Re: [PATCH v4 09/16] reset: starfive-jh7100: Add StarFive JH7100 reset driver

[Emil Renner Berthing <kernel@esmil.dk>]

On Tue, 16 Nov 2021 at 17:01, Andy Shevchenko <andy.shevchenko@gmail.com> wrote:
> On Tue, Nov 16, 2021 at 5:06 PM Emil Renner Berthing <kernel@esmil.dk> wrote:
> >
> > Add a driver for the StarFive JH7100 reset controller.
>
> Thanks!
> Couple of minor remarks below and take my
> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

Thank you.

> > Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>
> > ---
> >  MAINTAINERS                           |   7 +
> >  drivers/reset/Kconfig                 |   7 +
> >  drivers/reset/Makefile                |   1 +
> >  drivers/reset/reset-starfive-jh7100.c | 176 ++++++++++++++++++++++++++
> >  4 files changed, 191 insertions(+)
> >  create mode 100644 drivers/reset/reset-starfive-jh7100.c
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 2548ef1f8246..1152f5d94690 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -18137,6 +18137,13 @@ F:     Documentation/devicetree/bindings/clock/starfive,jh7100-clkgen.yaml
> >  F:     drivers/clk/starfive/clk-starfive-jh7100.c
> >  F:     include/dt-bindings/clock/starfive-jh7100.h
> >
> > +STARFIVE JH7100 RESET CONTROLLER DRIVER
> > +M:     Emil Renner Berthing <kernel@esmil.dk>
> > +S:     Maintained
> > +F:     Documentation/devicetree/bindings/reset/starfive,jh7100-reset.yaml
> > +F:     drivers/reset/reset-starfive-jh7100.c
> > +F:     include/dt-bindings/reset/starfive-jh7100.h
> > +
> >  STATIC BRANCH/CALL
> >  M:     Peter Zijlstra <peterz@infradead.org>
> >  M:     Josh Poimboeuf <jpoimboe@redhat.com>
> > diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
> > index 85024eb1d2ea..6f8ba0ddc05f 100644
> > --- a/drivers/reset/Kconfig
> > +++ b/drivers/reset/Kconfig
> > @@ -224,6 +224,13 @@ config RESET_SOCFPGA
> >           This enables the reset driver for the SoCFPGA ARMv7 platforms. This
> >           driver gets initialized early during platform init calls.
> >
> > +config RESET_STARFIVE_JH7100
> > +       bool "StarFive JH7100 Reset Driver"
> > +       depends on SOC_STARFIVE || COMPILE_TEST
> > +       default SOC_STARFIVE
> > +       help
> > +         This enables the reset controller driver for the StarFive JH7100 SoC.
> > +
> >  config RESET_SUNXI
> >         bool "Allwinner SoCs Reset Driver" if COMPILE_TEST && !ARCH_SUNXI
> >         default ARCH_SUNXI
> > diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
> > index 21d46d8869ff..bd0a97be18b5 100644
> > --- a/drivers/reset/Makefile
> > +++ b/drivers/reset/Makefile
> > @@ -29,6 +29,7 @@ obj-$(CONFIG_RESET_RZG2L_USBPHY_CTRL) += reset-rzg2l-usbphy-ctrl.o
> >  obj-$(CONFIG_RESET_SCMI) += reset-scmi.o
> >  obj-$(CONFIG_RESET_SIMPLE) += reset-simple.o
> >  obj-$(CONFIG_RESET_SOCFPGA) += reset-socfpga.o
> > +obj-$(CONFIG_RESET_STARFIVE_JH7100) += reset-starfive-jh7100.o
> >  obj-$(CONFIG_RESET_SUNXI) += reset-sunxi.o
> >  obj-$(CONFIG_RESET_TI_SCI) += reset-ti-sci.o
> >  obj-$(CONFIG_RESET_TI_SYSCON) += reset-ti-syscon.o
> > diff --git a/drivers/reset/reset-starfive-jh7100.c b/drivers/reset/reset-starfive-jh7100.c
> > new file mode 100644
> > index 000000000000..2f7615cbf1dc
> > --- /dev/null
> > +++ b/drivers/reset/reset-starfive-jh7100.c
> > @@ -0,0 +1,176 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * Reset driver for the StarFive JH7100 SoC
> > + *
> > + * Copyright (C) 2021 Emil Renner Berthing <kernel@esmil.dk>
> > + */
> > +
> > +#include <linux/bitmap.h>
> > +#include <linux/io.h>
> > +#include <linux/iopoll.h>
> > +#include <linux/mod_devicetable.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/reset-controller.h>
> > +#include <linux/spinlock.h>
> > +
> > +#include <dt-bindings/reset/starfive-jh7100.h>
> > +
> > +/* register offsets */
> > +#define JH7100_RESET_ASSERT0   0x00
> > +#define JH7100_RESET_ASSERT1   0x04
> > +#define JH7100_RESET_ASSERT2   0x08
> > +#define JH7100_RESET_ASSERT3   0x0c
> > +#define JH7100_RESET_STATUS0   0x10
> > +#define JH7100_RESET_STATUS1   0x14
> > +#define JH7100_RESET_STATUS2   0x18
> > +#define JH7100_RESET_STATUS3   0x1c
>
> > +#if BITS_PER_LONG == 64
> > +#define jh7100_reset_read      readq
> > +#define jh7100_reset_write     writeq
> > +#else
> > +#define jh7100_reset_read      readl
> > +#define jh7100_reset_write     writel
> > +#endif
>
> No need, just use always readq() / writeq() and include io-64-nonatomic-lo-hi

