deassert = mpfs_deassert,
>> +       .status = mpfs_status,
>> +};
>> +
>> +static int mpfs_reset_xlate(struct reset_controller_dev *rcdev,
>> +                           const struct of_phandle_args *reset_spec)
>> +{
>> +       unsigned int index = reset_spec->args[0];
>> +
>> +       /*
>> +        * CLK_RESERVED does not map to a clock, but it does map to a reset,
>> +        * so it has to be accounted for here. It is the reset for the fabric,
>> +        * so if this reset gets called - do not reset it.
>> +        */
>> +       if (index == CLK_RESERVED) {
>> +               dev_err(rcdev->dev, "Resetting the fabric is not supported\n");
>> +               return -EINVAL;
>> +       }
>> +
>> +       if (index < MPFS_PERIPH_OFFSET || index >= (MPFS_PERIPH_OFFSET + rcdev->nr_resets)) {
>> +               dev_err(rcdev->dev, "Invalid reset index %u\n", reset_spec->args[0]);
> 
> s/reset_spec->args[0]/index/
> 
>> +               return -EINVAL;
>> +       }
>> +
>> +       return index - MPFS_PERIPH_OFFSET;
>> +}
>> +
>> +static int mpfs_reset_probe(struct auxiliary_device *adev,
>> +                           const struct auxiliary_device_id *id)
>> +{
>> +       struct device *dev = &adev->dev;
>> +       struct reset_controller_dev *rcdev;
>> +       int ret;
>> +
>> +       rcdev = devm_kzalloc(dev, sizeof(*rcdev), GFP_KERNEL);
>> +       if (!rcdev)
>> +               return -ENOMEM;
>> +
>> +       rcdev->dev = dev;
>> +       rcdev->dev->parent = adev->dev.parent;
>> 
>> s/adev->dev./dev->/
>> 
>> +       rcdev->ops = &mpfs_reset_ops;
>> +       rcdev->of_node = adev->dev.parent->of_node;
>> 
>> s/adev->dev./dev->/
>> 
>> +       rcdev->of_reset_n_cells = 1;
>> +       rcdev->of_xlate = mpfs_reset_xlate;
>> +       rcdev->nr_resets = MPFS_NUM_RESETS;
>> +
>> +       ret = devm_reset_controller_register(dev, rcdev);
>> +       if (!ret)
>> +               dev_info(dev, "Registered MPFS reset controller\n");
> 
> Is this really useful information for most users?

Probably not, but it is useful for my CI haha.
If you don't like it, I will remove it.

> 
>> +
>> +       return ret;
>> +}
>> +
>> +static const struct auxiliary_device_id mpfs_reset_ids[] = {
>> +       {
>> +               .name = "clk_mpfs.reset-mpfs",
>> +       },
>> +       { }
>> +};
>> +MODULE_DEVICE_TABLE(auxiliary, mpfs_reset_ids);
>> +
>> +static struct auxiliary_driver mpfs_reset_driver = {
>> +       .probe          = mpfs_reset_probe,
>> +       .id_table       = mpfs_reset_ids,
>> +};
>> +
>> +module_auxiliary_driver(mpfs_reset_driver);
>> +
>> +MODULE_DESCRIPTION("Microchip PolarFire SoC Reset Driver");
>> +MODULE_AUTHOR("Conor Dooley <conor.dooley@...rochip.com>");
>> +MODULE_LICENSE("GPL");
>> +MODULE_IMPORT_NS(MCHP_CLK_MPFS);
>> 
> regards
> Philipp

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