Re: [PATCH RESEND v6 1/2] watchdog: ImgTec PDC Watchdog Timer Driver

[Guenter Roeck <linux-0h96xk9xTtrk1uMJSBkQmQ@public.gmane.org>]

On Thu, Nov 27, 2014 at 10:24:04AM +0530, Naidu Tellapati wrote:
> This commit adds support for ImgTec PowerDown Controller Watchdog Timer.
> 
> Signed-off-by: Naidu Tellapati <Naidu.Tellapati-1AXoQHu6uovQT0dZR+AlfA@public.gmane.org>
> Signed-off-by: Jude.Abraham <Jude.Abraham-1AXoQHu6uovQT0dZR+AlfA@public.gmane.org>
> Reviewed-by: Andrew Bresticker <abrestic-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
> Reviewed-by: Ezequiel Garcia <ezequiel.garcia-1AXoQHu6uovQT0dZR+AlfA@public.gmane.org>
> ---
>  drivers/watchdog/Kconfig      |   11 ++
>  drivers/watchdog/Makefile     |    1 +
>  drivers/watchdog/imgpdc_wdt.c |  298 +++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 310 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/watchdog/imgpdc_wdt.c
> 
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index d0107d4..a184f23 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -1235,6 +1235,17 @@ config BCM_KONA_WDT_DEBUG
>  
>  	  If in doubt, say 'N'.
>  
> +config IMGPDC_WDT
> +	tristate "Imagination Technologies PDC Watchdog Timer"
> +	depends on HAS_IOMEM
> +	depends on METAG || MIPS || COMPILE_TEST
> +	help
> +	  Driver for Imagination Technologies PowerDown Controller
> +	  Watchdog Timer.
> +
> +	  To compile this driver as a loadable module, choose M here.
> +	  The module will be called imgpdc_wdt.
> +
>  config LANTIQ_WDT
>  	tristate "Lantiq SoC watchdog"
>  	depends on LANTIQ
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index c569ec8..d4dfbb4 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -142,6 +142,7 @@ obj-$(CONFIG_OCTEON_WDT) += octeon-wdt.o
>  octeon-wdt-y := octeon-wdt-main.o octeon-wdt-nmi.o
>  obj-$(CONFIG_LANTIQ_WDT) += lantiq_wdt.o
>  obj-$(CONFIG_RALINK_WDT) += rt2880_wdt.o
> +obj-$(CONFIG_IMGPDC_WDT) += imgpdc_wdt.o
>  
>  # PARISC Architecture
>  
> diff --git a/drivers/watchdog/imgpdc_wdt.c b/drivers/watchdog/imgpdc_wdt.c
> new file mode 100644
> index 0000000..efb00b5
> --- /dev/null
> +++ b/drivers/watchdog/imgpdc_wdt.c
> @@ -0,0 +1,298 @@
> +/*
> + * Imagination Technologies PowerDown Controller Watchdog Timer.
> + *
> + * Copyright (c) 2014 Imagination Technologies Ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License version 2 as published by
> + * the Free Software Foundation.
> + *
> + * Based on drivers/watchdog/sunxi_wdt.c Copyright (c) 2013 Carlo Caione
> + *                                                     2012 Henrik Nordstrom
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/io.h>
> +#include <linux/log2.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +#include <linux/watchdog.h>
> +
> +/* registers */
> +#define PDC_WD_SW_RESET			0x000
> +
> +#define PDC_WD_CONFIG			0x004
> +#define PDC_WD_CONFIG_ENABLE		BIT(31)
> +#define PDC_WD_CONFIG_DELAY_MASK	0x0000001f
> +#define PDC_WD_CONFIG_DELAY_SHIFT	0
> +
> +#define PDC_WD_TICKLE1			0x008
> +#define PDC_WD_TICKLE1_MAGIC		0xabcd1234
> +
> +#define PDC_WD_TICKLE2			0x00c
> +#define PDC_WD_TICKLE2_MAGIC		0x4321dcba
> +
> +#define PDC_WD_TICKLE_STATUS_MASK	0x00000007
> +#define PDC_WD_TICKLE_STATUS_SHIFT	0
> +#define PDC_WD_TICKLE_STATUS_HRESET     0x0  /* Hard reset */
> +#define PDC_WD_TICKLE_STATUS_TIMEOUT    0x1  /* Timeout */
> +#define PDC_WD_TICKLE_STATUS_TICKLE     0x2  /* Tickled incorrectly */
> +#define PDC_WD_TICKLE_STATUS_SRESET     0x3  /* Soft reset */
> +#define PDC_WD_TICKLE_STATUS_USER       0x4  /* User reset */
> +
> +/* timeout in seconds */
> +#define PDC_WD_MIN_TIMEOUT		1
> +#define PDC_WD_DEFAULT_TIMEOUT		64
> +
> +static int timeout = PDC_WD_DEFAULT_TIMEOUT;
> +module_param(timeout, int, 0);
> +MODULE_PARM_DESC(timeout, "PDC watchdog delay in seconds (default 64s)");

