Re: [RFC PATCH 2/2] mux: mmio: Extend mmio-mux driver to configure mux with new DT property

[Andrew Davis <afd@ti.com>]

On 2/27/25 2:22 PM, Chintan Vankar wrote:
> MMIO mux driver is designed to parse "mux-reg-masks" and "idle-states"
> property independently to configure mux registers. Drawback of this
> approach is, while configuring mux-controller one need to specify every
> register of memory space with offset and mask in "mux-reg-masks" and
> register state to "idle-states", that would be more complex for devices
> with large memory space.
> 
> Add support to extend the mmio mux driver to configure a specific register
> or set of register in memory space.
> 
> Signed-off-by: Chintan Vankar <c-vankar@ti.com>
> ---
>   drivers/mux/mmio.c | 148 +++++++++++++++++++++++++++++++++++++--------
>   1 file changed, 122 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/mux/mmio.c b/drivers/mux/mmio.c
> index 30a952c34365..8937d0ea2b11 100644
> --- a/drivers/mux/mmio.c
> +++ b/drivers/mux/mmio.c
> @@ -2,7 +2,7 @@
>   /*
>    * MMIO register bitfield-controlled multiplexer driver
>    *
> - * Copyright (C) 2017 Pengutronix, Philipp Zabel <kernel@pengutronix.de>
> + * Copyright (C) 2017-2025 Pengutronix, Philipp Zabel <kernel@pengutronix.de>
>    */
>   
>   #include <linux/bitops.h>
> @@ -33,10 +33,84 @@ static const struct of_device_id mux_mmio_dt_ids[] = {
>   };
>   MODULE_DEVICE_TABLE(of, mux_mmio_dt_ids);
>   
> +static int reg_mux_get_controllers(const struct device_node *np, char *prop_name)
> +{
> +	int ret;
> +
> +	ret = of_property_count_u32_elems(np, prop_name);
> +	if (ret == 0 || ret % 2)
> +		ret = -EINVAL;
> +
> +	return ret;
> +}
> +
> +static int reg_mux_get_controllers_extended(const struct device_node *np, char *prop_name)
> +{
> +	int ret;
> +
> +	ret = of_property_count_u32_elems(np, prop_name);
> +	if (ret == 0 || ret % 3)
> +		ret = -EINVAL;
> +
> +	return ret;
> +}
> +
> +static int reg_mux_parse_dt(const struct device_node *np, bool *mux_reg_masks_state,
> +			    int *num_fields)
> +{
> +	int ret;
> +
> +	if (*mux_reg_masks_state) {
> +		ret = reg_mux_get_controllers_extended(np, "mux-reg-masks-state");
> +		if (ret < 0)
> +			return ret;
> +		*num_fields = ret / 3;
> +	} else {
> +		ret = reg_mux_get_controllers(np, "mux-reg-masks");
> +		if (ret < 0)
> +			return ret;
> +		*num_fields = ret / 2;
> +	}
> +	return ret;
> +}
> +
> +static int mux_reg_set_parameters(const struct device_node *np, char *prop_name, u32 *reg,
> +				  u32 *mask, int index)
> +{
> +	int ret;
> +
> +	ret = of_property_read_u32_index(np, prop_name,
> +					 2 * index, reg);
> +	if (!ret)
> +		ret = of_property_read_u32_index(np, prop_name,
> +						 2 * index + 1, mask);
> +
> +	return ret;
> +}
> +
> +static int mux_reg_set_parameters_extended(const struct device_node *np, char *prop_name, u32 *reg,
> +					   u32 *mask, u32 *state, int index)
> +{
> +	int ret;
> +
> +	ret = of_property_read_u32_index(np, prop_name,
> +					 3 * index, reg);

This is some odd line wrapping, why newline at 55 chars here?
You can go to 80 or 100 if it is readable.

> +	if (!ret) {

Just return early, no need for this MISRA-like "single return" junk.

