Date: Tue, 11 Jun 2024 14:55:55 +0800
From: Shengjiu Wang <shengjiu.wang@...il.com>
To: Frank Li <Frank.li@....com>
Cc: Marco Felsch <m.felsch@...gutronix.de>, Shengjiu Wang <shengjiu.wang@....com>, 
	p.zabel@...gutronix.de, abelvesa@...nel.org, peng.fan@....com, 
	mturquette@...libre.com, sboyd@...nel.org, robh@...nel.org, 
	krzk+dt@...nel.org, conor+dt@...nel.org, shawnguo@...nel.org, 
	s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com, 
	marex@...x.de, linux-clk@...r.kernel.org, imx@...ts.linux.dev, 
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 3/5] reset: imx-aux: Add i.MX auxiliary reset driver

On Fri, May 31, 2024 at 2:34 AM Frank Li <Frank.li@....com> wrote:
>
> On Thu, May 30, 2024 at 06:45:10PM +0200, Marco Felsch wrote:
> > On 24-05-30, Frank Li wrote:
> > > On Thu, May 30, 2024 at 11:05:58AM +0200, Marco Felsch wrote:
> > > > Hi,
> > > >
> > > > On 24-05-30, Shengjiu Wang wrote:
> > > > > Add support for the resets on i.MX8MP Audio Block Control module,
> > > > > which includes the EARC PHY software reset and EARC controller
> > > > > software reset. The reset controller is created using the auxiliary
> > > > > device framework and set up in the clock driver.
> > > > >
> > > > > Signed-off-by: Shengjiu Wang <shengjiu.wang@....com>
> > > > > ---
> > > > >  drivers/reset/Kconfig         |   8 ++
> > > > >  drivers/reset/Makefile        |   1 +
> > > > >  drivers/reset/reset-imx-aux.c | 217 ++++++++++++++++++++++++++++++++++
> > > >                       ^
> > > > You make use of the auxiliary bus but this isn't a aux driver, it's the
> > > > i.MX8MP EARC reset driver. According the TRM only the EARC reset bits
> > > > are covered by the AUDIOMIX blk-ctrl.
> > > >
> > > > >  3 files changed, 226 insertions(+)
> > > > >  create mode 100644 drivers/reset/reset-imx-aux.c
> > > > >
> > > > > diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
> > > > > index 7112f5932609..38fdf05b326b 100644
> > > > > --- a/drivers/reset/Kconfig
> > > > > +++ b/drivers/reset/Kconfig
> > > > > @@ -91,6 +91,14 @@ config RESET_IMX7
> > > > >         help
> > > > >           This enables the reset controller driver for i.MX7 SoCs.
> > > > >
> > > > > +config RESET_IMX_AUX
> > > > > +       tristate "i.MX Auxiliary Reset Driver"
> > > >                   ^
> > > >               Same applies here
> > > >
> > > > > +       depends on CLK_IMX8MP
> > > > > +       select AUXILIARY_BUS
> > > > > +       default CLK_IMX8MP
> > > > > +       help
> > > > > +         This enables the auxiliary reset controller driver for i.MX.
> > > > > +
> > > > >  config RESET_INTEL_GW
> > > > >         bool "Intel Reset Controller Driver"
> > > > >         depends on X86 || COMPILE_TEST
> > > > > diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
> > > > > index fd8b49fa46fc..f078da14c327 100644
> > > > > --- a/drivers/reset/Makefile
> > > > > +++ b/drivers/reset/Makefile
> > > > > @@ -14,6 +14,7 @@ obj-$(CONFIG_RESET_BRCMSTB_RESCAL) += reset-brcmstb-rescal.o
> > > > >  obj-$(CONFIG_RESET_GPIO) += reset-gpio.o
> > > > >  obj-$(CONFIG_RESET_HSDK) += reset-hsdk.o
> > > > >  obj-$(CONFIG_RESET_IMX7) += reset-imx7.o
> > > > > +obj-$(CONFIG_RESET_IMX_AUX) += reset-imx-aux.o
> > > > >  obj-$(CONFIG_RESET_INTEL_GW) += reset-intel-gw.o
> > > > >  obj-$(CONFIG_RESET_K210) += reset-k210.o
> > > > >  obj-$(CONFIG_RESET_LANTIQ) += reset-lantiq.o
> > > > > diff --git a/drivers/reset/reset-imx-aux.c b/drivers/reset/reset-imx-aux.c
> > > > > new file mode 100644
> > > > > index 000000000000..61c353abc84e
> > > > > --- /dev/null
> > > > > +++ b/drivers/reset/reset-imx-aux.c
> > > > > @@ -0,0 +1,217 @@
> > > > > +// SPDX-License-Identifier: GPL-2.0-or-later
> > > > > +/*
> > > > > + * Copyright 2024 NXP
> > > > > + */
> > > > > +
> > > > > +#include <linux/auxiliary_bus.h>
> > > > > +#include <linux/device.h>
> > > > > +#include <linux/io.h>
> > > > > +#include <linux/module.h>
> > > > > +#include <linux/of.h>
> > > > > +#include <linux/of_address.h>
> > > > > +#include <linux/of_platform.h>
