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Groups > linux.kernel > #1263562 > unrolled thread

[PATCH v4 0/2] imx6: Implement external watchdog reset

Started byAkshay Bhat <akshay.bhat@timesys.com>
First post2015-11-05 22:30 +0100
Last post2015-11-06 23:10 +0100
Articles 6 — 3 participants

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Contents

  [PATCH v4 0/2] imx6: Implement external watchdog reset Akshay Bhat <akshay.bhat@timesys.com> - 2015-11-05 22:30 +0100
    [PATCH v4 2/2] ARM: dts: ventana: Add ext-reset support Akshay Bhat <akshay.bhat@timesys.com> - 2015-11-05 22:30 +0100
    [PATCH v4 1/2] watchdog: imx2_wdt: add external reset support via 'ext-reset-output' dt prop Akshay Bhat <akshay.bhat@timesys.com> - 2015-11-05 22:30 +0100
      Re: [PATCH v4 1/2] watchdog: imx2_wdt: add external reset support  via 'ext-reset-output' dt prop Guenter Roeck <linux@roeck-us.net> - 2015-11-05 23:30 +0100
        Re: [PATCH v4 1/2] watchdog: imx2_wdt: add external reset support via  'ext-reset-output' dt prop Tim Harvey <tharvey@gateworks.com> - 2015-11-06 21:00 +0100
          Re: [PATCH v4 1/2] watchdog: imx2_wdt: add external reset support  via 'ext-reset-output' dt prop Guenter Roeck <linux@roeck-us.net> - 2015-11-06 23:10 +0100

#1263562 — [PATCH v4 0/2] imx6: Implement external watchdog reset

FromAkshay Bhat <akshay.bhat@timesys.com>
Date2015-11-05 22:30 +0100
Subject[PATCH v4 0/2] imx6: Implement external watchdog reset
Message-ID<qrAgy-3yX-9@gated-at.bofh.it>
[Rebase to next-20151105 and re-sending work done by Tim Harvey]

The IMX6 watchdog supports assertion of a signal (WDOG_B) which
can be pinmux'd to an external pin. This is typically used for boards that
have PMIC's in control of the IMX6 power rails. In fact, failure to use
such an external reset on boards with external PMIC's can result in various
hangs due to the IMX6 not being fully reset [1] as well as the board failing
to reset because its PMIC has not been reset to provide adequate voltate for
the CPU when comming out of reset at 800Mhz when it was at 400Mhz prior to
reset.
 
This adds a new device-tree property 'ext-reset-output' to fsl-imx-wdt in
order to indicate the board has such a reset and to cause the watchdog to be
configured to assert WDOG_B instead of an internal reset both on a
watchdog timeout and in system_restart.
 
The second patch adds the watchdog configuration and pinmux for Gateworks
Ventana boards.
 
[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-March/333689.html

Changes:
v3->v4:
- Rebase and test against linux-next tag next-20151105

History:
v1: http://lists.infradead.org/pipermail/linux-arm-kernel/2015-May/347168.html
v2: http://lists.infradead.org/pipermail/linux-arm-kernel/2015-June/348761.html
v3: http://lists.infradead.org/pipermail/linux-arm-kernel/2015-July/360188.html

Tim Harvey (2):
  watchdog: imx2_wdt: add external reset support via 'ext-reset-output'
    dt prop
  ARM: dts: ventana: Add ext-reset support

 .../devicetree/bindings/watchdog/fsl-imx-wdt.txt     |  2 ++
 arch/arm/boot/dts/imx6qdl-gw51xx.dtsi                | 12 ++++++++++++
 arch/arm/boot/dts/imx6qdl-gw52xx.dtsi                | 12 ++++++++++++
 arch/arm/boot/dts/imx6qdl-gw53xx.dtsi                | 13 +++++++++++++
 arch/arm/boot/dts/imx6qdl-gw54xx.dtsi                | 17 +++++++++++++++++
 arch/arm/boot/dts/imx6qdl-gw551x.dtsi                | 12 ++++++++++++
 arch/arm/boot/dts/imx6qdl-gw552x.dtsi                | 12 ++++++++++++
 drivers/watchdog/imx2_wdt.c                          | 20 ++++++++++++++++++--
 8 files changed, 98 insertions(+), 2 deletions(-)

-- 
2.6.2

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#1263565 — [PATCH v4 2/2] ARM: dts: ventana: Add ext-reset support

FromAkshay Bhat <akshay.bhat@timesys.com>
Date2015-11-05 22:30 +0100
Subject[PATCH v4 2/2] ARM: dts: ventana: Add ext-reset support
Message-ID<qrAgz-3yX-17@gated-at.bofh.it>
In reply to#1263562
From: Tim Harvey <tharvey@gateworks.com>

The Gateworks Ventana boards have a PMIC that can be used to regulate the
CPU voltage rails for DVFS support. In order to ensure this PMIC is properly
reset the watchdog needs to be configured to assert its external reset
signal.

