Subject: Re: [PATCH v6 4/8] phy: fsl: Add Lynx 10G SerDes driver

From: Vinod Koul <[email-masked]>
Date: Sat, 24 Sep 2022 12:24:44 +0530

On 20-09-22, 16:23, Sean Anderson wrote:
> This adds support for the Lynx 10G "SerDes" devices found on various NXP
> QorIQ SoCs. There may be up to four SerDes devices on each SoC, each
> supporting up to eight lanes. Protocol support for each SerDes is highly
> heterogeneous, with each SoC typically having a totally different
> selection of supported protocols for each lane. Additionally, the SerDes
> devices on each SoC also have differing support. One SerDes will
> typically support Ethernet on most lanes, while the other will typically
> support PCIe on most lanes.
> 
> There is wide hardware support for this SerDes. It is present on QorIQ
> T-Series and Layerscape processors. Because each SoC typically has
> specific instructions and exceptions for its SerDes, I have limited the
> initial scope of this module to just the LS1046A and LS1088A.
> Additionally, I have only added support for Ethernet protocols. There is
> not a great need for dynamic reconfiguration for other protocols (except
> perhaps for M.2 cards), so support for them may never be added.
> 
> Nevertheless, I have tried to provide an obvious path for adding support
> for other SoCs as well as other protocols. SATA just needs support for
> configuring LNmSSCR0. PCIe may need to configure the equalization
> registers. It also uses multiple lanes. I have tried to write the driver
> with multi-lane support in mind, so there should not need to be any
> large changes. Although there are 6 protocols supported, I have only
> tested SGMII and XFI. The rest have been implemented as described in
> the datasheet. Most of these protocols should work "as-is", but
> 10GBASE-KR will need PCS support for link training.
> 
> The PLLs are modeled as clocks proper. This lets us take advantage of
> the existing clock infrastructure. I have not given the same treatment
> to the per-lane clocks because they need to be programmed in-concert
> with the rest of the lane settings. One tricky thing is that the VCO
> (PLL) rate exceeds 2^32 (maxing out at around 5GHz). This will be a
> problem on 32-bit platforms, since clock rates are stored as unsigned
> longs. To work around this, the pll clock rate is generally treated in
> units of kHz.
> 
> The PLLs are configured rather interestingly. Instead of the usual direct
> programming of the appropriate divisors, the input and output clock rates
> are selected directly. Generally, the only restriction is that the input
> and output must be integer multiples of each other. This suggests some kind
> of internal look-up table. The datasheets generally list out the supported
> combinations explicitly, and not all input/output combinations are
> documented. I'm not sure if this is due to lack of support, or due to an
> oversight. If this becomes an issue, then some combinations can be
> blacklisted (or whitelisted). This may also be necessary for other SoCs
> which have more stringent clock requirements.
> 
> The general API call list for this PHY is documented under the driver-api
> docs. I think this is rather standard, except that most drivers configure
> the mode (protocol) at xlate-time. Unlike some other phys where e.g. PCIe
> x4 will use 4 separate phys all configured for PCIe, this driver uses one
> phy configured to use 4 lanes. This is because while the individual lanes
> may be configured individually, the protocol selection acts on all lanes at
> once. Additionally, the order which lanes should be configured in is
> specified by the datasheet.  To coordinate this, lanes are reserved in
> phy_init, and released in phy_exit.
> 
> This driver was written with reference to the LS1046A reference manual.
> However, it was informed by reference manuals for all processors with
> mEMACs, especially the T4240 (which appears to have a "maxed-out"
> configuration). The earlier P-Series processors appear to be similar, but
> have a different overall register layout (using "banks" instead of
> separate SerDes). Perhaps this those use a "5G Lynx SerDes."
> 
> Signed-off-by: Sean Anderson <[email-masked]>
> ---
> 
> Changes in v6:
> - Update MAINTAINERS to include new files
> - Include bitfield.h and slab.h to allow compilation on non-arm64
>   arches.
> - Depend on COMMON_CLK and either layerscape/ppc
> 
> Changes in v5:
> - Remove references to PHY_INTERFACE_MODE_1000BASEKX to allow this
>   series to be applied directly to linux/master.
> - Add fsl,lynx-10g.h to MAINTAINERS
> 
> Changes in v4:
> - Rework all debug statements to remove use of __func__. Additional
>   information has been provided as necessary.
> - Consider alternative parent rates in round_rate and not in set_rate.
>   Trying to modify out parent's rate in set_rate will deadlock.
> - Explicitly perform a stop/reset sequence in set_rate. This way we
>   always ensure that the PLL is properly stopped.
> - Set the power-down bit when disabling the PLL. We can do this now that
>   enable/disable aren't abused during the set rate sequence.
> - Fix typos in QSGMII_OFFSET and XFI_OFFSET
> - Rename LNmTECR0_TEQ_TYPE_PRE to LNmTECR0_TEQ_TYPE_POST to better
>   reflect its function (adding post-cursor equalization).