> > > > > +#include <linux/platform_device.h>
> > > > > +#include <linux/reset-controller.h>
> > > > > +
> > > > > +/*
> > > > > + * The reset does not support the feature and corresponding
> > > > > + * values are not valid
> > > > > + */
> > > > > +#define ASSERT_NONE     BIT(0)
> > > > > +#define DEASSERT_NONE   BIT(1)
> > > > > +#define STATUS_NONE     BIT(2)
> > > > > +
> > > > > +/* When set this function is activated by setting(vs clearing) this bit */
> > > > > +#define ASSERT_SET      BIT(3)
> > > > > +#define DEASSERT_SET    BIT(4)
> > > > > +#define STATUS_SET      BIT(5)
> > > > > +
> > > > > +/* The following are the inverse of the above and are added for consistency */
> > > > > +#define ASSERT_CLEAR    (0 << 3)
> > > > > +#define DEASSERT_CLEAR  (0 << 4)
> > > > > +#define STATUS_CLEAR    (0 << 5)
> > > > > +
> > > > > +/**
> > > > > + * struct imx_reset_ctrl - reset control structure
> > > > > + * @assert_offset: reset assert control register offset
> > > > > + * @assert_bit: reset assert bit in the reset assert control register
> > > > > + * @deassert_offset: reset deassert control register offset
> > > > > + * @deassert_bit: reset deassert bit in the reset deassert control register
> > > > > + * @status_offset: reset status register offset
> > > > > + * @status_bit: reset status bit in the reset status register
> > > > > + * @flags: reset flag indicating how the (de)assert and status are handled
> > > > > + */
> > > > > +struct imx_reset_ctrl {
> > > > > +       u32 assert_offset;
> > > > > +       u32 assert_bit;
> > > > > +       u32 deassert_offset;
> > > > > +       u32 deassert_bit;
> > > > > +       u32 status_offset;
> > > > > +       u32 status_bit;
> > > > > +       u32 flags;
> > > > > +};
> > > >
> > > > Why do we make it this compicated for an simple EARC module reset? I
> > > > understand that you want to provide a generic driver which can be
> > > > re-used but there is actual no other user and may will get no other user
> > > > in the future too. Therefore I would like to keep it simple at the
> > > > begin and adapt the code on-demand.
> > >
> > > There are many similar cases. such as
> > > https://elixir.bootlin.com/linux/v6.10-rc1/source/drivers/pci/controller/dwc/pci-layerscape.c#L251
> > >
> > > Previously it use syscon and regmap to a global register space region and
> > > direct operate the register. Now this way will not preferred. It needs
> > > export as reset driver. but actually, it just write some bits.
> >
> > It depends, if your reset-controller is part of an complete different
> > device like this EARC reset you're right else you can write to the reset
> > directly within you driver.
>
> These reset bits allocated a global register regions. Such as bit0 for
> pcie0, bit1 for pci1, bit2 for usb0, bit3 for usb1. Hardware pack these
> to misc mmio region.
>
> >
> > > We face the similar problem at difference driver when do upstream.
> > >
> > > One on going a discussion about sim module reset
> > > https://lore.kernel.org/imx/131e46b1-61d9-41de-a225-853b09c765d1@gmail.com/
> > >
> > > We hope an unified and simple method to handle these cases.
> >
> > An unified driver for non-unified reset modules? This makes no sense to
> > me. When it comes to possible quirk handling for different reset modules
> > your code gets even more complex.
> >
> > I'm fine with a common code base (driver) if NXP has an common reset
> > controller IP which is added to several SoC. There should be no common
> > code base if this isn't the case.
>
> Some chip have common reset controller IP. Some chip simple packed reset
> bits to one global misc mmio region with other misc control bit, such power
> on/off / clock source choose / enable debug features.
>
> Here we just consider the second case. Anyway we need handle these case at
> somewhere. 99% case just write bit<n> to register offset. Only difference
> is bit posstion and register offset. If write difference driver for these
> just because bit posstion or offset, there will be many duplicated codes
> under driver/reset.