Additionally the pad used for WDOG_B needs to be configured which we add to
iomux.

Cc: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Tim Harvey <tharvey@gateworks.com>
---
 arch/arm/boot/dts/imx6qdl-gw51xx.dtsi | 12 ++++++++++++
 arch/arm/boot/dts/imx6qdl-gw52xx.dtsi | 12 ++++++++++++
 arch/arm/boot/dts/imx6qdl-gw53xx.dtsi | 13 +++++++++++++
 arch/arm/boot/dts/imx6qdl-gw54xx.dtsi | 17 +++++++++++++++++
 arch/arm/boot/dts/imx6qdl-gw551x.dtsi | 12 ++++++++++++
 arch/arm/boot/dts/imx6qdl-gw552x.dtsi | 12 ++++++++++++
 6 files changed, 78 insertions(+)

diff --git a/arch/arm/boot/dts/imx6qdl-gw51xx.dtsi b/arch/arm/boot/dts/imx6qdl-gw51xx.dtsi
index 7b31fdb..d81bd72 100644
--- a/arch/arm/boot/dts/imx6qdl-gw51xx.dtsi
+++ b/arch/arm/boot/dts/imx6qdl-gw51xx.dtsi
@@ -210,6 +210,12 @@
 	status = "okay";
 };
 
+&wdog1 {
+	pinctrl-names = "default";
+	pinctrl-0 = <&pinctrl_wdog>;
+	ext-reset-output;
+};
+
 &iomuxc {
 	imx6qdl-gw51xx {
 		pinctrl_enet: enetgrp {
@@ -328,5 +334,11 @@
 				MX6QDL_PAD_EIM_D22__GPIO3_IO22		0x1b0b0 /* OTG_PWR_EN */
 			>;
 		};
+
+		pinctrl_wdog: wdoggrp {
+			fsl,pins = <
+				MX6QDL_PAD_DISP0_DAT8__WDOG1_B		0x1b0b0
+			>;
+		};
 	};
 };
diff --git a/arch/arm/boot/dts/imx6qdl-gw52xx.dtsi b/arch/arm/boot/dts/imx6qdl-gw52xx.dtsi
index 1b66328..0d8f201 100644
--- a/arch/arm/boot/dts/imx6qdl-gw52xx.dtsi
+++ b/arch/arm/boot/dts/imx6qdl-gw52xx.dtsi
@@ -326,6 +326,12 @@
 	status = "okay";
 };
 
+&wdog1 {
+	pinctrl-names = "default";
+	pinctrl-0 = <&pinctrl_wdog>;
+	ext-reset-output;
+};
+
 &iomuxc {
 	imx6qdl-gw52xx {
 		pinctrl_audmux: audmuxgrp {
@@ -501,5 +507,11 @@
 				MX6QDL_PAD_NANDF_CS1__SD3_VSELECT	0x170f9
 			>;
 		};
+
+		pinctrl_wdog: wdoggrp {
+			fsl,pins = <
+				MX6QDL_PAD_DISP0_DAT8__WDOG1_B		0x1b0b0
+			>;
+		};
 	};
 };
diff --git a/arch/arm/boot/dts/imx6qdl-gw53xx.dtsi b/arch/arm/boot/dts/imx6qdl-gw53xx.dtsi
index 7c51839..36f9ec6 100644
--- a/arch/arm/boot/dts/imx6qdl-gw53xx.dtsi
+++ b/arch/arm/boot/dts/imx6qdl-gw53xx.dtsi
@@ -332,7 +332,14 @@
 	status = "okay";
 };
 