> - Use of_clk_hw_onecell_get instead of a custom function.
> - Return struct clks from lynx_clks_init instead of embedding lynx_clk
>   in lynx_priv.
> - Rework PCCR helper functions; T-series SoCs differ from Layerscape SoCs
>   primarily in the layout and offset of the PCCRs. This will help bring a
>   cleaner abstraction layer. The caps have been removed, since this handles the
>   only current usage.
> - Convert to use new binding format. As a result of this, we no longer need to
>   have protocols for PCIe or SATA. Additionally, modes now live in lynx_group
>   instead of lynx_priv.
> - Remove teq from lynx_proto_params, since it can be determined from
>   preq_ratio/postq_ratio.
> - Fix an early return from lynx_set_mode not releasing serdes->lock.
> - Rename lynx_priv.conf to .cfg, since I kept mistyping it.
> 
> Changes in v3:
> - Rename remaining references to QorIQ SerDes to Lynx 10G
> - Fix PLL enable sequence by waiting for our reset request to be cleared
>   before continuing. Do the same for the lock, even though it isn't as
>   critical. Because we will delay for 1.5ms on average, use prepare
>   instead of enable so we can sleep.
> - Document the status of each protocol
> - Fix offset of several bitfields in RECR0
> - Take into account PLLRST_B, SDRST_B, and SDEN when considering whether
>   a PLL is "enabled."
> - Only power off unused lanes.
> - Split mode lane mask into first/last lane (like group)
> - Read modes from device tree
> - Use caps to determine whether KX/KR are supported
> - Move modes to lynx_priv
> - Ensure that the protocol controller is not already in-use when we try
>   to configure a new mode. This should only occur if the device tree is
>   misconfigured (e.g. when QSGMII is selected on two lanes but there is
>   only one QSGMII controller).
> - Split PLL drivers off into their own file
> - Add clock for "ext_dly" instead of writing the bit directly (and
>   racing with any clock code).
> - Use kasprintf instead of open-coding the snprintf dance
> - Support 1000BASE-KX in lynx_lookup_proto. This still requires PCS
>   support, so nothing is truly "enabled" yet.
> 
> Changes in v2:
> - Rename driver to Lynx 10G (etc.)
> - Fix not clearing group->pll after disabling it
> - Support 1 and 2 phy-cells
> - Power off lanes during probe
> - Clear SGMIIaCR1_PCS_EN during probe
> - Rename LYNX_PROTO_UNKNOWN to LYNX_PROTO_NONE
> - Handle 1000BASE-KX in lynx_proto_mode_prep
> 
>  Documentation/driver-api/phy/index.rst       |    1 +
>  Documentation/driver-api/phy/lynx_10g.rst    |   66 +
>  MAINTAINERS                                  |    7 +
>  drivers/phy/freescale/Kconfig                |   21 +
>  drivers/phy/freescale/Makefile               |    3 +
>  drivers/phy/freescale/lynx-10g.h             |   16 +
>  drivers/phy/freescale/phy-fsl-lynx-10g-clk.c |  503 ++++++++
>  drivers/phy/freescale/phy-fsl-lynx-10g.c     | 1162 ++++++++++++++++++
>  8 files changed, 1779 insertions(+)
>  create mode 100644 Documentation/driver-api/phy/lynx_10g.rst
>  create mode 100644 drivers/phy/freescale/lynx-10g.h
>  create mode 100644 drivers/phy/freescale/phy-fsl-lynx-10g-clk.c
>  create mode 100644 drivers/phy/freescale/phy-fsl-lynx-10g.c
> 
> diff --git a/Documentation/driver-api/phy/index.rst b/Documentation/driver-api/phy/index.rst
> index 69ba1216de72..c9b7a4698dab 100644
> --- a/Documentation/driver-api/phy/index.rst
> +++ b/Documentation/driver-api/phy/index.rst
> @@ -7,6 +7,7 @@ Generic PHY Framework
>  .. toctree::
>  
>     phy
> +   lynx_10g
>     samsung-usb2
>  
>  .. only::  subproject and html
> diff --git a/Documentation/driver-api/phy/lynx_10g.rst b/Documentation/driver-api/phy/lynx_10g.rst
> new file mode 100644
> index 000000000000..6e85dcd8fd71
> --- /dev/null
> +++ b/Documentation/driver-api/phy/lynx_10g.rst
> @@ -0,0 +1,66 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +===========================
> +Lynx 10G Phy (QorIQ SerDes)
> +===========================
> +
> +Using this phy
> +--------------
> +
> +The general order of calls should be::
> +
> +    [devm_][of_]phy_get()
> +    phy_init()
> +    phy_power_on()
> +    phy_set_mode[_ext]()
> +    ...
