[RFC PATCH 3/3] ARM: OMAP2+: Add command line parameter for debugSS module control

[hvaibhav at ti.com]

From: Vaibhav Hiremath <hvaibhav at ti.com>

Currently there is no clean mechanism to control debugSS module and
you have to always keep clocks enabled, either,

    - By enabling it during boot as part of clk_init function.
    Or
    - By having HWMOD_INIT_NO_IDLE flag in hwmod data.

Based on the discussion,
http://www.mail-archive.com/linux-omap@vger.kernel.org/msg81771.html

This patch introduces new kernel parameter "omap_debugss_en",
which will allow user to control debugSS module enable/disable
part during boot-time.

Signed-off-by: Vaibhav Hiremath <hvaibhav at ti.com>
Cc: Kevin Hilman <khilman at linaro.org>
Cc: Paul Walmsley <paul at pwsan.com>
Cc: Tony Lindgren <tony at atomide.com>
---
Tested on
	- AM335x based EVM and BeagleBone platforms

 Documentation/kernel-parameters.txt |    3 +
 arch/arm/mach-omap2/Makefile        |    2 +-
 arch/arm/mach-omap2/debugss.c       |   80 +++++++++++++++++++++++++++++++++++
 3 files changed, 84 insertions(+), 1 deletions(-)
 create mode 100644 arch/arm/mach-omap2/debugss.c

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 6c72381..bf1c822 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2051,6 +2051,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			For example, to override I2C bus2:
 			omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100

+	omap_debugss_en	[OMAP] Enable Debug Sub-System module required
+			for JTAG debugging.
+
 	oprofile.timer=	[HW]
 			Use timer interrupt instead of performance counters

diff --git a/arch/arm/mach-omap2/Makefile b/arch/arm/mach-omap2/Makefile
index d1156cf..aaf5cc2 100644
--- a/arch/arm/mach-omap2/Makefile
+++ b/arch/arm/mach-omap2/Makefile
@@ -5,7 +5,7 @@
 # Common support
 obj-y := id.o io.o control.o mux.o devices.o fb.o serial.o gpmc.o timer.o pm.o \
 	 common.o gpio.o dma.o wd_timer.o display.o i2c.o hdq1w.o omap_hwmod.o \
-	 omap_device.o sram.o
+	 omap_device.o sram.o debugss.o

 omap-2-3-common				= irq.o
 hwmod-common				= omap_hwmod.o \
diff --git a/arch/arm/mach-omap2/debugss.c b/arch/arm/mach-omap2/debugss.c
new file mode 100644
index 0000000..b45bf2c
--- /dev/null
+++ b/arch/arm/mach-omap2/debugss.c
@@ -0,0 +1,80 @@
+/*
+ * debugss.c: Debug Sus-System related code goes in here
+ *
+ * Copyright (C) {2013} Texas Instruments Incorporated - http://www.ti.com/
+ *
+ * This file is automatically generated from the AM33XX hardware databases.
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation version 2.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/init.h>
+#include <linux/err.h>
+#include <linux/clk.h>
+
+#include "omap_hwmod.h"
+
+static bool is_debugss_en;
+
+/**
+ * omap_debugss_en - Enable debugss clock/module based on user config
+ *
+ * During kernel bootup, omap2 hwmod framework will disable all the
+ * unused/unclaimed modules, which in turn also disables debugss module.
+ * This breaks any further debugging capability provided by HW.
+ *
+ *
+ * Introduce early param which allows user to enable clock/module -
+ *
+ *   omap_debugss_en	(For all OMAP2 architectures)
+ *
+ * Please note that, with this command-line param, module always remain
+ * enabled.
+ */
+static int __init omap_debugss_en(char *str)
+{
+	is_debugss_en = true;
+	return 0;
+}
+early_param("omap_debugss_en", omap_debugss_en);
+
+static int __init _omap2_debugss_enable(void)
+{
+	const char oh_name[10] = "debugss";
+	struct omap_hwmod *oh;
+	int ret;
+
+	if (is_debugss_en) {
+		struct omap_hwmod_opt_clk *oc;
+		int i;
+
+		oh = omap_hwmod_lookup(oh_name);
+		if (!oh) {
+			pr_err("debugss device not found\n");
+			return 0;
+		}
+
+		/* Make sure that hwmod internal data structures are setup */
+		ret = omap_hwmod_setup_one(oh_name);
+		if (ret) {
+			pr_err("failed to setup hwmod for %s\n", oh_name);
+			return 0;
+		}
+		/* Enable optional clocks */
+		for (i = oh->opt_clks_cnt, oc = oh->opt_clks; i > 0; i--, oc++)	{
+			if (oc->_clk)
+				clk_prepare_enable(oc->_clk);
+		}
+		/* Enable debugss clock/module  */
+		omap_hwmod_enable(oh);
+	}
+
+	return 0;
+}
+device_initcall(_omap2_debugss_enable);
--
1.7.0.4