+&wdog1 {
+	pinctrl-names = "default";
+	pinctrl-0 = <&pinctrl_wdog>;
+	ext-reset-output;
+};
+
 &iomuxc {
+
 	imx6qdl-gw53xx {
 		pinctrl_audmux: audmuxgrp {
 			fsl,pins = <
@@ -508,5 +515,11 @@
 				MX6QDL_PAD_NANDF_CS1__SD3_VSELECT	0x170f9
 			>;
 		};
+
+		pinctrl_wdog: wdoggrp {
+			fsl,pins = <
+				MX6QDL_PAD_DISP0_DAT8__WDOG1_B		0x1b0b0
+			>;
+		};
 	};
 };
diff --git a/arch/arm/boot/dts/imx6qdl-gw54xx.dtsi b/arch/arm/boot/dts/imx6qdl-gw54xx.dtsi
index 929e0b3..0c1150f 100644
--- a/arch/arm/boot/dts/imx6qdl-gw54xx.dtsi
+++ b/arch/arm/boot/dts/imx6qdl-gw54xx.dtsi
@@ -425,6 +425,17 @@
 	status = "okay";
 };
 
+&wdog1 {
+	status = "disabled";
+};
+
+&wdog2 {
+	pinctrl-names = "default";
+	pinctrl-0 = <&pinctrl_wdog>;
+	ext-reset-output;
+	status = "okay";
+};
+
 &iomuxc {
 	imx6qdl-gw54xx {
 		pinctrl_audmux: audmuxgrp {
@@ -600,5 +611,11 @@
 				MX6QDL_PAD_NANDF_CS1__SD3_VSELECT	0x170f9
 			>;
 		};
+
+		pinctrl_wdog: wdoggrp {
+			fsl,pins = <
+				MX6QDL_PAD_SD1_DAT3__WDOG2_B		0x1b0b0
+			>;
+		};
 	};
 };
diff --git a/arch/arm/boot/dts/imx6qdl-gw551x.dtsi b/arch/arm/boot/dts/imx6qdl-gw551x.dtsi
index 741f3d5..883e577 100644
--- a/arch/arm/boot/dts/imx6qdl-gw551x.dtsi
+++ b/arch/arm/boot/dts/imx6qdl-gw551x.dtsi
@@ -227,6 +227,12 @@
 	status = "okay";
 };
 
+&wdog1 {
+	pinctrl-names = "default";
+	pinctrl-0 = <&pinctrl_wdog>;
+	ext-reset-output;
+};
+
 &iomuxc {
 	imx6qdl-gw51xx {
 		pinctrl_flexcan1: flexcan1grp {
@@ -309,5 +315,11 @@
 				MX6QDL_PAD_GPIO_1__USB_OTG_ID		0x17059
 			>;
 		};
+
+		pinctrl_wdog: wdoggrp {
+			fsl,pins = <
+				MX6QDL_PAD_DISP0_DAT8__WDOG1_B		0x1b0b0
+			>;
+		};
 	};
 };
diff --git a/arch/arm/boot/dts/imx6qdl-gw552x.dtsi b/arch/arm/boot/dts/imx6qdl-gw552x.dtsi
index d1e5048..07674c2 100644
--- a/arch/arm/boot/dts/imx6qdl-gw552x.dtsi
+++ b/arch/arm/boot/dts/imx6qdl-gw552x.dtsi
@@ -185,6 +185,12 @@
 	status = "okay";
 };
 
+&wdog1 {
+	pinctrl-names = "default";
+	pinctrl-0 = <&pinctrl_wdog>;
+	ext-reset-output;
+};
+
 &iomuxc {
 	imx6qdl-gw552x {
 		pinctrl_gpio_leds: gpioledsgrp {
@@ -262,5 +268,11 @@
 				MX6QDL_PAD_KEY_ROW1__UART5_RX_DATA	0x1b0b1
 			>;
                 };
+
+		pinctrl_wdog: wdoggrp {
+			fsl,pins = <
+				MX6QDL_PAD_DISP0_DAT8__WDOG1_B		0x1b0b0
+			>;
+		};
 	};
 };
-- 
2.6.2

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#1263566 — [PATCH v4 1/2] watchdog: imx2_wdt: add external reset support via 'ext-reset-output' dt prop

FromAkshay Bhat <akshay.bhat@timesys.com>
Date2015-11-05 22:30 +0100
Subject[PATCH v4 1/2] watchdog: imx2_wdt: add external reset support via 'ext-reset-output' dt prop
Message-ID<qrAgz-3yX-19@gated-at.bofh.it>
In reply to#1263562
From: Tim Harvey <tharvey@gateworks.com>

The IMX6 watchdog supports assertion of a signal (WDOG_B) which
can be pinmux'd to an external pin. This is typically used for boards that
have PMIC's in control of the IMX6 power rails. In fact, failure to use
such an external reset on boards with external PMIC's can result in various
hangs due to the IMX6 not being fully reset [1] as well as the board failing
to reset because its PMIC has not been reset to provide adequate voltage for
the CPU when coming out of reset at 800Mhz.

