Date:	Tue, 8 Jul 2014 19:31:50 +0200
From:	Nicolas Ferre <nicolas.ferre@...el.com>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	<linux@...im.org.za>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	<dwmw2@...radead.org>, <dbaryshkov@...il.com>
CC:	Boris Brezillon <boris@...e-electrons.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Thomas Petazzoni <thomas@...e-electrons.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 06/18] power: reset: Add AT91 reset driver

On 07/07/2014 16:25, Maxime Ripard :
> Implement the reset behaviour of the various AT91 SoCS in drivers/power/reset.
> 
> It used to be (and still is) located in arch/arm/mach-at91, and in order to
> preserve bisectability is not removed yet, but every board should be converted
> to use this driver instead.
> 
> Signed-off-by: Maxime Ripard <maxime.ripard@...e-electrons.com>
> ---
>  drivers/power/reset/Kconfig      |   7 ++
>  drivers/power/reset/Makefile     |   1 +
>  drivers/power/reset/at91-reset.c | 246 +++++++++++++++++++++++++++++++++++++++
>  3 files changed, 254 insertions(+)
>  create mode 100644 drivers/power/reset/at91-reset.c
> 
> diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
> index 19d546c5edfa..b3fef01d7cbb 100644
> --- a/drivers/power/reset/Kconfig
> +++ b/drivers/power/reset/Kconfig
> @@ -14,6 +14,13 @@ config POWER_RESET_AS3722
>  	help
>  	  This driver supports turning off board via a ams AS3722 power-off.
>  
> +config POWER_RESET_AT91_RESET
> +	bool "Atmel AT91 reset driver"
> +	default SOC_AT91SAM9 || SOC_SAMA5
> +	help
> +	  This driver supports restart for Atmel AT91SAM9 and SAMA5
> +	  SoCs
> +
>  config POWER_RESET_AXXIA
>  	bool "LSI Axxia reset driver"
>  	depends on ARCH_AXXIA
> diff --git a/drivers/power/reset/Makefile b/drivers/power/reset/Makefile
> index dde2e8bbac53..1599214b91d9 100644
> --- a/drivers/power/reset/Makefile
> +++ b/drivers/power/reset/Makefile
> @@ -1,4 +1,5 @@
>  obj-$(CONFIG_POWER_RESET_AS3722) += as3722-poweroff.o
> +obj-$(CONFIG_POWER_RESET_AT91_RESET) += at91-reset.o
>  obj-$(CONFIG_POWER_RESET_AXXIA) += axxia-reset.o
>  obj-$(CONFIG_POWER_RESET_GPIO) += gpio-poweroff.o
>  obj-$(CONFIG_POWER_RESET_MSM) += msm-poweroff.o
> diff --git a/drivers/power/reset/at91-reset.c b/drivers/power/reset/at91-reset.c
> new file mode 100644
> index 000000000000..7b91ca82854e
> --- /dev/null
> +++ b/drivers/power/reset/at91-reset.c
> @@ -0,0 +1,246 @@
> +/*
> + * Atmel AT91 SAM9 SoCs reset code
> + *
> + * Copyright (C) 2007 Atmel Corporation.
> + * Copyright (C) BitBox Ltd 2010
> + * Copyright (C) 2011 Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...soft.com>
> + * Copyright (C) 2014 Free Electrons
> + *
> + * This file is licensed under the terms of the GNU General Public
> + * License version 2.  This program is licensed "as is" without any
> + * warranty of any kind, whether express or implied.
> + */
> +
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of_address.h>
> +#include <linux/platform_device.h>
> +#include <linux/reboot.h>
> +
> +#include <asm/system_misc.h>
> +
> +#include <mach/at91sam9_ddrsdr.h>
> +#include <mach/at91sam9_sdramc.h>
> +
> +#define AT91_RSTC_CR	0x00		/* Reset Controller Control Register */
> +#define AT91_RSTC_PROCRST	BIT(0)		/* Processor Reset */
> +#define AT91_RSTC_PERRST	BIT(2)		/* Peripheral Reset */
> +#define AT91_RSTC_EXTRST	BIT(3)		/* External Reset */
> +#define AT91_RSTC_KEY		(0xa5 << 24)	/* KEY Password */
> +
> +#define AT91_RSTC_SR	0x04		/* Reset Controller Status Register */
> +#define AT91_RSTC_URSTS		BIT(0)		/* User Reset Status */
> +#define AT91_RSTC_RSTTYP	GENMASK(10, 8)	/* Reset Type */
> +#define AT91_RSTC_NRSTL		BIT(16)		/* NRST Pin Level */
> +#define AT91_RSTC_SRCMP		BIT(17)		/* Software Reset Command in Progress */
> +
> +#define AT91_RSTC_MR	0x08		/* Reset Controller Mode Register */
> +#define AT91_RSTC_URSTEN	BIT(0)		/* User Reset Enable */
> +#define AT91_RSTC_URSTIEN	BIT(4)		/* User Reset Interrupt Enable */
> +#define AT91_RSTC_ERSTL		GENMASK(11, 8)	/* External Reset Length */
> +
> +enum reset_type {
> +	RESET_TYPE_GENERAL	= 0,
> +	RESET_TYPE_WAKEUP	= 1,
> +	RESET_TYPE_WATCHDOG	= 2,
> +	RESET_TYPE_SOFTWARE	= 3,
> +	RESET_TYPE_USER		= 4,
> +};
> +
> +static void __iomem *at91_ramc_base[2], *at91_rstc_base;
> +

