Re: [PATCH 2/3] watchdog: dw_wdt: get reset lines from dt

From: Guenter Roeck
Date: Thu Sep 22 2016 - 09:14:56 EST

On 09/22/2016 12:02 AM, Steffen Trumtrar wrote:
The dw_wdt has an external reset line, that can keep the device in reset
and therefore rendering it useless and also is the only way of stopping
the watchdog once it was started.

Get the reset lines for this core from the devicetree.
If resets are not specified just warn but don't fail probing to be compatible
with all users.

Signed-off-by: Steffen Trumtrar <s.trumtrar@xxxxxxxxxxxxxx>
Cc: Wim Van Sebroeck <wim@xxxxxxxxx>
Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
Cc: linux-watchdog@xxxxxxxxxxxxxxx
drivers/watchdog/dw_wdt.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/drivers/watchdog/dw_wdt.c b/drivers/watchdog/dw_wdt.c
index 2acb51cf5504..e024722e8b3b 100644
--- a/drivers/watchdog/dw_wdt.c
+++ b/drivers/watchdog/dw_wdt.c
@@ -31,6 +31,7 @@
#include <linux/pm.h>
#include <linux/platform_device.h>
#include <linux/reboot.h>
+#include <linux/reset.h>
#include <linux/watchdog.h>

@@ -56,6 +57,7 @@ struct dw_wdt {
struct clk *clk;
struct notifier_block restart_handler;
struct watchdog_device wdd;
+ struct reset_control *rst;

#define to_dw_wdt(wdd) container_of(wdd, struct dw_wdt, wdd)
@@ -231,6 +233,10 @@ static int dw_wdt_drv_probe(struct platform_device *pdev)
if (ret)
return ret;

+ dw_wdt->rst = devm_reset_control_get(&pdev->dev, "dw-wdt");
+ if (IS_ERR(dw_wdt->rst))
+ dev_warn(dev, "No reset lines. Will not be able to stop once started.\n");

This situation is already handled by the driver. Actually, I don't even
know what will happen, since the watchdog core will continue to ping
the watchdog after close, and it won't be possible to unload the driver
if the watchdog is running.

I don't think a warning is warranted in this case. We did not need one before,
we should not need one now.

wdd = &dw_wdt->wdd;
wdd->info = &dw_wdt_ident;
wdd->ops = &dw_wdt_ops;
@@ -268,6 +274,9 @@ static int dw_wdt_drv_probe(struct platform_device *pdev)
if (ret)
pr_warn("cannot register restart handler\n");

+ if (dw_wdt->rst)
+ reset_control_deassert(dw_wdt->rst);
return 0;