Re: [PATCH v5 3/9] reset: mpfs: add non-auxiliary bus probing

[Claudiu Beznea <claudiu.beznea@tuxon.dev>]

Hi, Conor,

On 10/13/25 20:45, Conor Dooley wrote:
> From: Conor Dooley <conor.dooley@microchip.com>
> 
> While the auxiliary bus was a nice bandaid, and meant that re-writing
> the representation of the clock regions in devicetree was not required,
> it has run its course. The "mss_top_sysreg" region that contains the
> clock and reset regions, also contains pinctrl and an interrupt
> controller, so the time has come rewrite the devicetree and probe the
> reset controller from an mfd devicetree node, rather than implement
> those drivers using the auxiliary bus. Wanting to avoid propagating this
> naive/incorrect description of the hardware to the new pic64gx SoC is a
> major motivating factor here.
> 
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> ---
> v4:
> - Only use driver specific lock for non-regmap writes
> 
> v2:
> - Implement the request to use regmap_update_bits(). I found that I then
>   hated the read/write helpers since they were just bloat, so I ripped
>   them out. I replaced the regular spin_lock_irqsave() stuff with a
>   guard(spinlock_irqsave), since that's a simpler way of handling the two
>   different paths through such a trivial pair of functions.
> ---
>  drivers/reset/reset-mpfs.c | 83 ++++++++++++++++++++++++++++++--------
>  1 file changed, 66 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/reset/reset-mpfs.c b/drivers/reset/reset-mpfs.c
> index f6fa10e03ea8..8e5ed4deecf3 100644
> --- a/drivers/reset/reset-mpfs.c
> +++ b/drivers/reset/reset-mpfs.c
> @@ -7,13 +7,16 @@
>   *
>   */
>  #include <linux/auxiliary_bus.h>
> +#include <linux/cleanup.h>
>  #include <linux/delay.h>
>  #include <linux/io.h>
> +#include <linux/mfd/syscon.h>

Should you add a depends on MFD_SYSCON ?

>  #include <linux/module.h>
>  #include <linux/of.h>
>  #include <linux/platform_device.h>
> -#include <linux/slab.h>
> +#include <linux/regmap.h>
>  #include <linux/reset-controller.h>
> +#include <linux/slab.h>
>  #include <dt-bindings/clock/microchip,mpfs-clock.h>
>  #include <soc/microchip/mpfs.h>
>  
> @@ -27,11 +30,14 @@
>  #define MPFS_SLEEP_MIN_US	100
>  #define MPFS_SLEEP_MAX_US	200
>  
> +#define REG_SUBBLK_RESET_CR	0x88u
> +
>  /* block concurrent access to the soft reset register */
>  static DEFINE_SPINLOCK(mpfs_reset_lock);
>  
>  struct mpfs_reset {
>  	void __iomem *base;
> +	struct regmap *regmap;
>  	struct reset_controller_dev rcdev;
>  };
>  
> @@ -46,41 +52,50 @@ static inline struct mpfs_reset *to_mpfs_reset(struct reset_controller_dev *rcde
>  static int mpfs_assert(struct reset_controller_dev *rcdev, unsigned long id)
>  {
>  	struct mpfs_reset *rst = to_mpfs_reset(rcdev);
> -	unsigned long flags;
>  	u32 reg;
>  
> -	spin_lock_irqsave(&mpfs_reset_lock, flags);
> +	if (rst->regmap) {
> +		regmap_update_bits(rst->regmap, REG_SUBBLK_RESET_CR, BIT(id), BIT(id));
> +		return 0;

You can:
		return regmap_update_bits();

