On 6/22/20 11:28 PM, Johnson CH Chen (陳昭勳) wrote:
> Hi,
>
> Thanks for your good detailed suggestions!
>
Other feedback suggests to convert the driver to use
the watchdog core in the rtc code. I would suggest to follow
that suggestion.
>>> + * It would be more efficient to use i2c msgs/i2c_transfer directly
>>> +but, as
>>> + * recommened in .../Documentation/i2c/writing-clients section
>>> + * "Sending and receiving", using SMBus level communication is preferred.
>>> + */
>>> +
>>> +#include <linux/kernel.h>
>>> +#include <linux/device.h>
>>> +#include <linux/module.h>
>>> +#include <linux/ioctl.h>
>>> +#include <linux/reboot.h>
>>> +#include <linux/watchdog.h>
>>> +#include <linux/workqueue.h>
>>> +#include <linux/platform_device.h>
>>> +#include <linux/i2c.h>
>>> +#include <linux/uaccess.h>
>>
>> Alphabetic order please.
>>
>>> +
>>> +#define DEVNAME "ds1374_wdt"
>>> +
>>> +#define DS1374_REG_WDALM0 0x04 /* Watchdog/Alarm */
>>> +#define DS1374_REG_WDALM1 0x05
>>> +#define DS1374_REG_WDALM2 0x06
>>> +#define DS1374_REG_CR 0x07 /* Control */
>>> +#define DS1374_REG_CR_AIE 0x01 /* Alarm Int. Enable */
>>> +#define DS1374_REG_CR_WDSTR 0x08 /* 1=INT, 0=RST */
>>> +#define DS1374_REG_CR_WDALM 0x20 /* 1=Watchdog, 0=Alarm */
>>> +#define DS1374_REG_CR_WACE 0x40 /* WD/Alarm counter enable */
>>> +
>>> +/* Default margin */
>>> +#define WD_TIMO 131762
>>> +#define TIMER_MARGIN_MIN 4096 /* 1s */
>>> +#define TIMER_MARGIN_MAX (60*60*24*4096) /* one day */
>>> +
>>> +static int wdt_margin = WD_TIMO;
>>
>> Sjould not be pre-initialized. Also, 131762 isn't 32 seconds, it is 131,762
>> seconds.
>>
>
> 131762 is 32 seconds actually because watchdog counter increases per
> 1/4096 seconds for DS1374. If DS1374_REG_CR_WDALM is set to 0 (alarm),
> alarm counter will increase per 1 second.
>
The watchdog core keeps timeouts in seconds. For the watchdog core,
131762 is 131,762 seconds. Your code assumes that the watchdog core
does not care about / need to scale, which is wrong. Besides,
MODULE_PARM_DESC below clearly states "Watchdog timeout _in seconds_"
(emphasis added).
>>> +module_param(wdt_margin, int, 0);
>>> +MODULE_PARM_DESC(wdt_margin, "Watchdog timeout in seconds (default
>>> +32s)");
>>> +
>>
>> As a new driver, it would be better to just use the customary "timeout".
>>
>>> +static bool nowayout = WATCHDOG_NOWAYOUT; module_param(nowayout,
>>> +bool, 0); MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped
>> once
>>> +started default ="
>>> + __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
>>> +
>>> +struct ds1374_wdt {
>>> + struct i2c_client *client;
>>> + struct watchdog_device *wdt;
>>> + struct work_struct work;
>>
>> Not used.
>>
>>> +
>>> + /* The mutex protects alarm operations, and prevents a race
>>> + * between the enable_irq() in the workqueue and the free_irq()
>>> + * in the remove function.
>>> + */
>>
>> There is no workqueue here, and the remove function is not needed.
>>
>>> + struct mutex mutex;
>>> +};
>>> +
>>> +static const struct watchdog_info ds1374_wdt_info = {
>>> + .identity = DEVNAME,
>>> + .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
>>> + WDIOF_MAGICCLOSE,
>>> +};
>>> +
>>> +static struct watchdog_device ds1374_wdd;
>>> +
>> Move declaration please.
>>
>>> +static int ds1374_wdt_settimeout(struct watchdog_device *wdt,
>>> + unsigned int timeout)
>>> +{
>>
>> How is this synchronized against accesses by the RTC driver ?
>>
> By original design in rtc-ds1374.c, it seems no synchronized problem between
> rtc and watchdog, but I think we can add mutex lock to deal with it.