> +    phy_power_off()
> +    phy_exit()
> +    [[of_]phy_put()]
> +
> +:c:func:`phy_get` just gets (or creates) a new :c:type:`phy` with the lanes
> +described in the phandle. :c:func:`phy_init` is what actually reserves the
> +lanes for use. Unlike some other drivers, when the phy is created, there is no
> +default protocol. :c:func:`phy_set_mode <phy_set_mode_ext>` must be called in
> +order to set the protocol.

This should be added/update to Generic phy documenetation and point that
from here please

> +
> +Supporting SoCs
> +---------------
> +
> +Each new SoC needs a :c:type:`struct lynx_conf <lynx_conf>`, containing the
> +number of lanes in each device, the endianness of the device, and the helper
> +functions to use when selecting protocol controllers. For example, the
> +configuration for the LS1046A is::
> +
> +    static const struct lynx_cfg ls1046a_cfg = {
> +        .lanes = 4,
> +        .endian = REGMAP_ENDIAN_BIG,
> +        .mode_conflict = lynx_ls_mode_conflict,
> +        .mode_apply = lynx_ls_mode_apply,
> +        .mode_init = lynx_ls_mode_init,
> +    };
> +
> +In addition, you will need to add a device node as documented in
> +``Documentation/devicetree/bindings/phy/fsl,lynx-10g.yaml``.  This lets the
> +driver know which lanes are available to configure.
> +
> +Supporting Protocols
> +--------------------
> +
> +Each protocol is a combination of values which must be programmed into the lane
> +registers. To add a new protocol, first add it to :c:type:`enum lynx_protocol
> +<lynx_protocol>`. Add a new entry to `lynx_proto_params`, and populate the
> +appropriate fields. Modify `lynx_lookup_proto` to map the :c:type:`enum
> +phy_mode <phy_mode>` to :c:type:`enum lynx_protocol <lynx_protocol>`. Update
> +the ``mode_conflict``, ``mode_apply``, and ``mode_init`` helpers are updated to
> +support your protocol.
> +
> +You may need to modify :c:func:`lynx_set_mode` in order to support your
> +protocol. This can happen when you have added members to :c:type:`struct
> +lynx_proto_params <lynx_proto_params>`. It can also happen if you have specific
> +clocking requirements, or protocol-specific registers to program.
> +
> +Internal API Reference
> +----------------------
> +
> +.. kernel-doc:: drivers/phy/freescale/phy-fsl-lynx-10g.c
> diff --git a/MAINTAINERS b/MAINTAINERS
> index d6b617bfd1bd..216a75e2eb2e 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -11974,6 +11974,13 @@ S:	Maintained
>  W:	http://linux-test-project.github.io/
>  T:	git git://github.com/linux-test-project/ltp.git
>  
> +LYNX 10G SERDES DRIVER
> +M:	Sean Anderson <[email-masked]>
> +S:	Maintained
> +F:	Documentation/driver-api/phy/lynx_10g.rst
> +F:	drivers/phy/freescale/*lynx-10g*
> +F:	include/dt-bindings/clock/fsl,lynx-10g.h
> +
>  LYNX 28G SERDES PHY DRIVER
>  M:	Ioana Ciornei <[email-masked]>
>  L:	[email-masked]
> diff --git a/drivers/phy/freescale/Kconfig b/drivers/phy/freescale/Kconfig
> index 853958fb2c06..40d3bfb36076 100644
> --- a/drivers/phy/freescale/Kconfig
> +++ b/drivers/phy/freescale/Kconfig
> @@ -47,3 +47,24 @@ config PHY_FSL_LYNX_28G
>  	  found on NXP's Layerscape platforms such as LX2160A.
>  	  Used to change the protocol running on SerDes lanes at runtime.
>  	  Only useful for a restricted set of Ethernet protocols.
> +
> +config PHY_FSL_LYNX_10G
> +	tristate "Freescale QorIQ Lynx 10G SerDes support"
> +	depends on COMMON_CLK
> +	depends on ARCH_LAYERSCAPE || PPC || COMPILE_TEST
> +	select GENERIC_PHY
> +	select REGMAP_MMIO
> +	help
> +	  This adds support for the Lynx "SerDes" devices found on various QorIQ
> +	  SoCs. There may be up to four SerDes devices on each SoC, and each
> +	  device supports up to eight lanes. The SerDes is configured by default
> +	  by the RCW, but this module is necessary in order to support dynamic
> +	  reconfiguration (such as to support 1G and 10G ethernet on the same
> +	  interface). The hardware supports a variety of protocols, including
> +	  Ethernet, SATA, PCIe, and more exotic links such as Interlaken and
> +	  Aurora. This driver only supports Ethernet, but it will try not to
> +	  touch lanes configured for other protocols.
> +
> +	  If you have a QorIQ processor and want to dynamically reconfigure your
> +	  SerDes, say Y. If this driver is compiled as a module, it will be
> +	  named phy-fsl-lynx-10g-drv.