> +	}
> +
> +	guard(spinlock_irqsave)(&mpfs_reset_lock);
>  
>  	reg = readl(rst->base);
>  	reg |= BIT(id);
>  	writel(reg, rst->base);
>  
> -	spin_unlock_irqrestore(&mpfs_reset_lock, flags);
> -
>  	return 0;
>  }
>  
>  static int mpfs_deassert(struct reset_controller_dev *rcdev, unsigned long id)
>  {
>  	struct mpfs_reset *rst = to_mpfs_reset(rcdev);
> -	unsigned long flags;
>  	u32 reg;
>  
> -	spin_lock_irqsave(&mpfs_reset_lock, flags);
> +	if (rst->regmap) {
> +		regmap_update_bits(rst->regmap, REG_SUBBLK_RESET_CR, BIT(id), 0);
> +		return 0;
> +	}
> +
> +	guard(spinlock_irqsave)(&mpfs_reset_lock);
>  
>  	reg = readl(rst->base);
>  	reg &= ~BIT(id);
>  	writel(reg, rst->base);
>  
> -	spin_unlock_irqrestore(&mpfs_reset_lock, flags);
> -
>  	return 0;
>  }
>  
>  static int mpfs_status(struct reset_controller_dev *rcdev, unsigned long id)
>  {
>  	struct mpfs_reset *rst = to_mpfs_reset(rcdev);
> -	u32 reg = readl(rst->base);
> +	u32 reg;
> +
> +	if (rst->regmap)
> +		regmap_read(rst->regmap, REG_SUBBLK_RESET_CR, &reg);
> +	else
> +		reg = readl(rst->base);
>  
>  	/*
>  	 * It is safe to return here as MPFS_NUM_RESETS makes sure the sign bit
> @@ -130,11 +145,45 @@ static int mpfs_reset_xlate(struct reset_controller_dev *rcdev,
>  	return index - MPFS_PERIPH_OFFSET;
>  }
>  
> -static int mpfs_reset_probe(struct auxiliary_device *adev,
> -			    const struct auxiliary_device_id *id)
> +static int mpfs_reset_mfd_probe(struct platform_device *pdev)
>  {
> -	struct device *dev = &adev->dev;
>  	struct reset_controller_dev *rcdev;
> +	struct device *dev = &pdev->dev;
> +	struct mpfs_reset *rst;
> +
> +	rst = devm_kzalloc(dev, sizeof(*rst), GFP_KERNEL);
> +	if (!rst)
> +		return -ENOMEM;
> +
> +	rcdev = &rst->rcdev;
> +	rcdev->dev = dev;
> +	rcdev->ops = &mpfs_reset_ops;
> +
> +	rcdev->of_node = pdev->dev.parent->of_node;
> +	rcdev->of_reset_n_cells = 1;
> +	rcdev->of_xlate = mpfs_reset_xlate;
> +	rcdev->nr_resets = MPFS_NUM_RESETS;
> +
> +	rst->regmap = device_node_to_regmap(pdev->dev.parent->of_node);
> +	if (IS_ERR(rst->regmap))
> +		dev_err_probe(dev, PTR_ERR(rst->regmap), "Failed to find syscon regmap\n");
> +
> +	return devm_reset_controller_register(dev, rcdev);
> +}
> +
> +static struct platform_driver mpfs_reset_mfd_driver = {
> +	.probe		= mpfs_reset_mfd_probe,
> +	.driver = {
> +		.name = "mpfs-reset",
> +	},
> +};
> +module_platform_driver(mpfs_reset_mfd_driver);
> +
> +static int mpfs_reset_adev_probe(struct auxiliary_device *adev,
> +				 const struct auxiliary_device_id *id)
> +{
> +	struct reset_controller_dev *rcdev;
> +	struct device *dev = &adev->dev;
>  	struct mpfs_reset *rst;
>  
>  	rst = devm_kzalloc(dev, sizeof(*rst), GFP_KERNEL);
> @@ -145,8 +194,8 @@ static int mpfs_reset_probe(struct auxiliary_device *adev,
>  
>  	rcdev = &rst->rcdev;
>  	rcdev->dev = dev;
> -	rcdev->dev->parent = dev->parent;
>  	rcdev->ops = &mpfs_reset_ops;
> +
>  	rcdev->of_node = dev->parent->of_node;
>  	rcdev->of_reset_n_cells = 1;
>  	rcdev->of_xlate = mpfs_reset_xlate;
> @@ -176,12 +225,12 @@ static const struct auxiliary_device_id mpfs_reset_ids[] = {
>  };
>  MODULE_DEVICE_TABLE(auxiliary, mpfs_reset_ids);
>  
> -static struct auxiliary_driver mpfs_reset_driver = {
> -	.probe		= mpfs_reset_probe,
> +static struct auxiliary_driver mpfs_reset_aux_driver = {
> +	.probe		= mpfs_reset_adev_probe,
>  	.id_table	= mpfs_reset_ids,
>  };
>  
> -module_auxiliary_driver(mpfs_reset_driver);
> +module_auxiliary_driver(mpfs_reset_aux_driver);
>  
>  MODULE_DESCRIPTION("Microchip PolarFire SoC Reset Driver");
>  MODULE_AUTHOR("Conor Dooley <conor.dooley@microchip.com>");