>
The mutex is used there where needed.
>>> + int ret = -ENOIOCTLCMD;
>>
>> Not an appropriate error code here.
>>
>>> + u8 buf[4];
>>> + int cr, i;
>>> + struct ds1374_wdt *drv_data = watchdog_get_drvdata(wdt);
>>> +
>>> + ret = cr = i2c_smbus_read_byte_data(drv_data->client, DS1374_REG_CR);
>>> + if (ret < 0)
>>> + goto out;
>>
>> "goto out;" is unnecessary. Just return the error. Same everywhere else below.
>>
>>> +
>>> + /* Disable any existing watchdog/alarm before setting the new one */
>>> + cr &= ~DS1374_REG_CR_WACE;
>>> +
>>> + ret = i2c_smbus_write_byte_data(drv_data->client, DS1374_REG_CR, cr);
>>> + if (ret < 0)
>>> + goto out;
>>> +
>>> + /* Set new watchdog time */
>>> + for (i = 0; i < 3; i++) {
>>> + buf[i] = timeout & 0xff;
>>> + timeout >>= 8;
>>> + }
>>
>> The value passed to this function from the watchdog core is the timeout in
>> seconds. I don't see a conversion to internal values here.
>>
>
> For original design in rtc-ds1374.c, ds1374_wdt_settimeout () will call
> ds1374_write_rtc() to write hardware register. To separate watchdog and rtc
> functions, expand code from ds1374_write_rtc() here, and final buf[] values
> will be written into hardware register for DS1374.
>
ds1374_wdt_settimeout() is an API function, It gets timeouts from the watchdog
core in seconds. Those timeouts have to be converted to chip internal values
in this function.
>>> +
>>> + ret = i2c_smbus_write_i2c_block_data(drv_data->client,
>>> + DS1374_REG_WDALM0, 3, buf);
>>> + if (ret) {
>>> + pr_info("couldn't set new watchdog time\n");
>>> + goto out;
>>> + }
>>
>>> +
>>> + /* Enable watchdog timer */
>>> + cr |= DS1374_REG_CR_WACE | DS1374_REG_CR_WDALM;
>>> + cr &= ~DS1374_REG_CR_WDSTR;/* for RST PIN */
>>> + cr &= ~DS1374_REG_CR_AIE;
>>> +
>>> + ret = i2c_smbus_write_byte_data(drv_data->client, DS1374_REG_CR, cr);
>>> + if (ret < 0)
>>> + goto out;
>>> +
>>> + return 0;
>>
>> Pointless. Just return ret.
>>
>> Also, this function needs to store the new timeout in struct watchdog_device.
>>
>>> +out:
>>> + return ret;
>>> +}
>>> +
>>> +
>>> +/*
>>> + * Read WD/Alarm counter to reload the watchdog timer. (ie, pat the
>>> +watchdog) */ static int ds1374_wdt_ping(struct watchdog_device *wdt)
>>> +{
>>> + struct ds1374_wdt *drv_data = watchdog_get_drvdata(wdt);
>>> + int ret;
>>> + u8 buf[4];
>>> +
>>> + ret = i2c_smbus_read_i2c_block_data(drv_data->client,
>>> + DS1374_REG_WDALM0, 3, buf);
>>> +
>>> + if (ret < 0 || ret < 3)
>>> + pr_info("WD TICK FAIL!!!!!!!!!! %i\n", ret);
>>> +
>>
>> This is not an info message, this is an error. Besides, it is just noise.
>> Just return the error and drop the message.
>>
>>> + return ret;
>>> +}
>>> +
>>> +static int ds1374_wdt_start(struct watchdog_device *wdt) {
>>> + int ret;
>>> +
>>> + ret = ds1374_wdt_settimeout(wdt, wdt_margin);
>>
>> This is wrong. The timeout may have been updated by userspace.
>> It is inappropriate to change it back to the default here.
>>
> Thanks, I will keep in mind.
>
>>> + if (ret)
>>> + return ret;
>>> +
>>> + ds1374_wdt_ping(wdt);
>>
>> Please do not ignore errors.
>>
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +static int ds1374_wdt_stop(struct watchdog_device *wdt) {
>>> + struct ds1374_wdt *drv_data = watchdog_get_drvdata(wdt);
>>> + int cr;
>>> +
>>> + if (nowayout)
>>> + return 0;
>>
>> Not needed.
