Re: [alsa-devel] [PATCH v2 2/4] watchdog: mtk_wdt: mt8183: Add reset controller

[Guenter Roeck <linux@roeck-us.net>]

On 9/27/19 3:31 AM, Jiaxin Yu wrote:
> From: "yong.liang" <yong.liang@mediatek.com>
> 
> Provide assert/deassert/reset API in watchdog driver.
> Register reset controller for toprgu device in watchdog probe.
> 
> Signed-off-by: yong.liang <yong.liang@mediatek.com>
> ---
>   drivers/watchdog/Kconfig   |   1 +
>   drivers/watchdog/mtk_wdt.c | 110 ++++++++++++++++++++++++++++++++++++-
>   2 files changed, 110 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index 2e07caab9db2..629249fe5305 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -717,6 +717,7 @@ config MEDIATEK_WATCHDOG
>   	tristate "Mediatek SoCs watchdog support"
>   	depends on ARCH_MEDIATEK || COMPILE_TEST
>   	select WATCHDOG_CORE
> +	select RESET_CONTROLLER
>   	help
>   	  Say Y here to include support for the watchdog timer
>   	  in Mediatek SoCs.
> diff --git a/drivers/watchdog/mtk_wdt.c b/drivers/watchdog/mtk_wdt.c
> index 9c3d0033260d..660fb0e48d8e 100644
> --- a/drivers/watchdog/mtk_wdt.c
> +++ b/drivers/watchdog/mtk_wdt.c
> @@ -20,6 +20,10 @@
>   #include <linux/types.h>
>   #include <linux/watchdog.h>
>   #include <linux/delay.h>
> +#include <linux/reset-controller.h>
> +#include <linux/slab.h>
> +#include <linux/reset.h>
> +#include <linux/of_device.h>
>   
>   #define WDT_MAX_TIMEOUT		31
>   #define WDT_MIN_TIMEOUT		1
> @@ -44,17 +48,113 @@
>   #define WDT_SWRST		0x14
>   #define WDT_SWRST_KEY		0x1209
>   
> +#define WDT_SWSYSRST		0x18U
> +#define WDT_SWSYS_RST_KEY	0x88000000
> +
>   #define DRV_NAME		"mtk-wdt"
>   #define DRV_VERSION		"1.0"
>   
>   static bool nowayout = WATCHDOG_NOWAYOUT;
>   static unsigned int timeout;
>   
> +struct toprgu_reset {
> +	spinlock_t lock; /* Protects reset_controller access */
> +	void __iomem *toprgu_swrst_base;
> +	int regofs;
> +	struct reset_controller_dev rcdev;
> +};
> +
>   struct mtk_wdt_dev {
>   	struct watchdog_device wdt_dev;
>   	void __iomem *wdt_base;
> +	struct toprgu_reset reset_controller;
> +	const struct mtk_wdt_compatible *dev_comp;

"dev_comp" suggests that this would be a device name. In practice,
the only value there is sw_rst_num, and the value is only
used in toprgu_register_reset_controller(). Might as well pass
it as argument and drop this pointer.

> +};
> +
> +struct mtk_wdt_compatible {
> +	int sw_rst_num;
> +};
> +
"compatible" is an odd name for this structure. I would suggest
to select a more common name such as "mtk_wdt_data".

> +static int toprgu_reset_assert(struct reset_controller_dev *rcdev,
> +			       unsigned long id)
> +{
> +	unsigned int tmp;
> +	unsigned long flags;
> +	struct toprgu_reset *data = container_of(rcdev,
> +				struct toprgu_reset, rcdev);
> +
> +	spin_lock_irqsave(&data->lock, flags);
> +
> +	tmp = __raw_readl(data->toprgu_swrst_base + data->regofs);
> +	tmp |= BIT(id);
> +	tmp |= WDT_SWSYS_RST_KEY;
> +	writel(tmp, data->toprgu_swrst_base + data->regofs);
> +
> +	spin_unlock_irqrestore(&data->lock, flags);
> +
> +	return 0;
> +}
> +
> +static int toprgu_reset_deassert(struct reset_controller_dev *rcdev,
> +				 unsigned long id)
> +{
> +	unsigned int tmp;
> +	unsigned long flags;
> +	struct toprgu_reset *data = container_of(rcdev,
> +					struct toprgu_reset, rcdev);
> +
> +	spin_lock_irqsave(&data->lock, flags);
> +
> +	tmp = __raw_readl(data->toprgu_swrst_base + data->regofs);
> +	tmp &= ~BIT(id);
> +	tmp |= WDT_SWSYS_RST_KEY;
> +	writel(tmp, data->toprgu_swrst_base + data->regofs);
> +
> +	spin_unlock_irqrestore(&data->lock, flags);
> +
> +	return 0;
> +}
> +
> +static int toprgu_reset(struct reset_controller_dev *rcdev,
> +			unsigned long id)
> +{
> +	int ret;
> +
> +	ret = toprgu_reset_assert(rcdev, id);
> +	if (ret)
> +		return ret;
> +
> +	return toprgu_reset_deassert(rcdev, id);

