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Message-Id: <aa5b4d11-9c8e-50bf-677e-95bed56cdddf@linux.vnet.ibm.com>
Date: Mon, 12 Jun 2017 15:30:19 -0500
From: Christopher Bostic <cbostic@...ux.vnet.ibm.com>
To: Guenter Roeck <linux@...ck-us.net>
Cc: wim@...ana.be, joel@....id.au, linux-kernel@...r.kernel.org,
linux-watchdog@...r.kernel.org, andrew@...id.au
Subject: Re: [PATCH] drivers/watchdog: Add sys files to modify watchdog
behavior
On 6/1/17 5:03 PM, Guenter Roeck wrote:
> On Thu, Jun 01, 2017 at 04:35:21PM -0500, Christopher Bostic wrote:
>> Add files to enable/disable Aspeed watchdog:
>> * External signal after timeout
>> * Reset system after timeout
>>
> The subject line is heavily misleading.
>
>> Signed-off-by: Christopher Bostic <cbostic@...ux.vnet.ibm.com>
>> ---
>> .../ABI/testing/sysfs-platform-aspeed-wdt | 40 +++++++++++
>> drivers/watchdog/aspeed_wdt.c | 79 +++++++++++++++++++++-
>> 2 files changed, 118 insertions(+), 1 deletion(-)
>> create mode 100644 Documentation/ABI/testing/sysfs-platform-aspeed-wdt
>>
>> diff --git a/Documentation/ABI/testing/sysfs-platform-aspeed-wdt b/Documentation/ABI/testing/sysfs-platform-aspeed-wdt
>> new file mode 100644
>> index 0000000..a582176
>> --- /dev/null
>> +++ b/Documentation/ABI/testing/sysfs-platform-aspeed-wdt
>> @@ -0,0 +1,40 @@
>> +What: /sys/bus/platform/devices/1e785000.wdt/watchdog/watchdog0/
>> + reset_system
>> +Date: May 2017
>> +KernelVersion: 4.12
>> +Contact: Christopher Bostic <cbostic@...ux.vnet.ibm.com>
>> +Description:
>> + Value indicates if a watchdog time out results in a reset of
>> + system. 'off': no system reset on timeout. 'on' there will
>> + be a system reset on timeout.
>> +
>> + Default: off
>> +
>> + - Enable 'reset system' on watchdog timeout:
>> + echo on > /sys/bus/platform/devices/1e785000.wdt/watchdog/
>> + watchdog0/reset_system;
>> +
>> + - Disable 'reset system' on watchdog timeout:
>> + echo off > /sys/bus/platform/devices/1e785000.wdt/watchdog/
>> + watchdog0/reset_system;
>> +
>> +What: /sys/bus/platform/devices/1e785000.wdt/watchdog/watchdog0/
>> + ext_signal
>> +Date: May 2017
>> +KernelVersion: 4.12
>> +Contact: Christopher Bostic <cbostic@...ux.vnet.ibm.com>
>> +Description:
>> + Value indicates if a watchdog time out results in an active
>> + high pulse sent out an output pin. 'off': No output pulse
>> + generated on watchdog time out. 'on': output pulse
>> + generated on watchdog time out.
>> +
>> + Default: off
>> +
>> + - Enable 'external signal' on watchdog timeout:
>> + echo on > /sys/bus/platform/devices/1e785000.wdt/watchdog/
>> + watchdog0/ext_signal;
>> +
>> + - Disable 'external signal' on watchdog timeout:
>> + echo off > /sys/bus/platform/devices/1e785000.wdt/watchdog/
>> + watchdog0/ext_signal;
> I'll want to see some discussion on those, both for the values written (on/off
> vs. 0/1) and the action to be taken. Both seem to be system parameters rather
> than something to set from user space. Also, there is no explanation what else
> the watchdog should do on timeout if not to reset the system. If it doesn't do
> anything, why run it in the first place ?
Hi Guenter,
I'll be resubmitting with a change to remove the sysfs files and instead
add a device tree attribute
that will be specific to the system affected.
Thanks
Chris
> Also, specifying absolute path names seems wrong. There is no real guarantee
> that the device is always watchdog0, that the path always includes
> "1e785000.wdt", or that the path name will always start with
> /sys/bus/platform/devices.
