Re: [PATCH v2 2/2] drivers/watchdog: ASPEED reference dev tree properties for config
From: Christopher Bostic
Date: Wed Jun 28 2017 - 12:09:40 EST
On 6/28/17 11:06 AM, Guenter Roeck wrote:
On Wed, Jun 28, 2017 at 10:55:08AM -0500, Christopher Bostic wrote:
On 6/28/17 10:08 AM, Guenter Roeck wrote:
On Wed, Jun 28, 2017 at 09:59:22AM -0500, Christopher Bostic wrote:
On 6/28/17 9:54 AM, Guenter Roeck wrote:
On Wed, Jun 28, 2017 at 09:29:50AM -0500, Christopher Bostic wrote:
On 6/28/17 6:31 AM, Guenter Roeck wrote:
On 06/27/2017 02:17 PM, Christopher Bostic wrote:
Reference the system device tree when configuring the watchdog
engines. Set external signal mode on timeout if specified.
Set system reset on timeout if specified.
Signed-off-by: Christopher Bostic <cbostic@xxxxxxxxxxxxxxxxxx>
---
v2 - Change of_get_property() to of_property_read_bool()
- Remove redundant check for NULL struct device_node pointer
- Optional property names now start with prefix 'aspeed,'
---
drivers/watchdog/aspeed_wdt.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/drivers/watchdog/aspeed_wdt.c
b/drivers/watchdog/aspeed_wdt.c
index 1c65258..71ce5f5 100644
--- a/drivers/watchdog/aspeed_wdt.c
+++ b/drivers/watchdog/aspeed_wdt.c
@@ -140,6 +140,7 @@ static int aspeed_wdt_probe(struct platform_device
*pdev)
{
struct aspeed_wdt *wdt;
struct resource *res;
+ struct device_node *np;
int ret;
wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
@@ -170,8 +171,16 @@ static int aspeed_wdt_probe(struct platform_device
*pdev)
* the SOC and not the full chip
*/
wdt->ctrl = WDT_CTRL_RESET_MODE_SOC |
- WDT_CTRL_1MHZ_CLK |
- WDT_CTRL_RESET_SYSTEM;
+ WDT_CTRL_1MHZ_CLK;
+
+ np = pdev->dev.of_node;
+ if (of_property_read_bool(np, "aspeed,sys-reset"))
+ wdt->ctrl |= WDT_CTRL_RESET_SYSTEM;
+
For backward compatibility, this should default to WDT_CTRL_RESET_SYSTEM
if no optional property is provided.
I had the logic inverted for this property in a previous patch. The
property was 'no-system-reset' so that when not present the default was to
set WDT_CTRL_RESET_SYSTEM. As it is in this patch, the only way to
indicate that no system reset is to be done is to not specify the property.
No system reset is desired under circumstances when another wdt engine is to
be responsible for this. Given the issue with backward compatibility
that's not a solution. Given this, would creating a property
'no-system-reset' be acceptable?
Sorry, I fail to see the problem. There are half a dozen properties. What is the
problem with having a default if no property is specified ? Your default is "do
nothing", which does not really make any sense to me. If the user wants the
watchdog to do nothing, the simple means to accomplish that would be to not
instantiate it.
Sure, that means specifying "system-reset" is redundant, but I don't see a
problem with that either. But I do see a problem with loading a watchdog driver
that doesn't do anything.
If there is really some use case where it makes sense to load a watchdog driver
and have it do nothing, please explain and provide a respective devicetree
property. "aspeed,do-nothing" (or whatever similar) doesn't sound good, but
at least makes it obvious that the driver isn't doing anything besides
creating a false sense of "the system is watchdog protected".
If system-reset is not wanted there are other properties that might still be
needed, for example
ARM reset only. We'd still want to instantiate it.
But then you would presumably specify that property, so there would be one.
The question here is what to do if _no_ property is provided.
I agree that the default should be to perform a system reset when no
property is provided. I will make that change. Additionally for backwards
compatibility the SOC reset should be enabled by default when no property is
provided. The other parameters are not configured in the watchdog control
register if no property is provided.
There is still a need to to configure for no system reset. For example,
optional parameter 'aspeed,no-sys-reset' that can be specified if system
reset is to be disabled. In addition the default 'SOC reset enabled'
behavior could be disabled with an optional parameter 'aspeed,no-soc-reset'.
Why would there even be a need configure for no system reset? The external
mode 'wdt ext: External signal enable after timeout' can be sent off chip
even if system reset is disabled. The watchdog is doing something in this
case and would require wdt instantiation.
Wouldn't that be "aspeed,external-signal" ?
Yes that optional parameter would need to be specified in that
situation, as well as 'aspeed,no-system-reset'.
Chris
Guenter
Hope this is more clear, sorry for the confusion.
Thanks,
-Chris AST2500 Software Programming Guide
Sorry, I don't get your point.
Guenter
Thanks,
Chris
Thanks,
Guenter
Thanks,
Chris
+ if (of_property_read_bool(np, "aspeed,external-signal"))
+ wdt->ctrl |= WDT_CTRL_WDT_EXT;
+
+ writel(wdt->ctrl, wdt->base + WDT_CTRL);
if (readl(wdt->base + WDT_CTRL) & WDT_CTRL_ENABLE) {
aspeed_wdt_start(&wdt->wdd);
--
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