Re: [PATCH v2 05/15] watchdog: orion: Make RSTOUT register a separate resource

[Ezequiel Garcia <ezequiel.garcia@free-electrons.com>]

On Wed, Jan 22, 2014 at 01:21:36PM -0300, Ezequiel Garcia wrote:
> > I don't see a good way out that would preserve backwards compatibility,
> > other than hardcoding the physical address in the driver, which seems
> > just as bad as breaking compatibility. That said, it is always the
> > same constant (0xf1000000 + 0x20000 + 0x0108) on Dove, Kirkwood and
> > Orion5x (not on mv78xx0, but that doesn't use the wdt), so hardcoding
> > a fallback would technically work, but we should print a fat warning at
> > boot time if we actually fall back to that.
> > 
> 
> Yes, I was thinking just about this. Namely:
> 
[..]

How about something like this?

diff --git a/drivers/watchdog/orion_wdt.c b/drivers/watchdog/orion_wdt.c
index a861b88..0014d23 100644
--- a/drivers/watchdog/orion_wdt.c
+++ b/drivers/watchdog/orion_wdt.c
@@ -26,6 +26,9 @@
 #include <linux/of.h>
 #include <mach/bridge-regs.h>
 
+/* RSTOUT mask register physical address for Orion5x, Kirkwood and Dove */
+#define ORION_RSTOUT_MASK	0xf1020108
+
 /*
  * Watchdog timer block registers.
  */
@@ -119,6 +122,30 @@ static irqreturn_t orion_wdt_irq(int irq, void *devid)
 	return IRQ_HANDLED;
 }
 
+/*
+ * The original devicetree binding for this driver specified only
+ * one memory resource, so in order to keep DT backwards compatibility
+ * we try to fallback to a hardcoded register address, if the resource
+ * is missing from the devicetree.
+ */
+static void __iomem * try_compat_rstout_ioremap(struct platform_device *pdev)
+{
+	struct resource *res;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+	if (res)
+		return devm_ioremap(&pdev->dev, res->start,
+				    resource_size(res));
+
+	/* This workaround works only for "orion-wdt", DT-enabled */
+	if (!of_device_is_compatible(pdev->dev.of_node, "marvell,orion-wdt"))
+		return NULL;
+
+	dev_warn(&pdev->dev, "falling back to harcoded RSTOUT reg 0x%x\n",
+		 ORION_RSTOUT_MASK);
+	return devm_ioremap(&pdev->dev, ORION_RSTOUT_MASK, 0x4);
+}
+
 static int orion_wdt_probe(struct platform_device *pdev)
 {
 	struct resource *res;
@@ -139,10 +166,7 @@ static int orion_wdt_probe(struct platform_device *pdev)
 	if (!wdt_reg)
 		return -ENOMEM;
 
-	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
-	if (!res)
-		return -ENODEV;
-	wdt_rstout = devm_ioremap(&pdev->dev, res->start, resource_size(res));
+	wdt_rstout = try_compat_rstout_ioremap(pdev);
 	if (!wdt_rstout)
 		return -ENOMEM;
 
-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com
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