linux-kernel - Re: [PATCH v3 4/9] reset: mpfs: add non-auxiliary bus probing

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Message-ID: <905dc44cf6e7fc4d4500b47f493ec073991a849b.camel@pengutronix.de>
Date: Fri, 27 Jun 2025 18:01:52 +0200
From: Philipp Zabel <p.zabel@...gutronix.de>
To: Conor Dooley <conor@...nel.org>, sboyd@...nel.org
Cc: Conor Dooley <conor.dooley@...rochip.com>, Daire McNamara
 <daire.mcnamara@...rochip.com>, pierre-henry.moussay@...rochip.com, 
 valentina.fernandezalanis@...rochip.com, Michael Turquette
 <mturquette@...libre.com>, Rob Herring <robh@...nel.org>, Krzysztof
 Kozlowski <krzk+dt@...nel.org>, Jassi Brar <jassisinghbrar@...il.com>, Lee
 Jones <lee@...nel.org>, Paul Walmsley <paul.walmsley@...ive.com>, Palmer
 Dabbelt <palmer@...belt.com>, linux-riscv@...ts.infradead.org, 
 linux-clk@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/9] reset: mpfs: add non-auxiliary bus probing

On Mo, 2025-06-23 at 13:56 +0100, Conor Dooley wrote:
> From: Conor Dooley <conor.dooley@...rochip.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@...rochip.com>
> ---
> 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 | 81 ++++++++++++++++++++++++++++++--------
>  1 file changed, 65 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/reset/reset-mpfs.c b/drivers/reset/reset-mpfs.c
> index 574e59db83a4f..9c3e996f3a099 100644
> --- a/drivers/reset/reset-mpfs.c
> +++ b/drivers/reset/reset-mpfs.c
> @@ -7,12 +7,15 @@
>   *
>   */
>  #include <linux/auxiliary_bus.h>
> +#include <linux/cleanup.h>
>  #include <linux/delay.h>
>  #include <linux/io.h>
> +#include <linux/mfd/syscon.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
>  #include <linux/platform_device.h>
>  #include <linux/slab.h>
> +#include <linux/regmap.h>

Maybe sort these alphabetically.

>  #include <linux/reset-controller.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);
> +	guard(spinlock_irqsave)(&mpfs_reset_lock);
> +
> +	if (rst->regmap) {
> +		regmap_update_bits(rst->regmap, REG_SUBBLK_RESET_CR, BIT(id), BIT(id));

mpfs_reset_lock is only needed for the readl()/writel() below.
regmap has its own locking.

> +		return 0;
> +	}
>  
>  	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);
> +	guard(spinlock_irqsave)(&mpfs_reset_lock);
> +
> +	if (rst->regmap) {
> +		regmap_update_bits(rst->regmap, REG_SUBBLK_RESET_CR, BIT(id), 0);

Same as above.


regards
Philipp