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From:   Ivan Mikhaylov <i.mikhaylov@yadro.com>
To:     Guenter Roeck <linux@roeck-us.net>,
        Wim Van Sebroeck <wim@linux-watchdog.org>
CC:     Joel Stanley <joel@jms.id.au>, Andrew Jeffery <andrew@aj.id.au>,
        <linux-watchdog@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-aspeed@lists.ozlabs.org>, <linux-kernel@vger.kernel.org>,
        Alexander Amelkin <a.amelkin@yadro.com>,
        <openbmc@lists.ozlabs.org>, Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        <devicetree@vger.kernel.org>,
        Ivan Mikhaylov <i.mikhaylov@yadro.com>
Subject: [PATCH v3 4/4] aspeed/watchdog: Add access_cs0 option for alt-boot
Date:   Tue, 27 Aug 2019 19:54:26 +0300
Message-ID: <20190827165426.17037-5-i.mikhaylov@yadro.com>
In-Reply-To: <20190827165426.17037-1-i.mikhaylov@yadro.com>
References: <20190827165426.17037-1-i.mikhaylov@yadro.com>
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The option for the ast2400/2500 to get access to CS0 at runtime.

Signed-off-by: Ivan Mikhaylov <i.mikhaylov@yadro.com>
---
 .../ABI/testing/sysfs-class-watchdog          | 34 +++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-class-watchdog b/Documentation/ABI/testing/sysfs-class-watchdog
index 6317ade5ad19..675f9b537661 100644
--- a/Documentation/ABI/testing/sysfs-class-watchdog
+++ b/Documentation/ABI/testing/sysfs-class-watchdog
@@ -72,3 +72,37 @@ Description:
 		It is a read/write file. When read, the currently assigned
 		pretimeout governor is returned.  When written, it sets
 		the pretimeout governor.
+
+What:		/sys/class/watchdog/watchdog1/access_cs0
+Date:		August 2019
+Contact:	Ivan Mikhaylov <i.mikhaylov@yadro.com>,
+		Alexander Amelkin <a.amelkin@yadro.com>
+Description:
+		It is a read/write file. This attribute exists only if the
+		system has booted from the alternate flash chip due to
+		expiration of a watchdog timer of AST2400/AST2500 when
+		alternate boot function was enabled with 'aspeed,alt-boot'
+		devicetree option for that watchdog or with an appropriate
+		h/w strapping (for WDT2 only).
+
+		At alternate flash the 'access_cs0' sysfs node provides:
+			ast2400: a way to get access to the primary SPI flash
+				chip at CS0 after booting from the alternate
+				chip at CS1.
+			ast2500: a way to restore the normal address mapping
+				from (CS0->CS1, CS1->CS0) to (CS0->CS0,
+				CS1->CS1).
+
+		Clearing the boot code selection and timeout counter also
+		resets to the initial state the chip select line mapping. When
+		the SoC is in normal mapping state (i.e. booted from CS0),
+		clearing those bits does nothing for both versions of the SoC.
+		For alternate boot mode (booted from CS1 due to wdt2
+		expiration) the behavior differs as described above.
+
+		This option can be used with wdt2 (watchdog1) only.
+
+		When read, the current status of the boot code selection is
+		shown. When written with any non-zero value, it clears
+		the boot code selection and the timeout counter, which results
+		in chipselect reset for AST2400/AST2500.
-- 
2.20.1