This uses a new device-tree property 'ext-reset-output' to indicate the
board has such a reset and to cause the watchdog to be configured to assert
WDOG_B instead of an internal reset both on a watchdog timeout and in
system_restart.

[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-March/333689.html

Cc: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Tim Harvey <tharvey@gateworks.com>
---
 .../devicetree/bindings/watchdog/fsl-imx-wdt.txt     |  2 ++
 drivers/watchdog/imx2_wdt.c                          | 20 ++++++++++++++++++--
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt b/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt
index 8dab6fd..9b89b3a 100644
--- a/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt
+++ b/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt
@@ -9,6 +9,8 @@ Optional property:
 - big-endian: If present the watchdog device's registers are implemented
   in big endian mode, otherwise in native mode(same with CPU), for more
   detail please see: Documentation/devicetree/bindings/regmap/regmap.txt.
+- ext-reset-output: If present the watchdog device is configured to assert its
+  external reset (WDOG_B) instead of issuing a software reset.
 
 Examples:
 
diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c
index 29ef719..84bfec4 100644
--- a/drivers/watchdog/imx2_wdt.c
+++ b/drivers/watchdog/imx2_wdt.c
@@ -41,6 +41,8 @@
 
 #define IMX2_WDT_WCR		0x00		/* Control Register */
 #define IMX2_WDT_WCR_WT		(0xFF << 8)	/* -> Watchdog Timeout Field */
+#define IMX2_WDT_WCR_WDA	(1 << 5)	/* -> External Reset WDOG_B */
+#define IMX2_WDT_WCR_SRS	(1 << 4)	/* -> Software Reset Signal */
 #define IMX2_WDT_WCR_WRE	(1 << 3)	/* -> WDOG Reset Enable */
 #define IMX2_WDT_WCR_WDE	(1 << 2)	/* -> Watchdog Enable */
 #define IMX2_WDT_WCR_WDZST	(1 << 0)	/* -> Watchdog timer Suspend */
@@ -65,6 +67,7 @@ struct imx2_wdt_device {
 	struct timer_list timer;	/* Pings the watchdog when closed */
 	struct watchdog_device wdog;
 	struct notifier_block restart_handler;
+	bool ext_reset;
 };
 
 static bool nowayout = WATCHDOG_NOWAYOUT;
@@ -90,6 +93,13 @@ static int imx2_restart_handler(struct notifier_block *this, unsigned long mode,
 	struct imx2_wdt_device *wdev = container_of(this,
 						    struct imx2_wdt_device,
 						    restart_handler);
+
+	/* Use internal reset or external - not both */
+	if (wdev->ext_reset)
+		wcr_enable |= IMX2_WDT_WCR_SRS; /* do not assert int reset */
+	else
+		wcr_enable |= IMX2_WDT_WCR_WDA; /* do not assert ext-reset */
+
 	/* Assert SRS signal */
 	regmap_write(wdev->regmap, IMX2_WDT_WCR, wcr_enable);
 	/*
@@ -119,8 +129,12 @@ static inline void imx2_wdt_setup(struct watchdog_device *wdog)
 	val |= IMX2_WDT_WCR_WDZST;
 	/* Strip the old watchdog Time-Out value */
 	val &= ~IMX2_WDT_WCR_WT;
-	/* Generate reset if WDOG times out */
-	val &= ~IMX2_WDT_WCR_WRE;
+	/* Generate internal chip-level reset if WDOG times out */
+	if (!wdev->ext_reset)
+		val &= ~IMX2_WDT_WCR_WRE;
+	/* Or if external-reset assert WDOG_B reset only on time-out */
+	else
+		val |= IMX2_WDT_WCR_WRE;
 	/* Keep Watchdog Disabled */
 	val &= ~IMX2_WDT_WCR_WDE;
 	/* Set the watchdog's Time-Out value */
@@ -267,6 +281,8 @@ static int __init imx2_wdt_probe(struct platform_device *pdev)
 	regmap_read(wdev->regmap, IMX2_WDT_WRSR, &val);
 	wdog->bootstatus = val & IMX2_WDT_WRSR_TOUT ? WDIOF_CARDRESET : 0;
 
