linux-kernel - Re: [PATCH v6 3/9] reset: add BCM6345 reset controller driver

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Date:   Wed, 17 Jun 2020 11:35:36 +0200
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Álvaro Fernández Rojas <noltari@...il.com>,
        robh+dt@...nel.org, tsbogend@...ha.franken.de,
        f.fainelli@...il.com, jonas.gorski@...il.com,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mips@...r.kernel.org, bcm-kernel-feedback-list@...adcom.com
Subject: Re: [PATCH v6 3/9] reset: add BCM6345 reset controller driver

Hi Álvaro,

thank you for the patch. A few comments below:

On Wed, 2020-06-17 at 10:32 +0200, Álvaro Fernández Rojas wrote:
> Add support for resetting blocks through the Linux reset controller
> subsystem for BCM63xx SoCs.
> 
> Signed-off-by: Álvaro Fernández Rojas <noltari@...il.com>
> Reviewed-by: Florian Fainelli <F.fainelli@...il.com>
> ---
>  v6: driver improvements:
>      - use devm_platform_ioremap_resource.
>      - simplify bcm6345_reset_probe return.
>      - introduce and use to_bcm6345_reset function.
>  v5: fix kbuild robot error (drop __init).
>  v4: no changes.
>  v3: using reset-simple isn't possible since sleeping after performing the
>      reset is also needed.
>  v2: add compatibility to reset-simple instead of adding a new driver.
> 
>  drivers/reset/Kconfig         |   7 ++
>  drivers/reset/Makefile        |   1 +
>  drivers/reset/reset-bcm6345.c | 132 ++++++++++++++++++++++++++++++++++
>  3 files changed, 140 insertions(+)
>  create mode 100644 drivers/reset/reset-bcm6345.c
> 
> diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
> index d9efbfd29646..9f1da978cef6 100644
> --- a/drivers/reset/Kconfig
> +++ b/drivers/reset/Kconfig
> @@ -41,6 +41,13 @@ config RESET_BERLIN
>  	help
>  	  This enables the reset controller driver for Marvell Berlin SoCs.
>  
> +config RESET_BCM6345
> +	bool "BCM6345 Reset Controller"
> +	depends on BMIPS_GENERIC || COMPILE_TEST
> +	default BMIPS_GENERIC
> +	help
> +	  This enables the reset controller driver for BCM6345 SoCs.
> +

Please sort these alphabetically.

>  config RESET_BRCMSTB
>  	tristate "Broadcom STB reset controller"
>  	depends on ARCH_BRCMSTB || COMPILE_TEST
> diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
> index 249ed357c997..e642aae42f0f 100644
> --- a/drivers/reset/Makefile
> +++ b/drivers/reset/Makefile
> @@ -6,6 +6,7 @@ obj-$(CONFIG_ARCH_TEGRA) += tegra/
>  obj-$(CONFIG_RESET_A10SR) += reset-a10sr.o
>  obj-$(CONFIG_RESET_ATH79) += reset-ath79.o
>  obj-$(CONFIG_RESET_AXS10X) += reset-axs10x.o
> +obj-$(CONFIG_RESET_BCM6345) += reset-bcm6345.o

This is the right place.

>  obj-$(CONFIG_RESET_BERLIN) += reset-berlin.o
>  obj-$(CONFIG_RESET_BRCMSTB) += reset-brcmstb.o
>  obj-$(CONFIG_RESET_BRCMSTB_RESCAL) += reset-brcmstb-rescal.o
> diff --git a/drivers/reset/reset-bcm6345.c b/drivers/reset/reset-bcm6345.c
> new file mode 100644
> index 000000000000..3eedea226028
> --- /dev/null
> +++ b/drivers/reset/reset-bcm6345.c
> @@ -0,0 +1,132 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * BCM6345 Reset Controller Driver
> + *
> + * Copyright (C) 2020 Álvaro Fernández Rojas <noltari@...il.com>
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/init.h>
> +#include <linux/io.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/platform_device.h>
> +#include <linux/reset-controller.h>
> +
> +#define BCM6345_RESET_NUM		32
> +#define BCM6345_RESET_SLEEP_MIN_US	10000
> +#define BCM6345_RESET_SLEEP_MAX_US	20000
> +
> +struct bcm6345_reset {
> +	struct reset_controller_dev rcdev;
> +	void __iomem *base;
> +	spinlock_t lock;
> +};
> +
> +static inline struct bcm6345_reset *
> +to_bcm6345_reset(struct reset_controller_dev *rcdev)
> +{
> +	return container_of(rcdev, struct bcm6345_reset, rcdev);
> +}
> +
> +static void bcm6345_reset_update(struct reset_controller_dev *rcdev,
> +				 unsigned long id, bool assert)
> +{
> +	struct bcm6345_reset *bcm6345_reset = to_bcm6345_reset(rcdev);
> +	unsigned long flags;
> +	uint32_t val;
> +
> +	spin_lock_irqsave(&bcm6345_reset->lock, flags);
> +	val = __raw_readl(bcm6345_reset->base);
> +	if (assert)
> +		val &= ~BIT(id);
> +	else
> +		val |= BIT(id);
> +	__raw_writel(val, bcm6345_reset->base);
> +	spin_unlock_irqrestore(&bcm6345_reset->lock, flags);
> +}
> +
> +static int bcm6345_reset_assert(struct reset_controller_dev *rcdev,
> +				unsigned long id)
> +{
> +	bcm6345_reset_update(rcdev, id, true);
> +
> +	return 0;
> +}
> +
> +static int bcm6345_reset_deassert(struct reset_controller_dev *rcdev,
> +				  unsigned long id)
> +{
> +	bcm6345_reset_update(rcdev, id, false);
> +
> +	return 0;

These two could be shortened if you let bcm6345_reset_update() return 0:

	return bcm6345_reset_update(rcdev, id, false);

> +}

> +
> +static int bcm6345_reset_reset(struct reset_controller_dev *rcdev,
> +			       unsigned long id)
> +{
> +	bcm6345_reset_update(rcdev, id, true);
> +	usleep_range(BCM6345_RESET_SLEEP_MIN_US,
> +		     BCM6345_RESET_SLEEP_MAX_US);
> +
> +	bcm6345_reset_update(rcdev, id, false);

This second sleep is unusual:

> +	usleep_range(BCM6345_RESET_SLEEP_MIN_US,
> +		     BCM6345_RESET_SLEEP_MAX_US);

Could you add a comment describing why it is needed?

Otherwise,

Reviewed-by: Philipp Zabel <p.zabel@...gutronix.de>

regards
Philipp