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Date: Mon, 24 Apr 2017 23:05:14 +0200
From: Peter Rosin <peda@...ntia.se>
To: Philipp Zabel <p.zabel@...gutronix.de>
CC: Rob Herring <robh+dt@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Sakari Ailus <sakari.ailus@....fi>,
Steve Longerbeam <slongerbeam@...il.com>,
<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<kernel@...gutronix.de>
Subject: Re: [RFC v2 2/2] mux: mmio-based syscon mux controller
On 2017-04-24 18:12, Philipp Zabel wrote:
> This adds a driver for mmio-based syscon multiplexers controlled by a
> single bitfield in a syscon register range.
Single bitfield?
>
> Signed-off-by: Philipp Zabel <p.zabel@...gutronix.de>
> ---
> Changes since v1:
> - Renamed MUX_SYSCON to MUX_MMIO. Instead of obtaining the regmap via syscon,
> this could just as well map its own MMIO register range if a reg property
> was added.
> - Replaced reg, bit-mask, and bit-shift properties with mux-reg-masks array
> to allow defining multiple mux bit-fields per mmio-mux instance.
> - Changed mux-control-cells value to <1>, the cell value is an index into
> the mux-reg-masks array.
> - Replaced idle-state with idle-states array.
> - Stopped clobbering mux->cached_state, that is internal to the mux core.
> ---
> drivers/mux/Kconfig | 13 ++++
> drivers/mux/Makefile | 1 +
> drivers/mux/mux-mmio.c | 162 +++++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 176 insertions(+)
> create mode 100644 drivers/mux/mux-mmio.c
>
> diff --git a/drivers/mux/Kconfig b/drivers/mux/Kconfig
> index 34b8284d6d29e..e2bee25a1586e 100644
> --- a/drivers/mux/Kconfig
> +++ b/drivers/mux/Kconfig
> @@ -43,4 +43,17 @@ config MUX_GPIO
> To compile the driver as a module, choose M here: the module will
> be called mux-gpio.
>
> +config MUX_MMIO
> + tristate "MMIO register bitfield-controlled Multiplexer"
> + depends on OF && MFD_SYSCON
> + help
> + MMIO register bitfield-controlled Multiplexer controller.
> +
> + The driver builds a single multiplexer controller using a bitfield
> + in a syscon register. For N bit wide bitfields, there will be 2^N
> + possible multiplexer states.
Multiple multiplexer controllers....
> +
> + To compile the driver as a module, choose M here: the module will
> + be called mux-mmio.
> +
> endif
> diff --git a/drivers/mux/Makefile b/drivers/mux/Makefile
> index b00a7d37d2fbe..6bac5b0fea137 100644
> --- a/drivers/mux/Makefile
> +++ b/drivers/mux/Makefile
> @@ -5,3 +5,4 @@
> obj-$(CONFIG_MULTIPLEXER) += mux-core.o
> obj-$(CONFIG_MUX_ADG792A) += mux-adg792a.o
> obj-$(CONFIG_MUX_GPIO) += mux-gpio.o
> +obj-$(CONFIG_MUX_MMIO) += mux-mmio.o
> diff --git a/drivers/mux/mux-mmio.c b/drivers/mux/mux-mmio.c
> new file mode 100644
> index 0000000000000..0b011fb59f99b
> --- /dev/null
> +++ b/drivers/mux/mux-mmio.c
> @@ -0,0 +1,162 @@
> +/*
> + * MMIO register bitfield-controlled multiplexer driver
> + *
> + * Copyright (C) 2017 Pengutronix, Philipp Zabel <kernel@...gutronix.de>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/err.h>
> +#include <linux/mfd/syscon.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/regmap.h>
> +
> +static int mux_mmio_set(struct mux_control *mux, int state)
> +{
> + struct regmap_field **fields = mux_chip_priv(mux->chip);
> + int index = mux - mux->chip->mux;
mux_control_get_index(mux) does exactly this.
