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Message-ID: <20140924155854.GA12620@roeck-us.net>
Date: Wed, 24 Sep 2014 08:58:54 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Josh Cartwright <joshc@...eaurora.org>
Cc: Wim Van Sebroeck <wim@...ana.be>, linux-watchdog@...r.kernel.org,
Grant Likely <grant.likely@...aro.org>,
Rob Herring <robh+dt@...nel.org>,
linux-arm-msm@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
Kumar Gala <galak@...eaurora.org>,
linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 1/3] watchdog: qcom: add support for KPSS WDT
On Tue, Sep 23, 2014 at 06:04:36PM -0500, Josh Cartwright wrote:
> Add a driver for the watchdog timer block found in the Krait Processor
> Subsystem (KPSS) on the MSM8960, APQ8064, and IPQ8064.
>
> Signed-off-by: Josh Cartwright <joshc@...eaurora.org>
Hi Josh,
looks much better. Couple of comments inline.
Thanks,
Guenter
> ---
> drivers/watchdog/Kconfig | 13 ++++
> drivers/watchdog/Makefile | 1 +
> drivers/watchdog/qcom-wdt.c | 176 ++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 190 insertions(+)
> create mode 100644 drivers/watchdog/qcom-wdt.c
>
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index 1d1330a..0479e3f 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -443,6 +443,19 @@ config TEGRA_WATCHDOG
> To compile this driver as a module, choose M here: the
> module will be called tegra_wdt.
>
> +config QCOM_WDT
> + tristate "QCOM watchdog"
> + depends on HAS_IOMEM
> + depends on ARCH_QCOM
> + select WATCHDOG_CORE
> + help
> + Say Y here to include Watchdog timer support for the watchdog found
> + on QCOM chipsets. Currently supported targets are the MSM8960,
> + APQ8064, and IPQ8064.
> +
> + To compile this driver as a module, choose M here: the
> + module will be called qcom_wdt.
> +
> # AVR32 Architecture
>
> config AT32AP700X_WDT
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index 468c320..d645448 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -57,6 +57,7 @@ obj-$(CONFIG_RETU_WATCHDOG) += retu_wdt.o
> obj-$(CONFIG_BCM2835_WDT) += bcm2835_wdt.o
> obj-$(CONFIG_MOXART_WDT) += moxart_wdt.o
> obj-$(CONFIG_SIRFSOC_WATCHDOG) += sirfsoc_wdt.o
> +obj-$(CONFIG_QCOM_WDT) += qcom-wdt.o
> obj-$(CONFIG_BCM_KONA_WDT) += bcm_kona_wdt.o
> obj-$(CONFIG_TEGRA_WATCHDOG) += tegra_wdt.o
>
> diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
> new file mode 100644
> index 0000000..d5e46e2
> --- /dev/null
> +++ b/drivers/watchdog/qcom-wdt.c
> @@ -0,0 +1,176 @@
> +/* Copyright (c) 2014, The Linux Foundation. All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 and
> + * only version 2 as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + */
> +#include <linux/clk.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/watchdog.h>
> +
> +#define WDT_RST 0x0
> +#define WDT_EN 0x8
> +#define WDT_BITE_TIME 0x24
> +
> +struct qcom_wdt {
> + struct watchdog_device wdd;
> + struct clk *clk;
> + void __iomem *base;
> +};
> +
> +static inline
> +struct qcom_wdt *to_qcom_wdt(struct watchdog_device *wdd)
> +{
> + return container_of(wdd, struct qcom_wdt, wdd);
> +}
> +
> +static int qcom_wdt_start(struct watchdog_device *wdd)
> +{
> + struct qcom_wdt *wdt = to_qcom_wdt(wdd);
> + unsigned long bite_time;
> +
> + bite_time = wdd->timeout * clk_get_rate(wdt->clk);
> +
> + writel(0, wdt->base + WDT_EN);
> + writel(1, wdt->base + WDT_RST);
> + writel(bite_time, wdt->base + WDT_BITE_TIME);
> + writel(1, wdt->base + WDT_EN);
> + return 0;
> +}
> +
> +static int qcom_wdt_stop(struct watchdog_device *wdd)
> +{
> + struct qcom_wdt *wdt = to_qcom_wdt(wdd);
> +
> + writel(0, wdt->base + WDT_EN);
> + return 0;
> +}
> +
> +static int qcom_wdt_ping(struct watchdog_device *wdd)
> +{
> + struct qcom_wdt *wdt = to_qcom_wdt(wdd);
> +