+	wdev->ext_reset = of_property_read_bool(pdev->dev.of_node,
+						"ext-reset-output");
 	wdog->timeout = clamp_t(unsigned, timeout, 1, IMX2_WDT_MAX_TIME);
 	if (wdog->timeout != timeout)
 		dev_warn(&pdev->dev, "Initial timeout out of range! Clamped from %u to %u\n",
-- 
2.6.2

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#1263587 — Re: [PATCH v4 1/2] watchdog: imx2_wdt: add external reset support via 'ext-reset-output' dt prop

FromGuenter Roeck <linux@roeck-us.net>
Date2015-11-05 23:30 +0100
SubjectRe: [PATCH v4 1/2] watchdog: imx2_wdt: add external reset support via 'ext-reset-output' dt prop
Message-ID<qrBcC-4gD-19@gated-at.bofh.it>
In reply to#1263566
On Thu, Nov 05, 2015 at 04:19:21PM -0500, Akshay Bhat wrote:
> From: Tim Harvey <tharvey@gateworks.com>
> 
> The IMX6 watchdog supports assertion of a signal (WDOG_B) which
> can be pinmux'd to an external pin. This is typically used for boards that
> have PMIC's in control of the IMX6 power rails. In fact, failure to use
> such an external reset on boards with external PMIC's can result in various
> hangs due to the IMX6 not being fully reset [1] as well as the board failing
> to reset because its PMIC has not been reset to provide adequate voltage for
> the CPU when coming out of reset at 800Mhz.
> 
> This uses a new device-tree property 'ext-reset-output' to indicate the
> board has such a reset and to cause the watchdog to be configured to assert
> WDOG_B instead of an internal reset both on a watchdog timeout and in
> system_restart.
> 
> [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-March/333689.html
> 
> Cc: Lucas Stach <l.stach@pengutronix.de>
> Signed-off-by: Tim Harvey <tharvey@gateworks.com>
> ---
>  .../devicetree/bindings/watchdog/fsl-imx-wdt.txt     |  2 ++
>  drivers/watchdog/imx2_wdt.c                          | 20 ++++++++++++++++++--
>  2 files changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt b/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt
> index 8dab6fd..9b89b3a 100644
> --- a/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt
> +++ b/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt
> @@ -9,6 +9,8 @@ Optional property:

properties ?

>  - big-endian: If present the watchdog device's registers are implemented
>    in big endian mode, otherwise in native mode(same with CPU), for more
>    detail please see: Documentation/devicetree/bindings/regmap/regmap.txt.
> +- ext-reset-output: If present the watchdog device is configured to assert its

Should that have a vendor prefix ? Also, not sure if "-output"
has any real value in the property name. "fsl,external-reset", maybe ?