It might be better to use  __MODULE_STRING(PDC_WD_DEFAULT_TIMEOUT)
to encode the default timeout.

> +
> +static bool nowayout = WATCHDOG_NOWAYOUT;
> +module_param(nowayout, bool, 0);
> +MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started");
> +
> +struct pdc_wdt_dev {
> +	struct watchdog_device wdt_dev;
> +	struct clk *wdt_clk;
> +	struct clk *sys_clk;
> +	int min_delay;
> +	void __iomem *base;
> +};
> +
> +static int pdc_wdt_keepalive(struct watchdog_device *wdt_dev)
> +{
> +	struct pdc_wdt_dev *wdt = watchdog_get_drvdata(wdt_dev);
> +
> +	writel(PDC_WD_TICKLE1_MAGIC, wdt->base + PDC_WD_TICKLE1);
> +	writel(PDC_WD_TICKLE2_MAGIC, wdt->base + PDC_WD_TICKLE2);
> +
> +	return 0;
> +}
> +
> +static int pdc_wdt_stop(struct watchdog_device *wdt_dev)
> +{
> +	unsigned int val;
> +	struct pdc_wdt_dev *wdt = watchdog_get_drvdata(wdt_dev);
> +
> +	val = readl(wdt->base + PDC_WD_CONFIG);
> +	val &= ~PDC_WD_CONFIG_ENABLE;
> +	writel(val, wdt->base + PDC_WD_CONFIG);
> +
> +	/* Must tickle to finish the stop */
> +	pdc_wdt_keepalive(wdt_dev);
> +
> +	return 0;
> +}
> +
> +static int pdc_wdt_set_timeout(struct watchdog_device *wdt_dev,
> +			       unsigned int new_timeout)
> +{
> +	unsigned int val;
> +	struct pdc_wdt_dev *wdt = watchdog_get_drvdata(wdt_dev);
> +
> +	wdt->wdt_dev.timeout = new_timeout;
> +	/* round up to the next power of 2 */
> +	new_timeout = order_base_2(new_timeout);
> +	val = readl(wdt->base + PDC_WD_CONFIG);
> +	val &= ~PDC_WD_CONFIG_DELAY_MASK;
> +	val |= (new_timeout + wdt->min_delay) << PDC_WD_CONFIG_DELAY_SHIFT;
> +	writel(val, wdt->base + PDC_WD_CONFIG);
> +
> +	return 0;
> +}
> +
> +/* Start the watchdog timer (delay should already be set) */
> +static int pdc_wdt_start(struct watchdog_device *wdt_dev)
> +{
> +	unsigned int val;
> +	struct pdc_wdt_dev *wdt = watchdog_get_drvdata(wdt_dev);
> +
> +	val = readl(wdt->base + PDC_WD_CONFIG);
> +	val |= PDC_WD_CONFIG_ENABLE;
> +	writel(val, wdt->base + PDC_WD_CONFIG);
> +
> +	return 0;
> +}
> +
> +static struct watchdog_info pdc_wdt_info = {
> +	.identity	= "IMG PDC Watchdog",
> +	.options	= WDIOF_SETTIMEOUT |
> +			  WDIOF_KEEPALIVEPING |
> +			  WDIOF_MAGICCLOSE,
> +};
> +
> +/* Kernel interface */
> +static const struct watchdog_ops pdc_wdt_ops = {
> +	.owner		= THIS_MODULE,
> +	.start		= pdc_wdt_start,
> +	.stop		= pdc_wdt_stop,
> +	.ping		= pdc_wdt_keepalive,
> +	.set_timeout	= pdc_wdt_set_timeout,
> +};
> +
> +static int pdc_wdt_probe(struct platform_device *pdev)
> +{
> +	int ret, val;
> +	unsigned long clk_rate;
> +	struct resource *res;
> +	struct pdc_wdt_dev *pdc_wdt;
> +
> +	pdc_wdt = devm_kzalloc(&pdev->dev, sizeof(*pdc_wdt), GFP_KERNEL);
> +	if (!pdc_wdt)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	pdc_wdt->base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(pdc_wdt->base))
> +		return PTR_ERR(pdc_wdt->base);
> +
> +	pdc_wdt->sys_clk = devm_clk_get(&pdev->dev, "sys");
> +	if (IS_ERR(pdc_wdt->sys_clk)) {
> +		dev_err(&pdev->dev, "failed to get the sys clock.\n");
> +		ret = PTR_ERR(pdc_wdt->wdt_clk);