> + writel(1, wdt->base + WDT_RST);
> + return 0;
> +}
> +
> +static int qcom_wdt_set_timeout(struct watchdog_device *wdd,
> + unsigned int timeout)
> +{
> + wdd->timeout = timeout;
> + return qcom_wdt_start(wdd);
> +}
> +
> +static const struct watchdog_ops qcom_wdt_ops = {
> + .start = qcom_wdt_start,
> + .stop = qcom_wdt_stop,
> + .ping = qcom_wdt_ping,
> + .set_timeout = qcom_wdt_set_timeout,
> + .owner = THIS_MODULE,
> +};
> +
> +static const struct watchdog_info qcom_wdt_info = {
> + .options = WDIOF_KEEPALIVEPING
> + | WDIOF_MAGICCLOSE
> + | WDIOF_SETTIMEOUT,
> + .identity = KBUILD_MODNAME,
> +};
> +
> +static int qcom_wdt_probe(struct platform_device *pdev)
> +{
> + struct qcom_wdt *wdt;
> + struct resource *res;
> + unsigned long freq;
> + int ret;
> +
> + wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
> + if (!wdt)
> + return -ENOMEM;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + wdt->base = devm_ioremap_resource(&pdev->dev, res);
> + if (IS_ERR(wdt->base))
> + return PTR_ERR(wdt->base);
> +
> + wdt->clk = devm_clk_get(&pdev->dev, NULL);
> + if (IS_ERR(wdt->clk))
> + return PTR_ERR(wdt->clk);
> +
> + ret = clk_prepare_enable(wdt->clk);
> + if (ret) {
> + dev_err(&pdev->dev, "failed to setup clock\n");
> + return ret;
> + }
> +
> + /*
> + * We use the clock rate to calculate the max timeout, so ensure it's
> + * not zero to avoid a divide-by-zero exception.
> + */
> + freq = clk_get_rate(wdt->clk);
> + if (freq == 0) {
> + dev_err(&pdev->dev, "invalid clock rate\n");
> + return -EINVAL;
> + }
This will need clk_disable_unprepare().
Since you are reading the frequency here, it might make sense to store it
in struct qcom_wdt so you don't have to call clk_get_rate() again in the
start function.
> +
> + wdt->wdd.dev = &pdev->dev;
> + wdt->wdd.info = &qcom_wdt_info;
> + wdt->wdd.ops = &qcom_wdt_ops;
> + wdt->wdd.min_timeout = 1;
> + wdt->wdd.max_timeout = 0x10000000U / freq;
What if the frequency turns out to be larger than 8947848 Hz ?
Then your maximum timeout is below the default timeout.
And if the frequency is larger than 268435456 Hz, the maximum
timeout would be 0.
> +
> + /*
> + * If 'timeout-sec' unspecified in devicetree, assume a 30 second
> + * default.
> + */
> + if (watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev))
> + wdt->wdd.timeout = 30;
You can just initialize timeout above with 30 seconds. Saves you the if
statement here.
> +
> + ret = watchdog_register_device(&wdt->wdd);
> + if (ret) {
> + dev_err(&pdev->dev, "failed to register watchdog\n");
This will need a clk_disable_unprepare().
Given that this is needed twice, you might want to consider using
error exit code below, as suggested in CodingStyle.
> + return ret;
> + }
> +
> + platform_set_drvdata(pdev, wdt);
> + return 0;
> +}
> +
> +static int qcom_wdt_remove(struct platform_device *pdev)
> +{
> + struct qcom_wdt *wdt = platform_get_drvdata(pdev);
> +
> + watchdog_unregister_device(&wdt->wdd);
> + clk_disable_unprepare(wdt->clk);
> + return 0;
> +}
> +
> +static const struct of_device_id qcom_wdt_of_table[] = {
> + { .compatible = "qcom,kpss-wdt-msm8960", },
> + { .compatible = "qcom,kpss-wdt-apq8064", },
> + { .compatible = "qcom,kpss-wdt-ipq8064", },
> + { },
> +};
> +MODULE_DEVICE_TABLE(of, qcom_wdt_of_table);
> +
> +static struct platform_driver qcom_watchdog_driver = {
> + .probe = qcom_wdt_probe,
> + .remove = qcom_wdt_remove,
> + .driver = {
> + .name = KBUILD_MODNAME,
> + .of_match_table = qcom_wdt_of_table,
> + },
> +};
> +module_platform_driver(qcom_watchdog_driver);
> +
> +MODULE_DESCRIPTION("QCOM KPSS Watchdog Driver");
> +MODULE_LICENSE("GPL v2");
> --
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> hosted by The Linux Foundation
>
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