> +  external reset (WDOG_B) instead of issuing a software reset.
>  
>  Examples:
>  
> diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c
> index 29ef719..84bfec4 100644
> --- a/drivers/watchdog/imx2_wdt.c
> +++ b/drivers/watchdog/imx2_wdt.c
> @@ -41,6 +41,8 @@
>  
>  #define IMX2_WDT_WCR		0x00		/* Control Register */
>  #define IMX2_WDT_WCR_WT		(0xFF << 8)	/* -> Watchdog Timeout Field */
> +#define IMX2_WDT_WCR_WDA	(1 << 5)	/* -> External Reset WDOG_B */
> +#define IMX2_WDT_WCR_SRS	(1 << 4)	/* -> Software Reset Signal */
>  #define IMX2_WDT_WCR_WRE	(1 << 3)	/* -> WDOG Reset Enable */
>  #define IMX2_WDT_WCR_WDE	(1 << 2)	/* -> Watchdog Enable */
>  #define IMX2_WDT_WCR_WDZST	(1 << 0)	/* -> Watchdog timer Suspend */
> @@ -65,6 +67,7 @@ struct imx2_wdt_device {
>  	struct timer_list timer;	/* Pings the watchdog when closed */
>  	struct watchdog_device wdog;
>  	struct notifier_block restart_handler;
> +	bool ext_reset;
>  };
>  
>  static bool nowayout = WATCHDOG_NOWAYOUT;
> @@ -90,6 +93,13 @@ static int imx2_restart_handler(struct notifier_block *this, unsigned long mode,
>  	struct imx2_wdt_device *wdev = container_of(this,
>  						    struct imx2_wdt_device,
>  						    restart_handler);
> +
> +	/* Use internal reset or external - not both */
> +	if (wdev->ext_reset)
> +		wcr_enable |= IMX2_WDT_WCR_SRS; /* do not assert int reset */
> +	else
> +		wcr_enable |= IMX2_WDT_WCR_WDA; /* do not assert ext-reset */
> +
>  	/* Assert SRS signal */
>  	regmap_write(wdev->regmap, IMX2_WDT_WCR, wcr_enable);
>  	/*
> @@ -119,8 +129,12 @@ static inline void imx2_wdt_setup(struct watchdog_device *wdog)
>  	val |= IMX2_WDT_WCR_WDZST;
>  	/* Strip the old watchdog Time-Out value */
>  	val &= ~IMX2_WDT_WCR_WT;
> -	/* Generate reset if WDOG times out */
> -	val &= ~IMX2_WDT_WCR_WRE;
> +	/* Generate internal chip-level reset if WDOG times out */
> +	if (!wdev->ext_reset)
> +		val &= ~IMX2_WDT_WCR_WRE;
> +	/* Or if external-reset assert WDOG_B reset only on time-out */
> +	else
> +		val |= IMX2_WDT_WCR_WRE;

I don't really understand what this means. Normally I would hope that a watchdog
only generates a reset if/when it times out.

>  	/* Keep Watchdog Disabled */
>  	val &= ~IMX2_WDT_WCR_WDE;
>  	/* Set the watchdog's Time-Out value */
> @@ -267,6 +281,8 @@ static int __init imx2_wdt_probe(struct platform_device *pdev)
>  	regmap_read(wdev->regmap, IMX2_WDT_WRSR, &val);
>  	wdog->bootstatus = val & IMX2_WDT_WRSR_TOUT ? WDIOF_CARDRESET : 0;
>  
> +	wdev->ext_reset = of_property_read_bool(pdev->dev.of_node,
> +						"ext-reset-output");
>  	wdog->timeout = clamp_t(unsigned, timeout, 1, IMX2_WDT_MAX_TIME);
>  	if (wdog->timeout != timeout)
>  		dev_warn(&pdev->dev, "Initial timeout out of range! Clamped from %u to %u\n",
> -- 
> 2.6.2
> 
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#1264380 — Re: [PATCH v4 1/2] watchdog: imx2_wdt: add external reset support via 'ext-reset-output' dt prop

FromTim Harvey <tharvey@gateworks.com>
Date2015-11-06 21:00 +0100
SubjectRe: [PATCH v4 1/2] watchdog: imx2_wdt: add external reset support via 'ext-reset-output' dt prop
Message-ID<qrVl2-nS-61@gated-at.bofh.it>
In reply to#1263587
On Thu, Nov 5, 2015 at 2:23 PM, Guenter Roeck <linux@roeck-us.net> wrote:
> On Thu, Nov 05, 2015 at 04:19:21PM -0500, Akshay Bhat wrote:
>> From: Tim Harvey <tharvey@gateworks.com>
>>
>> The IMX6 watchdog supports assertion of a signal (WDOG_B) which
>> can be pinmux'd to an external pin. This is typically used for boards that
>> have PMIC's in control of the IMX6 power rails. In fact, failure to use
>> such an external reset on boards with external PMIC's can result in various
>> hangs due to the IMX6 not being fully reset [1] as well as the board failing
>> to reset because its PMIC has not been reset to provide adequate voltage for
>> the CPU when coming out of reset at 800Mhz.
>>
>> This uses a new device-tree property 'ext-reset-output' to indicate the
>> board has such a reset and to cause the watchdog to be configured to assert
>> WDOG_B instead of an internal reset both on a watchdog timeout and in
>> system_restart.
>>
>> [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-March/333689.html
>>
>> Cc: Lucas Stach <l.stach@pengutronix.de>
>> Signed-off-by: Tim Harvey <tharvey@gateworks.com>
>> ---
>>  .../devicetree/bindings/watchdog/fsl-imx-wdt.txt     |  2 ++
>>  drivers/watchdog/imx2_wdt.c                          | 20 ++++++++++++++++++--
>>  2 files changed, 20 insertions(+), 2 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt b/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt
>> index 8dab6fd..9b89b3a 100644
>> --- a/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt
>> +++ b/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt
>> @@ -9,6 +9,8 @@ Optional property:
>
> properties ?
>
>>  - big-endian: If present the watchdog device's registers are implemented
>>    in big endian mode, otherwise in native mode(same with CPU), for more
>>    detail please see: Documentation/devicetree/bindings/regmap/regmap.txt.
>> +- ext-reset-output: If present the watchdog device is configured to assert its
>
> Should that have a vendor prefix ? Also, not sure if "-output"
> has any real value in the property name. "fsl,external-reset", maybe ?

