Re: [PATCH v3 4/8] mux: sparx5: Add Sparx5 SPI mux driver

[Peter Rosin]

Hi!

On 2020-07-02 12:13, Lars Povlsen wrote:
> The Sparx5 mux driver may be used to control selecting between two
> alternate SPI bus segments connected to the SPI controller
> (spi-dw-mmio).
> 
> Signed-off-by: Lars Povlsen <lars.povlsen@xxxxxxxxxxxxx>
> ---
>  drivers/mux/Makefile     |   2 +
>  drivers/mux/sparx5-spi.c | 138 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 140 insertions(+)
>  create mode 100644 drivers/mux/sparx5-spi.c
> 
> diff --git a/drivers/mux/Makefile b/drivers/mux/Makefile
> index 6e9fa47daf566..18c3ae3582ece 100644
> --- a/drivers/mux/Makefile
> +++ b/drivers/mux/Makefile
> @@ -8,9 +8,11 @@ mux-adg792a-objs		:= adg792a.o
>  mux-adgs1408-objs		:= adgs1408.o
>  mux-gpio-objs			:= gpio.o
>  mux-mmio-objs			:= mmio.o
> +mux-sparx5-objs			:= sparx5-spi.o
>  
>  obj-$(CONFIG_MULTIPLEXER)	+= mux-core.o
>  obj-$(CONFIG_MUX_ADG792A)	+= mux-adg792a.o
>  obj-$(CONFIG_MUX_ADGS1408)	+= mux-adgs1408.o
>  obj-$(CONFIG_MUX_GPIO)		+= mux-gpio.o
>  obj-$(CONFIG_MUX_MMIO)		+= mux-mmio.o
> +obj-$(CONFIG_SPI_DW_MMIO)	+= mux-sparx5.o
> diff --git a/drivers/mux/sparx5-spi.c b/drivers/mux/sparx5-spi.c
> new file mode 100644
> index 0000000000000..5fe9025b96a5e
> --- /dev/null
> +++ b/drivers/mux/sparx5-spi.c
> @@ -0,0 +1,138 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Sparx5 SPI MUX driver
> + *
> + * Copyright (c) 2019 Microsemi Corporation
> + *
> + * Author: Lars Povlsen <lars.povlsen@xxxxxxxxxxxxx>
> + */
> +
> +#include <linux/err.h>
> +#include <linux/module.h>
> +#include <linux/mux/driver.h>
> +#include <linux/of_platform.h>
> +#include <linux/platform_device.h>
> +#include <linux/property.h>
> +#include <linux/mux/driver.h>
> +#include <linux/mfd/syscon.h>
> +#include <linux/regmap.h>
> +#include <linux/bitfield.h>
> +
> +#define MSCC_IF_SI_OWNER_SISL			0
> +#define MSCC_IF_SI_OWNER_SIBM			1
> +#define MSCC_IF_SI_OWNER_SIMC			2
> +
> +#define SPARX5_CPU_SYSTEM_CTRL_GENERAL_CTRL	0x88
> +#define SPARX5_IF_SI_OWNER			GENMASK(7, 6)
> +#define SPARX5_IF_SI2_OWNER			GENMASK(5, 4)
> +
> +#define SPARX5_MAX_CS	16
> +
> +struct mux_sparx5 {
> +	struct regmap *syscon;
> +	u8 bus[SPARX5_MAX_CS];
> +	int cur_bus;

Surplus unused variable?

> +};
> +
> +/*
> + * Set the owner of the SPI interfaces
> + */
> +static void mux_sparx5_set_owner(struct regmap *syscon,
> +				 u8 owner, u8 owner2)
> +{
> +	u32 val, msk;
> +
> +	val = FIELD_PREP(SPARX5_IF_SI_OWNER, owner) |
> +		FIELD_PREP(SPARX5_IF_SI2_OWNER, owner2);
> +	msk = SPARX5_IF_SI_OWNER | SPARX5_IF_SI2_OWNER;
> +	regmap_update_bits(syscon,
> +			   SPARX5_CPU_SYSTEM_CTRL_GENERAL_CTRL,
> +			   msk, val);
> +}
> +
> +static void mux_sparx5_set_cs_owner(struct mux_sparx5 *mux_sparx5,
> +				    u8 cs, u8 owner)
> +{
> +	u8 other = (owner == MSCC_IF_SI_OWNER_SIBM ?
> +		    MSCC_IF_SI_OWNER_SIMC : MSCC_IF_SI_OWNER_SIBM);

Empty line missing here.