>
> For example:
> Misc: 0x1000
>       bit0: pcie0 reset
>       bit2: usb0 reset
>       bit3-bit4: pcie clk source select
>       bit5-bit6: usb0 clk source select
>       bit7: pcie0 phy power on
>       bit8: usb0 phy power on.
>
> The difference chip, bit possition will be changed.
> How handle this case corporately?

What's the conclusion for this topic?
Should be the driver general for other cases or specific
for i.MX8MP AudioMIX?

Best regards
Shengjiu Wang
>
> >
> > Regards,
> >   Marco
> >
> >
> > >
> > > Frank
> > >
> > > >
> > > > Regards,
> > > >   Marco
> > > >
> > > > > +struct imx_reset_data {
> > > > > +       const struct imx_reset_ctrl *rst_ctrl;
> > > > > +       size_t rst_ctrl_num;
> > > > > +};
> > > > > +
> > > > > +struct imx_aux_reset_priv {
> > > > > +       struct reset_controller_dev rcdev;
> > > > > +       void __iomem *base;
> > > > > +       const struct imx_reset_data *data;
> > > > > +};
> > > > > +
> > > > > +static int imx_aux_reset_assert(struct reset_controller_dev *rcdev,
> > > > > +                               unsigned long id)
> > > > > +{
> > > > > +       struct imx_aux_reset_priv *priv = container_of(rcdev,
> > > > > +                                       struct imx_aux_reset_priv, rcdev);
> > > > > +       const struct imx_reset_data *data = priv->data;
> > > > > +       void __iomem *reg_addr = priv->base;
> > > > > +       const struct imx_reset_ctrl *ctrl;
> > > > > +       unsigned int mask, value, reg;
> > > > > +
> > > > > +       if (id >= data->rst_ctrl_num)
> > > > > +               return -EINVAL;
> > > > > +
> > > > > +       ctrl = &data->rst_ctrl[id];
> > > > > +
> > > > > +       /* assert not supported for this reset */
> > > > > +       if (ctrl->flags & ASSERT_NONE)
> > > > > +               return -EOPNOTSUPP;
> > > > > +
> > > > > +       mask = BIT(ctrl->assert_bit);
> > > > > +       value = (ctrl->flags & ASSERT_SET) ? mask : 0x0;
> > > > > +
> > > > > +       reg = readl(reg_addr + ctrl->assert_offset);
> > > > > +       writel(reg | value, reg_addr + ctrl->assert_offset);
> > > > > +
> > > > > +       return 0;
> > > > > +}
> > > > > +
> > > > > +static int imx_aux_reset_deassert(struct reset_controller_dev *rcdev,
> > > > > +                                 unsigned long id)
> > > > > +{
> > > > > +       struct imx_aux_reset_priv *priv = container_of(rcdev,
> > > > > +                                       struct imx_aux_reset_priv, rcdev);
> > > > > +       const struct imx_reset_data *data = priv->data;
> > > > > +       void __iomem *reg_addr = priv->base;
> > > > > +       const struct imx_reset_ctrl *ctrl;
> > > > > +       unsigned int mask, value, reg;
> > > > > +
> > > > > +       if (id >= data->rst_ctrl_num)
> > > > > +               return -EINVAL;
> > > > > +
> > > > > +       ctrl = &data->rst_ctrl[id];
> > > > > +
> > > > > +       /* deassert not supported for this reset */
> > > > > +       if (ctrl->flags & DEASSERT_NONE)
> > > > > +               return -EOPNOTSUPP;
> > > > > +
> > > > > +       mask = BIT(ctrl->deassert_bit);
> > > > > +       value = (ctrl->flags & DEASSERT_SET) ? mask : 0x0;
> > > > > +
> > > > > +       reg = readl(reg_addr + ctrl->deassert_offset);
> > > > > +       writel(reg | value, reg_addr + ctrl->deassert_offset);
> > > > > +
> > > > > +       return 0;
> > > > > +}
> > > > > +
> > > > > +static int imx_aux_reset_status(struct reset_controller_dev *rcdev,
> > > > > +                               unsigned long id)
> > > > > +{
> > > > > +       struct imx_aux_reset_priv *priv = container_of(rcdev,
> > > > > +                                       struct imx_aux_reset_priv, rcdev);
> > > > > +       const struct imx_reset_data *data = priv->data;
> > > > > +       void __iomem *reg_addr = priv->base;
> > > > > +       const struct imx_reset_ctrl *ctrl;
> > > > > +       unsigned int reset_state;