					sys_clk
> +		return ret;

		return PTR_ERR(pdc_wdt->sys_clk);

On a higher level, what is sys_clk needed and used for in the first place ?
The need for wdt_clk is obvious, but there is no explanation for the need
of sys_clk, and the bindings file doesn't give a hint either.

> +	}
> +
> +	pdc_wdt->wdt_clk = devm_clk_get(&pdev->dev, "wdt");
> +	if (IS_ERR(pdc_wdt->wdt_clk)) {
> +		dev_err(&pdev->dev, "failed to get the wdt clock.\n");
> +		ret = PTR_ERR(pdc_wdt->wdt_clk);
> +		return ret;

		return PTR_ERR(pdc_wdt->wdt_clk);

> +	}
> +
> +	ret = clk_prepare_enable(pdc_wdt->sys_clk);
> +	if (ret) {
> +		dev_err(&pdev->dev, "could not prepare or enable sys clock.\n");
> +		return ret;
> +	}
> +
> +	ret = clk_prepare_enable(pdc_wdt->wdt_clk);
> +	if (ret) {
> +		dev_err(&pdev->dev, "could not prepare or enable wdt clock.\n");
> +		goto disable_sys_clk;

I would suggest to drop the '.' in those messages.

> +	}
> +
> +	/* We use the clock rate to calculate the max timeout */
> +	clk_rate = clk_get_rate(pdc_wdt->wdt_clk);
> +	if (clk_rate == 0) {
> +		dev_err(&pdev->dev, "failed to get clock rate\n");
> +		ret = -EINVAL;
> +		goto disable_wdt_clk;
> +	}
> +
> +	if (order_base_2(clk_rate) > PDC_WD_CONFIG_DELAY_MASK + 1) {
> +		dev_err(&pdev->dev, "invalid clock rate\n");
> +		ret = -EINVAL;
> +		goto disable_wdt_clk;
> +	}
> +
> +	if (order_base_2(clk_rate) == 0)
> +		pdc_wdt->wdt_dev.min_timeout = PDC_WD_MIN_TIMEOUT + 1;
> +	else
> +		pdc_wdt->wdt_dev.min_timeout = PDC_WD_MIN_TIMEOUT;
> +
> +	pdc_wdt->min_delay = order_base_2(clk_rate) - 1;

Ultimately this means that min_delay can be smaller than 0,
which makes it quite difficult to validate the rest of the code
to ensure that it handles this case correctly.

Give that a clock rate of 1 is somewhere between highly unlikely and
unreasonable, wouldn't it be much easier to consider it to be invalid
and not try to handle it ?