> diff --git a/drivers/phy/freescale/Makefile b/drivers/phy/freescale/Makefile
> index cedb328bc4d2..1f18936507e0 100644
> --- a/drivers/phy/freescale/Makefile
> +++ b/drivers/phy/freescale/Makefile
> @@ -3,4 +3,7 @@ obj-$(CONFIG_PHY_FSL_IMX8MQ_USB)	+= phy-fsl-imx8mq-usb.o
>  obj-$(CONFIG_PHY_MIXEL_LVDS_PHY)	+= phy-fsl-imx8qm-lvds-phy.o
>  obj-$(CONFIG_PHY_MIXEL_MIPI_DPHY)	+= phy-fsl-imx8-mipi-dphy.o
>  obj-$(CONFIG_PHY_FSL_IMX8M_PCIE)	+= phy-fsl-imx8m-pcie.o
> +phy-fsl-lynx-10g-drv-y			+= phy-fsl-lynx-10g.o
> +phy-fsl-lynx-10g-drv-y			+= phy-fsl-lynx-10g-clk.o

You should use a single line for this or even better:

obj-$(CONFIG_PHY_FSL_LYNX_10G)               += phy-fsl-lynx-10g.o phy-fsl-lynx-10g-clk.o

> +obj-$(CONFIG_PHY_FSL_LYNX_10G)		+= phy-fsl-lynx-10g-drv.o
>  obj-$(CONFIG_PHY_FSL_LYNX_28G)		+= phy-fsl-lynx-28g.o
> diff --git a/drivers/phy/freescale/lynx-10g.h b/drivers/phy/freescale/lynx-10g.h
> new file mode 100644
> index 000000000000..75d9353a867b
> --- /dev/null
> +++ b/drivers/phy/freescale/lynx-10g.h
> @@ -0,0 +1,16 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2022 Sean Anderson <[email-masked]>
> + */
> +
> +#ifndef LYNX_10G
> +#define LYNX_10G
> +
> +struct clk;
> +struct device;
> +struct regmap;

why do you want to forward declaration for these?

> +
> +int lynx_clks_init(struct device *dev, struct regmap *regmap,
> +		   struct clk *plls[2], struct clk *ex_dlys[2]);
> +
> +#endif /* LYNX 10G */
> diff --git a/drivers/phy/freescale/phy-fsl-lynx-10g-clk.c b/drivers/phy/freescale/phy-fsl-lynx-10g-clk.c
> new file mode 100644
> index 000000000000..6ec32bdfb9dd
> --- /dev/null
> +++ b/drivers/phy/freescale/phy-fsl-lynx-10g-clk.c
> @@ -0,0 +1,503 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2022 Sean Anderson <[email-masked]>
> + *
> + * This file contains the implementation for the PLLs found on Lynx 10G phys.
> + *
> + * XXX: The VCO rate of the PLLs can exceed ~4GHz, which is the maximum rate
> + * expressable in an unsigned long. To work around this, rates are specified in
> + * kHz. This is as if there was a division by 1000 in the PLL.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/clk-provider.h>
> +#include <linux/device.h>
> +#include <linux/bitfield.h>
> +#include <linux/math64.h>
> +#include <linux/regmap.h>
> +#include <linux/slab.h>
> +#include <linux/units.h>
> +#include <dt-bindings/clock/fsl,lynx-10g.h>
> +
> +#include "lynx-10g.h"
> +
> +#define PLL_STRIDE	0x20
> +#define PLLa(a, off)	((a) * PLL_STRIDE + (off))
> +#define PLLaRSTCTL(a)	PLLa(a, 0x00)
> +#define PLLaCR0(a)	PLLa(a, 0x04)
> +
> +#define PLLaRSTCTL_RSTREQ	BIT(31)
> +#define PLLaRSTCTL_RST_DONE	BIT(30)
> +#define PLLaRSTCTL_RST_ERR	BIT(29)
> +#define PLLaRSTCTL_PLLRST_B	BIT(7)
> +#define PLLaRSTCTL_SDRST_B	BIT(6)
> +#define PLLaRSTCTL_SDEN		BIT(5)
> +
> +#define PLLaRSTCTL_ENABLE_SET	(PLLaRSTCTL_RST_DONE | PLLaRSTCTL_PLLRST_B | \
> +				 PLLaRSTCTL_SDRST_B | PLLaRSTCTL_SDEN)
> +#define PLLaRSTCTL_ENABLE_MASK	(PLLaRSTCTL_ENABLE_SET | PLLaRSTCTL_RST_ERR)
