Re: [PATCH net-next v12 03/12] dpll: add basic SiTime SiT9531x support

[Ivan Vecera <ivecera@redhat.com>]

On 10/9/26 20:31, Ali Rouhi wrote:
> From: Oleg Zadorozhnyi <Oleg.Zadorozhnyi@devoxsoftware.com>
> 
> The SiT9531x is an I2C clock generator with four independent PLLs, up to
> eight input clocks and up to twelve outputs.  Later patches register the
> PLLs with the DPLL subsystem and expose the clocks as pins; this one adds
> only what is needed to reach the device.
> 
> The register space is paged: 32 pages of 256 registers, selected by
> writing the page number to offset 0xFF, which is present in every page.
> A regmap range configuration describes that window, so the rest of the
> driver addresses a register as a page and an offset and never touches the
> selector itself.  Pages come in pairs for the PLLs (0x0A/0x1A for PLLA,
> and so on).
> 
> Probe reads the rate of the crystal feeding XIN, since every frequency
> the driver later computes derives from it; takes the optional reset line
> and leaves it deasserted, because the device configuration comes from
> efuse or from a blob applied before probe and a reset would discard it;
> then identifies the variant from the single byte at page 0 offset 0x02
> and refuses to bind on anything unknown.
> 
> Suggested-by: Ivan Vecera <ivecera@redhat.com>
> Signed-off-by: Oleg Zadorozhnyi <Oleg.Zadorozhnyi@devoxsoftware.com>
> Assisted-by: LLM
> Signed-off-by: Ali Rouhi <arouhi@sitime.com>
> ---
>   MAINTAINERS                    |   1 +
>   drivers/dpll/Kconfig           |   2 +
>   drivers/dpll/Makefile          |   1 +
>   drivers/dpll/sit9531x/Kconfig  |  13 ++
>   drivers/dpll/sit9531x/Makefile |   4 +
>   drivers/dpll/sit9531x/core.c   | 320 +++++++++++++++++++++++++++++++++
>   drivers/dpll/sit9531x/core.h   |  91 ++++++++++
>   drivers/dpll/sit9531x/regs.h   |  44 +++++
>   8 files changed, 476 insertions(+)
>   create mode 100644 drivers/dpll/sit9531x/Kconfig
>   create mode 100644 drivers/dpll/sit9531x/Makefile
>   create mode 100644 drivers/dpll/sit9531x/core.c
>   create mode 100644 drivers/dpll/sit9531x/core.h
>   create mode 100644 drivers/dpll/sit9531x/regs.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 858fe1c4332c..64e15831055e 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -25187,6 +25187,7 @@ M:      Ali Rouhi <arouhi@sitime.com>
>   L:     netdev@vger.kernel.org
>   S:     Maintained
>   F:     Documentation/devicetree/bindings/dpll/sitime,sit95316.yaml
> +F:     drivers/dpll/sit9531x/
> 
>   SL28 CPLD MFD DRIVER
>   M:     Michael Walle <mwalle@kernel.org>
> diff --git a/drivers/dpll/Kconfig b/drivers/dpll/Kconfig
> index be98969f040a..f8f7ca121b93 100644
> --- a/drivers/dpll/Kconfig
> +++ b/drivers/dpll/Kconfig
> @@ -23,6 +23,8 @@ config DPLL_REFCNT_TRACKER
> 
>            If unsure, say N.
> 
> +source "drivers/dpll/sit9531x/Kconfig"
> +
>   source "drivers/dpll/zl3073x/Kconfig"
> 
>   endmenu
> diff --git a/drivers/dpll/Makefile b/drivers/dpll/Makefile
> index 9e7a3a3e592e..4adc50d748d4 100644
> --- a/drivers/dpll/Makefile
> +++ b/drivers/dpll/Makefile
> @@ -8,4 +8,5 @@ dpll-y                  += dpll_core.o
>   dpll-y                  += dpll_netlink.o
>   dpll-y                  += dpll_nl.o
> 
> +obj-$(CONFIG_SIT9531X_DPLL)    += sit9531x/
>   obj-$(CONFIG_ZL3073X)  += zl3073x/
> diff --git a/drivers/dpll/sit9531x/Kconfig b/drivers/dpll/sit9531x/Kconfig
> new file mode 100644
> index 000000000000..ac5b7f31a034
> --- /dev/null
> +++ b/drivers/dpll/sit9531x/Kconfig
> @@ -0,0 +1,13 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +
> +config SIT9531X_DPLL
> +       tristate "SiTime SiT9531x DPLL driver"
> +       depends on I2C && NET
> +       select DPLL
> +       select REGMAP_I2C
> +       help
> +         Driver for SiTime SiT9531x family clock generators
> +         (SiT95317, SiT95316).
> +