Hmm.. how would that work on a 32bit architecture where sizeof(long)
== 4? The whole point of this is to read chunks in sizes matching the
words in the bitmap later on.

> > +/*
> > + * Writing a 1 to the n'th bit of the m'th ASSERT register asserts
> > + * line 32m + n, and writing a 0 deasserts the same line.
> > + * Most reset lines have their status inverted so a 0 bit in the STATUS
> > + * register means the line is asserted and a 1 means it's deasserted. A few
> > + * lines don't though, so store the expected value of the status registers when
> > + * all lines are asserted.
> > + */
> > +static const DECLARE_BITMAP(jh7100_reset_asserted, 4 * 32) = {
> > +       BITMAP_FROM_U64(BIT_ULL_MASK(JH7100_RST_U74) |
> > +                       BIT_ULL_MASK(JH7100_RST_VP6_DRESET) |
> > +                       BIT_ULL_MASK(JH7100_RST_VP6_BRESET) |
> > +                       BIT_ULL_MASK(JH7100_RST_HIFI4_DRESET) |
> > +                       BIT_ULL_MASK(JH7100_RST_HIFI4_BRESET)),
> > +       BITMAP_FROM_U64(BIT_ULL_MASK(JH7100_RST_E24)),
> > +};
> > +
> > +struct jh7100_reset {
> > +       struct reset_controller_dev rcdev;
> > +       /* protect registers against concurrent read-modify-write */
> > +       spinlock_t lock;
> > +       void __iomem *base;
> > +};
> > +
> > +static inline struct jh7100_reset *
> > +jh7100_reset_from(struct reset_controller_dev *rcdev)
> > +{
> > +       return container_of(rcdev, struct jh7100_reset, rcdev);
> > +}
> > +
> > +static int jh7100_reset_update(struct reset_controller_dev *rcdev,
> > +                              unsigned long id, bool assert)
> > +{
> > +       struct jh7100_reset *data = jh7100_reset_from(rcdev);
> > +       unsigned long offset = id / BITS_PER_LONG;
> > +       void __iomem *reg_assert = data->base + JH7100_RESET_ASSERT0 + offset * sizeof(long);
> > +       void __iomem *reg_status = data->base + JH7100_RESET_STATUS0 + offset * sizeof(long);
> > +       unsigned long mask = BIT_MASK(id);
>
> It's better to group offset and mask, so it will give a hint to human
> and compiler that
> '/' + '%' can be optimized to one assembly instructions on some
> architectures (in case of compile-test or new RISC-V types, I dunno if
> they have it now).
>
> And use BIT_WORD() for offset calculation. Same for the above function.

Makes sense. Thanks.