> +
> +#define PLLaCR0_POFF		BIT(31)
> +#define PLLaCR0_RFCLK_SEL	GENMASK(30, 28)
> +#define PLLaCR0_PLL_LCK		BIT(23)
> +#define PLLaCR0_FRATE_SEL	GENMASK(19, 16)
> +#define PLLaCR0_DLYDIV_SEL	GENMASK(1, 0)
> +
> +#define PLLaCR0_DLYDIV_SEL_16		0b01
> +
> +/**
> + * struct lynx_clk - Driver data for the PLLs
> + * @pll: The PLL clock
> + * @ex_dly: The "PLLa_ex_dly_clk" clock
> + * @ref: Our reference clock
> + * @dev: The serdes device
> + * @regmap: Our registers
> + * @idx: Which PLL this clock is for
> + */
> +struct lynx_clk {
> +	struct clk_hw pll, ex_dly;
> +	struct clk_hw *ref;
> +	struct device *dev;
> +	struct regmap *regmap;
> +	unsigned int idx;
> +};
> +
> +static u32 lynx_read(struct lynx_clk *clk, u32 reg)
> +{
> +	unsigned int ret = 0;
> +
> +	WARN_ON_ONCE(regmap_read(clk->regmap, reg, &ret));
> +	return ret;
> +}
> +
> +static void lynx_write(struct lynx_clk *clk, u32 val, u32 reg)
> +{
> +	WARN_ON_ONCE(regmap_write(clk->regmap, reg, val));
> +}
> +
> +static struct lynx_clk *lynx_pll_to_clk(struct clk_hw *hw)
> +{
> +	return container_of(hw, struct lynx_clk, pll);
> +}
> +
> +static struct lynx_clk *lynx_ex_dly_to_clk(struct clk_hw *hw)
> +{
> +	return container_of(hw, struct lynx_clk, ex_dly);
> +}
> +
> +static void lynx_pll_stop(struct lynx_clk *clk)
> +{
> +	u32 rstctl;
> +
> +	rstctl = lynx_read(clk, PLLaRSTCTL(clk->idx));
> +	rstctl &= ~PLLaRSTCTL_SDRST_B;
> +	lynx_write(clk, rstctl, PLLaRSTCTL(clk->idx));
> +
> +	ndelay(50);
> +
> +	rstctl = lynx_read(clk, PLLaRSTCTL(clk->idx));
> +	rstctl &= ~(PLLaRSTCTL_SDEN | PLLaRSTCTL_PLLRST_B);
> +	lynx_write(clk, rstctl, PLLaRSTCTL(clk->idx));
> +
> +	ndelay(100);
> +}
> +
> +static void lynx_pll_disable(struct clk_hw *hw)
> +{
> +	struct lynx_clk *clk = lynx_pll_to_clk(hw);
> +	u32 cr0;
> +
> +	dev_dbg(clk->dev, "disable pll%d\n", clk->idx);
> +
> +	lynx_pll_stop(clk);
> +
> +	cr0 = lynx_read(clk, PLLaCR0(clk->idx));
> +	cr0 |= PLLaCR0_POFF;
> +	lynx_write(clk, cr0, PLLaCR0(clk->idx));
> +}
> +
> +static int lynx_pll_reset(struct lynx_clk *clk)
> +{
> +	int ret;
> +	u32 rstctl = lynx_read(clk, PLLaRSTCTL(clk->idx));
> +
> +	rstctl |= PLLaRSTCTL_RSTREQ;
> +	lynx_write(clk, rstctl, PLLaRSTCTL(clk->idx));
> +	ret = read_poll_timeout(lynx_read, rstctl,
> +				rstctl & (PLLaRSTCTL_RST_DONE | PLLaRSTCTL_RST_ERR),
> +				100, 5000, true, clk, PLLaRSTCTL(clk->idx));
> +	if (rstctl & PLLaRSTCTL_RST_ERR)
> +		ret = -EIO;
> +	if (ret) {
> +		dev_err(clk->dev, "pll%d reset failed\n", clk->idx);
> +		return ret;
> +	}
> +
> +	rstctl |= PLLaRSTCTL_SDEN | PLLaRSTCTL_PLLRST_B | PLLaRSTCTL_SDRST_B;
> +	lynx_write(clk, rstctl, PLLaRSTCTL(clk->idx));
> +	return 0;
> +}
> +
> +static int lynx_pll_prepare(struct clk_hw *hw)
> +{
> +	struct lynx_clk *clk = lynx_pll_to_clk(hw);
> +	u32 rstctl = lynx_read(clk, PLLaRSTCTL(clk->idx));
> +	u32 cr0 = lynx_read(clk, PLLaCR0(clk->idx));
> +
> +	/*
> +	 * "Enabling" the PLL involves resetting it (and all attached lanes).
> +	 * Avoid doing this if we are already enabled.