> +         To compile this driver as a module, choose M here: the
> +         module will be called sit9531x.
> diff --git a/drivers/dpll/sit9531x/Makefile b/drivers/dpll/sit9531x/Makefile
> new file mode 100644
> index 000000000000..a221fe55386a
> --- /dev/null
> +++ b/drivers/dpll/sit9531x/Makefile
> @@ -0,0 +1,4 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +
> +obj-$(CONFIG_SIT9531X_DPLL) += sit9531x.o
> +sit9531x-y := core.o
> diff --git a/drivers/dpll/sit9531x/core.c b/drivers/dpll/sit9531x/core.c
> new file mode 100644
> index 000000000000..c7c14442df92
> --- /dev/null
> +++ b/drivers/dpll/sit9531x/core.c
> @@ -0,0 +1,320 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * SiTime SiT9531x DPLL core driver
> + *
> + * Copyright (C) 2026 SiTime Corp.
> + * Author: Ali Rouhi <arouhi@sitime.com>
> + * Author: Oleg Zadorozhnyi <Oleg.Zadorozhnyi@devoxsoftware.com>
> + *
> + * I2C probe, paged regmap configuration and register access helpers.
> + */
> +
> +#include <linux/bits.h>
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/dev_printk.h>
> +#include <linux/device.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/i2c.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/property.h>
> +#include <linux/regmap.h>
> +
> +#include "core.h"
> +#include "regs.h"
> +
> +#define SIT9531X_CHIP(_id, _nin, _nout, _name, _map) \
> +       { .id = (_id), .num_inputs = (_nin), .num_outputs = (_nout), \
> +         .name = (_name), .clkout_map = (_map) }
> +
> +/* Per-variant output index -> physical slot mapping */
> +static const u8 clkout_map_95317[] = {0, 3, 4, 5, 7, 8, 9, 11};
> +static const u8 clkout_map_95316[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11};
> +
> +static const struct sit9531x_chip_info sit9531x_chip_ids[] = {
> +       SIT9531X_CHIP(SIT9531X_VARIANT_ID_95317, 8, 8, "SiT95317",
> +                     clkout_map_95317),
> +       SIT9531X_CHIP(SIT9531X_VARIANT_ID_95316, 8, 12, "SiT95316",
> +                     clkout_map_95316),
> +};
> +
> +#define SIT9531X_RANGE_OFFSET  SIT9531X_PAGE_SIZE
> +
> +/*
> + * Everything the device holds can change without the driver writing it,
> + * so nothing here is cacheable except the page selector.  Caching that
> + * one spares a read of it before every access: the range code selects
> + * the page through a read-modify-write, and with no cache that read goes
> + * to the bus each time.
> + *
> + * The cached value is only as good as the last transfer, though.  A
> + * transfer that fails can leave the part on another page than the cache
> + * records, so every accessor drops the entry on an error and the next
> + * access reads the selector again.
> + */
> +static bool sit9531x_volatile_reg(struct device *dev __maybe_unused,
> +                                 unsigned int reg)
> +{
> +       return reg != SIT9531X_PAGE_SEL;
> +}
> +
> +static const struct regmap_range_cfg sit9531x_regmap_range = {
> +       .range_min      = SIT9531X_RANGE_OFFSET,
> +       .range_max      = SIT9531X_RANGE_OFFSET +
> +                         (SIT9531X_NUM_PAGES * SIT9531X_PAGE_SIZE) - 1,
> +       .selector_reg   = SIT9531X_PAGE_SEL,
> +       .selector_mask  = GENMASK(7, 0),
> +       .selector_shift = 0,
> +       .window_start   = 0,
> +       .window_len     = SIT9531X_PAGE_SIZE,
> +};
> +
> +const struct regmap_config sit9531x_regmap_config = {
> +       .reg_bits       = 8,
> +       .val_bits       = 8,
> +       .max_register   = SIT9531X_RANGE_OFFSET +
> +                         (SIT9531X_NUM_PAGES * SIT9531X_PAGE_SIZE) - 1,
> +       .ranges         = &sit9531x_regmap_range,
> +       .num_ranges     = 1,
> +       .volatile_reg   = sit9531x_volatile_reg,
> +       .cache_type     = REGCACHE_MAPLE,
> +};

This is only referenced from core.c. Could it be static, with the extern
declarations dropped from core.h?

The same for sit9531x_dev_probe().

Thanks,
Ivan