> > > > > +
> > > > > +       if (id >= data->rst_ctrl_num)
> > > > > +               return -EINVAL;
> > > > > +
> > > > > +       ctrl = &data->rst_ctrl[id];
> > > > > +
> > > > > +       /* status not supported for this reset */
> > > > > +       if (ctrl->flags & STATUS_NONE)
> > > > > +               return -EOPNOTSUPP;
> > > > > +
> > > > > +       reset_state = readl(reg_addr + ctrl->status_offset);
> > > > > +
> > > > > +       return !(reset_state & BIT(ctrl->status_bit)) ==
> > > > > +               !(ctrl->flags & STATUS_SET);
> > > > > +}
> > > > > +
> > > > > +static const struct reset_control_ops imx_aux_reset_ops = {
> > > > > +       .assert   = imx_aux_reset_assert,
> > > > > +       .deassert = imx_aux_reset_deassert,
> > > > > +       .status   = imx_aux_reset_status,
> > > > > +};
> > > > > +
> > > > > +static int imx_aux_reset_probe(struct auxiliary_device *adev,
> > > > > +                              const struct auxiliary_device_id *id)
> > > > > +{
> > > > > +       struct imx_reset_data *data = (struct imx_reset_data *)(id->driver_data);
> > > > > +       struct imx_aux_reset_priv *priv;
> > > > > +       struct device *dev = &adev->dev;
> > > > > +
> > > > > +       priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> > > > > +       if (!priv)
> > > > > +               return -ENOMEM;
> > > > > +
> > > > > +       priv->rcdev.owner     = THIS_MODULE;
> > > > > +       priv->rcdev.nr_resets = data->rst_ctrl_num;
> > > > > +       priv->rcdev.ops       = &imx_aux_reset_ops;
> > > > > +       priv->rcdev.of_node   = dev->parent->of_node;
> > > > > +       priv->rcdev.dev       = dev;
> > > > > +       priv->rcdev.of_reset_n_cells = 1;
> > > > > +       priv->base            = of_iomap(dev->parent->of_node, 0);
> > > > > +       priv->data            = data;
> > > > > +
> > > > > +       return devm_reset_controller_register(dev, &priv->rcdev);
> > > > > +}
> > > > > +
> > > > > +#define EARC  0x200
> > > > > +
> > > > > +static const struct imx_reset_ctrl imx8mp_audiomix_rst_ctrl[] = {
> > > > > +       {
> > > > > +               .assert_offset = EARC,
> > > > > +               .assert_bit = 0,
> > > > > +               .deassert_offset = EARC,
> > > > > +               .deassert_bit = 0,
> > > > > +               .flags  = ASSERT_CLEAR | DEASSERT_SET | STATUS_NONE,
> > > > > +       },
> > > > > +       {
> > > > > +               .assert_offset = EARC,
> > > > > +               .assert_bit = 1,
> > > > > +               .deassert_offset = EARC,
> > > > > +               .deassert_bit = 1,
> > > > > +               .flags  = ASSERT_CLEAR | DEASSERT_SET | STATUS_NONE,
> > > > > +       },
> > > > > +};
> > > > > +
> > > > > +static const struct imx_reset_data imx8mp_audiomix_rst_data = {
> > > > > +       .rst_ctrl = imx8mp_audiomix_rst_ctrl,
> > > > > +       .rst_ctrl_num = ARRAY_SIZE(imx8mp_audiomix_rst_ctrl),
> > > > > +};
> > > > > +
> > > > > +static const struct auxiliary_device_id imx_aux_reset_ids[] = {
> > > > > +       {
> > > > > +               .name = "clk_imx8mp_audiomix.reset",
> > > > > +               .driver_data = (kernel_ulong_t)&imx8mp_audiomix_rst_data,
> > > > > +       },
> > > > > +       { }
> > > > > +};
> > > > > +MODULE_DEVICE_TABLE(auxiliary, imx_aux_reset_ids);
> > > > > +
> > > > > +static struct auxiliary_driver imx_aux_reset_driver = {
> > > > > +       .probe          = imx_aux_reset_probe,
> > > > > +       .id_table       = imx_aux_reset_ids,
> > > > > +};
> > > > > +
> > > > > +module_auxiliary_driver(imx_aux_reset_driver);
> > > > > +
> > > > > +MODULE_AUTHOR("Shengjiu Wang <shengjiu.wang@....com>");
> > > > > +MODULE_DESCRIPTION("Freescale i.MX auxiliary reset driver");
> > > > > +MODULE_LICENSE("GPL");
> > > > > --
> > > > > 2.34.1
> > > > >
> > > > >
> > > > >
> > >

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