> +	 */
> +	if (!(cr0 & PLLaCR0_POFF) &&
> +	    (rstctl & PLLaRSTCTL_ENABLE_MASK) == PLLaRSTCTL_ENABLE_SET) {
> +		dev_dbg(clk->dev, "pll%d already prepared\n", clk->idx);
> +		return 0;
> +	}
> +
> +	dev_dbg(clk->dev, "prepare pll%d\n", clk->idx);
> +
> +	cr0 &= ~PLLaCR0_POFF;
> +	lynx_write(clk, cr0, PLLaCR0(clk->idx));
> +
> +	return lynx_pll_reset(clk);
> +}
> +
> +static int lynx_pll_is_enabled(struct clk_hw *hw)
> +{
> +	struct lynx_clk *clk = lynx_pll_to_clk(hw);
> +	u32 cr0 = lynx_read(clk, PLLaCR0(clk->idx));
> +	bool enabled = !(cr0 & PLLaCR0_POFF);
> +
> +	dev_dbg(clk->dev, "pll%d %s enabled\n", clk->idx,
> +		enabled ? "is" : "is not");
> +
> +	return enabled;
> +}
> +
> +static const u32 rfclk_sel_map[8] = {
> +	[0b000] = 100000000,
> +	[0b001] = 125000000,
> +	[0b010] = 156250000,
> +	[0b011] = 150000000,
> +};
> +
> +/**
> + * lynx_rfclk_to_sel() - Convert a reference clock rate to a selector
> + * @rate: The reference clock rate
> + *
> + * To allow for some variation in the reference clock rate, up to 100ppm of
> + * error is allowed.
> + *
> + * Return: An appropriate selector for @rate, or -%EINVAL.
> + */
> +static int lynx_rfclk_to_sel(u32 rate)
> +{
> +	int ret;
> +
> +	for (ret = 0; ret < ARRAY_SIZE(rfclk_sel_map); ret++) {
> +		u32 rfclk_rate = rfclk_sel_map[ret];
> +		/* Allow an error of 100ppm */
> +		u32 error = rfclk_rate / 10000;
> +
> +		if (rate > rfclk_rate - error && rate < rfclk_rate + error)
> +			return ret;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static const u32 frate_sel_map[16] = {
> +	[0b0000] = 5000000,
> +	[0b0101] = 3750000,
> +	[0b0110] = 5156250,
> +	[0b0111] = 4000000,
> +	[0b1001] = 3125000,
> +	[0b1010] = 3000000,
> +};
> +
> +/**
> + * lynx_frate_to_sel() - Convert a VCO clock rate to a selector
> + * @rate_khz: The VCO frequency, in kHz
> + *
> + * Return: An appropriate selector for @rate_khz, or -%EINVAL.
> + */
> +static int lynx_frate_to_sel(u32 rate_khz)
> +{
> +	int ret;
> +
> +	for (ret = 0; ret < ARRAY_SIZE(frate_sel_map); ret++)
> +		if (frate_sel_map[ret] == rate_khz)
> +			return ret;
> +
> +	return -EINVAL;
> +}
> +
> +static u32 lynx_pll_ratio(u32 frate_sel, u32 rfclk_sel)
> +{
> +	u64 frate;
> +	u32 rfclk, error, ratio;
> +
> +	frate = frate_sel_map[frate_sel] * (u64)HZ_PER_KHZ;
> +	rfclk = rfclk_sel_map[rfclk_sel];
> +
> +	if (!frate || !rfclk)
> +		return 0;
> +
> +	ratio = div_u64_rem(frate, rfclk, &error);
> +	if (!error)
> +		return ratio;
> +	return 0;
> +}
> +
> +static unsigned long lynx_pll_recalc_rate(struct clk_hw *hw,
> +					  unsigned long parent_rate)
> +{
> +	struct lynx_clk *clk = lynx_pll_to_clk(hw);
> +	u32 cr0 = lynx_read(clk, PLLaCR0(clk->idx));
> +	u32 frate_sel = FIELD_GET(PLLaCR0_FRATE_SEL, cr0);
> +	u32 rfclk_sel = FIELD_GET(PLLaCR0_RFCLK_SEL, cr0);
> +	u32 ratio = lynx_pll_ratio(frate_sel, rfclk_sel);
> +	unsigned long ret;
> +
> +	/* Ensure that the parent matches our rfclk selector */
> +	if (rfclk_sel == lynx_rfclk_to_sel(parent_rate))
> +		ret = mult_frac(parent_rate, ratio, HZ_PER_KHZ);
> +	else
> +		ret = 0;
> +
> +	dev_dbg(clk->dev, "recalc pll%d new=%llu parent=%lu\n", clk->idx,
> +		(u64)ret * HZ_PER_KHZ, parent_rate);
> +	return ret;
> +}
> +
> +static long lynx_pll_round_rate(struct clk_hw *hw, unsigned long rate_khz,
> +				unsigned long *parent_rate)
> +{
> +	int frate_sel, rfclk_sel;
> +	struct lynx_clk *clk = lynx_pll_to_clk(hw);