Here I want to add the comments that we put in the assembly file:

"
* unless the SDRAM is cleanly shutdown before we hit the
* reset register it can be left driving the data bus and
* killing the chance of a subsequent boot from NAND
"

Just to keep people informed right above the code that implement it...

> +static void at91sam9260_restart(enum reboot_mode mode, const char *cmd)
> +{
> +	asm volatile(
> +		/* Align to cache lines */
> +		".balign 32\n\t"
> +
> +		/* Disable SDRAM accesses */
> +		"str	%2, [%0, #" __stringify(AT91_SDRAMC_TR) "]\n\t"
> +
> +		/* Power down SDRAM */
> +		"str	%3, [%0, #" __stringify(AT91_SDRAMC_LPR) "]\n\t"
> +
> +		/* Reset CPU */
> +		"str	%4, [%1, #" __stringify(AT91_RSTC_CR) "]\n\t"
> +
> +		"b	.\n\t"
> +		:
> +		: "r" (at91_ramc_base[0]),
> +		  "r" (at91_rstc_base),
> +		  "r" (1),
> +		  "r" (AT91_SDRAMC_LPCB_POWER_DOWN),
> +		  "r" (AT91_RSTC_KEY | AT91_RSTC_PERRST | AT91_RSTC_PROCRST));
> +}
> +
> +
> +static void at91sam9g45_restart(enum reboot_mode mode, const char *cmd)
> +{
> +	asm volatile(
> +		/*
> +		 * Test wether we have a second RAM controller to care
> +		 * about.
> +		 *
> +		 * First, test that we can dereference the virtual address.
> +		 */
> +		"cmp	%1, #0\n\t"
> +		"beq	1f\n\t"
> +
> +		/* Then, test that the RAM controller is enabled */
> +		"ldr	r0, [%1]\n\t"
> +		"cmp	r0, #0\n\t"
> +
> +		/* Align to cache lines */
> +		".balign 32\n\t"
> +
> +		/* Disable SDRAM0 accesses */
> +		"1:	str	%3, [%0, #" __stringify(AT91_DDRSDRC_RTR) "]\n\t"
> +		/* Power down SDRAM0 */
> +		"	str	%4, [%0, #" __stringify(AT91_DDRSDRC_RTR) "]\n\t"
> +		/* Disable SDRAM1 accesses */
> +		"	strne	%3, [%1, #" __stringify(AT91_DDRSDRC_RTR) "]\n\t"
> +		/* Power down SDRAM1 */
> +		"	strne	%4, [%1, #" __stringify(AT91_DDRSDRC_RTR) "]\n\t"
> +		/* Reset CPU */
> +		"	str	%5, [%2, #" __stringify(AT91_RSTC_CR) "]\n\t"
> +
> +		"	b	.\n\t"
> +		:
> +		: "r" (at91_ramc_base[0]),
> +		  "r" (at91_ramc_base[1]),
> +		  "r" (at91_rstc_base),
> +		  "r" (1),
> +		  "r" (AT91_DDRSDRC_LPCB_POWER_DOWN),
> +		  "r" (AT91_RSTC_KEY | AT91_RSTC_PERRST | AT91_RSTC_PROCRST)
> +		: "r0");
> +}
> +
> +static void __init at91_reset_status(struct platform_device *pdev)
> +{
> +	u32 reg = readl(at91_rstc_base + AT91_RSTC_SR);
> +	char *reason;
> +
> +	switch ((reg & AT91_RSTC_RSTTYP) >> 8) {
> +	case RESET_TYPE_GENERAL:
> +		reason = "general reset";
> +		break;
> +	case RESET_TYPE_WAKEUP:
> +		reason = "wakeup";
> +		break;
> +	case RESET_TYPE_WATCHDOG:
> +		reason = "watchdog reset";
> +		break;
> +	case RESET_TYPE_SOFTWARE:
> +		reason = "software reset";
> +		break;
> +	case RESET_TYPE_USER:
> +		reason = "user reset";
> +		break;
> +	default:
> +		reason = "unknown reset";
> +		break;
> +	}
> +
> +	pr_info("AT91: Starting after %s\n", reason);
> +}
> +
> +static struct of_device_id at91_ramc_of_match[] = {
> +	{ .compatible = "atmel,at91sam9260-sdramc", },
> +	{ .compatible = "atmel,at91sam9g45-ddramc", },
> +	{ /* sentinel */ }
> +};
> +
> +static struct of_device_id at91_reset_of_match[] = {
> +	{ .compatible = "atmel,at91sam9260-rstc", .data = at91sam9260_restart },
> +	{ .compatible = "atmel,at91sam9g45-rstc", .data = at91sam9g45_restart },