> +
> +	pdc_wdt->wdt_dev.info = &pdc_wdt_info;
> +	pdc_wdt->wdt_dev.ops = &pdc_wdt_ops;
> +	pdc_wdt->wdt_dev.max_timeout =
> +			(1 << (PDC_WD_CONFIG_DELAY_MASK - pdc_wdt->min_delay));
> +	pdc_wdt->wdt_dev.parent = &pdev->dev;
> +
> +	ret = watchdog_init_timeout(&pdc_wdt->wdt_dev, timeout, &pdev->dev);
> +	if (ret < 0) {
> +		pdc_wdt->wdt_dev.timeout = pdc_wdt->wdt_dev.max_timeout;
> +		dev_warn(&pdev->dev,
> +			 "Initial timeout out of range! setting max timeout\n");
> +	}
> +
> +	pdc_wdt_stop(&pdc_wdt->wdt_dev);
> +
> +	/* Find what caused the last reset */
> +	val = readl(pdc_wdt->base + PDC_WD_TICKLE1);
> +	val = (val & PDC_WD_TICKLE_STATUS_MASK) >> PDC_WD_TICKLE_STATUS_SHIFT;
> +	switch (val) {
> +	case PDC_WD_TICKLE_STATUS_TICKLE:
> +	case PDC_WD_TICKLE_STATUS_TIMEOUT:
> +		pdc_wdt->wdt_dev.bootstatus |= WDIOF_CARDRESET;
> +		dev_info(&pdev->dev,
> +			 "watchdog module last reset due to timeout\n");
> +		break;
> +	case PDC_WD_TICKLE_STATUS_HRESET:
> +		dev_info(&pdev->dev,
> +			 "watchdog module last reset due to hard reset\n");
> +		break;
> +	case PDC_WD_TICKLE_STATUS_SRESET:
> +		dev_info(&pdev->dev,
> +			 "watchdog module last reset due to soft reset\n");
> +		break;
> +	case PDC_WD_TICKLE_STATUS_USER:
> +		dev_info(&pdev->dev,
> +			 "watchdog module last reset due to user reset\n");
> +		break;
> +	default:
> +		dev_info(&pdev->dev,
> +			 "contains an illegal status code (%08x)\n", val);
> +		break;
> +	}
> +
> +	watchdog_set_nowayout(&pdc_wdt->wdt_dev, nowayout);
> +
> +	platform_set_drvdata(pdev, pdc_wdt);
> +	watchdog_set_drvdata(&pdc_wdt->wdt_dev, pdc_wdt);
> +
> +	ret = watchdog_register_device(&pdc_wdt->wdt_dev);
> +	if (ret)
> +		goto disable_wdt_clk;
> +
> +	return 0;
> +
> +disable_wdt_clk:
> +	clk_disable_unprepare(pdc_wdt->wdt_clk);
> +disable_sys_clk:
> +	clk_disable_unprepare(pdc_wdt->sys_clk);
> +	return ret;
> +}
> +
> +static void pdc_wdt_shutdown(struct platform_device *pdev)
> +{
> +	struct pdc_wdt_dev *pdc_wdt = platform_get_drvdata(pdev);
> +
> +	pdc_wdt_stop(&pdc_wdt->wdt_dev);
> +}
> +
> +static int pdc_wdt_remove(struct platform_device *pdev)
> +{
> +	struct pdc_wdt_dev *pdc_wdt = platform_get_drvdata(pdev);
> +
> +	pdc_wdt_stop(&pdc_wdt->wdt_dev);
> +	watchdog_unregister_device(&pdc_wdt->wdt_dev);
> +	clk_disable_unprepare(pdc_wdt->wdt_clk);
> +	clk_disable_unprepare(pdc_wdt->sys_clk);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id pdc_wdt_match[] = {
> +	{ .compatible = "img,pdc-wdt" },

Will "img" be added to the list of vendor prefixes with some other patch ?

> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, pdc_wdt_match);
> +
> +static struct platform_driver pdc_wdt_driver = {
> +	.driver = {
> +		.name = "imgpdc-wdt",
> +		.of_match_table	= pdc_wdt_match,
> +	},
> +	.probe = pdc_wdt_probe,
> +	.remove = pdc_wdt_remove,
> +	.shutdown = pdc_wdt_shutdown,
> +};
> +module_platform_driver(pdc_wdt_driver);
> +
> +MODULE_AUTHOR("Jude Abraham <Jude.Abraham-1AXoQHu6uovQT0dZR+AlfA@public.gmane.org>");
> +MODULE_AUTHOR("Naidu Tellapati <Naidu.Tellapati-1AXoQHu6uovQT0dZR+AlfA@public.gmane.org>");
> +MODULE_DESCRIPTION("Imagination Technologies PDC Watchdog Timer Driver");
> +MODULE_LICENSE("GPL v2");
> -- 
> 1.7.0.4
> 
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