> +	if (mux_sparx5->bus[cs])
> +		/* SPI2 */
> +		mux_sparx5_set_owner(mux_sparx5->syscon, other, owner);
> +	else
> +		/* SPI1 */
> +		mux_sparx5_set_owner(mux_sparx5->syscon, owner, other);
> +}


This smells like there are only two states for this mux control, and that
the whole point of this driver is to make the exact numbering selectable.
I don't see the point of that. To me, it looks like the pre-existing
mmio-mux should be able to work. Something like this? Untested of course,
and I might easily have misunderstood something...

mux: mux-controller {
	compatible = "mmio-mux"
	#mux-control-cells = <1>;

	/* SI_OWNER and SI2_OWNER in GENERAL_CTRL */
	mux-reg-masks = <0x88 0xf0>;
};


spi0: spi@600104000 {
	compatible = "microchip,sparx5-spi";
	spi@0 {
		compatible = "spi-mux";
		mux-controls = <&mux 0>;
		reg = <0>;
		/* SI_OWNER = SIMC, SI2_OWNER = SIBM  --->  mux value 9 */
		spi-flash@9 {
			compatible = "jedec,spi-nor";
			reg = <9>;
		};
	};
	spi@e {
		compatible = "spi-mux";
		mux-controls = <&mux 0>;
		reg = <14>;
		/* SI_OWNER = SIBM, SI2_OWNER = SIMC  --->  mux value 6 */
		spi-flash@6 {
			compatible = "spi-nand";
			reg = <6>;
		};
	};
};

> +
> +static int mux_sparx5_set(struct mux_control *mux, int state)
> +{
> +	struct mux_sparx5 *mux_sparx5 = mux_chip_priv(mux->chip);
> +
> +	mux_sparx5_set_cs_owner(mux_sparx5, state, MSCC_IF_SI_OWNER_SIMC);
> +
> +	return 0;
> +}
> +
> +static const struct mux_control_ops mux_sparx5_ops = {
> +	.set = mux_sparx5_set,
> +};
> +
> +static const struct of_device_id mux_sparx5_dt_ids[] = {
> +	{ .compatible = "microchip,sparx5-spi-mux", },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, mux_sparx5_dt_ids);
> +
> +static int mux_sparx5_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct mux_chip *mux_chip;
> +	struct mux_sparx5 *mux_sparx5;
> +	struct device_node *nc;
> +	const char *syscon_name = "microchip,sparx5-cpu-syscon";
> +	int ret;
> +
> +	mux_chip = devm_mux_chip_alloc(dev, 1, sizeof(*mux_sparx5));
> +	if (IS_ERR(mux_chip))
> +		return PTR_ERR(mux_chip);
> +
> +	mux_sparx5 = mux_chip_priv(mux_chip);
> +	mux_chip->ops = &mux_sparx5_ops;
> +
> +	mux_sparx5->syscon =
> +		syscon_regmap_lookup_by_compatible(syscon_name);
> +	if (IS_ERR(mux_sparx5->syscon)) {
> +		dev_err(dev, "No syscon map %s\n", syscon_name);
> +		return PTR_ERR(mux_sparx5->syscon);
> +	}
> +
> +	/* Get bus interface mapping */
> +	for_each_available_child_of_node(dev->of_node, nc) {
> +		u32 cs, bus;
> +
> +		if (of_property_read_u32(nc, "reg", &cs) == 0 &&
> +		    cs < SPARX5_MAX_CS &&
> +		    of_property_read_u32(nc, "microchip,bus-interface",
> +					 &bus) == 0)
> +			mux_sparx5->bus[cs] = bus;

The above if is a mess. The kernel model is to handle the exceptional cases
first and break/goto/continue/return/whatever so that the interesting code
can happen at lower indentation level.

		if (of_property_read_u32(nc, "reg", &cs))
			continue;
		if (cs >= SPARX5_MAX_CS)
			continue;
		if (of_property_read_u32(nc, "microchip,bus-interface", &bus))
			continue;

		mux_sparc5->bus[cs] = bus;

Cheers,
Peter

> +	}
> +
> +	mux_chip->mux->states = SPARX5_MAX_CS;
> +
> +	ret = devm_mux_chip_register(dev, mux_chip);
> +	if (ret < 0)
> +		return ret;
> +
> +	dev_info(dev, "%u-way mux-controller registered\n",
> +		 mux_chip->mux->states);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver mux_sparx5_driver = {
> +	.driver = {
> +		.name = "sparx5-mux",
> +		.of_match_table	= of_match_ptr(mux_sparx5_dt_ids),
> +	},
> +	.probe = mux_sparx5_probe,
> +};
> +module_platform_driver(mux_sparx5_driver);
>