For the *future*, we have to keep in mind that we have another choice
with sama5d3: this SoC doesn't have to implement the workaround. But for
sure, it is another patch/"patch series".

> +	{ /* sentinel */ }
> +};
> +
> +static int at91_reset_of_probe(struct platform_device *pdev)
> +{
> +	const struct of_device_id *match;
> +	struct device_node *np;
> +	int idx = 0;
> +
> +	at91_rstc_base = of_iomap(pdev->dev.of_node, 0);
> +	if (!at91_rstc_base) {
> +		dev_err(&pdev->dev, "Could not map reset controller address\n");
> +		return -ENODEV;
> +	}
> +
> +	for_each_matching_node(np, at91_ramc_of_match) {
> +		at91_ramc_base[idx] = of_iomap(np, 0);
> +		if (!at91_ramc_base[idx]) {
> +			dev_err(&pdev->dev, "Could not map ram controller address\n");
> +			return -ENODEV;
> +		}
> +		idx++;
> +	}
> +
> +	match = of_match_node(at91_reset_of_match, pdev->dev.of_node);
> +	arm_pm_restart = match->data;
> +
> +	return 0;
> +}
> +
> +static int at91_reset_platform_probe(struct platform_device *pdev)
> +{
> +	const struct platform_device_id *match;
> +	struct resource *res;
> +	int idx = 0;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	at91_rstc_base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(at91_rstc_base)) {
> +		dev_err(&pdev->dev, "Could not map reset controller address\n");
> +		return PTR_ERR(at91_rstc_base);
> +	}
> +
> +	for (idx = 0; idx < 2; idx++) {
> +		res = platform_get_resource(pdev, IORESOURCE_MEM, idx + 1 );
> +		at91_ramc_base[idx] = devm_ioremap(&pdev->dev, res->start,
> +						   resource_size(res));
> +		if (IS_ERR(at91_ramc_base[idx])) {
> +			dev_err(&pdev->dev, "Could not map ram controller address\n");
> +			return PTR_ERR(at91_rstc_base);
> +		}
> +	}
> +
> +	match = platform_get_device_id(pdev);
> +	arm_pm_restart = (void (*)(enum reboot_mode, const char*))
> +		match->driver_data;
> +
> +	return 0;
> +}
> +
> +static int at91_reset_probe(struct platform_device *pdev)
> +{
> +	int ret;
> +
> +	if (pdev->dev.of_node)
> +		ret = at91_reset_of_probe(pdev);
> +	else
> +		ret = at91_reset_platform_probe(pdev);
> +
> +	if (ret)
> +		return ret;
> +
> +	at91_reset_status(pdev);
> +
> +	return 0;
> +}
> +
> +static struct platform_device_id at91_reset_plat_match[] = {
> +	{ "at91-sam9260-reset", (unsigned long)at91sam9260_restart },
> +	{ "at91-sam9g45-reset", (unsigned long)at91sam9g45_restart },
> +	{ /* sentinel */ }
> +};
> +
> +static struct platform_driver at91_reset_driver = {
> +	.probe = at91_reset_probe,
> +	.driver = {
> +		.name = "at91-reset",
> +		.of_match_table = at91_reset_of_match,
> +	},
> +	.id_table = at91_reset_plat_match,
> +};
> +module_platform_driver(at91_reset_driver);
> 


-- 
Nicolas Ferre
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