> +	u32 ratio;
> +
> +	dev_dbg(clk->dev, "round pll%d new=%llu parent=%lu\n", clk->idx,
> +		(u64)rate_khz * HZ_PER_KHZ, *parent_rate);
> +
> +	frate_sel = lynx_frate_to_sel(rate_khz);
> +	if (frate_sel < 0)
> +		return frate_sel;
> +
> +	/* Try the current parent rate */
> +	rfclk_sel = lynx_rfclk_to_sel(*parent_rate);
> +	if (rfclk_sel >= 0) {
> +		ratio = lynx_pll_ratio(frate_sel, rfclk_sel);
> +		if (ratio)
> +			return mult_frac(*parent_rate, ratio, HZ_PER_KHZ);
> +	}
> +
> +	/* Try all possible parent rates */
> +	for (rfclk_sel = 0;
> +	     rfclk_sel < ARRAY_SIZE(rfclk_sel_map);
> +	     rfclk_sel++) {
> +		unsigned long new_parent_rate;
> +
> +		ratio = lynx_pll_ratio(frate_sel, rfclk_sel);
> +		if (!ratio)
> +			continue;
> +
> +		/* Ensure the reference clock can produce this rate */
> +		new_parent_rate = rfclk_sel_map[rfclk_sel];
> +		new_parent_rate = clk_hw_round_rate(clk->ref, new_parent_rate);
> +		if (rfclk_sel != lynx_rfclk_to_sel(new_parent_rate))
> +			continue;
> +
> +		*parent_rate = new_parent_rate;
> +		return mult_frac(new_parent_rate, ratio, HZ_PER_KHZ);
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static int lynx_pll_set_rate(struct clk_hw *hw, unsigned long rate_khz,
> +			   unsigned long parent_rate)
> +{
> +	int frate_sel, rfclk_sel;
> +	struct lynx_clk *clk = lynx_pll_to_clk(hw);
> +	u32 ratio, cr0 = lynx_read(clk, PLLaCR0(clk->idx));
> +
> +	dev_dbg(clk->dev, "set rate pll%d new=%llu parent=%lu\n", clk->idx,
> +		(u64)rate_khz * HZ_PER_KHZ, parent_rate);
> +
> +	frate_sel = lynx_frate_to_sel(rate_khz);
> +	if (frate_sel < 0)
> +		return frate_sel;
> +
> +	rfclk_sel = lynx_rfclk_to_sel(parent_rate);
> +	if (rfclk_sel < 0)
> +		return rfclk_sel;
> +
> +	ratio = lynx_pll_ratio(frate_sel, rfclk_sel);
> +	if (!ratio)
> +		return -EINVAL;
> +
> +	lynx_pll_stop(clk);
> +	cr0 &= ~(PLLaCR0_RFCLK_SEL | PLLaCR0_FRATE_SEL);
> +	cr0 |= FIELD_PREP(PLLaCR0_RFCLK_SEL, rfclk_sel);
> +	cr0 |= FIELD_PREP(PLLaCR0_FRATE_SEL, frate_sel);
> +	lynx_write(clk, cr0, PLLaCR0(clk->idx));
> +	/* Don't bother resetting if it's off */
> +	if (cr0 & PLLaCR0_POFF)
> +		return 0;
> +	return lynx_pll_reset(clk);
> +}
> +
> +static const struct clk_ops lynx_pll_clk_ops = {
> +	.prepare = lynx_pll_prepare,
> +	.disable = lynx_pll_disable,
> +	.is_enabled = lynx_pll_is_enabled,
> +	.recalc_rate = lynx_pll_recalc_rate,
> +	.round_rate = lynx_pll_round_rate,
> +	.set_rate = lynx_pll_set_rate,
> +};
> +
> +static void lynx_ex_dly_disable(struct clk_hw *hw)
> +{
> +	struct lynx_clk *clk = lynx_ex_dly_to_clk(hw);
> +	u32 cr0 = lynx_read(clk, PLLaCR0(clk->idx));
> +
> +	cr0 &= ~PLLaCR0_DLYDIV_SEL;
> +	lynx_write(clk, PLLaCR0(clk->idx), cr0);
> +}
> +
> +static int lynx_ex_dly_enable(struct clk_hw *hw)
> +{
> +	struct lynx_clk *clk = lynx_ex_dly_to_clk(hw);
> +	u32 cr0 = lynx_read(clk, PLLaCR0(clk->idx));
> +
> +	cr0 &= ~PLLaCR0_DLYDIV_SEL;
> +	cr0 |= FIELD_PREP(PLLaCR0_DLYDIV_SEL, PLLaCR0_DLYDIV_SEL_16);
> +	lynx_write(clk, PLLaCR0(clk->idx), cr0);
> +	return 0;
> +}
> +
> +static int lynx_ex_dly_is_enabled(struct clk_hw *hw)
> +{
> +	struct lynx_clk *clk = lynx_ex_dly_to_clk(hw);
> +
> +	return lynx_read(clk, PLLaCR0(clk->idx)) & PLLaCR0_DLYDIV_SEL;
> +}
> +
> +static unsigned long lynx_ex_dly_recalc_rate(struct clk_hw *hw,
> +					     unsigned long parent_rate)
> +{
> +	return parent_rate / 16;
> +}
> +