Unless there is additional synchronization elsewhere, parallel calls
to the -> assert, and ->reset callbacks may result in the reset being
deasserted while at least one caller (the one who called the ->assert
function) believes that it is still asserted.

[ ... and if there _is_ additional synchronization elsewhere, the
   local spinlock would be unnecessary ]

> +}
> +
> +static struct reset_control_ops toprgu_reset_ops = {
> +	.assert = toprgu_reset_assert,
> +	.deassert = toprgu_reset_deassert,
> +	.reset = toprgu_reset,
>   };
>   
> +static void toprgu_register_reset_controller(struct platform_device *pdev,
> +					     int regofs)

Since there is only one well defined offset, it seems unnecessary to pass
regofs as parameter.

> +{
> +	int ret;
> +	struct mtk_wdt_dev *mtk_wdt = platform_get_drvdata(pdev);
> +
> +	spin_lock_init(&mtk_wdt->reset_controller.lock);
> +
> +	mtk_wdt->dev_comp = of_device_get_match_data(&pdev->dev);

Duplicate, and not really needed. Just pass sw_rst_num as argument.

> +	mtk_wdt->reset_controller.toprgu_swrst_base = mtk_wdt->wdt_base;
> +	mtk_wdt->reset_controller.regofs = regofs;
> +	mtk_wdt->reset_controller.rcdev.owner = THIS_MODULE;
> +	mtk_wdt->reset_controller.rcdev.nr_resets =
> +				mtk_wdt->dev_comp->sw_rst_num;
> +	mtk_wdt->reset_controller.rcdev.ops = &toprgu_reset_ops;
> +	mtk_wdt->reset_controller.rcdev.of_node = pdev->dev.of_node;
> +	ret = reset_controller_register(&mtk_wdt->reset_controller.rcdev);
> +	if (ret != 0)
> +		dev_err(&pdev->dev,
> +			"couldn't register wdt reset controller: %d\n", ret);
> +}
> +
>   static int mtk_wdt_restart(struct watchdog_device *wdt_dev,
>   			   unsigned long action, void *data)
>   {
> @@ -187,9 +287,12 @@ static int mtk_wdt_probe(struct platform_device *pdev)
>   	if (unlikely(err))
>   		return err;
>   
> -	dev_info(dev, "Watchdog enabled (timeout=%d sec, nowayout=%d)\n",
> +	dev_info(&pdev->dev, "Watchdog enabled (timeout=%d sec, nowayout=%d)\n",
>   		 mtk_wdt->wdt_dev.timeout, nowayout);
>   
> +	mtk_wdt->dev_comp = of_device_get_match_data(&pdev->dev);
> +	if (mtk_wdt->dev_comp)
> +		toprgu_register_reset_controller(pdev, WDT_SWSYSRST);
>   	return 0;
>   }
>   
> @@ -217,7 +320,12 @@ static int mtk_wdt_resume(struct device *dev)
>   }
>   #endif
>   
> +static const struct mtk_wdt_compatible mt8183_compat = {
> +	.sw_rst_num = 18,

Please no such magic numbers. This should be a define in an include file.

> +};
> +
>   static const struct of_device_id mtk_wdt_dt_ids[] = {
> +	{ .compatible = "mediatek,mt8183-wdt", .data = &mt8183_compat },
>   	{ .compatible = "mediatek,mt6589-wdt" },
>   	{ /* sentinel */ }
>   };
> 

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