Hi Guenter,

I don't see why a vendor prefix is necessary - its a feature of the
IMX6 watchdog supported by this driver to be able to trigger an
internal chip-level reset and/or an external signal that can be hooked
to additional hardware.

I started with ext-reset, but it was suggested
(http://lists.infradead.org/pipermail/linux-arm-kernel/2015-May/347437.html)
to also make it clear that this is an 'output' and not a reset input.

>
>> +  external reset (WDOG_B) instead of issuing a software reset.
>>
>>  Examples:
>>
>> diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c
>> index 29ef719..84bfec4 100644
>> --- a/drivers/watchdog/imx2_wdt.c
>> +++ b/drivers/watchdog/imx2_wdt.c
>> @@ -41,6 +41,8 @@
>>
>>  #define IMX2_WDT_WCR         0x00            /* Control Register */
>>  #define IMX2_WDT_WCR_WT              (0xFF << 8)     /* -> Watchdog Timeout Field */
>> +#define IMX2_WDT_WCR_WDA     (1 << 5)        /* -> External Reset WDOG_B */
>> +#define IMX2_WDT_WCR_SRS     (1 << 4)        /* -> Software Reset Signal */
>>  #define IMX2_WDT_WCR_WRE     (1 << 3)        /* -> WDOG Reset Enable */
>>  #define IMX2_WDT_WCR_WDE     (1 << 2)        /* -> Watchdog Enable */
>>  #define IMX2_WDT_WCR_WDZST   (1 << 0)        /* -> Watchdog timer Suspend */
>> @@ -65,6 +67,7 @@ struct imx2_wdt_device {
>>       struct timer_list timer;        /* Pings the watchdog when closed */
>>       struct watchdog_device wdog;
>>       struct notifier_block restart_handler;
>> +     bool ext_reset;
>>  };
>>
>>  static bool nowayout = WATCHDOG_NOWAYOUT;
>> @@ -90,6 +93,13 @@ static int imx2_restart_handler(struct notifier_block *this, unsigned long mode,
>>       struct imx2_wdt_device *wdev = container_of(this,
>>                                                   struct imx2_wdt_device,
>>                                                   restart_handler);
>> +
>> +     /* Use internal reset or external - not both */
>> +     if (wdev->ext_reset)
>> +             wcr_enable |= IMX2_WDT_WCR_SRS; /* do not assert int reset */
>> +     else
>> +             wcr_enable |= IMX2_WDT_WCR_WDA; /* do not assert ext-reset */
>> +
>>       /* Assert SRS signal */
>>       regmap_write(wdev->regmap, IMX2_WDT_WCR, wcr_enable);
>>       /*
>> @@ -119,8 +129,12 @@ static inline void imx2_wdt_setup(struct watchdog_device *wdog)
>>       val |= IMX2_WDT_WCR_WDZST;
>>       /* Strip the old watchdog Time-Out value */
>>       val &= ~IMX2_WDT_WCR_WT;
>> -     /* Generate reset if WDOG times out */
>> -     val &= ~IMX2_WDT_WCR_WRE;
>> +     /* Generate internal chip-level reset if WDOG times out */
>> +     if (!wdev->ext_reset)
>> +             val &= ~IMX2_WDT_WCR_WRE;
>> +     /* Or if external-reset assert WDOG_B reset only on time-out */
>> +     else
>> +             val |= IMX2_WDT_WCR_WRE;
>
> I don't really understand what this means. Normally I would hope that a watchdog
> only generates a reset if/when it times out.