> +static const struct clk_ops lynx_ex_dly_clk_ops = {
> +	.enable = lynx_ex_dly_enable,
> +	.disable = lynx_ex_dly_disable,
> +	.is_enabled = lynx_ex_dly_is_enabled,
> +	.recalc_rate = lynx_ex_dly_recalc_rate,
> +};
> +
> +static int lynx_clk_init(struct clk_hw_onecell_data *hw_data,
> +			 struct device *dev, struct regmap *regmap,
> +			 unsigned int index)
> +{
> +	const struct clk_hw *pll_parents, *ex_dly_parents;
> +	struct clk_init_data pll_init = {
> +		.ops = &lynx_pll_clk_ops,
> +		.parent_hws = &pll_parents,
> +		.num_parents = 1,
> +		.flags = CLK_GET_RATE_NOCACHE | CLK_SET_RATE_PARENT |
> +			 CLK_OPS_PARENT_ENABLE,
> +	};
> +	struct clk_init_data ex_dly_init = {
> +		.ops = &lynx_ex_dly_clk_ops,
> +		.parent_hws = &ex_dly_parents,
> +		.num_parents = 1,
> +	};
> +	struct clk *ref;
> +	struct lynx_clk *clk;
> +	char *ref_name;
> +	int ret;
> +
> +	clk = devm_kzalloc(dev, sizeof(*clk), GFP_KERNEL);
> +	if (!clk)
> +		return -ENOMEM;
> +
> +	clk->dev = dev;
> +	clk->regmap = regmap;
> +	clk->idx = index;
> +
> +	ref_name = kasprintf(GFP_KERNEL, "ref%d", index);
> +	pll_init.name = kasprintf(GFP_KERNEL, "%s.pll%d_khz", dev_name(dev),
> +				  index);
> +	ex_dly_init.name = kasprintf(GFP_KERNEL, "%s.pll%d_ex_dly_khz",
> +				     dev_name(dev), index);
> +	if (!ref_name || !pll_init.name || !ex_dly_init.name) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
> +
> +	ref = devm_clk_get(dev, ref_name);
> +	if (IS_ERR(clk->ref)) {
> +		ret = PTR_ERR(clk->ref);
> +		dev_err_probe(dev, ret, "could not get %s\n", ref_name);
> +		goto out;
> +	}
> +
> +	clk->ref = __clk_get_hw(ref);
> +	pll_parents = clk->ref;
> +	clk->pll.init = &pll_init;
> +	ret = devm_clk_hw_register(dev, &clk->pll);
> +	if (ret) {
> +		dev_err_probe(dev, ret, "could not register %s\n",
> +			      pll_init.name);
> +		goto out;
> +	}
> +
> +	ex_dly_parents = &clk->pll;
> +	clk->ex_dly.init = &ex_dly_init;
> +	ret = devm_clk_hw_register(dev, &clk->ex_dly);
> +	if (ret)
> +		dev_err_probe(dev, ret, "could not register %s\n",
> +			      ex_dly_init.name);
> +
> +	hw_data->hws[LYNX10G_PLLa(index)] = &clk->pll;
> +	hw_data->hws[LYNX10G_PLLa_EX_DLY(index)] = &clk->ex_dly;
> +
> +out:
> +	kfree(ref_name);
> +	kfree(pll_init.name);
> +	kfree(ex_dly_init.name);
> +	return ret;
> +}
> +
> +#define NUM_PLLS 2
> +#define NUM_CLKS (NUM_PLLS * LYNX10G_CLKS_PER_PLL)
> +
> +int lynx_clks_init(struct device *dev, struct regmap *regmap,
> +		   struct clk *plls[2], struct clk *ex_dlys[2])
> +{
> +	int ret, i;
> +	struct clk_hw_onecell_data *hw_data;
> +
> +	hw_data = devm_kzalloc(dev, struct_size(hw_data, hws, NUM_CLKS),
> +			       GFP_KERNEL);
> +	if (!hw_data)
> +		return -ENOMEM;
> +	hw_data->num = NUM_CLKS;
> +
> +	for (i = 0; i < NUM_PLLS; i++) {
> +		ret = lynx_clk_init(hw_data, dev, regmap, i);
> +		if (ret)
> +			return ret;
> +
> +		plls[i] = hw_data->hws[LYNX10G_PLLa(i)]->clk;
> +		ex_dlys[i] = hw_data->hws[LYNX10G_PLLa_EX_DLY(i)]->clk;
> +	}
> +
> +	ret = devm_of_clk_add_hw_provider(dev, of_clk_hw_onecell_get, hw_data);
> +	if (ret)
> +		dev_err_probe(dev, ret, "could not register clock provider\n");
> +
> +	return ret;
> +}

Why is this not a clock driver in drivers/clk/ ?

> +#define abs_diff(a, b) ({ \
> +	typeof(a) _a = (a); \
> +	typeof(b) _b = (b); \
> +	_a > _b ? _a - _b : _b - _a; \
> +})

are you sure there is not existing helper which can help you with this?
-- 
~Vinod