>>
> Thanks!, it has been implemented in watchdog_stop().
>
>>> +
>>> + cr = i2c_smbus_read_byte_data(drv_data->client, DS1374_REG_CR);
>>> + /* Disable watchdog timer */
>>> + cr &= ~DS1374_REG_CR_WACE;
>>> +
>>> + return i2c_smbus_write_byte_data(drv_data->client, DS1374_REG_CR,
>>> +cr); }
>>> +
>>> +/*
>>> + * Handle commands from user-space.
>>> + */
>>> +static long ds1374_wdt_ioctl(struct watchdog_device *wdt, unsigned int
>> cmd,
>>> + unsigned long arg)
>>
>> The whole point of using the watchdog subsystem is to not need a local ioctl
>> function - and most definitely not one that duplicates watchdog core
>> functionality.
>>
>>> +{
>>> + int new_margin, options;
>>> +
>>> + switch (cmd) {
>>> + case WDIOC_GETSUPPORT:
>>> + return copy_to_user((struct watchdog_info __user *)arg,
>>> + &ds1374_wdt_info, sizeof(ds1374_wdt_info)) ? -EFAULT : 0;
>>> +
>>> + case WDIOC_GETSTATUS:
>>> + case WDIOC_GETBOOTSTATUS:
>>> + return put_user(0, (int __user *)arg);
>>> + case WDIOC_KEEPALIVE:
>>> + ds1374_wdt_ping(wdt);
>>> + return 0;
>>> + case WDIOC_SETTIMEOUT:
>>> + if (get_user(new_margin, (int __user *)arg))
>>> + return -EFAULT;
>>> +
>>> + /* the hardware's tick rate is 4096 Hz, so
>>> + * the counter value needs to be scaled accordingly
>>> + */
>>> + new_margin <<= 12;
>>> + if (new_margin < 1 || new_margin > 16777216)
>>> + return -EINVAL;
>>> +
>>> + wdt_margin = new_margin;
>>> + ds1374_wdt_settimeout(wdt, new_margin);
>>
>> Is the idea here to bypass the watchdog subsystem's notion of keeping the
>> timeout in seconds ? If so, that would be wrong and unacceptable.
>>
> It seems take care about 4096Hz for original design in rtc-ds1374.c. I think we
> can just use ioctl() which watchdog core provides and input margin time
> appropriately.
>
>
>>> + ds1374_wdt_ping(wdt);
>>> + fallthrough;
>>> + case WDIOC_GETTIMEOUT:
>>> + /* when returning ... inverse is true */
>>> + return put_user((wdt_margin >> 12), (int __user *)arg);
>>> + case WDIOC_SETOPTIONS:
>>> + if (copy_from_user(&options, (int __user *)arg, sizeof(int)))
>>> + return -EFAULT;
>>> +
>>> + if (options & WDIOS_DISABLECARD) {
>>> + pr_info("disable watchdog\n");
>>> + ds1374_wdt_stop(wdt);
>>> + return 0;
>>> + }
>>> +
>>> + if (options & WDIOS_ENABLECARD) {
>>> + pr_info("enable watchdog\n");
>>> + ds1374_wdt_settimeout(wdt, wdt_margin);
>>> + ds1374_wdt_ping(wdt);
>>> + return 0;
>>> + }
>>> + return -EINVAL;
>>> + }
>>> + return -ENOTTY;
>>> +}
>>> +
>>> +static int ds1374_wdt_notify_sys(struct notifier_block *this,
>>> + unsigned long code, void *unused)
>>> +{
>>> + if (code == SYS_DOWN || code == SYS_HALT)
>>> + /* Disable Watchdog */
>>> + ds1374_wdt_stop(&ds1374_wdd);
>>> + return NOTIFY_DONE;
>>> +}
>>> +
>> Not needed - see below.
