linux-kernel - [RFC PATCH 2/3] ARM: omap: add DT support for deasserting hardware reset lines

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Date:	Wed, 26 Sep 2012 09:44:30 -0400
From:	Matt Porter <mporter@...com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Hans J. Koch" <hjk@...sjkoch.de>,
	Benoit Cousson <b-cousson@...com>,
	Paul Walmsley <paul@...an.com>
Cc:	Tony Lindgren <tony@...mide.com>,
	Linux OMAP List <linux-omap@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH 2/3] ARM: omap: add DT support for deasserting hardware reset lines

This optional binding extension allows specification of a hwmod
and associate hardware reset line which should be deasserted for
the device to be functional.

The implementation works for reference as to the problem that
exists for utilizing uio_pruss on AM33xx but is suboptimal. The
problem is that this deassertion occurs before clocks are enabled
and we are warned that the hard reset failed. Ideally the list of
rst lines requested to be deasserted would be cached and used within
the hwmod enable sequencing (instead of it just returning if any
hardware reset line is asserted).

Signed-off-by: Matt Porter <mporter@...com>
---
 .../devicetree/bindings/arm/omap/omap.txt          |    2 ++
 arch/arm/plat-omap/omap_device.c                   |   25 ++++++++++++++++++--
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/arm/omap/omap.txt b/Documentation/devicetree/bindings/arm/omap/omap.txt
index d0051a7..3133a4b 100644
--- a/Documentation/devicetree/bindings/arm/omap/omap.txt
+++ b/Documentation/devicetree/bindings/arm/omap/omap.txt
@@ -21,6 +21,8 @@ Required properties:
 Optional properties:
 - ti,no_idle_on_suspend: When present, it prevents the PM to idle the module
   during suspend.
+- ti,deassert-hard-reset: list of hwmod and hardware reset line name pairs
+  (ascii strings) to be deasserted upon device instantiation.
 
 
 Example:
diff --git a/arch/arm/plat-omap/omap_device.c b/arch/arm/plat-omap/omap_device.c
index d5f617c..d1ae68c 100644
--- a/arch/arm/plat-omap/omap_device.c
+++ b/arch/arm/plat-omap/omap_device.c
@@ -330,8 +330,8 @@ static int omap_device_build_from_dt(struct platform_device *pdev)
 	struct omap_device *od;
 	struct omap_hwmod *oh;
 	struct device_node *node = pdev->dev.of_node;
-	const char *oh_name;
-	int oh_cnt, i, ret = 0;
+	const char *oh_name, *rst_name;
+	int oh_cnt, dstr_cnt, i, ret = 0;
 
 	oh_cnt = of_property_count_strings(node, "ti,hwmods");
 	if (!oh_cnt || IS_ERR_VALUE(oh_cnt)) {
@@ -376,6 +376,27 @@ static int omap_device_build_from_dt(struct platform_device *pdev)
 	if (of_get_property(node, "ti,no_idle_on_suspend", NULL))
 		omap_device_disable_idle_on_suspend(pdev);
 
+	dstr_cnt =
+		of_property_count_strings(node, "ti,deassert-hard-reset");
+	if (dstr_cnt > 0) {
+		for (i = 0; i < dstr_cnt; i += 2) {
+			of_property_read_string_index(
+				node, "ti,deassert-hard-reset", i,
+				&oh_name);
+			of_property_read_string_index(
+				node, "ti,deassert-hard-reset", i+1,
+				&rst_name);
+			oh = omap_hwmod_lookup(oh_name);
+			if (!oh) {
+				dev_warn(&pdev->dev,
+				"Cannot parse deassert property for '%s'\n",
+				oh_name);
+				break;
+			}
+			omap_hwmod_deassert_hardreset(oh, rst_name);
+		}
+	}
+
 	pdev->dev.pm_domain = &omap_device_pm_domain;
 
 odbfd_exit1:
-- 
1.7.9.5

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