I think we went a couple of rounds on the info in the comment as well
in the previous patch reversions.

It is a feature of the IMX6 watchdog supported by this driver to be
able to trigger an internal chip-level reset and/or an external signal
that can be hooked to additional hardware.

In the case of using a PMIC that can regulate it's own rails (ie the
Freescale SabreSD reference design) an SoC chip-level reset will not
reset the PMIC and thus if the PMIC's rails have been driven down by
DVFS to a value below the necessary value for the chip to come up you
will hang (which is certainly not what you want to do when a watchdog
timeout occurs). The solution for designs that have a PMIC that is
able to change its voltage levels is to 'not' have the SoC internally
reset and to 'instead' drive an external reset signal that should
reset the PMIC (and possibly other chips if needed). The reason for
not allowing the internal reset is because as soon as the SoC goes
into reset it de-asserts the external reset which makes the time the
output is asserted un-deterministic.

Tim
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#1264597 — Re: [PATCH v4 1/2] watchdog: imx2_wdt: add external reset support via 'ext-reset-output' dt prop

FromGuenter Roeck <linux@roeck-us.net>
Date2015-11-06 23:10 +0100
SubjectRe: [PATCH v4 1/2] watchdog: imx2_wdt: add external reset support via 'ext-reset-output' dt prop
Message-ID<qrXmO-21f-21@gated-at.bofh.it>
In reply to#1264380
On Fri, Nov 06, 2015 at 11:53:42AM -0800, Tim Harvey wrote:
> On Thu, Nov 5, 2015 at 2:23 PM, Guenter Roeck <linux@roeck-us.net> wrote:
> > On Thu, Nov 05, 2015 at 04:19:21PM -0500, Akshay Bhat wrote:
> >> From: Tim Harvey <tharvey@gateworks.com>
> >>
> >> The IMX6 watchdog supports assertion of a signal (WDOG_B) which
> >> can be pinmux'd to an external pin. This is typically used for boards that
> >> have PMIC's in control of the IMX6 power rails. In fact, failure to use
> >> such an external reset on boards with external PMIC's can result in various
> >> hangs due to the IMX6 not being fully reset [1] as well as the board failing
> >> to reset because its PMIC has not been reset to provide adequate voltage for
> >> the CPU when coming out of reset at 800Mhz.
> >>
> >> This uses a new device-tree property 'ext-reset-output' to indicate the
> >> board has such a reset and to cause the watchdog to be configured to assert
> >> WDOG_B instead of an internal reset both on a watchdog timeout and in
> >> system_restart.
> >>
> >> [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-March/333689.html
> >>
> >> Cc: Lucas Stach <l.stach@pengutronix.de>
> >> Signed-off-by: Tim Harvey <tharvey@gateworks.com>
> >> ---
> >>  .../devicetree/bindings/watchdog/fsl-imx-wdt.txt     |  2 ++
> >>  drivers/watchdog/imx2_wdt.c                          | 20 ++++++++++++++++++--
> >>  2 files changed, 20 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt b/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt
> >> index 8dab6fd..9b89b3a 100644
> >> --- a/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt
> >> +++ b/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt
> >> @@ -9,6 +9,8 @@ Optional property:
> >
> > properties ?
> >
> >>  - big-endian: If present the watchdog device's registers are implemented
> >>    in big endian mode, otherwise in native mode(same with CPU), for more
> >>    detail please see: Documentation/devicetree/bindings/regmap/regmap.txt.
> >> +- ext-reset-output: If present the watchdog device is configured to assert its
> >
> > Should that have a vendor prefix ? Also, not sure if "-output"
> > has any real value in the property name. "fsl,external-reset", maybe ?
> 
> Hi Guenter,
> 
> I don't see why a vendor prefix is necessary - its a feature of the
> IMX6 watchdog supported by this driver to be able to trigger an
> internal chip-level reset and/or an external signal that can be hooked
> to additional hardware.
> 
Sounded like vendor specific to me, but then I am not a devicetree maintainer,
so I am not an authority on the subject.

> I started with ext-reset, but it was suggested
> (http://lists.infradead.org/pipermail/linux-arm-kernel/2015-May/347437.html)
> to also make it clear that this is an 'output' and not a reset input.
> 
No problem, as long as you get an Ack from a devicetree maintainer.

Guenter
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