>>
>>> +static struct notifier_block ds1374_wdt_notifier = {
>>> + .notifier_call = ds1374_wdt_notify_sys, };
>>> +
>>> +static int ds1374_wdt_probe(struct platform_device *pdev) {
>>> + struct ds1374_wdt *drv_data;
>>> + struct i2c_client *client = to_i2c_client(pdev->dev.parent);
>>> + int ret;
>>> +
>>> + drv_data = devm_kzalloc(&pdev->dev, sizeof(struct ds1374_wdt),
>>> + GFP_KERNEL);
>>> + if (!drv_data)
>>> + return -ENOMEM;
>>> +
>>> + drv_data->wdt = &ds1374_wdd;
>>> + drv_data->client = client;
>>> + mutex_init(&drv_data->mutex);
>>> +
>>> + watchdog_init_timeout(drv_data->wdt, wdt_margin, &pdev->dev);
>>> + watchdog_set_nowayout(drv_data->wdt, nowayout);
>>> +
>>> + watchdog_set_drvdata(drv_data->wdt, drv_data);
>>> + platform_set_drvdata(pdev, drv_data);
>>> +
>>> + ret = watchdog_register_device(drv_data->wdt);
>>
>> Use devm_watchdog_register_device()
>>
>>> + if (ret) {
>>> + dev_err(&pdev->dev, "failed to register Watchdog device\n");
>>> + return ret;
>>> + }
>>> +
>>> + ret = register_reboot_notifier(&ds1374_wdt_notifier);
>>
>> Call watchdog_stop_on_reboot() before calling watchdog_register_device()
>> instead.
>>
>>> + if (ret) {
>>> + watchdog_unregister_device(drv_data->wdt);
>>> + return ret;
>>> + }
>>> +
>>> + ds1374_wdt_settimeout(drv_data->wdt, wdt_margin);
>>
>> Unnecessary here; called from start function.
>>
>>> + dev_info(&pdev->dev, "Dallas/Maxim DS1374 watchdog device
>>> +enabled\n");
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +static int ds1374_wdt_remove(struct platform_device *pdev) {
>>> + struct ds1374_wdt *drv_data = platform_get_drvdata(pdev);
>>> +
>>> + dev_warn(&pdev->dev, "Unregister DS1374 watchdog device\n");
>>> + watchdog_unregister_device(drv_data->wdt);
>>> + unregister_reboot_notifier(&ds1374_wdt_notifier);
>>> +
>>
>> Call watchdog_stop_on_unregister() before calling
>> watchdog_register_device().
>>
>>> + return 0;
>>> +}
>>> +
>>> +static void ds1374_wdt_shutdown(struct platform_device *pdev) {
>>> + struct ds1374_wdt *drv_data = platform_get_drvdata(pdev);
>>> +
>>> + mutex_lock(&drv_data->mutex);
>>> + ds1374_wdt_stop(drv_data->wdt);
>>> + mutex_unlock(&drv_data->mutex);
>>
>> Unnecessary and pointless.
>>
>>> +}
>>> +
>>> +static const struct watchdog_ops ds1374_wdt_fops = {
>>> + .owner = THIS_MODULE,
>>> + .start = ds1374_wdt_start,
>>> + .stop = ds1374_wdt_stop,
>>> + .ping = ds1374_wdt_ping,
>>> + .set_timeout = ds1374_wdt_settimeout,
>>> + .ioctl = ds1374_wdt_ioctl,
>>> +};
>>> +
>>> +static struct watchdog_device ds1374_wdd = {
>>> + .info = &ds1374_wdt_info,
>>> + .ops = &ds1374_wdt_fops,
>>> + .min_timeout = TIMER_MARGIN_MIN,
>>> + .max_timeout = TIMER_MARGIN_MAX,
>>
>> .timeout should be set here.
>>
>> Also, there can (at least in theory) be more than one ds1374 in the system. The
>> code does not support this case. ds1374_wdd should be moved into struct
>> ds1374_wdt.
>>
> Thanks for good suggestion.
>>> +};
>>> +
>>> +static struct platform_driver ds1374_wdt = {
>>> + .driver = {
>>> + .owner = THIS_MODULE,
>>> + .name = DEVNAME,
>>> + },
>>> + .probe = ds1374_wdt_probe,
>>> + .remove = ds1374_wdt_remove,
>>> + .shutdown = ds1374_wdt_shutdown,
>>> +};
>>> +
>>> +module_platform_driver(ds1374_wdt);
>>> +
>>> +MODULE_AUTHOR("Johnson Chen <johnsonch.chen@xxxxxxxx>");
>>> +MODULE_DESCRIPTION("Dallas/Maxim DS1374 Watchdog Driver");
>>> +MODULE_LICENSE("GPL"); MODULE_ALIAS("Platform:ds1374_wdt");
>>>
>
> Best regards,
> Johnson
>