>
> Thanks,
> Guenter
>
>> diff --git a/drivers/watchdog/aspeed_wdt.c b/drivers/watchdog/aspeed_wdt.c
>> index 1c65258..66b27e8 100644
>> --- a/drivers/watchdog/aspeed_wdt.c
>> +++ b/drivers/watchdog/aspeed_wdt.c
>> @@ -136,6 +136,83 @@ static int aspeed_wdt_restart(struct watchdog_device *wdd,
>> .identity = KBUILD_MODNAME,
>> };
>>
>> +static ssize_t aspeed_wdt_cntl_get_state(struct device *dev, char *buf,
>> + uint32_t mask)
>> +{
>> + struct platform_device *pdev = to_platform_device(dev);
>> + struct aspeed_wdt *wdt = platform_get_drvdata(pdev);
>> + int ret;
>> +
>> + if (readl(wdt->base + WDT_CTRL) & mask)
>> + ret = sprintf(buf, "on\n");
>> + else
>> + ret = sprintf(buf, "off\n");
>> +
>> + return ret;
>> +}
>> +
>> +static ssize_t aspeed_wdt_cntl_set_state(struct device *dev, const char *buf,
>> + size_t count, uint32_t mask)
>> +{
>> + struct platform_device *pdev = to_platform_device(dev);
>> + struct aspeed_wdt *wdt = platform_get_drvdata(pdev);
>> +
>> + if (!strncmp(buf, "on", strlen("on"))) {
>> + wdt->ctrl |= mask;
>> + writel(wdt->ctrl, wdt->base + WDT_CTRL);
>> + } else if (!strncmp(buf, "off", strlen("off"))) {
>> + wdt->ctrl &= ~mask;
>> + writel(wdt->ctrl, wdt->base + WDT_CTRL);
>> + } else {
>> + dev_warn(dev, "Unknown reset system mode command: [%s]\n", buf);
>> + return -EINVAL;
>> + }
>> +
>> + return count;
>> +}
>> +
>> +static ssize_t aspeed_wdt_reset_system_store(struct device *dev,
>> + struct device_attribute *attr,
>> + const char *buf, size_t count)
>> +{
>> + return aspeed_wdt_cntl_set_state(dev, buf, count,
>> + WDT_CTRL_RESET_SYSTEM);
>> +}
>> +
>> +static ssize_t aspeed_wdt_reset_system_show(struct device *dev,
>> + struct device_attribute *attr,
>> + char *buf)
>> +{
>> + return aspeed_wdt_cntl_get_state(dev, buf, WDT_CTRL_RESET_SYSTEM);
>> +}
>> +
>> +static DEVICE_ATTR(reset_system, 0644,
>> + aspeed_wdt_reset_system_show, aspeed_wdt_reset_system_store);
>> +
>> +static ssize_t aspeed_wdt_ext_signal_store(struct device *dev,
>> + struct device_attribute *attr,
>> + const char *buf, size_t count)
>> +{
>> + return aspeed_wdt_cntl_set_state(dev, buf, count, WDT_CTRL_WDT_EXT);
>> +}
>> +
>> +static ssize_t aspeed_wdt_ext_signal_show(struct device *dev,
>> + struct device_attribute *attr,
>> + char *buf)
>> +{
>> + return aspeed_wdt_cntl_get_state(dev, buf, WDT_CTRL_WDT_EXT);
>> +}
>> +
>> +static DEVICE_ATTR(ext_signal, 0644,
>> + aspeed_wdt_ext_signal_show, aspeed_wdt_ext_signal_store);
>> +
>> +static struct attribute *aspeed_wdt_attrs[] = {
>> + &dev_attr_reset_system.attr,
>> + &dev_attr_ext_signal.attr,
>> + NULL
>> +};
>> +ATTRIBUTE_GROUPS(aspeed_wdt);
>> +
>> static int aspeed_wdt_probe(struct platform_device *pdev)
>> {
>> struct aspeed_wdt *wdt;
>> @@ -160,7 +237,7 @@ static int aspeed_wdt_probe(struct platform_device *pdev)
>> wdt->wdd.ops = &aspeed_wdt_ops;
>> wdt->wdd.max_hw_heartbeat_ms = WDT_MAX_TIMEOUT_MS;
>> wdt->wdd.parent = &pdev->dev;
>> -
>> + wdt->wdd.groups = aspeed_wdt_groups;
>> wdt->wdd.timeout = WDT_DEFAULT_TIMEOUT;
>> watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev);
>>
>> --
>> 1.8.2.2
>>
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