> > +       unsigned long done = jh7100_reset_asserted[offset] & mask;
> > +       unsigned long value;
> > +       unsigned long flags;
> > +       int ret;
> > +
> > +       if (!assert)
> > +               done ^= mask;
> > +
> > +       spin_lock_irqsave(&data->lock, flags);
> > +
> > +       value = jh7100_reset_read(reg_assert);
> > +       if (assert)
> > +               value |= mask;
> > +       else
> > +               value &= ~mask;
> > +       jh7100_reset_write(value, reg_assert);
> > +
> > +       /* if the associated clock is gated, deasserting might otherwise hang forever */
> > +       ret = readx_poll_timeout_atomic(jh7100_reset_read, reg_status, value,
> > +                                       (value & mask) == done, 0, 1000);
> > +
> > +       spin_unlock_irqrestore(&data->lock, flags);
> > +       return ret;
> > +}
> > +
> > +static int jh7100_reset_assert(struct reset_controller_dev *rcdev,
> > +                              unsigned long id)
> > +{
> > +       return jh7100_reset_update(rcdev, id, true);
> > +}
> > +
> > +static int jh7100_reset_deassert(struct reset_controller_dev *rcdev,
> > +                                unsigned long id)
> > +{
> > +       return jh7100_reset_update(rcdev, id, false);
> > +}
> > +
> > +static int jh7100_reset_reset(struct reset_controller_dev *rcdev,
> > +                             unsigned long id)
> > +{
> > +       int ret;
> > +
> > +       ret = jh7100_reset_assert(rcdev, id);
> > +       if (ret)
> > +               return ret;
> > +
> > +       return jh7100_reset_deassert(rcdev, id);
> > +}
> > +
> > +static int jh7100_reset_status(struct reset_controller_dev *rcdev,
> > +                              unsigned long id)
> > +{
> > +       struct jh7100_reset *data = jh7100_reset_from(rcdev);
> > +       unsigned long offset = id / BITS_PER_LONG;
> > +       void __iomem *reg_status = data->base + JH7100_RESET_STATUS0 + offset * sizeof(long);
> > +       unsigned long value = jh7100_reset_read(reg_status);
> > +       unsigned long mask = BIT_MASK(id);
> > +
> > +       return !((value ^ jh7100_reset_asserted[offset]) & mask);
> > +}
> > +
> > +static const struct reset_control_ops jh7100_reset_ops = {
> > +       .assert         = jh7100_reset_assert,
> > +       .deassert       = jh7100_reset_deassert,
> > +       .reset          = jh7100_reset_reset,
> > +       .status         = jh7100_reset_status,
> > +};
> > +
> > +static int __init jh7100_reset_probe(struct platform_device *pdev)
> > +{
> > +       struct jh7100_reset *data;
> > +
> > +       data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
> > +       if (!data)
> > +               return -ENOMEM;
> > +
> > +       data->base = devm_platform_ioremap_resource(pdev, 0);
> > +       if (IS_ERR(data->base))
> > +               return PTR_ERR(data->base);
> > +
> > +       data->rcdev.ops = &jh7100_reset_ops;
> > +       data->rcdev.owner = THIS_MODULE;
> > +       data->rcdev.nr_resets = JH7100_RSTN_END;
> > +       data->rcdev.dev = &pdev->dev;
> > +       data->rcdev.of_node = pdev->dev.of_node;
> > +       spin_lock_init(&data->lock);
> > +
> > +       return devm_reset_controller_register(&pdev->dev, &data->rcdev);
> > +}
> > +
> > +static const struct of_device_id jh7100_reset_dt_ids[] = {
> > +       { .compatible = "starfive,jh7100-reset" },
> > +       { /* sentinel */ }
> > +};
> > +
> > +static struct platform_driver jh7100_reset_driver = {
> > +       .driver = {
> > +               .name = "jh7100-reset",
> > +               .of_match_table = jh7100_reset_dt_ids,
> > +               .suppress_bind_attrs = true,
> > +       },
> > +};
> > +builtin_platform_driver_probe(jh7100_reset_driver, jh7100_reset_probe);
> > --
> > 2.33.1
> >
>
>
> --
> With Best Regards,
> Andy Shevchenko