> +		ret = of_property_read_u32_index(np, prop_name,
> +						 3 * index + 1, mask);
> +		if (!ret)
> +			ret = of_property_read_u32_index(np, prop_name,
> +							 3 * index + 2, state);
> +	}
> +
> +	return ret;
> +}
> +
>   static int mux_mmio_probe(struct platform_device *pdev)
>   {
>   	struct device *dev = &pdev->dev;
>   	struct device_node *np = dev->of_node;
> +	bool mux_reg_masks_state = false;
>   	struct regmap_field **fields;
>   	struct mux_chip *mux_chip;
>   	struct regmap *regmap;
> @@ -59,15 +133,19 @@ static int mux_mmio_probe(struct platform_device *pdev)
>   		return dev_err_probe(dev, PTR_ERR(regmap),
>   				     "failed to get regmap\n");
>   
> -	ret = of_property_count_u32_elems(np, "mux-reg-masks");
> -	if (ret == 0 || ret % 2)
> -		ret = -EINVAL;
> +	if (of_property_present(np, "mux-reg-masks-state"))
> +		mux_reg_masks_state = true;
> +
> +	ret = reg_mux_parse_dt(np, &mux_reg_masks_state, &num_fields);

Why are you passing this bool by pointer? You don't modify it in the function..

>   	if (ret < 0) {
> -		dev_err(dev, "mux-reg-masks property missing or invalid: %d\n",
> -			ret);
> +		if (mux_reg_masks_state)
> +			dev_err(dev, "mux-reg-masks-state property missing or invalid: %d\n",
> +				ret);
> +		else
> +			dev_err(dev, "mux-reg-masks property missing or invalid: %d\n",
> +				ret);
>   		return ret;
>   	}
> -	num_fields = ret / 2;
>   
>   	mux_chip = devm_mux_chip_alloc(dev, num_fields, num_fields *
>   				       sizeof(*fields));
> @@ -79,19 +157,25 @@ static int mux_mmio_probe(struct platform_device *pdev)
>   	for (i = 0; i < num_fields; i++) {
>   		struct mux_control *mux = &mux_chip->mux[i];
>   		struct reg_field field;
> -		s32 idle_state = MUX_IDLE_AS_IS;
> +		s32 state, idle_state = MUX_IDLE_AS_IS;
>   		u32 reg, mask;
>   		int bits;
>   
> -		ret = of_property_read_u32_index(np, "mux-reg-masks",
> -						 2 * i, &reg);
> -		if (!ret)
> -			ret = of_property_read_u32_index(np, "mux-reg-masks",
> -							 2 * i + 1, &mask);
> -		if (ret < 0) {
> -			dev_err(dev, "bitfield %d: failed to read mux-reg-masks property: %d\n",
> -				i, ret);
> -			return ret;
> +		if (!mux_reg_masks_state) {
> +			ret = mux_reg_set_parameters(np, "mux-reg-masks", &reg, &mask, i);
> +			if (ret < 0) {
> +				dev_err(dev, "bitfield %d: failed to read mux-reg-masks property: %d\n",
> +					i, ret);
> +				return ret;
> +			}
> +		} else {
> +			ret = mux_reg_set_parameters_extended(np, "mux-reg-masks-state", &reg,
> +							      &mask, &state, i);
> +			if (ret < 0) {
> +				dev_err(dev, "bitfield %d: failed to read custom-states property: %d\n",
> +					i, ret);
> +				return ret;
> +			}
>   		}
>   
>   		field.reg = reg;
> @@ -115,16 +199,28 @@ static int mux_mmio_probe(struct platform_device *pdev)
>   		bits = 1 + field.msb - field.lsb;
>   		mux->states = 1 << bits;
>   
> -		of_property_read_u32_index(np, "idle-states", i,
> -					   (u32 *)&idle_state);
> -		if (idle_state != MUX_IDLE_AS_IS) {
> -			if (idle_state < 0 || idle_state >= mux->states) {
> -				dev_err(dev, "bitfield: %d: out of range idle state %d\n",
> -					i, idle_state);
> -				return -EINVAL;
> +		if (!mux_reg_masks_state) {
> +			of_property_read_u32_index(np, "idle-states", i,
> +						   (u32 *)&idle_state);

 From here down, both branches of this are almost identical, idle_state and
your new "state" var do the same thing, why do you need both?

Andrew

> +			if (idle_state != MUX_IDLE_AS_IS) {
> +				if (idle_state < 0 || idle_state >= mux->states) {
> +					dev_err(dev, "bitfield: %d: out of range idle state %d\n",
> +						i, idle_state);
> +					return -EINVAL;
> +				}
> +
> +				mux->idle_state = idle_state;
> +			}
> +		} else {
> +			if (state != MUX_IDLE_AS_IS) {
> +				if (state < 0 || state >= mux->states) {
> +					dev_err(dev, "bitfield: %d: out of range idle state %d\n",
> +						i, state);
> +					return -EINVAL;
> +				}
> +
> +				mux->idle_state = state;
>   			}
> -
> -			mux->idle_state = idle_state;
>   		}
>   	}
>