Message-ID: <df782fe9-4c2d-5df7-f3ba-78eae6f0cfbd@microchip.com>
Date:   Fri, 1 Jul 2022 16:20:52 +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 17:20, Conor Dooley - M52691 wrote:
> 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?

I'm going to respin with the two net patches removed.
I'll operate on the assumption of adding a comment here...

> 
>>>
>>> +}
>>> +
>>> +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.

...and removal here.
Thanks for your review Philipp :)
Conor.

> 
>>
>>> +
>>> +       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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