> +
> + return regmap_field_write(fields[index], state);
> +}
> +
> +static const struct mux_control_ops mux_mmio_ops = {
> + .set = mux_mmio_set,
> +};
> +
> +static const struct of_device_id mux_mmio_dt_ids[] = {
> + { .compatible = "mmio-mux", },
> + { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, mux_mmio_dt_ids);
> +
> +static int mux_mmio_probe(struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct device_node *np = dev->of_node;
> + struct regmap_field **fields;
> + struct mux_chip *mux_chip;
> + struct regmap *regmap;
> + s32 *idle_states;
> + u32 *reg_masks;
> + int num_fields;
> + int ret;
> + int i;
> +
> + regmap = syscon_node_to_regmap(np->parent);
> + if (IS_ERR(regmap)) {
> + ret = PTR_ERR(regmap);
> + dev_err(dev, "failed to get syscon regmap: %d\n", ret);
> + return ret;
> + }
> +
> + ret = of_property_count_u32_elems(np, "mux-reg-masks");
> + if (ret == 0 || ret % 2)
> + ret = -EINVAL;
> + if (ret > 0) {
> + num_fields = ret / 2;
> +
> + reg_masks = devm_kmalloc(dev, ret * sizeof(u32), GFP_KERNEL);
> + if (!reg_masks)
> + return -ENOMEM;
> +
> + ret = of_property_read_u32_array(np, "mux-reg-masks",
> + reg_masks, ret);
> + }
> + if (ret < 0) {
> + dev_err(dev, "mux-reg-masks property missing or invalid: %d\n",
> + ret);
> + return ret;
> + }
> +
> + mux_chip = devm_mux_chip_alloc(dev, num_fields, num_fields *
> + sizeof(*fields));
> + if (IS_ERR(mux_chip))
> + return PTR_ERR(mux_chip);
> +
> + fields = mux_chip_priv(mux_chip);
> +
> + for (i = 0; i < num_fields; i++) {
> + struct mux_control *mux = &mux_chip->mux[i];
> + struct reg_field field;
> + u32 *reg_mask = reg_masks + 2 * i;
> + int bits;
u32 mask;
> +
> + field.reg = reg_mask[0];
> + field.msb = fls(reg_mask[1]) - 1;
> + field.lsb = ffs(reg_mask[1]) - 1;
Perhaps add a sanity check? (untested, but you get the idea...)
mask = (BIT(field.msb + 1) - 1) ^ (BIT(field.lsb) - 1);
if (WARN_ON(reg_mask[1] != mask)) {
/* Catches empty reg_mask[1] as well. */
dev_err(...)
return -EINVAL;
}
> + bits = 1 + field.msb - field.lsb;
> +
> + fields[i] = devm_regmap_field_alloc(&pdev->dev, regmap, field);
> + if (IS_ERR(fields[i])) {
> + ret = PTR_ERR(fields[i]);
> + dev_err(&pdev->dev, "failed to get bit-field %d: %d\n",
> + i, ret);
> + return ret;
> + }
> +
> + mux->states = 1 << bits;
> + }
> +
> + devm_kfree(dev, reg_masks);
> +
> + if (of_find_property(np, "idle-states", NULL)) {
> + ret = of_property_count_u32_elems(np, "idle-states");
> + if (ret == num_fields) {
> + idle_states = devm_kmalloc(dev, ret * sizeof(s32),
> + GFP_KERNEL);
> + if (!idle_states)
> + return -ENOMEM;
> +
> + ret = of_property_read_u32_array(np, "idle-states",
> + idle_states, ret);
> + } else {
> + idle_states = NULL;
> + if (ret >= 0)
> + ret = -EINVAL;
> + }
> + if (ret < 0) {
> + dev_err(dev, "idle-states property invalid: %d\n", ret);
> + return ret;
> + }
> +
> + for (i = 0; i < num_fields; i++) {
Hmm, this is the second loop over num_fields with accesses to a complete
copy of a DT array. Is it not possible to use one loop and set up all
aspects of each mux-control using of_property_read_u32_index calls in that
loop? I have the feeling that will look neater...
> + struct mux_control *mux = &mux_chip->mux[i];
> +
> + if (idle_states[i] != MUX_IDLE_AS_IS) {
> + if (idle_states[i] < 0 ||
> + idle_states[i] >= mux->states) {
> + dev_err(dev, "invalid idle-state %u\n",
> + idle_states[i]);
> + return -EINVAL;
> + }
> +
> + mux->idle_state = idle_states[i];
> + }
> + }
> +
> + devm_kfree(dev, idle_states);
> + }
> +
> + mux_chip->ops = &mux_mmio_ops;
> +
> + return devm_mux_chip_register(dev, mux_chip);
> +}
> +
> +static struct platform_driver mux_mmio_driver = {
> + .driver = {
> + .name = "mmio-mux",
> + .of_match_table = of_match_ptr(mux_mmio_dt_ids),
> + },
> + .probe = mux_mmio_probe,
> +};
> +module_platform_driver(mux_mmio_driver);
> +
> +MODULE_DESCRIPTION("MMIO register bitfield-controlled multiplexer driver");
> +MODULE_AUTHOR("Philipp Zabel <p.zabel@...gutronix.de>");
> +MODULE_LICENSE("GPL v2");
>
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