linux-kernel - Re: [PATCH 3/4] drivers: reset: Add STM32 reset driver

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Date:	Tue, 05 Jul 2016 15:28:29 +0200
From:	Philipp Zabel <p.zabel@...gutronix.de>
To:	gabriel.fernandez@...com
Cc:	Rob Herring <robh+dt@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Russell King <linux@...linux.org.uk>, patrice.chotard@...com,
	alexandre.torgue@...com, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] drivers: reset: Add STM32 reset driver

Am Montag, den 04.07.2016, 15:47 +0200 schrieb gabriel.fernandez@...com:
> From: Gabriel Fernandez <gabriel.fernandez@...com>
> 
> The STM32 MCUs family IPs can be reset by accessing some registers
> from the RCC block.
> 
> The list of available reset lines is documented in the DT bindings.
> 
> Signed-off-by: Maxime Coquelin <mcoquelin.stm32@...il.com>
> Signed-off-by: Gabriel Fernandez <gabriel.fernandez@...com>
> ---
>  drivers/reset/Makefile      |   1 +
>  drivers/reset/reset-stm32.c | 113 ++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 114 insertions(+)
>  create mode 100644 drivers/reset/reset-stm32.c
> 
> diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
> index 03dc1bb..3776b7b 100644
> --- a/drivers/reset/Makefile
> +++ b/drivers/reset/Makefile
> @@ -4,6 +4,7 @@ obj-$(CONFIG_ARCH_SOCFPGA) += reset-socfpga.o
>  obj-$(CONFIG_ARCH_BERLIN) += reset-berlin.o
>  obj-$(CONFIG_MACH_PISTACHIO) += reset-pistachio.o
>  obj-$(CONFIG_ARCH_MESON) += reset-meson.o
> +obj-$(CONFIG_ARCH_STM32) += reset-stm32.o
>  obj-$(CONFIG_ARCH_SUNXI) += reset-sunxi.o
>  obj-$(CONFIG_ARCH_STI) += sti/
>  obj-$(CONFIG_ARCH_HISI) += hisilicon/
> diff --git a/drivers/reset/reset-stm32.c b/drivers/reset/reset-stm32.c
> new file mode 100644
> index 0000000..be42bff
> --- /dev/null
> +++ b/drivers/reset/reset-stm32.c
> @@ -0,0 +1,113 @@
> +/*
> + * Copyright (C) Maxime Coquelin 2015
> + * Author:  Maxime Coquelin <mcoquelin.stm32@...il.com>
> + * License terms:  GNU General Public License (GPL), version 2
> + *
> + * Heavily based on sunxi driver from Maxime Ripard.
> + */
> +
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/platform_device.h>
> +#include <linux/reset-controller.h>
> +#include <linux/slab.h>
> +#include <linux/spinlock.h>
> +#include <linux/types.h>
> +
> +struct stm32_reset_data {
> +	spinlock_t			lock;
> +	void __iomem			*membase;
> +	struct reset_controller_dev	rcdev;
> +};
> +
> +static int stm32_reset_assert(struct reset_controller_dev *rcdev,
> +			      unsigned long id)
> +{
> +	struct stm32_reset_data *data = container_of(rcdev,
> +						     struct stm32_reset_data,
> +						     rcdev);
> +	int bank = id / BITS_PER_LONG;
> +	int offset = id % BITS_PER_LONG;
> +	unsigned long flags;
> +	u32 reg;
> +
> +	spin_lock_irqsave(&data->lock, flags);
> +
> +	reg = readl_relaxed(data->membase + (bank * 4));
> +	writel_relaxed(reg | BIT(offset), data->membase + (bank * 4));

Please also switch to the non-relaxed variants. It shouldn't make a
difference here, and as Arnd points out, reduces the risk of new
developers using readl/writel_relaxed without thinking about the
consequences.
Further, this will make the stm32, sunxi, and socfpga accessors look the
same. I'd like to try and combine them after this is merged.

regards
Philipp